'^i-SjV. i.j'SCi V BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIFT OF m^nvu ^^ Sage 1891 4.xmsf. ^/m/a'^... 9963 Date Due Cornell University Library QE 262.F18H64 1906 The geology of Falmouth and Truro and of 3 1924 004 543 694 s<#^ Cornell University Library The original of tiiis book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924004543694 MEMOIRS OF THE GEOLOGICAL SURVEY. ENGLAND AND WALES. EXPLANATION OF SHEET 352. THE GEOLOGY OF FALMOUTH AND TRURO AND OF THE MINING DISTRICT OF CAMBORNE AND REDRUTH. J. B. HILl,, E.N, ^ AND D. A. MacALTSTER, A.R.S.M., F.G.S. WITH PETROLOGICAL NOTES BY J. S. FLETT, M.B., D.Sc. PUBLISHED BY ORDER OF THE LORDS COMMISSIONERS OP HIS MAJESTY'S TREASURY. LONDON: PRINTED FOR HIS" MAJESTY'S STATIONERY OFFICE, By WYMAN & SONS, Limited, Fetter Lane, E.G. And to be purchased from E. STANFORD, 12, 13, and 14, Long Aoee, London ; W. & A. K. JOHNSTON, Ltd., 20, South St. Andrew Street, EDiNBUEan ; HODGES, FIGGIS & Co., Grafton Street, Dublin ; From any Agent for the sale of Ordnance Survey Maps ; or through any Bookseller from the Ordnance Survey Office, Southampton. 1906. Priap, 7.1. fid. ]\ ''^■Mo'^-^Z HI PREFACE. The region described in this memoir includes that portion of West Cornwall which is represented by Sheet 352 of the new series one-inch map of England and Wales. The original geological survey was carried out by De la Beche in connection with the Trigonometrical Survey of Great Britain, then under the superintendence of Colonel Colby, E.E., F.R.S., and in the course of his work De la Beche received valuable assistance from two Ordnance Surveyors, Mr. Henry McLauchlan, F.G.S., and Mr. Henry Still, F.G.S. The results of the original survey were published in 1839 on the old series maps 31 and 33, and in the well-known Report on the Geology of Cornwall, Devon and West Somerset, Additional lodes were inserted on the maps at a later date by Sir W. W. Smyth, and new editions of the maps were published in 1866. On comparing the new map with the corresponding portions of the older maps it will be noted that important additions have been made. The area formerly represented as Devonian has been separated into Lower Devonian, and into three sub- divisions, based on lithological characters, to which the terms Portscatho, Falinouth and Mylor have been applied. These three sub-divisions, together with the Veryan beds, which were classed as Lower Silurian on the earlier maps in consequence of the discovery of fossils near Gorran Haven by Mr. C. W. Peach, are now regarded as Lower Palaeozoic, mainly on account of the evidence supplied by a coarse conglomerate which is well exposed at Flushing on the south side of the Helford River (^one-inch map 359). This conglomerate contains rounded fragments and large masses of Portscatho rocks which were veined prior to their inclusion in the conglomerate ; and the detailed mapping proves that it comes in contact with various members of the earlier series in such a way as to indicate an important unconformability. No recognisable Devonian fossils have been found in the conglomerate or associated deposits, but the stratigraphical evidence is regarded as sufficient to justify the conclusion that it is of Lower Devonian age. In the sheet to which this memoir" refers the grits of Grampound and Probus are taken as the equivalents of the conglomerate on the Helford River ; and the line at their base which runs near to and parallel with the northern margin of the map therefore represents the boundary between the Devonian and pre-Devonian rocks. Amongst the igneous rocks the dominant representative is granite, with which the mineral products of the area are so intimately associated. As this district contains the principal seat of the Cornish tin industry it has IV PREFACE. been described in more detail than is usual in a sheet explanation. The geological survey of the area on the six-inch scale was carried out during the years 1897-1903 by Mr. Hill, with the exception of a narrow tract near the north coast that was mapped by Mr. E. E. L. Dixon. The mineral survey has been done by Mr. MacAlister under the supervision of Mr. Hill ; and the survey of the entire area since 1901 has been under the charge of Mr. Clement Eeid as District Geologist. The rbemoir has been written by Mr. Hill and Mr. MacAlister, while Mr. Dixon has contributed notes of the area which he surveyed. The microscopic examination of the rocks previous to 1901 was done by Mr. Hill, and subsequently by Dr. Flett. The petrographical descriptions of the rocks referred to in Part I. are based on detailed notes supplied to Mr. Hill by Dr. Flett. Mr. MacAlister is responsible for the petrographical and mineralogical information contained in Part II. The photographs which have been reproduced as plates, with the exception of those representing microscopic features, have been taken by Mr. T. C. Hall, of the Geological Survey. The MS. six-inch maps of the district, included within the area of the one-inch map, have been deposited in the Library for reference, and copies of them may be obtained. J. J. H. Teall, Director. Geological Survey Office, 28, Jermyn Street, London, November 20th, 1906. CONTENTS. ^^""^ Preface by the Director ... _. ... ... iii CHAPTER I. Introduction ... ... ... ... ... 1 PAET I.-GEOLOGY. ClJAPTER II. Formations and their Oeneral Distribution ... ... 13 CHAPTER III. The Killas— General Descripfcioa and Tectonics ... ... 16 CHAPTER IV. Lower FalcBozoic — I. — Mylor Series ... ... ... ... '25 XL— Falmouth Series ... ... ... ... 29 III. — Portscatho Series ... ... ... 33 IV. — Veryan Series ... ... ... ... 37 CHAPTER V. Devonian Mocks — Grampound and Probus Series ... ... ... 39 CHAPTER VI. Igneous Mocks — I. — Greenstone ... ... ... ... 41 II.— Granite... ... ... ... ... 52 III— Elvan ... ... ... ... ... 64 IV. —Mica Traps ... ... ... ... 74 CHAPTER VII. Coniact MetaTnarphism effected by the Ch-anite ... ... 81 CHAPTER VIII. Faults ... ... ... ... ... ■•• 87 CHAPTER IX. Pliocene Deposits — Polcrebo Gravels ... ... ... • • • 88 Vi CONTENTS. CHAPTER X. Pleistocene Deposits — I. — Raised Beaches ... II.-Head " III.— Stream Tin and Submerged Valley Deposits 90 93 95 CHAPTER XI. Recent Deposits — I. — Submerged Forests II. — Marine Alluvia ... III. — Freshwater Alluvia (Valley Systems, &c.) IV— Blown Sand 99 100 101 103 CHAPTER XII. Economic Resources (excluding the Ores) 104 PABT II.-MINING. CHAPTER XIII. Geology of the Mineral Area 113 CHAPTER XIV. Natural History of the Lodes — I. — Distribution of the Lodes ... II. — Geological Age of the Lodes III. — Relative Age of the Tin-Copper and Silver Lead Lodes . . . IV. — Structure of the Lodes V. — Caunter Lodes ... VI. — Intersection of Lodes VII. — Faulting by Lodes VIIL— Trend of the Lodes IX. — Underlie of the Lodes X. — Length of the Lodes XI. — Breadth of the Lodes XII. — Veinstone of the Lodes 125 130 130 131 140 143 146 148 149 152 153 154 CHAPTER XV. Gross-Courses, Cross-Flvxans, and Slides 157 CONTENTS. vn CHAPTER XVI. Natural History of the Ores — L— The Ore Bodies 161 "ll. — Genesis of the Ores ... ... ... 167 III. — Distribution of the Ores ... ... ... 171 IV. — Order of Arrival of the Ores ... ... 182 V. — Local Conditions Influencing Ore Deposit ... 184 VI. — Decomposition and Kedistribution of the Ores 187 VII.— Minerals of the Ores ... ... ... 194 CHAPTER XVII. The Mines — I. — Linear Distribution of the Principal Mines ... 205 II. — Particulars relating to the Mines ... ... 207 CHAPTER XVIII. Mining Economics ... ... ... ■■• 25§ APPENDIX. Bibliography ... ... ... ... ... 315 Index ... ... ... ... ... ... 325 Vlll LIST OF ILLUSTRATIONS. Plate I. — Swanpool, Falmouth. Lake formed by a natural dam of a Beach piled up across the front of the valley. Cliff Section of Falmouth Slate Series in the foreground (Frontispiece.) AT END OF VOLIJME. Plate II. — Trefusis, Falmouth Harbour. The Pliocene platform is seen along the sky-line. The Pleistocene platform, capped by Raised Beach and Head, makes the feature skirting the shore of the estuary ... ... ,, Plate III. — The Camborne mining district with Carn Brea in the distance ... ... ... „ Plate IV. — Sunny Cove, Falmouth. Portscatho Slate Series, showing contortion and quartz veining ... ... ... ... „ Plate V. — Sunny Cove, Falmouth. Portscatto Series, showing bedding, cleavage, and jointing. In the sandy bands the cleavage is. seen oblique to the bedding .. . ... ... „ Plate VI. — Restronguet Point, Carrick Roads. Mylor Series, showing brecciation resulting in the production of pseudo-conglomerate. The large quartz vein exhibits initial stages of the process ... ... ... ... „ Plate' VII. — Cam Brea. Granite tor with stratiform weathering ... ... ... ... „ Plate VIII. — Sunny Cove, Falmouth. Pleistocene plat- forms slightly above the modern coastal shelf. They are carved out of the Ports- catho Series, and capped on the landward side by Head. A relic of the Raised Beach is seen in the foreground at the base of the Head ... ... ... ... „ Plate IX, — Longdowns. Mabe. Granite quarry (worked by Messrs. Freeman & Co.), displaying the characteristic jointing ... ... Plate X. — Lode structures, (a) Middle lode. South Crofty Mine, (b) Gaunter lode. East Pool ^ Mine ... ... ... ... ., Plate XI. — Specimens of veinstone, (a) Wheal Gren- ville, 300-fathom .level. It is a tough brecciated tourmaline peach cemented by quartz. (6) East Pool. Quartz, wolfram, and mispickel. (c) Dolcoath, 475-fathom level. Tough tourmaline peach, finely brecciated, and cemented by cassiterjte ... „ LIST OF ILLUSTRATIONS. ix AT UND OF VOLUME. Plate Xll. — Microphotographs of veinstones... ... „ Plate XIII. — Cornish stamps. South Crofty Dressing Floors Plate XIY. — Frue Vanners. Dolcoath Dressing Floors Plate XV. — Wilfley Tables. Dolcoath Dressing Floors Plate XVI.^ — Acme Table. Dolcoath Dressing Floors ... Plate XVII. — Convex Buddie. Dolcoath Dressing Floors Plate XVIII. — Concave Buddie. South Crofty Dressing Floors Plate XIX. — Dumb pit. South Crofty Dressing Floors Plate XX. — Kieves. Dolcoath Dressing Floors Plate XXI. — Slime pits. Kieve Mill, Reskudinnick ... Plate XXII. — Products from ore dressing Pl.\te XXIII. — Products from ore dressing ... Plate XXIV. — Ragging Frames. Kieve Mill, Reskudin- nick... FIGURES IN TEXT. Fig. PAOf. ]. — Sketch map to illustrate the geology of the Falmouth sheet (352) ... ... ... 8 2. — Subterranean contour of the granite ... ... 116 3.— Great Wheal Baddern . .. ... ... ... 1:^0 4.— Great Wheal Busy ... ■ ... ... ... 121 5. — Sithney and Carnmeal Mine ... ... ... 122 6.— West Stray Park Mine .. ... ... 123 7. — Section from South Tolcarne Mine to New Wheal Seton ... ... ... ... ... 125 8. — Section from West Wheal Buller to West Wheal Seton ... ... ... ... ... 125 9. — Section from Grillis to Wheal Emily Henrietta ... 126 10.— Section from Filtrick to New North Pcfol ... 126 11. — Section from Wheal Basset to North Pool ... 127 12. — Section from Bulier and Basset United to Wheal Tolgus ... ... ... ... ... 127 13.— Section from West of Penstruthal to Tolgus United 128 14. — Section from Trelusback Mine to Wheal Montagu ... 128 15. — Section from Tresavean Mine to Treleigh Consols Mine ... ... ... ... ... 129 16. — Section from Ting Tang Mine to North Downs Mine ... ... ... ... ... 129 17.— WhealJane ... ... ... ... ... 151 18.— Killifreth Mine ... ... ... ... 151 19. — Longitudinal Section of the Main Lode of Dolcoath and Carn Brea Mines ... ... . • . 1 <>2 20.— Wheal Music... ... ... ... ■■ 165 21.— Diagram to show Linear Distribution of the Principal Mines ... ... ... ... .■• 206 22.— West Basset North Lode (longitudinal section) ... 220 23.— Clifford Amalgamated Mines ... ... ... 224 X LIST OF ILLUSTRATIONS. PIG. PAQK. ^4.— Poldice ... ... ... ... ... 224 25.— United Mines ... ... ... ... 224 26.— Consolidated Mines ... ... ... ... 225 27.— East Wheal Lovell ... ... ... ... 227 28. — Great Wheal Fortune ... ... . . .' ... 228 29.— Wheal Gorland ... ... ... ... 229 30 & 31.— The Lovell Mine... ... ... ... 231 32. — Wheal Liishington ... ... ... ... 231 3?. — Wheal Vincent (part of Wheal Lushington) ... 232 34. — Nangiles ... ... ... ... .. 232 35. — North Downs ... ... ... ... 233 36. — Pedn an Drea Mine ... ... ... ... 234 37. — Porkellis United Mines ... ... ... 237 38 & 39.— Wheal Seton ... ... ... ... 238 40.— South Wheal Seton ... ... ... ... 241 41. — South Wheal To wan ... ... ... ... 241 42. — Ti-esavean Mine ... ... ... . . , 214 43. — Treskerby Mine ... ... ... ... 245- 44. — United Hills .. . ... ... ,. ... 246 4.').— Killifreth. Unity Wood ... ... ... 248' 4ft.— West Fold ice. Unity Wood ... ... ... 248 47 & 48. — Great Wheal Vor (sections showing proximity of shafts to lodes) ... ... ... ... 249 49.— Sithney Wheal Metal ... ... ... ... 250 50. — Great Wheal Vor (longitudinal sketch of main lodes) ... ... ... ... "* ... 251 51.— Penhale Wheal Vor ... ... ... ... 251 52. — West Condurrow ... ... ... .. 253 53._Wheal Christopher ... ... ... ... 254 54.— Cliff Down Mine ... ... ... ... 255 55. — Cliff' Down Mine (section in valley) ... . . 255 56. — Clyjah and Wentworth ... ... ... 255 57.— Wheal Wentwsrth ... ... ... ... 256 58.— Medlyn Moor Mine ... ... .. ... 256 59. — Nancekuke Mines (Wheal Clarence) ... ... 256 60.— North Pool Mine ... ... ... ... 256 6].— North Wheal Vor ... ... ... . 256 62.— Polrose Mine... ... ... ... ... 257 63.— South Lovell Mine ... ... ... ... 257- 64. — Plan of Restronguet Creek Mine ... ... 257 65.^ — Diagram showing the yield of metallic tin and copper in Cornwall, estimated from public sales of ore ... ... ^ ... ... ... 307 THE GEOLOGY OF FALMOUTH AND TRURO AND OF THE MINING DISTRICT OF CAMBORNE AND REDRUTH. CHAPTER I. INTEODUCTION. By J. B. Hill, R.N. This memoir describes an area of 216 square miles, of which 186 represent the land surface, while the remainder is occupied by the sea.* Whereas the north coast forms a line of cliffs extending for about 6 miles from Forth Towan to Eeskajeage Downs, and broken only by minor indentations, the southern seaboard presents a more sinuous course dominated by the bays of P'almouth and Gerrans. Moreover, the arms of the sea, repre- sented by Falmouth harbour and its confluent creeks, penetrate far into the interior of the county. While the coast line facing the English Channel is less than 12 miles, the inner waters border 80 miles of shore, extending to Trethem, Euan Lanihorne, Tre- silian, Truro, Perranarworthal, Mylor Bridge, and Penryn. Those estuaries that make so prominent a feature in the eastern belt are the seaward extension of the valleys into which they merge, and it requires little geological discernment to recognise their origin in the submergence of that valley system. The extensive sheet of water forming the Carrick Eoads covers an ancient alluvial plain in which the lower reaches of the Fal channelled their course to the sea. The broader physical features of the area are intimately related to its geology : the districts occupied by the dominant rock types, killas and granite, being strongly contrasted. The granite region, between Budock and Camborne, forms high land culminating in the hill of Carnmenellis, with an altitude of 819 feet, while the summits of Carn Marth and Carn Brea attain heights of 771 feet and 740 feet respectively. The district occupied by the killas is by comparison low lying ; it rarely attains an elevatipn of 500 feet, and by far the greater portion lies below the level of 300 feet. Notwithstanding the greater elevation and more rugged * See Sketch Map of the Area, Fig. 1, page 8. i 9255. 750— Wt. 5440. 12/06. Wy. & S, B 2 INTBODTTCTION. character of the granite, its surface is, on the whole, less deeply trenched than the killas. The latter, in spite of its smooth upland features, has been more extensively channelled by the drainage system, which over large parts of the area has produced a set of deep valleys in such close contiguity that stretches of flat land are comparatively rare. This is particularly the case in the Fal basin, which drains nearly two-thirds of the entire district. The rivers that water the region are small and of low gradient, affording a strong contrast to the deep and extensive valleys which they traverse. Those which empty on the north coast are short, with a general north-westerly course. The larger of these are the Bed Eiver, so called from the mine washings which discolour it, and the stream that joins the sea at Portreath. The straight valley between Ptirsley and Forth Towan is watered by a very small rivulet, and forms a striking feature from the steepness of its slopes. Its coincidence with a line of fracture has doubtless facilitated its excavation. Dissecting a moorland district covered with heath, its beauty is unfortunately marred by the mining operations that follow its course. The south-western district is mainly drained by the River Cober, which after traversing a large granite tract south of Calvadnack, flows past Helston to the Loe Pool. The northern district, lying on the outer fringe of the Pal basin, and extending approximately from Tregavethan to Skin- ner's Bottom, in the parish of St. Agnes, is comparatively flat. The adjacent tract, situated between the granite region and the north coast, although trenched by numerous valleysj has a far more even surface than the corresponding slopes of the eastern area. Notwithstanding the sharp physical characteristics that distin- guish the tracts occupied respectively by granite and killas, that differentiation is mainly confined to those major formations. Neither the multitude of elvan dykes, the greenstones, nor the mica traps are expressed on the topography, and the same may be said as regards the smaller granite intrusions that flank the larger bosses. Moreover, the killas itself, notwithstanding its lithological variations from arenaceous to argillaceous, exhibits a general absence both of rock protrusion and features. The inequalities of its surface appear to have resulted almost entirely from river erosion, so that if the valleys were refilled the outline so restored would constitute an undulating platform. The latter would slope seaward to either coast from more elevated land situated on the northern margin of the map between Trevissome and Mount Hawke, where about three square miles range from 400 to 500 feet above sea level. Thus almost the whole of this plain, built up chiefly of killas, and extending across the county from the English to the Bristol Channel, lies below a level of 400 feet, while the greater part does not attain a height of 300 feet. Moreover, the line of cliffs, sometimes reaching 250 feet on the north coast and 100 feet on the southern seafront, tends still further to bring out the even surface of the platform, which, AREA AND PHYSICAL FEATURES. 3 devoid of craggy features, is suggestive of a plain of marine denudation that was upheaved in comparatively late geological times. Although the gravels of Polcrebo represent the sole evi- dence of deposit between the Palaeozoic period and the era of the Pleistocene raised beaches, the adjoining districts on the north, west and south contain the relics of Tertiary sediments that in all probability were formerly spread over the less elevated portion of this sheet. The Tertiary beds of St. Agnes are indeed only a mile distant, where they reach a height of 375 feet. The gravel deposit of Crousa Downs, in the map to the south, occurs at 360 feet above sea level, while the Pliocene beds of St. Erth, on the map to the west, attain an elevation of 150 feet. From these considerations it appears probable that the killas platform was entirely buried beneath the Pliocene seas, from which the granite domes of Carnmenellis, Carn Marth, and Cam Brea rose out as islands, The scenery of the area, therefore, has been mainly sculptured since the early part of the Pliocene period, although the solid structure from which it has been evolved is of Palaeozoic age : the post-Tertiary accumulations being comparatively meagre, while Tertiary deposits are marked by the solitary instance at Polcrebo. Although the greater part of the rock platform consists of killas, the less elevated granite tracts likewise cover a considerable area. The killas is of " Silurian "* age, with the exception of a narrow tract across the northern edge of the map, forming the most elevated killas area, that represents the basal Devonian, and marks an important unconformity between the older and newer Palaeozoic formations of Cornwall. In the original Greological Survey map of Cornwall, De la Eeche separated the killas into two divisions, viz., a grauwacke group and a carbonaceous series. Thus the former, lying below the Culm-measures, was undifferentiated for the reason, as explained in his Eeportjt that the progress of geology at that time only warranted the broadest generalisations. He then expressed the opinion that the terms Cambrian and Silurian should be restricted to the areas that gave rise to the prolonged researches of Sedg- wick and Murchison, and deprecated the extension of that no- menclature to districts that had not received the same detailed investigations. Iny a later and undated issue of the map the grauwacke group is divided into Devonian and Silurian, presum- ably by the authority of Murchison. The Devonian colour was not only applied to the fossiliferous strata of East and Mid-Corn- wall but likewise to the unfossiliferous strata in the west. The Silurian colour, on the other hand, was restricted to a belt that had yielded organic remains. Murchison, however, was of opinion that the older division extended far beyond those limits into the barren strata coloured as Devonian, and it is evident that the latter tint was adopted as a matter of convenience, in the absence of sufficient data to go upon, as no re-examination of the area * The term Silurian is Iiere used in the sense adopted by Murchison for the Upper SUurian and Lower Silurian (Ordovieian). t " Keport on the Geology of Cornwall, Devon and West Somerset," pp. 38 to4X. b2 4 INTRODUCTION. seems to have been undertaken.* The known Silurian region was confined to the coastal belt between Chapel Point and Grerrans Bay, a boundary connecting those localities admitting of the ready isolation of that region from the rest of the country. That such a broad generalisation, however, was only regarded as provisional, may be inferred from the absence of a line on the map between the two divisions. It will be seen, therefore, that the sub-division of the killas as the result of the recent survey in no sense invalidates the map published by De la Beche, who made no attempt to distinguish between Silurian and Devonian, while as regards the amended issue of the map, the boundary between those systems, evidently intended as provisional, and for which no line was attempted, has been replaced by a line that more accurately demarcates their limitsc In the present state of our knowledge with regard to South- West Cornwall it is clear that the main portion of the rocks originally grouped as " Silurian " is of Lower Silurian or Ordo- vioian age ; that some bands of Silurian proper, or Upper Silurian, also occur in places ; and that some of the killas may possibly be of older date. Therefore, in referring generally to these rocks, the term Lower Palaeozoic will be most appropriate. Prior to the accumulation of the Devonian sediments, these older strata were consolidated, cleaved, and brecciated, and to some extent upheaved. At the close of the Carboniferous period these Lower Pateozoic rocks were again brought within the influence of crustal disturb- ance, by which they were folded, fractured, and cleaved in common with the overlying Devonian. As a result of this deformation, almost all trace of organic life appears to have been obliterated from the killas represented in this sheet. With the exception of an occasional crinoid fragment, the sole relics of life that have survived are radiolaria, the preservation of their casts being in no small measure due to the minuteness of these tiny creatures, as well as to the siliceous nature of their skeletons. Although it is to be hoped that definite species of fossils may yet be obtained in our district from these strata, they have yielded nothing to warrant their precise correlation with the well-known Lower Palaeozoic sub-divisions. The small Devonian tract along the northern edge of the sheet has hitherto proved unfossiliferous, but its northerly extension in the adjoining map has yielded Lower Devonian fossils. The post-Carboniferous crustal movements ultimately found relief in the intrusions of granite that enter so largely into the geology of this area. These igneous irruptions have metamor- phosed the adjacent killas, so that in addition to mechanical alteration induced by the earth movements, the killas lying within that metamorphic aureole has been subjected to chemical change,, resulting in the production of new minerals. These granites are also flanked by intrusive greenstones that share both in the pre- * See references, p. 19. AREA AND PHYSICAL FEATURES. 5 granitic earth-movements and in the subsequent contact meta- morphism. After the solidification of the granite' the igneous disturbances were still further expressed by an extensive Assuring of the area. While some of these fractures were occupied by elvan intrusions, others became the repositories of the mineral ores. At the close of the Carboniferous period the rockbuilding of the area had apparently been completed, with the doubtful excep- tion 01 the small assemblage of mica traps that are possibly of Permian age. The geological history is not again taken up until the emergence of the plain of marine denudation from beneath the Pliocene sea. The uprise of that sea floor, with its islands of granite, produced a land surface that has since been deeply fur- rowed by erosion. The sculpture of the district has not, however, been confined to denudation, but oscillatory movements, involving fluctuations in the mutual boundary of land and sea, have been potent factors in determining the character of the scenery. Thus while erosion has been in constant operation on the body of the land, its coastal fringe has been subjected to oscillations that have checked the ravages of the waves. The preservation of shreds of the Pleistocene beach at only a few feet above high-water mark shows that the modern clifif line has undergone but slight modifi- cation since pre-glacial times. Similar evidence demonstrates that the existence of the Carrick Eoads as an arm of the sea is of like antiquity, and that its divergent estuaries penetrated the adjacent valley system, at least as far as the tidal waters do to-day. After the close of the glacial period the land stood fully fiO feet higher, so that the sea must have retreated from the river valleys of the Fal. Finally, the land surface so upheaved once more began to sink, and the valley floors from which the sea had been excluded were again buried beneath the waves. Moreover, the ancient woodlands that flourished in those vales are still partially preserved beneath the shingle, as the existence of the submarine forests fronting the valleys so clearly testifies. That submergence has resulted in the general coincidence of the modern shore line with that of the Pleistocene sea, (Plate II,) The geological history, therefore, since the evolution of the Pliocene valley system, records two submergences of approximately equal magnitude, divided by a period of elevation. The latter was characterised by the rigorous climatic conditions of the glacial age, during which glaciers issuing from the ice-field of South Wales reached the Bristol Channel. Although this district lay beyond the southerly limits of the mh" de glace beneath which the greater part of Britain was buried, and therefore escaped the devastating effects of glacial action, to which immunity we owe the preservation of the china clay deposits, that epoch nevertheless set its mark on the topography. In winter, while the higher ground was covered by snow, the soil cap on the barren slopes was deeply frozen, so that the summer thaws, acting on a surface unchecked by vegetation, induced an extensive sweeping of the subsoil to the lower lands, which creeping seaward, ultimately found repose on the elevated platform 6 IJTTRODtrCTlOlT. of the Pleistocene beach. The pogt-glacial subsidence brought this " head " within the destructive action of the breakers, but sufficient yet remains on the more sheltered portions of the sea- front to modify the coastal scenery. Concomitant with this great surface creep over the body of the land, the valleys were swept out and deepened by the torrential conditions that then prevailed, under which only the heaviest materials could find a resting-place along their beds. It is to the violence of those denuding agencies that we owe the formation of the stream tin deposits, that not only were the means of bringing Cornwall into contact with the ancient civilisations of the East, but afforded its inhabitants a thriving industry for many centuries. The history of the topography would be incomplete without a brief reference to tne later physical changes that not only bring the cycle of evolution down to historic times, but carry it for- ward to the present day, so that by studying the geographical modifications that are yet taking place within our own observation we may anticipate the chp,nges that the future has in store. That the present denudation of the land is undoubtedly slower than of old may be gathered from the small volume and sluggish currents of the streams that now water valleys of considerable magnitude. This inference is confirmed by the scanty alluvial deposits that have accumulated on the valley floors since the glacial period. That denudation is nevertheless effecting its influence on the configuration of the area is vividly brought home by the rapid silting up of some of the estuaries. This is well exemplified by the mud flats of the Eiver Fal, which below Ardevora are creeping rapidly seaward. Above Lamorran and Ruan Lanihorne the alluvial terrace has been formed since the sixteenth century, while the upper extension of that flat as far as Tregoney has been recovered from the sea since the time of the Roman occupation, when that place served as a port accessible to shipping. The seaward growth of the valleys and the shallowing of the tidal estuaries are further discussed in the subsequent chapters. While denudation, therefore, in spite of lowering the surface of the land, is gradually extending its frontiers within the sheltered estuaries, the sea front is brought under the ceaseless action of the breakers, and the cliffs are undergoing a slow but constant degradation. During the last quarter of a century the footpaths skirting Gerrans Bay have been gradually shifted back, consequent on the landslips that accompany the undermining of the cliff foot, while the picturesque caverns along the seaboard have undergone extensive alteration. It is evident, therefore, that the effects of coastal erosion alone, if unchecked by elevatory movements of the land, will gradually evolve a submarine plain from which the granite domes will emerge as islets, and that the general conditions of the ancient Pliocene sea will be reproduced.* The mineral area is practically restricted to the western * For a fuller account ol the evolution of the valley system, its relation to the estuaries, and the history of the deposits that line the r respective floors, the reader is refen-ed to the sequel. (Chapters X, and XI ) ^^^^^"''^^^ AREA AND PHYSICAL FEATURES. 7 half of the sheet. A line drawn from Metheruny on the extreme south, to Baldhu, and from thence in a north-west direction to the coast, defines the eastern limits of the principal metalliferous zones. Between that line and the meridian of Truro the mineral ores are sparsely distributed, while the area farther to the east has proved unproductive. The belt of country enclosing Camborne and Redruth has ever been and still remains the principal seat of the Cornish mining industry. Mihing operations within this sheet are practically confiined to that limited tract, beyond which, where not entirely discontinued they are conducted on a restricted scale. A glance at the map reveals the close connection between the metalliferous deposits and the granite. The eastern half of the Carnmenellis mass is comparatively free from mineral veining, and this has materially contributed to the commercial value of the granite which has been so largely wrought in that area. Proceed- ing westward, however, from the parish of Wendron, mineral veins make their appearance. They reach their greatest extent on the north-westerly margin of the granite, while the tract enclosing the two adjacent masses of Carn Biea and Cam Marth constitutes the heart of the mineral area. (Fig. 1.) The granites are dome-shaped masses and slope beneath the killas for considerable distances from their surface outcrops. The sediments which flank them have been considerably altered by contact action, producing an encircling metamorphic belt the variable width of which is controlled by the angle at which the granite slopes below the surface. This dip is by no means constant, as mining operations show. The unevenness of the granite surface is exemplified by the Carn Brea mass, which has been shown to be connected with the granite of Carnmeneilis beneath the basin of killas that divides them. The aureole of metamorphism flanking the eastern portion of the Carnmenellis granite seldom exceeds a width of a thousand yards, and is in some places considerably less ; that area, both as regards the granite and the metamorphic belt, being comparatively non-metalliferous. On the western side, however, the granite plunges less steeply beneath the surface, and the metamorphic aureole is therefore considerably larger. Between the Cober Valley and Crowan its average breadth is about a mile. From the granites of Carn Brea and Carn Marth, in the direction of the north coast, the killas is metamorphosed for distances of two and even three miles, and it may be confidently inferred that this tract is underlain by granite, in some places within a thousand feet of the surface. The mineral district of Grwennap, St. Day, and Baldhu occupies the Cam Marth aureole on its western side, while its eastern extension is characterised by a plexus of elvan dykes amongst killas which exhibits a feeble degree of metamorphism, as indicated by the development of an incipient type of spotting. The south- western region of Orowan and Wendron contains mineral lodes nob only within the Carnmenellis granite, but in the intervening killas area, separating that mass from the granite of G-odolphin. INTRODUCTIOiSr. AREA AND PHYSICAL FEATURES. 9 In the remaining district west of Truro and the Carrick Eoads the lodes are scattered and of comparative unimportance, and mainly confined to ores of lead and zinc. These minerals, how- ever, have no necessary connection with the granite intrusions, as is the case with tin and copper. It will be seen, therefore, that not only are the tin and copper lodes restricted to the granite regions and the adjacent killas, but -that they principally occur in areas where the granite plunges beneath the sediments at a low angle. The ores oj tin and copper have furnished the staple mining industry of the district, the metals with which they are associated being seldom sufficiently abundant to be profitably wrought on their own account. Beyond the tin and copper districts, however, lead ores have proved remunerative, but mainly from their argentiferous products, which in some cases have yielded a high percentage of silver. The concentration of the mineral ores is intimately related to the rock structure of the district. Besides the restriction of the tin and copper ores to the granite, and the killas that is immediately contiguous, their concentration in the form of lodes has been controlled by the system of rock fracture per- taining to the area, the fissures having afforded the necessary channels by which the metallic vapours and solutions have travelled, while their walls have received the metallic and other contents with which those currents have parted. The tin and copper lodes are probably of late Carboniferous age, and followed closely on that phase of volcanic activity which is represented by the cooling of the granite and the disruptions that accom- panied it. The absence of those metals in the cross-courses, that represent lines of fissure transverse to the Carboniferous fractures, shows that their deposit had ceased prior to that later phase of disruption which there is reason to suppose was brought about by the volcanic disturbances of early Tertiary times.* The deposition of other ores, however, and notably those of lead, silver, and zinc, have continued into Tertiary^ times, and are of common occurrence in the cross courses. The decadence of the mining industry has proved a serious obstacle to the survey of the mineral area, and the limited number of workings available for inspection has precluded such systematic investigation as would warrant the formulating of general laws governing the vein deposits of the region. The active mines have been explored by Mr. MacAlister, but much of the mining material in the subsequent chapters has necessarily been derived from previous publications, the authority for which has been acknowledged. The most laborious work in connection with the mineral survey has consisted in the reduction of the lodes to a uniform scale from the mine plans. Most of the latter are laid down to their individual magnetic meridians, so that a plan in use for many years contains errors due to compass variation. Each mine has its own datum line, the depths being taken either from the brace of its shaft, or its adit, which may occur at any depth down to the 40-fathom level. The depths, more- * .1. B Hill. Irmt. Roy. Geol. Sae. Corn., 190i, vol, xii., p. 599. 10 INTRODUCTION. over, instead of being vertical, are calculated along the under- lie of the lode. The scales adopted in the different mines likewise vary from 4 to 20 fathoms to the inch. While the accuracy of the plans of the mines now working leaves nothing to be desired, those relating to many of the abandoned undertakings abound with errors, and in some cases Mr. MacAlister has been unable to obtain any plans. On the map the tops of the lodes only have been delineated. On the 6-inch mining maps, however, the most important of which will be published, they are also represented by underground parallels, the highest of which is at sea level, while the remainder are drawn at uniform vertical distances from Ordnance datum, so that their subterranean behaviour may be grasped. The lodes of the principal mineral areas have also been drawn in MS. on 25- nch maps, which may be consulted in the Geological Survey Office in London. With the revival of the Cornish mining industry that is now taking place, the mapping of these underground fissures on a uniform scale, with the depths to which they have been proved and by which they can be systematically traced, should materially facilitate future exploration for their mineral wealth. Even if the present attempts to resuscitate the industry should prove abortive, this mineral region is in no sense an abandoned mining field in which the products have been exhausted. The history of Cornish mining presents times of prosperity succeeded by periods of depression, and whatever may be the outcome in the immediate future the time will inevitably recui when economic conditions will again justify a vigorous prosecution of the industry. , The scenery of the area is strongly contrasted. While the eastern region constitutes one of the most picturesque districts of Southern England, the central and western areas are com- paratively tame. Moreover, the despoiling of large tracts in the west by the many centuries of mining still further acientuates these scenic contrasts. Although the former region, extending to the west as far as Penryn, Perranwell, Killiow, and the valley of the Kenwyn, is highly fertile and entirely under cultivation, and broken by deep valleys along the slopes of which woodland tracts are profusely scattered, the dominant feature in the topography is the submerged valley system, which has given access to the sea along the numerous creeks that penetrate the very heart of the district. The navigable waters of the Fal, winding amid verdant slopes that are sometimes clothed with woodland to the water's brink, constitute a waterway the beauty of which is probably unrivalled in England, while its seaward extension has furnished one of the finest harbours of the world. Whereas beyond Truro and Falmouth the passage westward into tamer scenery is somewhat gradual, the central belt between Truro and Perranwell is suddenly replaced by a dreary tract, the bleakness of which is accentuated by the most abrupt transition. The oncoming of these conditions is due to the presence of the mineral belt extending from Caraon and Baldhu AREA AND PHYSICAL FEATURES. 11 to St. Day. Although mining operations in the district have ceased, a considerable part of the ground is out of cultivation, and large tracts mark the site of the old spoil heaps which in the district east of St. Day cover a considerable area. This wide expanse, that may be described as a vast wreckage, is dotted by engine houses and mine stacks in various stages of decay that still further add to the unsightliness of the landscape. The borders of this tract have in some cases been reclaimed from the dreary features of an abandoned mining district by the planting of timber, as at Gwennap and Scorrier. The Pinus msignis and other conifers easily thrive on such burrows as do not carry a high percentage of arsenic, and it cannot be doubted that much of the landscape could be restored by judicious planting from the waste to which mining operations have reduced it. The extensive nature of the subterranean excavations is vividly brought home in this district by the steam which issues from some of the shafts that reach the heated waters below. The extension of this mineral belt from Eedruth to Camborne is accompanied by a softening of the scenery. That tract forms a slope extending to the north coast. Not only does the land- scape improve from its blending with the sea, but it is backed by the rugged and picturesque peak of Carn Brea, which commands a magnificent prospect extending right across the county from sea to sea. Viewed from that summit the vast array of stacks forms an imposing scene, and in spite of the large number that repre- sent abandoned operations, the principal seat of Cornish mining still lies beneath the shadow of Carn Brea, and contains the deepest tin mine in the world. (Plate III.) The decadence of mining after the abandonment of operations in the outlying mineral districts, has driven the industry back to its last hold, and on the ability of this mining centre to emerge successfully from the recent period of depression lies the hope of the regeneration of Cornish mining in the immediate future. The south-western district is dominated by the Carnmenellis granite that forms an elevated dome without conspicuous features. Except on its flanks the population is sparse, and the area is largely made up of moorland out of cultivation and given over to gorse and heath. The western portion, especially in the parish of Wendron, marks the site of an abandoned tin industry. Many valleys and basins, in which the stream-tin has been worked, are choked from side to side with disordered ground. Large tracts of such waste land occur in the upper parts of the Cober Valley, and notably at Porkellis Moor, while another basin similarly desolated lies between Calvadnack and Menerdue. The eastern portion of the granite region is more thickly populated, and forms the seat of the important granite industry, the headquarters of'whichisat Penryn. The rudely stratiform weathering of the granite frequently results in the production of picturesque tors, of which Carn Brea forms a conspicuous example, while Crowan Beacon and other summits display the same type of scenery on a less imposing scale. The scenic contrasts of the tracts bordering the northern 12 INTEODTJCTION. coast and those fronting the English. Channel are most marked. Although somewhat similar in their geological characters, the greater elevation and bleaker aspect of the former has produced large expanses of moorland represented by Eeskajeage Downs, Carvannel Downs, and Nancekuke Common. The southern slopes, on the other hand, are in a high state of cultivation, diversified by luxuriant hedgerows and frequent clumps of woodland, while the more sheltered hollows are capable of sustaining a sub-tropical vegetation that has induced the garden culture of palms and other exotics. The inland area is entirely devoid of lakes, with the exception of those artificially formed near Antron and Crowan by damming the streams, for the water supply of Falmouth, Penryn, and Camborne. At Swanpool, however, a storm beach that has been piled up across the mouth of the valley has succeeded in ponding back a freshwater lake. (Plate I.) A conspicuous feature in the upland areas is the presence of shallow basins, which are especially common at the heads of the valleys. They are largely composed of clay, and the want of fall -rendering drainage difficult, their bottoms are frequently lined with marshes. Being on this account unsuitable for cultivation, these moors are given over to scrub and gorse and afford coverts for game, just as many of the rocky slopes in the granite district consist of moorland stretches, clothed with gorse and bracken, the recesses of which form the congenial haunts of the fox. The larger towns in the area coinprise Falmouth, Truro, Eedruth, and Camborne. While the latter is the principal mining centre, Redruth serves, in addition, as a market town for the western region, while Truro and Falmouth fulfil a similar object for the eastern districts. Although the shipping trade of Falmouth has suffered a serious decline since the advent of steam, it still yields employment to a considerable section of the popu- lation, both ashore and afloat. Of late years the town has advanced rapidly in favour as a health resort, the mildness of the climate and the beauty of its surroundings being responsible for a large influx of winter visitors. 13 PART I. GEOLOGY. BY J. B. HILL, R.N. CHAPTER IL FORMATIONS AND THEIR GENERAL DISTRIBUTION. As a glance at the map will show, the south-western portion of the area is occupied mainly by granite. The principal mass, the most elevated portion of which forms the hill of Carnmenellis, is rudely circular in shape, and, with the exception of a small portion of its southern edge, falls entirely within the district. It extends from Budock on the east to the neighbourhood of Crowan on the west, while its northern limits occur at Buller Downs, about a mile to the south of Redruth. The lenticular mass of Cam Brea, with a linear extent exceeding four miles, is an inlier of the Carn- menellis granite, and separated from it by a narrow basin of slate. The granite situated between Redruth and St. Day, the highest point of which forms the bill of Cam Marth, is boss-like in form, and its southern edge is separated from the Carnmenellis granite in the neighbourhood of Lanner by less than half a mile, Besides the masses of Cam Brea and Carn Marth, the Carn- menellis granite is fringed by smaller granite intrusions between Crowan and the valley of the Cober, numerous sections of which are exposed in the cuttings of the railway between Praze and Helston. On the east two small bosses of granite. are seen at Budock, and fine-grained granite is also exposed close to the main mass in the railway cutting near Treluswell. The GREENSTONES are mainly confined to the neighbourhood of the granite aureole. They are most extensively developed between Camborne and Coswinsawsin, and continue from the former locality as far as Redruth, in which direction, however, they are seldom visible at the surface. They occur also in the park of Pendarves House, but do not protrude there from beneath the soil. A fairly extensive mass of greenstone lies to the south of Grwennap, between Treviskey and Pengreep, and it follows the same line in close contiguity to the granite between Ponsanooth and Lower Treluswell, Rocks of this group occur on both sides of Penryn Creek, between Flushing and Falmouth, and a few ex- posures of small size are seen at Carclew and Restronguet Creek. On. the southern fringe of the granite, extending from Budock and Praze to the southern limit of the sheet, the sole greenstone that has been recognised is situated in the valley of the Cober, near Tregannock Mill, and is a member of an important group lying further south in the vicinity of Helston. 14 FORMATIONS AND THEIR DISTRIBUTION. Elvan dykes are abundantly distributed along a belt of country about three miles in breadth, extending from Truro to the neigh- bourhood of Camborne, and includmg the districts of Chacewater Gwennap, and Eedruth. Beyond that belt they are sparsely met with west of the Carriek Eoads, and the contmuation of that waterway to Truro and the valley of the Keiiwyn. In the remaining area to the east of that line they have not been detected. , , ^^ e l The Mica traps are confined to a narrow belt ot country between Pendennis Point and Malpas, and to a small isolated tract at Shortland End, lying to the north-west of Truro. Of the " Killas " or Slate divisions the Myloe series is largely developed in the south-west. It completely encloses the granite masses and the greenstones, and contains also the bulk of the elvan dykes. It is bounded approximately by a line drawn from Falmouth along the Carriek Koads to Restronguet Creek, whence it extends north-west to Carrine Common, Baldhu, and the vicinity of Mawla. Thence the line sweeps to the south-west by Illogan, Tehidy House, and Kehellan, at the western margin of the map. The Falmouth series is not so extensive as the Mylor and Portscatho series which it divides. It likewise occurs as lenticles within those groups. To the north-west it occupies a narrow strip which reaches the sea at Reskajeage Downs. A broad tract extends from Chacewater to Truro, from which it branches irregularly to the north-east, south-east, and south. Numerous lenticles occur amongst the Portscatho slates in the basin of the Fal, where they are well developed between Euan Lanihorne and Philleigh, and from Coombe to Feock. Similar strips appear on the eastern side of the Carriek Eoads between Turnaware Point and St. Just, while further to the south these slates are developed at St. Mawes. A wide belt of this series extends from Falmouth to Pennance, and a smaller band occurs at Maen Porth. This group, situated in the neighbourhood of Falmouth, presents favourable facilities for its study from the excellent coast sections in that vicinity. The Portscatho series occupies almost the entire area east of the Carriek Eoads and Truro. It extends west of the Fal from Feock to Killiow and Truro. From Truro to Porth Towan it is developed in a continuous belt. In the neighbourhood of Port- reath a large mass borders the north coast with a sea frontage of nearly three miles. The extensive coast sections, both along the seaboard and those afforded by the estuaries that have pene- trated far into the interior of the area, present unrivalled oppor- tunities for the investigation of this series. The Veryan series occupies a small tract on the north of Grerrans Bay to the east of Pendower. The Geampound and Proeus series forms a narrow strip across the northern edge of the map between Probus and Porth Towan. The superficial deposits are of relative unimportance. The gravels referred to the Pliocene occupy an insignificant tract in the vicinity of Polcrebo. Although the extensive valley system is a marked feature in the district, its floors are seldom TABULAR STATEMENT OF FORMATIONS, 15 lined with alluvial deposits at all commensurate vfith the mag- nitude of the valleys. Moreover, the margins of the alluvia are generally far less defined than is usual with this class of deposit, and it has been found desirable in some instances to include within the alluvial boundary tracts which in other districts would have been excluded. Marine alluvia are mainly confined to the estuaries diverging from the Carrick Roads, which, on the recession of the tide, reveal extensive tracts of mud and clay. The raised beaches are merely expressed by discontinuous shreds still adhering to the present clifif faces. The stream-tin deposits have been worked over so extensively that they are now represented largely by tumbled and disordered ground along the valleys and hollows, many of which are included amongst the alluvial deposits. Blown sand is rare ; a patch occurs on the north coast at Forth Towan, and smaller tracts are seen at Pendower in Gerrans Bay. Deposits of " head " are practically restricted to the coastal areas, where they form strips mainly in sheltered bays, with a very small landward extension. Submerged forests are known at Falmouth, Maen Porth, Pendower, and Porthcurnick. The following table shows the various formations occurring in the area. In the chapters which follow they are successively described in chronological order, commencing with the most ancient : — }■ Blown sand Freshwater alluvia - \ n . Marine alluvia - J"itecent. Submerged forests - Stream r tin and submerged \ valley deposits - - I pleistocene Head - ' " f Eaised beaches - j Polcrebo gravels - Pliocene. Killas, -viz., slate deposits : — Grrampound and Probus series Lower Devonian. Veryan series - Ordovician (Lower Silurian). Portscatho series - "i Falmouth series - - I Lower Palaeozoic. Mylor series - - - J Igneous. Granite. El van (Quartz-Porphyry, &o.). Mica Trap. Greenstone. 16 CHAPTEE III. THE K I L ]. A S . General Description and Tectonics. The rock formations that enter mainly into the geology of the sheet are killas. Notwithstanding a general uniformity in the killas or slate formation of this part of Cornwall, it has been found possible to differentiate it into certain divisions. Owing, however, to the practical absence of organic remains, the zones so differen- tiated are purely lithological. The impersistence of lithological types, added to the advanced stage of decomposition of many inland areas, and the paucity of sections, has in many cases rendered the mapping of definite boundaries impossible. Nevertheless, the demarcation of these rock bands over the area generally has been accomplished with sufficient accuracy for the interpretation of the general tectonic arrangement of the district. As the extreme plication which has prevailed over the area renders the dip valueless as a stratigraphical criterion, there is still, in the absence of palasontological evidence, some uncertainty as to what is the upward succession. For the same reason the thickness of the bands defies any attempts at calculation. All that can be said with certainty is that they are immeasurably thinner than their surface indications would appear to indicate, and that the immense thickness ascribed to the killas by the early observers is based on data that are erroneous. The four lithological divisions enumerated below represent the older Palaeozoic strata, and succeed one another from east to west in the order named : — Veryan series. Portscatho series. Falmouth series. Mylor series. A fifth, the Grrampound and Probus series, which represents the newer Palaeozoic, departs from that succession and extends right across the area from east to west. The distinctive characteristics of the various groups are as follows : — Mylor Series. — This series consists of blue argillaceous and fine sandy beds. The latter are often more quartzose than in the Portscatho series, and occasionally a thin quartzite seam is met with. In addition to the more siliceous character of the sandy alternations, the latter are usually of finer texture than in the Portscatho group. The distinguishing feature of this series, however, is its usual striped and ribbon-like appearance, due to very fine interlaminations of siliceous and argillaceous material. In some cases, however, the laminae are argillaceous only, but of varying composition and colour. This interlaminated character which distinguishes the group is rarely absent, but it is not to be understood that it is confined to this series. It is sometimes seen DESCRIFnON OF THE KILLAS. 17 in the Falmouth division, and is frequently strongly developed in the Portscatho beds, especially in the district extending from Chacewater to the north coast. Falmouth Series. — This series comprises alternations of argillaceous and fine sandy material, varying in colour from green to grey and buff, though occasionally blue argillaceous bands are seen amongst them. The colour, which varies with the character of the sediment, produces the general variegated appearance common to this series. Their mode of decomposition is equally characteristic. The beds become extremely friable, especially those of a sandy nature, are unctuous to the touch, and weather into a deep buff colour. On the whole the material is finer than in the Portscatho series, and the strong grit bands which occur in the latter are absent. Occasionally a narrow zone is seen of purple and green slate, often strongly contrasted, which forms a valuable guide in correlating these beds throughout the district, especially in the absence of the characteristics already described. Portscatho Series. — This consists of blue and grey clay slates, alternating with harder beds, which show every gradation from a sandy slate to a fairly strong grit. The sandy beds are of the same bluish hues as the argillaceous, and are characterised by the large amount of clastic mica which is scattered through them. The great feature, however, which distinguishes them from the Veryan series is the absence of limestone, except at their junction with the latter. This absence of calcareous material distinguishes also the Falmouth and Mylor series. Veryan Series. — This group, so far as it enters the area of this sheet, consists of blue and grey slate with alternations of sandy beds, thin dark limestones, and dark-coloured cherts, some of which are graphitic. Notwithstanding the occurrence of chert and limestone, the sandy interlaminations are frequently coarse, but are largely made up of soft grains, so that these coarser seams are well cleaved. The series is characterised in this area by the presence of manganese, which stains the slate. G-RAMPOUND AND Probus Series. — This Series consists of fine- grained conglomerates, sandstones, and clay slates. They repre- sent the base of the Devonian, and are distinguished from the underlying Portscatho division by a general calcareous character which never, however, gives rise to limestone, and by a more feeble degree of metamorphism. Natural Sequence of the Lower Paleozoic Divisions. The Veryan series lies in the western portion of the area coloured as Silurian in the later issues of the old map. The Portscatho series lies immediately next to it, and falls within the area formerly coloured as Devonian. The two groups, "however, pass uninterruptedly into one another without any stratigraphical break. Although the appearance within the Veryan series of limestone serves to indicate the apparent incoming of another division of the stratigraphical series, there is no evidence here for drawing a sharp divisional line to mark off two distinct geological formati6ns. Not only does the Veryan series pass uninterruptedly into the 18 THE KILLAS, Portscatbo group, but these latter also graduate imperceptibly into the Falmouth series, whicb in their turn merge insensibly into the Mylor beds. While advantage has been taken of lithd- logical distinctions to separate them into divisions, that repre- sented on the map would explain the stratigraphy, it must be distinctly borne in mind that we are apparently dealing with a continuous series of deposits. Evidence of G-eological Age. — Notwithstanding the com- parative absence of palseontological data, the researches of Mr. Howard Fox and other observers on the radiolarian cherts of South Cornwall tend to confirm the conclusions already set forth of the unbroken sequence of these deposits. The radiolarian beds are not always confined to chert, but these organisms sometimes occur in cherty shales. They have been found by Mr. Fox in the cherts of the Veryan series east of Pendower, and near Middle Point, Falmouth, close to the junction of the Falmouth and Portscatho series. Mr. F. J. Stephens* has also described radio- larian cherts from Little Falmouth and other localities in the Penryn Creek, within the Mylor series, which Mr. Fox's researches in that area have confirmed. They have not been observed in the Portscatho series, but the locality near Middle Point, although within the Falmouth series, is only about 35 yards distant from the line adopted as the boundary of the Falmouth and Portscatho groups, which merge almost insensibly into one another, but in the adjoining sheet to the south their presence within the Portscatho series has been detected. Messrs. Fox and Hinde have also found radiolarian beds in North-Eastern Cora- wall at the base of the Culm- measures, but the intermediate region, which is mainly made up of Devonian rocks, has hitherto billed to yield radiolaria. That is to say, these organisms have not been detected on any horizons that are known to be of Devonian age. Mr. Fox in his paperf assigns the age of the Veryan cherts to the Lower Silurian (Ordovician) period ; the other radiolarian localities at Falmouth and Penryn Creek have been subsequently discovered. The occurrence of chert pebbles in the conglomerate at Nare Point tends to confirm Mr. Fox's hypothesis. The presence of radiolaria in this otherwise barren sequence, and their absence in the Devonian formation, undoubtedly accentuates the divergence between these deposits. It will be seen in the description of the Probus grits that there is reason to correlate those beds with the well-known conglomerate south of the Helford Eiver, and that both rest unconformably on the Portscatho beds. The survey of the " killas " area in the adjoining map to the south has thrown much light on the elucidation of the geology of this district. For a detailed account of the evidence the reader is referred to a recent publication by the author.^ The main con- clusions therein arrived at are as follows : — * Buy. Com.. Polytechnic Soc, 1897. t Trims. Boij. Geol. Soc. Cornwall, 1896. X Qeol. Mag. 1906, p. 206. STRUCTURES OF THE KILLAS, 19 1. The Veryan series includes Quartzite of Lower Silurian age. 2. The Veryan, Portscatho, Falmouth and Mylor groups form a natural sequence. 3. That the evidence favours a descending sequence from the Veryan to the Mylor groups. 4. That these Lower Palaeozoic rbckswere extensively deformed by earth movements in pre-Devonian times. 5. That the Lower Palaeozoics are unconformably overlain by the basement beds of the Devonian. The evidence therefore at our disposal may be summarised as follows : — ^The killas divisions occupying this sheet are below the Probus grits and the Meneage conglomerate. The nearest fossiliferous horizon is the Lower Silurian Quartzite, which also underlies the conglomerate. There is no evidence at present for separating any of these killas divisions from the Lower Silurian. The age of the conglomerate has not been definitely proved, but there is a general consensus of opinion that it defines at least the local base of the Devonian. Moreover, its apparent continuity with that formation in the adjoining areas to the north lends support to that conclusion.* Structures of the Killas. Before tracing further the local stratigraphy it will be con- venient to refer to the typical structures of the killas. Isoclinal FoldznGt. — A detailed study of the coast sections reveals a complex set of structures that have been brought about as the result of compression. Folds and faults may be * Sir R. I. Mnrchison expressed the opinion in 1846 that the killas oetween Gerrans Bay and Falmouth was of Silurian age {Royal Geol. Son, Cornwall, vol. vi., p. 322). Mr. J. H. Collins published a sketch map with a paper on the "Geology of Central and West Cornwall " in 1881 (Journ. Roy . Inst. Com,., vol. rii., p. 17), in which he marks the killas (included in Sheet 352) as mainly pre-Devonian. Mr. A. Somervail (in the same volume, pp. 262-273) contro- verts some of Mr. Collins' conclusions, but assigns a Lower Silurian age to the slates from near Penryn to Gerrans Bay, most of which had been similarly classified by Mr. Collins. Mr. Somervail suggested that they were of Llandeilo age. The author, who has been engaged on the survey of West Cornwall since 1897, has always considered these barren strata (Mylor, Falmouth, and Portscatho series) to be linked with the Silurian system, for reasons set forth in the " Summaries of Progress of the Geological Survey from 1897 onwards." (See also papers by J. B. HUl, Trcms. Roy, Geol. Soc, Cornwall, 1899 and 1901). Mr. Upfield Green has claimed these beds as Lower Devonian, of which the Dartmouth slates represent the upper member, while the base is marked by the conglomerate of Meneage, &c. {Geol. Mag., 1904, p. 403). Mr. Green's con- clusions were criticised by Mr. Ussher, who contended that the superposition of the Dartmouth slates to the Mylor, Falmouth, and Portscatho series was not supported by pi-oof (Geol. Mag., 1904, p. 590). Mr. Ussher recalled that although he formerly correlated the Grampound grits with the Gedinnien, he would now hesitate to do so, the inference apparently being that they might occupy a higher horizon. In the map accoflipanying his previous paper (Roy. Geol. Soc. Corn., 1891) Mr. Ussher has coloured the killas (now repre- senting the Mylor, Falmoath,and Portscatho series) as " (?) pre-Devonian " and has placed the Grampound grits at the base of the series classed as undoubted Devonian. From a persual of his paper it would appear that these particular beds had not been studied by him on the grouud, but that his remarks were based on his interpretation of the observations recorded in De la Beche's report. (See pages 32 and 54.) The Lower Silurian Quartzite occurs within the Gorran Sheet, and its included fossils have been determined by paleontologists as Garadoc. c2 20 THE KILLAS. detected immediately in any of the divisions, but as the folds are generally isoclinal, the plication is not so conspicuous as in a region of normal folding. But the evidence of plication is every- where so marked that the apparent dip can only be interpreted as the inclination of limbs of folds, (Plate IV.) The plication has been accompanied by rock fracture, the faults being almost as numerous as the folds to which they bear a direct relation. Cleavage.— Under the influence of earth movements not only have the strata been closely folded until relief has been finally obtained from the strains by actual disruption, but the material of which the strata is composed has been also afifected. Of the mechanical changes which the rocks have undergone, the most conspicuous are undoubtedly the cleavage planes that have produced the slates. These cleavage planes have been among the last mechanical changes effected by the lateral strains. They traverse the strata independent of the original stratification, and to some extent of the folding in which the stratification has been involved. Although bearing no relation to the original bedding, their disposition in regard to the flexures is more defined, as the cleavage planes show a marked tendency to lie parallel with the axial planes of the folds. When the material so cleaved was originally pure and of uniform consistency, the result has been a perfect slate in which the earlier structures of stratification and folding have been either completely obliterated or faintly pre- served by colour banding. Instead, however, of possessing these necessary characters for the production of roofing slate, the killas consists of such an intimate banding of diverse material that the cleavage is subject to marked variations; so that slate of commercial value is rare, and it is doubtful if any such has been successfully wrought in the area under description. The " killas " being largely made up of alternating bands of diverse texture, its compression has introduced a complex set of structures. Where cleavage has been set up in alternating layers strongly contrasted, such as shale and sandstone, the cleavage planes change their character according to the nature of the layer which they traverse. Those which cross the argillaceous baud are not only more numerous than those which traverse the arenaceous layer, but incline at different angles ; so that two shale bands which are divided by a sandstone display parallel cleavage, but this parallelism is broken in the interposing sandstone. Moreover, if the latter is sufficiently massive, it has resisted cleavage altogether, so that we see the phenomena of fissility in perfect parallelism as regards the upper and lower members, while it is absolutely severed by an intermediate band in which this structure is wanting. As the arenaceous beds present every, gradation in their texture, there are corresponding gradations in the degree of fissility which they exhibit. Another factor which constitutes a disturbing element is the disruption of the rocks; the fractures produced having acted as planes of relief bringing about a cessation of stresses in their neighbourhood, so that beds' of similar crushing strength present different degrees of fissility. In studying the effects of cleavage on the strata of the area the CLEAVAGE — FOLDING — PSEUDO-CONGLOMERATES. 2 1 fact is appareut that flexure, fracture, and cleavage are intimately related, and express different phases of rock deformation. The coast sections display marked variation in the degree of deforma- tion, both as regards the intensity of folding and the nature of the fissility in strata of similar lithological type. Secondary Cleavage, Overfolds, and Shear Structures. — While the cleavage has resulted merely in the flattening of the component particles of the strata, the rearrangement of material does not always stop at this process, but the crushing to which the rocks have been subjected has set up further interstitial movements. These latter resolve themselves into a succession of small slips along the cleavage planes, and have often been sufficiently pronounced to produce a transverse cleavage which may locally develop to such an extent as to constitute the dominant cleavage of the rock. In response to lateral pressure the strata have been folded, the flexures have been closely packed together, bringing their limbs into a general parallelism, so that no further relief from pressure is to be obtained by plication. But the strength of the rock sometimes fails before the stresses which still continue to bear, and rupture occurs. The fractures still follow the disposition of the folds and snap their arches, the planes so formed allowing one part of the mass to override its neighbour, and the rock is divided into segments bounded by miniature faults and thrusts. While the strata on the large scale have been thus modified, their component particles have been undergoing on the small scale precisely the same process which has set up interstitial movements. The individual layers which form the beds have been thrown into a set of minute folds, the arches of which have been broken by tiny cleavage planes which resolve themselves into miniature faults, and there is the same tendency to override as is seen in the larger divisions of the beds. On examination, the rock is frequently seen to be full of such small folds and thrust planes, with a disposition to a secondary cleavage, while minor movement planes appear in the more resisting core itself, with accompanying strain-slip cleavage ; and the cleavage planes which pass through the axes of the minute folds often culminate in small thrusts. Pseudo-Conglomerates. — Besides the structures already enu- merated, these crushing processes, acting on heterogeneous strata, have in this region produced a set of widely distributed breccias which closely simulate the coarser products of erosion. These breccias or pseudo-conglomerates are well developed on the western side of the Carrick Eoads, in a belt that extends from Feock to Falmouth; that tract of country is broken by the estuaries which form the creeks of Penryn, Mylor, and Restronguet, along the banks of which they may be conveniently studied. They consist of slate fragments enclosed within the strata, ranging from the size of peas up to five or six inches in length, with their flat sides lying in more or less parallel planes. As a rule the larger fragments are angular, while the smaller are sub- angular and sometimes perfectly rounded. They may consist 22 THE KILIAS. of either siliceous or argillaceous material, and are identical in composition with the matrix of the slate in which they are enveloped, and from which they have obviously been derived. Instead, however, of being waterworn, as their appear- ance suggests, they are the products of brecciation. The Mylor beds, in which these phenomena are best displayed, a,re, as already pointed out, an interlaminated series, in which the thin bands vary in composition. The changing nature of these interlaminations, and the corresponding variation in their limits of compression, have resulted in dififerent degrees of resistance to the crustal movements, the softer beds having easily yielded, while the more resistant strata, separated from each other by bands which are beginning to yield, and being thus deprived of support, are smashed, and the fragments become involved in the more plastic mass. Under the influence of these movements the particles not only become detached from the parent rock, but are frequently so rolled in the process as to simulate pebbles. In tracing the normal laminated beds into the fragmental or brecoiated type it is seen that the former gradually lose their regular appearance, and^ become disturbed by small folds and thrusts, finally culminating in a mass of segments more or less detached, and it becomes apparent that the breccia has originated in little overfolds which have been isolated by small thrust faults. Although direct evidence of this origin is not always forthcoming, we occasionally see, step by step, every stage in the process, beginning with a regular banded rock, followed by minute folding and small thrust planes, partially severing the bands, until at last these processes have not only succeeded in brecciating the rock, but have culminated in the rolling and rounding of the fragments to such an extent that a pseudo-conglomerate has been produced. This type of rock brecciation has sometimes been brought about without folding ; instead of fractures succeeding plication, the stresses have resulted ,in the direct production of movement planes, which have isolated the fragments from the main mass, Fbacthkes. — Faults often occur every few yards, both parallel to the strike and in oblique directions, with the result that the whole rook mass when seen in ground plan presents the appear- ance of a huge mosaic. Over the district generally neither large faults nor deep folds are common. It would appear that at an early stage of the folding process the resistance to the strains was so feeble that fractures were readily produced, and in many districts reversed faults are as numerous as those of normal type. Eelation of Cleavage to Bedding. — Although the rocks are everywhere cleaved, the argillaceous and arenaceous alternations are so numerous that the bedding can usually be detected.. Be- sides the deflection of cleavage in crossing from an argillaceous to an arenaceous bed, to which allusion has already been made, there is a general tendency for the cleavage to cross the bedding somewhat obliquely. The obliquity between cleavage and bed- ding is not constant. As the cleavage and folding have both been brought about by the same agencies, we see every variation STRUCTURES — DIRECTION OF STRESS. 23 depending on the character and curvature of the fold, and the obliquity of the cleavage to the bedding will often vary over the different portions of the fold. Although the cleavage is often transverse to the bedding, the general tendency has been for the beds to be thrown into a set of isoclinal folds with a definite general hade, and for the cleavage to cross somewhat obliquely at a low angle. The more the folds depart from this general hade, the greater are the variations between cleavage and bed- ding. (Plate V.) Schistose Structures. — Besides cleavage, the slates, as already noticed, are traversed by other structural planes which are analogous to those found in schistose rocks. Indeed, in highly mineralised areas, such as those on the granite margin, the phyllites have often been converted into mica schists, and, given the necessary mineralisation, the bulk of the killas of this part of Cornwall would readily be transformed into typical crystalline schists. Direction of Stress. — In spite of various exceptions, the constancy of the cleavage dips and the hades of the axial planes is so general over the whole region that there can be little doubt that the later stresses to which the rocks owe their deformation acted from a direction about south-south-e^st. Over the eastern part of the district, where sections are most numerous, a large series of observations show that the bedding has an average south- easterly dip, and the cleavage, which is somewhat oblique, averages about south-south-east. The most marked deviation from this general dip is seen on the beds that abut on the granite margin between Penryn and Lanner, where the hade is to the north- east. The deflection of the strike here is well brought out by the greenstone masses ; and it probably indicates the vertical uprise of the granite column before it spread laterally as a laccolite. Between the granite masses of Carn Marth and Carn Brea and the north coast, the dip is frequently reversed, but this may to some extent be due to the presence of granite under- lying the killas at no great depth. Effect of Superinduced Structures on ti^e General Tectonics. — Owing to the folded nature of the killas, the various lithological divisions, instead of occupying well-defined areas, tend to encroach on one another, and lenticles of one division are commonly foflnd in the adjacent group. This is more especialh' , the case as regards the Portscatho and Falmouth groups. The Veryan series occupies but a very small tract on the eastern part of the sheet to the north of Gerrans Bay. The granite masses of Carnmenellis, Carn Brea, and Carn Marth that are entirely enveloped by the Mylor series, are lying in a major fold which dies out to the north-east in the vicinity of Truro. The Falmouth and Portscatho groups, in spite of irregularities due to lenticular inclusions previously referred to, sweep round this irregular curve of the Mylor group, from the north-west coast to the south-east coast, and occupy between them not only most of the northern part of the map, but the greater portion of the eastern area lying beyond Truro and the Carrick Eoads. If, as appears probable, the 24 THE KILLAS. Veryan series represents the top of the sequence, the major fold would be an anticline. The characteristic structure of the district is well illustrated in the area between Falmouth and Truro. Here, although we are apparently crossing the strike from the coast to the heart of the county with a steady south-easterly dip, yet instead of getting deeper in the stratigraphical sequence, we are on precisely the same geological horizon at Truro as at Falmouth, the intervening ground being made up of a succession of isoclinal folds. The general features of the killas having now been described, the two succeeding chapters will be devoted to a brief sketch of the distribution and field relations of the various divisions, to- gether with any local points of interest that they present. 25 CHAPTER IV. LOWER PALEOZOIC. I. Myloe Series. This division of the killas occupies a large area on the south- western portion of the map. It encloses the granite masses of Carnmenellis, Cam Brea, and Cam Marth, the various green- stones, together with the greater portion of the elvan dykes. It contains, moreover, in conjunction with the' granites, almost the whole of the mineral lodes. The group, therefore, has not only been metamorphosed by the granites for large distances from their margins, but has been fissured to a much greater extent than the other divisions, and has over large tracts been impregnated by mineral solutions that have affected the nature of its decomposi- tion. This is especially shown by the iron oxide with which it has often been richly charged, and by the amount of vein quartz that is frequently so abundant as to impoverish the soil. This group, which is succeeded by the Falmouth series, contains few infolds of that division, in striking contrast to the Portscatho beds. In the area between Perranwell and Falmouth, beyond the limit of the granite aureole which is here of slight extent, the group is seen in its normal condition, lying outside the tracts of important mineral alteration. This district, therefore, will be described first. As pointed out in a previous section, this division is essentially an interlaminated series, in which the ribbon-like structure is often modified by brecciation, that has been set up by the stresses which have folded, cleaved, and fractured the killas. This minute type of brecciation presents every variation : from beds in which the fragments are rare, to others in which this structure so far predominates as to pervade the whole rock mass. This superinduced structure, however, instead of producing a rock of incohesive type, has generally had just the opposite eff'ect, so that the series, notwithstanding its broken condition, has a more homogeneous and massive appearance than the less heterogeneous Portscatho group. These beds are exposed along the shore of Falmouth Harbour from Arwenack to the Penryn Creek, In the section between the piers at Market Strand and Grreenbank they are of the brecciated type, in parts so coarse that some of the fragments exceed 2 inches in length. As the stone has been largely utilised for building purposes, the structure of the Mylor crush breccias can be admirably studied in the blocks contained in the walls and buildings. The railway cuttings between Falmouth and Penryn also afford sections of the different phases of the Mylor series. The cutting, for instance, between Kimberley Park and Penmere, shows these slates dipping south-east, with fine pale coloured siliceous partings, and brecciation in its initial stage. The cleavage is regular, and traverses the bedding. Similar beds, but without brecciation, are seen in the cutting at 26 LOWEH PALEOZOIC. Tregenver. The partings, when of a siliceous character, give a massive character to the section. The rocks are frequently very dark in colour, and must contain much carbonaceous material, as in the railway cutting north of the bridge near Trescobeas. Frequently the beds are purely argillaceous. Grood sections are exposed along the Penryn Creek, at the • upper portion of which the dips frequently change their direction. Between Boyers Cellars and Tehidy Terrace, and also on the north side of the creek, the brecciated type is seen, and when fine sandy beds alternate with argillaceous, the folding is at once apparent. On the north side of Grreenbank Quay typical brecci- ated beds, with fragments from 2 to 3 inches in size, are succeeded by banded slates in which the dark and pale layers are from 2 to 3 inches thick. In the same vicinity two outcrops of fine-grained greyish-blue quartzite occur, about a foot in breadth. The old quarry adjoining the High Street at Flushing has been worked in brecciated Mylor slate. It is a coarse, massive detrital rock, in which the fragments are angular, sub-angular, and rounded, and range to an inch in size and even larger. The individuals are of argillaceous or of fine-grained ■ quartzose material, and the matrix is massive. The rock has been sub- jected to movements and is highly disturbed, and even on the small scale minute puckering is general. The cleavage planes usually curve round , the fragments but traverse some of the argillaceous individuals. The coast between Flushing and Trefusis Point affords an excellent dip section that is more or less continuous and easily accessible. Commencing at Wheal Clinton, brecciated slates appear in which fragments of slate, some dark in colour, are embedded in a pale greyish-green matrix. These are succeeded by very dark argillaceous slates, in which the striping, although visible, is of a very fine charaeteiv This dark, carbonaceous- looking rock is replaced about 150 yards west of the quay by striped grey and blue slate much fractured and disturbed, with some quartz veining. East of the quay these fissile beds are succeeded by greenish bands, rather massive, and containing the pebble-like fragments due to brecciation. These again are re- placed by hard slates, much faulted, and veined with quartz, in which small pebbly beds occasionally appear. At Trefusis Point fine sandy bands alternate with blue argillaceous slates, and striping is conspicuous, especially in the latter. The sandy beds frequently reveal the isoclinal folding. The cleavage-dip along the whole section is to the south-east, varying from 30 deg. to 45 deg., but minor faults and folds are so numerous that the dip is most inconstant. On the shores of Mylor Creek the brecciated beds or pseudo-conglomerates are well seen, alternating with more argillaceous zones in which this structure has not been developed. On the north side of that creek, and about one-third of a mile south-east of Mylor Bridge, the beds have an unaltered appear- ance, and contain a seam of massive mudstone 2 or 3 feet in thickness. This, submitted to microscopic examination (3,573) proves to be a fine micaceous shale, with very small angular MYLOR SERIES. 27 fragments of quartz, scales of mica, and dark carbonaceous streaks, wbich give the rock a well-defined bedding. The quarry at Enys presents a good illustration of the inter- laminated character of the Mylor series, where it has not been sub- jected to the brecciation that has evolved the crush conglomerates. The slate is very massive, and coarsely stripeil ; the cleavage and bedding planes both hade to the south-east, the former at 45 deg., and the latter at 25 deg. It consists of alternations of pale and dark material, the latter being always argillaceous, while the former varies from argillaceous to siliceous. The pale bands predominate, and are often half an inch in thickness. This com- posite structure enables the fractures and folds to be readily detected. The brecciated structure is absent, but where the pale laminations are severed by small shear planes the first stage in the process has been set up. The pseudo-conglomerates are conspicuously developed along the southern shore of Eestronguet Creek. Commencing at Weir Point, the slates are brecciated. Below Weir Villa thin bluish argillaceous rocks enclose flattened lenses of rather harder materials, but the slate here is fairly homogeneous, without bedding planes. A little further west, just before reaching Post, a brecciated structure appears, which is more pronounced, how- ever, in the vicinity of faulting. To the west of Post, and immediately opposite Eestronguet Point, the slate is massive and homogeneous, with a cleavage dip of 35 deg. to east-north-east. A little further up the creek the beds are well striped, both in thin laminations and in coarser seams an inch in thickness, of pale argillaceous, alternating with dark seams. Brecciation here is slight, and the mass is fairly homogeneous. The cleavage, which is still in the same direction, crosses the bands at all angles. The massive blue slates with occasional striping, and often studded with cubes of pyrites, continue to the Ship Inn. At the quay similar beds occur with a low cleavage dip to east-north-east, and are striped. The dominant cleavage here is often at right angles to the bedding, which is puckered, while the cleavage planes are regular. The quartz veins, moreover, have shared in the folding. In the neighbourhood of a fault, carrying a quartz vein, 1 foot in thickness, brecciation again appears. The striped slates, much disturbed with faulting and folding, can be followed along the shore to the bay below Tregunwith, to the south of which some greenstone bands and an elvan occur, all in a highly decomposed condition. On the north side of this bay the interlaminated character of the beds is pronounced. The dip is irregular, as the bands are much folded. These contorted zones alternate with others of regular hade, but the former predominate. Occasionally bands with brecciated slate appear about a foot or so in thickness, the isolated fragments being clearlji due to rock fracture. These pseudo-conglomerates soon get more conspicuous, but are still subordinate to the normal rock type. At Eestronguet Point the coarse brecciated structure is ex- ceedingly well developed. (Plate VI.) Fragments up to an inch 28 LOWER PALEOZOIC. or more in length are profusely scattered in a darker matrix. Amongst the argillaceous beds thin gritty seams are observed, in which deformation has commenced. The killas here has been so involved in these movements that in many places the entire rock mass has undergone mechanical reconstruction. The structures are analogous to those of schistose rocks, but have stopped short at these mechanical processes. Chemical changes have, however, been initiated, as in many parts of this section the slates have been converted into phyllite, with micaceous lustre clearly defined. The brecciated structure is most pronounced where the fragments are of a quartzose nature, as being less flattened they protrude from the rock surface. Some quartz veining occurs in the section which has been involved in the folding. Occasionally a coarser bed occurs revealing the dip; these limbs, however, are generally parallel to the dominant cleavage. On the side of Eestronguet Point fronting the Carrick Roads numerous small faults, slightly oblique to the strike, are seen to repeat the beds. Indeed, the whole section proceeding north along this coast is of a most disturbed and plicated character, consisting of a series of segments and lenticles that have been torn from the original homogeneous mass. In this brecciated series there are, nevertheless, some zones in which such deformation is absent. This is seen about 200 yards north-east of Eestronguet Point, where the undisturbed seam is a hard, dark arenaceous bed. The disrupted condition of the section, as well as its re-duplication, is clearly illustrated by a quartzite seam which occurs along the coast for a distance of about a third of a mile from Eestronguet Point. This quartzite is about a foot in thick- ness and is probably related to the quartzite already referred to, at the entrance to Penryn Creek, near Grreenbank Quay. It is rather dark in colour and is often associated with much vein quartz. The quartzite, instead of forming a continuous seam, is represented by a series of detached lenticles, some of which arc several feet in length. At its most northern exposure the quartzite has been folded on itself, causing thickening, bat in places the limb thins out entirely. The " head " which fringes the shore here contains at its base some lenticular blocks of quartzite about three feet across. A quartzose band from Carclew, a specimen of which was sliced, shows under the microscope (3,389) fragments of organisms which Mr. E. T. Newton believes to be pieces of much altered echino- derms, perhaps crinoids. Dr. Flett considers that the rock has the appearance of a modified chert. From Eestronguet Creek the Mylor beds swing round to the north-west of the map, as already indicated, in conformity with the Falmouth and Portscatho groups, the Mylor beds forming the inner zone. From Eestronguet Creek they extend to Carrine Common, near Truro, whence they curve round to the west through the districts of Baldhu, St. Day, and Scorrier, to Stencoose and Mawla. Thence they follow a south-westerly course through the parishes of Eedruth, Illogan, and Camborne. From Camborne they extend southwards through the districts of Crowan and FALMOUTH SERIES. 29 Breage, occupying the area between the margin of the Carn- menellis granite and the western edge, of the sheet. Over the greater part of the area between Baldhu and Camborne they are highly decomposed, their surface debris being stained deep red and various shades of buff by the iron oxides with which they are frequently charged in the mineral area. In the south-western portions of the sheet, however, in the parishes of Breage and Sithney, this discoloration is comparatively rare, and the rock is often extremely fresh at the surface. That part of the Mylor series which more immediately fringes the granite masses will be treated separately in the section, dealing with the contact metamorphism produced by those granites. Mr. F. J. Stephens* has recorded various localities between Trefusis Point and Penryn where radiolarian cherts occur. These have since been supplemented by Mr. Howard Fox.f The micro- sections were submitted to Dr. G. J. Hinde, who determined some of them to be full of radiolaria, although the rock shows evidence of great distortion. II. Falmouth Series. On the southern side of Falmouth a strong band of this series extends from the Pendennis peninsula to Swanpool and Penrose. From the latter locality to Carlidnack it contracts, but widens again in the neighbourhood of Mawnan Smith, where it is con- tinuous with a band that reaches the coast between Maen Porth and High Cliff. It can thus be demonstrated that the Falmouth and Maen Porth bands, separated by the Portscatho slates between Pennance Point and Maen Porth, are in reality a single unit repeated by folding. The coast between Swanpool and the vicinity of the Falmouth Hotel presents an excellent section of this group, and was described by De la Beche as a variegated series. J. The prevailing blue colour of the adjoining Portscatho group has been replaced by tints that vary from green to grey and buff, although blue argillaceous bands are still to be seen amongst them. The deep cliff sections, moreover, frequently display a reddish hue from the presence of iron oxide. The strata consist of alternations of argillaceous and fine sandy material, the colour varying with the character of the sediment ; hence the general variegated appearance of the series. The weathering is equally characteristic ; the beds become extremely friable, especially those of a sandy nature, and assume a deep buff colour. Lamination is sometimes conspicuous, thus linking them with the Mylor beds on the north-west. Although there is a general dip to the south-east, the section shows a high degree of disturbance. The amount of minor contortion and fracture is such that a most con- fused section is the result, and this is accentuated by the presence of much quartz veining. Within this series a small zone of sharply contrasted purple and green slate is seen in the large dry * Boyal Cornwall Polyteclmic Society, 1897, p. 104, • + From unpublished information furnished by Mr. Fox. i " Report on the Geology of Cornwall," &c., p. 93. 30 LOWER PALJBOZOIC. dock at Falmouth. Three purple bands, one of which is 10 feet in thickness, are separated by green slate. On the eastern side of the Carrick Roads an infold of the Falmouth series occurs within the Portsoatho beds. It forms a strip skirting St. Mawes Harbour between Castle Cove and Polvarth Point. Here the buff beds seen at Falmouth are practically absent, and the rocks are distinguished from the adjacent Portscatho group, into which they insensibly merge, by pale greenish hues, which not only pervade the killas but also occur occasionally amongst the quartz veining. Like the band, how- ever, at Falmouth, the slaty beds here contain the characteristic purple and green zone, which is exposed at Castle Point, and again on the shore to the north-east of the quay at St. Mawes. The section between St. Mawes and Polvarth Point illustrates the constant repetition by folding. Being transverse to the strike, the various fluctuations in the plication are brought out, and notwithstanding that the beds are often nearly horizontal, with slight undulations as exhibited by the harder sandy bands, the prevailing dip of the various limbs, whether regular or contorted, is to the south-east. Further to the north a band of variegated buff and green beds occurs at St. Just Creek. They are much crumpled, and in places show small thrnsts from the south-east. About half a mile north of Messack Point the typical purple and green slates form a small belt, into which a mica trap has been intruded. Another band of the Falmouth series occupies a strip running nearly south to the coast from Camerance Wood, where purple and green slates are exposed. Near Turnaware Point a band occurs containing purple and green beds, pale greyish green slate, and some of the buff beds. From the amount of plication exhibited there can be little doubt that they represent isolated lenticles due to folding. To the west of Philleigh, a band which passes through Polmesk can be traced by the purple and green slate, both in the solid condition and as surface debris. Between Euan Laaihorne and Philleigh an extensive strip of Falmouth beds occurs in which the sandy buff beds predominate, but the purple and green bands have not been noted. Along this comparatively low-lying land they disintegrate more rapidly than the Portscatho group which they adjoin, and thus form a deeper soil, as can be well seen at the promontory at Ardevora Veor, which stands higher than the land further east ; the former being occupied by the .Portscatho series aiid the latter by the Falmouth beds. The lenticles that occur still further east, at Trenestrall and Treworga. are characterised by the typical buff beds, but as they appear to be intermixed with some Portscatho slate the boundaries drawn are necessarily general. Between Merther and Trevervoe buff beds of this type occur infolded with the Portscatho group, but whether they form a continuous band or consist of a line of lenticles the eWdence IS insufficient to show. The infolds of this group amongst the Portscatho series between the Truro River and Feock call for no special comment; they consist of the usual variegated and buff beds of this series. At Malpas, however, the FalrSouth beds are FALMOUTH SERIES. 31 associated with some of the greenish and purple bands that still further define the horizon. We will now more particularly refer to the occurrence of the Falmouth beds on their true geological position, separating the Portscatho from the Mylor group. Their position at Falmouth between those groups has already been referred to. These marginal relations are then broken by the estuary of the Carrick Eoads, at the head of which, in the district of Feock, the geo- logical sequence, represented by the Mylor, Falmouth, and Ports- catho groups, sweeps round in a big curve to the north-west, the apex of which lies in the neighbourhood of Truro. This great fold, is, of course, complicated by the general isoclinal plication and accompanying fracture that has involved the whole area. In spite of this disturbing element, however, the larger fold is sufficiently brought out by the mapping, showing an inner ring of Ulylor beds partially encircled by the Falmouth and Portscatho groups respectively. Notwithstanding this generalisation, how- ever, the marginal lines are necessarily irregular, on account of the disturbing elements already referred to. Thus the subdivision of the killas is often a matter of great difficulty, owing to the impersistence of lithological types, and in some cases to their close resemblance to one another. Not only do the Portscatho and Mylor groups sometimes shade into types that are practically indistinguishable, but the Falmouth group which divides them, and on the whole exhibits a stronger lithological contrast to either, is not always persistent in character. Nevertheless, the correct identification of the Falmouth group furnishes the key to the interpretation of the major geological structure of the area. Notwithstanding the many fluctuations in lithological condition exhibited by this series, the Falmouth beds are evidently much thinner than the Mylor and Portscatho groups which they separate, so that in some areas, where the surface geology is obscure, they either cannot be identified at all or their recognition is attended with much uncertainty. In mapping this group, however, the presence of the purple and green zone in any recognisable form is of the utmost value, and fixes the horizon with precision. So far is this the case that a band of this nature, however narrow, and unaccompanied by the more general buff and decomposing strata of Falmouth type, would be confidently interpreted as unmistakable evidence of the geological horizon. The Falmouth beds will now be briefly described in their passage round the great fold in their relation to the Portscatho and Mylor groups which they divide. In the neighbourhood of Feock and Eestronguet Oreek,although all three groups are in close proximity, their boundaries seem to be marked by north-westerly faults, the evidence of which is clearly seen along the banks of that creek. Between Porthgwidden and Eestronguet Point a fault is seen with three or four feet of vein breccia, which apparently brings the Mylor and Portscatho beds in juxtaposition. On the north side of Re&trenguet Creek a strip of the Falmouth beds fringes the' coastifor about half a mile, extending as far north as Pen Poll Creek; it succeeds the Mylor beds, but its relations to the 32 LOWER PALAEOZOIC. Portscatho group are not seen. The Falmonth beds are not again recognised between this and the north of Carnon Downs, near Killiganoon, and if they occur can only be feebly represented. They are probably cut out by a fault extending from the north side of Carnon Downs to the south side of Feoek Downs. In this band they are far from typical, and good sections are rare. Between Killiow and Truro the band cannot be satisfactorily followed owing to the absence of sections, and to some extent also to the nondescript character of the rooks. In the neighbourhood of Truro this group is strongly represented by deep sections of the characteristic bright buff beds, highly decomposed, that alternate with the fresher and more solid blue slates of the Portscatho group. The irregularity of the outcrops at Truro is due to the nose of the major fold acting on the close isoclinal plication, and to the broken nature of the topography represented by the extensive valleys that radiate from that centre. From thence to Chacewater the band extends in a westerly direction ; it is necessarily very generalised, and contains portions of the adjacent groups which cannot be separated. Over a great part of this belt the country is flat and practically devoid of sections, more especially in the district lying to the north of Chacewater. Moreover, the mineralisation in these metalliferous areas has contributed to obscure the nature of the killas. Here and there, however, traces of the purple and green zone have been noted. Purple and green detritus is also seen at Creegbrose, and between that locality and Grreystown. On a mine burrow at Cox Hill, just within the Mylor group, some large blocks of purple and green slate were observed that had apparently been raised from the mine. Moreover, De la Beche records the occurrence of this kind of slate in the mines at Grwennap.* So far as it goes, therefore, this might be taken as evidence of the superposition of the Mylor beds to the Falmouth group, and that the sequence from the Mylor series to the Veryan beds may be a descending succession, but the area is too folded to warrant such a deduction. Perhaps the best section of the Falmouth beds in this locality is that formed by the road cutting at Green Bottom, on the north side of Saveock Water. Between Blackwater and Parsley they have not been detected, a fact due perhaps to the paucity of sections, but they may possibly have been cut out by the fault that meets the coast at Porth Towan. From Parsley, however, to Eeskajeage Downs on the north coast, and to Treswithian Downs, the purple and green beds are abundantly developed, and the zone has been traced by Mr. Dixon between the Mylor and Portscatho groups. The purple and green huPs so characteristic of this formation are well exhibited in the north-western region in the cove south of Gnllyn Kock, in quarries between the latter and North View, and in the cliffs facing Eeskajeage Downs. Inland the colours are seldom clearly seen, so that the boundary between these slates and those of the Mylor beds is not well defined. The sole organic remains at present known from the Falmouth beds are the radiolaria, discovered by Mr. Howard Fox, near * Report previously cited, p. 93. POKTSCATHO SERIES. 33 Middle Point, Falmouth, to which attention has already been drawn. III. PORTSCATHO SERIES. This series immediately succeeds the Veryan group in a westerly direction. Its principal distinguishing feature frora the latter is the total absence of limestone, except at their mutual junotion. Although the coast line south of Pendower forms the boundary of this series, yet small calcareous layers, linking it with the Veryan group, are seen along the shore as far south as Creek Stephen. The true boundary between the two divisions possibly includes a little of this southern coast line. The natural transition between the Veryan and Portscatho types along the shore between Pendower and Creek Stephen Point is sufficiently attested by the gradual dying out of the limestone. Excellent clifif sections of the Portscatho series are exhibited between Grerrans Bay and the Zoze Point. Estuary sections of shallower depth are continuous for several miles along the various creeks converging to the Eiver Fal and the eastern side of the Carrick Roads. On the north coast this series can be studied along the shore for at least four miles between Porth Towan and Reskajeage Downs. The section between Pendower and the Zoze Point admirably illustrates the disturbed nature of the killas. The beds are frequently wavy, while the sandy seams reveal the curving and nosing out of folds. Faults often occur every few yards, and even feet : either of normal type coincident with strike or dip, or small reversed faults or slides hading at a low angle. They appear to have but small throw, often being limited to a foot or so. The picturesque caverns which make a feature of this coast have been formed along the strike faults. Vein quartz is often very abundant, and has frequently shared in the folding. Here and there the argillaceous beds show striping like that seen in the Mylor series. In the neighbourhood of faults the clay slates sometimes take on a phyllitio aspect. Notwithstanding the general south-easterly dip, the coast is so broken by faults that there are numerous deflections, both as regards direction and hade, beds comparatively flat being closely adjacent to those highly inclined ; others, again, with even bedding, are sharply succeeded by strata highly contorted. The Shag Rock at St. Anthony Head affords an excellent section of the constant repetition by small folds and faults hading to the south-east. At the Lighthouse, although the individual beds are folded, there is a steady cleavage dip. The Portscatho beds from the St. Anthony peninsula re- appear at Pendennis Point on the western entrance of the Carrick Roads, and are seen also on the Black Rocks which project at low water at the mouth of the harbour. At Pendennis Point they occupy a strip about a third of a mile wide when they merge into the Falmouth beds. The Pendennis section is a repetition of Ihat of St. Anthony, being made up of fairly hard, wavy, argillaceous slates, with sandy alternations. 34 LOWEB PALJEOZOIC. There is a moderate amount of vein quartz, and small faults are numerous, especially those following the trend of the strike along which gullies, locally known as "drangs," have been excavated on the coast. This band, after crossing Falmouth Bay, re-emerges close to Pennance Point, and is admirably dis- played on the coast section from thence to Maen Porth. At Pen- nance Point the beds are fairly free from contortion. They are hard, and of the nature of fine arenaceous slate, being well cleaved with regular linear striping, but without the conspicuous sandy alternations. Between Sunny Cove and Newporth Head the typical dark blue argillaceous slates reappear, with a dip of 48 deg. to the south-east, and a cleavage dip of 60 deg. in the same direction. (Plate VI.) At Newporth Head the finely quartzose beds recur with a brown weathering, and producing an uneven rockshelf. On the eastern side of the Carrick Koads the continuity of the Portscatho series is broken by no less than five infolded len- ticles of the Falmouth beds, and others occur south of the River Fal between Euan Lanihorne and Philleigh. The tract between the River Fal and the Tresilian River is almost entirely confined to the Portscatho group, except for a strip of Falmouth slate between Merther and Trevervoe. West of the Fal several infolds of the Falmouth beds occur between Truro and Feock. In this broad tract between Truro and Gerrans Bay the con- stancy of the dips of both cleavage and bedding in a south- easterly direction is well marked. Notwithstanding contortion and small faults, which are as frequent as on the coast section at Gerrans Bay, it is unusual to find the dip reversed. In spite also of the fractured nature of the district, as indicated by the in- numerable small faults, there is no evidence in this wide tract of the existence of faults of suflBcient magnitude to be shown on the map. It is true that the uniform nature of the strata is un- favourable for their detection, but the many miles of section afforded by the estuaries would be expected to reveal fault breccia if fractures of any magnitude were present. Moreover, the absence of elvan dykes and mineral lodes, tends to confirm the conclusion that Assuring on the large scale is not prevalent in this district. The killas, which is so frequently decomposed in inland seetioni for some depth from the surface, presents in some localities ex- posures that are singularly fresh. This is especially the case in the parishes of St. Michael Penkevil, St. Clement, and Merther. The Portscatho beds usually weather to different shades of brown, but in the mineral areas, like the rest of the killas, they fre- quently become deep red from the oxidation of the iron ores, and shades of rich buff and even very pale whitish grey are also common. At Governs, about Si^ miles west-north-west of Truro, some very massive greenish slate is seen in a quarry. The massiveness of the rock is due to its silieification, which takes the form of fine interlaminations of quartz between the argillaceous folia that at first sight suggest original bedding, as they share in the undula- PORTSCATHO SERIES. 35 tions of the rock. But the silicification has followed the folding, although it has taken advantage of the lamination with singular regularity. At times, however, patches of phyllite are seen entirely enclosed by quartz, while isolated quartz fragments point to a certain amount of brecciation. As this quarry occurs in the vicinity of abandoned mine workings, it is. possible that the unusual green hues are due to secondary mineralisation. Still further to the westward, between Croft West and Treveskas, some of the Portscatho sandy beds are similarly tinted with a greenish hue, but this is also in the vicinity of a mineral lode, and a little of the argillaceous rock exhibits tiny knotting. Thence to the westward the mineral area has been reached, and the reddening of the surface rocks is a common feature. Moreover, this coloration is sometimes accompanied by greenish hues, which, beyond the area of mineralisation, would have led to the supposition that the debris was derived from Falmouth beds. Within the mineral region the- evidence of colour is no longer a safe criterion in mapping the lithological divisions, and has to be used with caution. Thus, large tracts of the mineral area lie in comparatively flat country, buried under a covering of decomposed rock or debris, which is variously coloured by iron oxides, as in the area surrounding Chacewater, Blackwater, and Skinner's Bottom. In these districts, however, the contents of the mine-burrows often afford good evidence of the nature of the underlying killas. For instance, to the north-west of Carnhot, where the surface debris is often of a red and greenish tint, the mine tips show the solid rock to belong to the Portscatho group, though often very pale in colour, due to bleaching. Occasionally, however, the argillaceous members are more interlaminated than in the typical areas. Further to the west, in the district of Blackwater, the evidence of the burrows shows this interlamination to be a common feature, and it retains this characteristic in its westerly extension to the north coast. The depth of the decomposition and mineral staining is well seen in the cuttings of the new railway connecting Chace- water with St. Agnes. The cutting .^t Blackwater affords a vertical section from 12 to 20 feet deep, in which the sandy and argillaceous beds are stained deep red for the entire depth of the exposure. In spite of the obscurity caused by this soaking in iron oxide, the resemblance to the Portscatho type is sufficiently retained, while folds and small faults are often seen. The red staining is sometimes replaced by buff hues. The fault planes contain little quartz, but are often richly charged with hematite. The reddened slate, moreover, sometimes suddenly ceases, and is succeeded laterally by bluish slate, in which the upper surface is often of a buff colour for a depth of 2 or 3 feet. Some of the fine bleached arenaceous beds readily crumble into a clay-like substance. Mr. Dixon has observed that the Portscatho series of Porth Towan pitch to the south-west, and disappear in that direction beneath the Falmouth beds. Along the northern margiri of the Portreath mass the cleavage generally inclines north-north-west, 36 LOWER PALEOZOIC. while north-east of Portreath the folds are generally Inclined to the south-south-east. In the cliff south of Gullyfl Eook, and beneath Tregea Hill, slides of different inclinations intersect, and the steeper faults hading south disturb the others, which incline to the north. At the latter locality the later faulting is clearly of normal type. The most conspicuous cross courses seen along the northern coast are as follows : Cliff, south-west of Tobban Horse (2) ; Cove, south of GuUyn Eock (1); Cove, .south of Gooden Heane Point (2); Porthcadjack Cove (1). With the exception of odb of those occurring at Tobban Horse, they all hade to the west. Their throw is not known ; they are accompanied by thick vein quartz, and most of them discharge water. A little iron, lead, and copper staining is the sole indication of their metalliferous contents. In several cases valleys have been eroded along lines of fault. Along the northern edge of the map this division of the Lower Palaeozoic group is unconformably overlain by the Probus series of the Lower Devonian formation, and their marginal relations are described in the chapters devoted to the latter. Under the microscope the Portscatho slates show no character- istics of special interest. The argillaceous seams can be seen to contain minute grains of quartz, together with films of biotite and muscovite (3,392). Sometimes, besides cleavage, a well- defined parallel structure representing bedding is seen, and there is occasionally minute brown staining, due to iron oxide (3,574). The grit bands are principally composed of quartz, mica, and slate fragments. Felspar also occurs, but in small quantity as compared with quartz. The small dark concretions of nodular form that are often scattered in the slate are quartzose lenticles, consisting chiefly of very finely granular quartz with a few larger grains, and only imperfectly cleaved. Mr. J. H. Collins has recorded the presence of corals at Lower Newham, in the neighbourhood of Truro. The late Dr. P. M. Duncan, to whom he submitted specimens, suggested that the markings on the surface of some of the schistose planes resembled infiltrated corallites of a genus like Favosites, and concluded that it was probably a metamorphosed coral.* The siliceous schist containing these suggested coralline mark- ings was analysed by Mr. Collins, with the following result: — a. b. Silica - - - - - Ferric oxide and alumina Magnesia - - - - Lime - . - _ Phosphoric acid Moisture - - . . * Joum. Boy. Inst. Cornwall, vol. vii., p. 31. Messrs. Upfield Green and Sherhorn, however, regard the structure as inorganic- 66-81 69-88 27-21 23-28 •75 1-17 ■08 •15 trace 5-62 6-11 100-47 ] 00-59 VERYAN SERIES. 37 Mr. Collins suggests that the low percentage of lime is due to change in chemical composition since the formation of the rock.* Mr. C. W. Peach found part of the stem of an encrinite at Truro, in a quarry near the Patent Wood Works, where he also observed other indistinct fossiliferous marks.f IV. Yeeyan Series. This group is restricted on the map to a triangular tract of about half a square mile lying to the east of the valley connecting Pendower and Crugaillick. An excellent section is afforded by the coast of Grerrans Bay, extending from Pendower to the eastern margin of the sheet. It is composed mainly of dark slate, with subordinate sandy seams, but it is especially characterised by the presence of limestone and chert. These members, so hetero- geneous in type, are closely associated ; slates, sandstones, lime- stones, and chert occurring together in a limited section. The sandy beds, moreover, are frequently coarse, but shale fragments enter largely into their composition, so that they readily cleave. The limestonef occurs in thin bands, ranging from a few feet to a few inches in thickness. This section has been described by Mr. Howard Fox,§ who states that the limestones increase in thickness and frequency towards the eastern part of the section, which our examination confirms, A little to the east of Pendower the lime- stone is represented by a few thin seams, which westward become still more attenuated as they are traced within the Portscatho series, where they soon die out altogether, the calcareous zones forming the connecting link between the two groups. The lime- stones, although containing organic fragments, have failed to yield recognisable fossils. The chert beds on the western part of Pendower Beach have been figured in the work already cited by Mr. Fox, who states that black chert is there seen interbedded with shales on the foreshore and also at the base of the clifif, which is " occasionally composed of black chert several feet thick, at other times of chert sheared into thin bands, which are more or less disturbed." In one place Mr. Fox observed the apparent passage of chert into quartz, and he states that " black chert occurs at intervals in the foreshore and cliff for more than 1,000 yards eastward," and gradually becomes thinner and less frequent, as well as more impure and decomposed. This decomposition was attributed by Dr. Teall to the decay of pyrites crystals, which the microscope shows to be present in the chert. Micro-sections of the chert examined by Dr. G-. J. Hinde reveal indications of radiolaria with marked signs of shearings In the shales associated with the chert crinoidal remains have been found. The Veryan beds yield appreciable quantities of mang£^nese in association with oxide of * Jown. Roy. Inst. Gornmall, vol, vi., p. 418. t Tra/m. Roy. Qeol. Soc. Cornmall, vol. vl., p. 181. X Tnese limestones were described in 1818 by Mr. S. J. Trist and the Kev. J. Kogers. Tram. Royal 6feol, Soe. Cornwall, 1818, vol. i., pp. 107 and 114. § Tram. Roy. Qeol. Soe. Cormiall, 1896, 38 LOWEE PALEOZOIC. iron, which occur along the divisional planes. Near the western end of the section the slates are studded by circular bodies, some of which attain half an inch in size; a specimen, tested by Dr. Flett, consisted mainly of impure limonite, with little or no manganese. They are surrounded by a thin periphery of quartz, and, owing to the weathering of the decomposed core, they are frequently represented by cup-shaped hollows lined with quartz. Considering the disturbed state of the slates and the absence of distortion in these spherical bodies the latter are not likely to be organic. Below high-water mark the slates are very dark in colour, at times almost black, while the bulk of the sandy alterna- tions are of a pale colour and therefore strongly contrasted. In the cliff sections, however, where the beds are more decomposed, the weathering of the slates exhibits strong colour contrasts, some parts being pale yellow and brown, while seams a foot or more in thickness of rusty brown material probably indicate beds cljarged with manganese and iron oxide, the varied colour of the phyllite being doubtless due to the presence of these oxides in a less concentrated form. A quantitative analysis of the manganiferous band undertaken by Dr. Pollard revealed the presence of a small quantity of carbonate, in addition to man- ganese and iron, and manganese is in excess of iron. While the general dip of the beds is to the east, they are frequently lying at a very low angle not far from the horizontal, with gentle undulations, so that their thickness may be slight not- withstanding a considerable breadth of outcrop. Mr. J. H. Collins has published an analysis of the limestone.* He describes it as " a very dark-coloured rock, occurring in narrow bands in the dark slate of Grerrans Bay. It contains microscopic organisms in abundance," some of which are fragments of encrinite.-]- The analysis is as follows : — Silica 6-67 Alumina and ferric oxide - - - 2'55 Magnesia --...-- 1-71 Lime 43-45 Phosphoric acid - ... traces Carbonic acid --._.. 39"42 Moisture 5-69 99-49 * Jown. Roy. Inst. Commall, vol, vi., p. 419. t Irons. Qeol. Soo. Commall, vol. x., p. 5. Mr. J. H. Collins " On the Stratigraphy of West Cornwall." CHAPTER V. DEVONIAN ROOKS. GrEAMPOUND AND PfiOBITS SERIES. This series, consisting of fine-grained conglomerates, sandstones, and clay slates, is slightly calcareous, and is equivalent to the Manaccan series that occurs in the adjoining map to the south of the Helford River, except that in the latter locality, besides the fine-grained conglomerates like those of Probus and Grampound, these beds frequently attain an extreme coarseness, many of the included boulders exceeding a foot in size. The conglomerate in that area is by no means continuous, but the base of the formation is frequently of fine texture. There is, moreover, a tendency for the coarser conglomerate to die out in a westerly direction, so that the demarcation of the Manaccan series from the older Palaeozoics is attended with diflBcuIties in the cultivated areas. These con- ditions are exactly reproduced in the Probus beds, the coarse conglomerates, analogous to those of Manaccan, occurring only in the Grorran district to the east of this map, while in a western direction towards the coast of the Bristol Channel the fine-grained conglomerates of Probus disappear. The Probus series likewise corresponds in strike with the -beds of Manaccan, these lower Devonian strata having a general east and west trend, oblique to that of the underlying Lower Palaeozoic strata. The fine- grained conglomerates of the Probus area were recognised from their lithological characters in 1902* as the equivalent of the Manaccan conglomerate. This likeness is borne out by micro- scopic examination, from which they are seen to contain a similar assemblage of rock fragments, resembling one another so closely as practically to preclude the possibility of their derivation from different sources, or from the same source at widely different periods. From these considerations it was at the same time recognised that it might represent an unconformity between the Silurian or older rocks and the Devonian rocks of Cornwall. The detailed investigation of the Manaccan district has proved the correctness of that interpretation.t The coarseness of the con- glomerate in that area enables its constituents to be easily identified, and where it is closely associated with the Portscatho beds it is seen to be almost entirely composed of fragments derived from that series. The fact, moreover, that the boulders were veined with quartz prior to their incorporation in the con- glomerate sufficiently indicates the magnitude of the break. The Probus series follows a westerly course across the northern * J. B. Hill. "Summary of Progress of the Geological Survey for 1902," p. 25. + J. B. Hill. "Summary of Progress of the Geological Survey for 1906,' and Geol. Mag., 1906, pp. 206-216. 40 DEVONIAir ROCKS. edge of the area to the coast at Forth Towan with an average width of a mile. Although no fossils have been found within this narrow strip, its northward extension in the adjoining map contains Lower Devonian fossils. The sandy beds are frequently very tough and highly siliceous, and constitute good road metal. They are, moreover, often veined with calcite. Their common characteristic, however, is the thick- ness of the bands, which may sometimes attain to 20 feet, whereas the sandy beds of the Portscatho group seldom exceed a few feet in breadth, so that this feature, as well as the coarser texture and presence of lime, help to distinguish them. These grits contain pebbles of fine slate, sandy slate, fine impure grit or grauwacke, granular quartzite, sheared quartz, felsitic igneous rocks rich in felspar, and fine quartz-felsite, together with pyrites, tourmaline, muscovite, chlorite and limonite. The igneous pebbles sometimes include fluidal felspathic rocks, which Dr. Flett considers to be probably trachytes or orthophyres. Pebbles of felspar often occur in large numbers (3,870).* A specimen from a more quartzose type (3,871)* contains pebbles of quartz, orthoolase, oligoclase, felsite, and fine grit, lying in a fine quartzose matrix. There is less slate and fewer igneous fragments than in the preceding, but one or two small pieces of the characteristic igneous rocks are to be found, together with the sheared meta- morphic quartzite. The discontinuous nature of the coarser beds and the frequent paucity of rock sections has precluded its boundary being traced with accuracy ; nevertheless, its east and west trend is sutE- ciently apparent, as a glance at the map will show ; and in spite of the general absence of its coarser representatives, the group forms more elevated features than the Lower Palaeozoic tract. At Forth Towan, where it reaches the coast, it is separated from the Portscatho group to the south by a fault. The latter group consists of sandy and argillaceous beds ; while on the north side of the fault sandstones are rare, although some of the fine- grained sandy silts weather out into conspicuous bands from the argillaceous alternations. These beds are, moreover, slightly calcareous, and effervesce with cold hydrochloric acid, both as regards the normal rock and the small brown veins that ramify through it. * These specimens were obtained from the area closely adjacent in Sheet 346. 41 CHAPTEE VI. IGNEOUS EOCKS. I. Greenstone. The greenstones that occur within this area are largely refer- able to the group of epidiorites. Taking Cornwall, however, as a whole, these rocks could not be conveniently classed with the latter, as many of them still retain original augite. It has been found convenient, therefore, to retain the older synonym, which is sufficiently wide to embrace the various petrological types that are nevertheless linked together by close ties of affinity. The dominant minerals in these rocks are hornblende and felspar, while chlorite, biotite, epidote, iron ores, and quartz form the most important accessories ; augite, garnet and axinite are in this area exceptionally present. They occur in elongated sill- like masses, some of which attain considerable size. As they have been involved in the earth movements that have affected this region, they have to a very large extent shared in the process of deformation to which the slates have been subjected. More- over, their great development within the granite aureole of con- tact alteration has involved thermal metamorphism in addition. As the result of these changes they have often been profoundly modified, both as regards structure and mineral composition. So far as this area is concerned, there is no good evidence that the group contains either lavas or tuffs. The coarser varieties are almost certainly intrusive, and the absence of well-defined ash beds points to the conclusion that the Palaeozoic sediments of this part of Cornwall were unaccompanied by volcanic products. On the other hand, the decomposition of these greenstones and the adja- cent killas obscures the junctions. Moreover, the mechanical deformation to which the rocks have been subjected still further masks their mutual relations ; whilst, finally, the paucity of marginal sections is such that deductions based on such data are far from conclusive. Although these rocks have a considerable petrological range, it is clear that most of them were originally dolerites or basalts, in which the primary augite has been replaced by hornblende. The researches of Messrs. AUport and Phillips* on the Cornish green- stones conclusively demonstrate this fact. While .the more massive varieties of the rock have so far resisted dynamic meta- morphism as to still preserve much of the original felspar, in others that mineral is recrystallised or profoundly altered. More- over, considerable variation attends the relative proportions of the hornblende and felspar that form the principal constituents, while in the crushed varieties the secondary products may be so widely diffused as to efface the original character of the rook. The green - * QJ.Cr.8., vol. xxxii., pp. 155 and 407, and vol. xxxiv., p. 471. 42 IGNEOUS EOCKS. stones, however, are not confined to the basic types, but rocks of intermediate and possibly even of acid composition find their place within that group. That members of the andesitic family are present is certain, and it appears highly probable that trachytes are represented also. For convenience, the greenstones will be described under four heads, according to districts, as follows :— Firstly, those in the granite aureole between Grwennap and Penryn. Secondly, those occurring to the east of Penryn, which are scattered over a broad tract west of the Oarrick Eoads, between Devoran and Falmouth, and lying mainly beyond the granite aureole. Thirdly, those between Camborne and Redruth that flank the smaller granite masses of Carn Brea and Carn Marth ; and, lastly, the greenstone flanking the south-western margin of the Carnmenellis granite. Area between G-vfennap and Penryn. — From Bellevue to Ponsanooth there appears to be a continuous line of greenstone. After a break of about a mile and a quarter, it is again seen between Pengreep and Treviskey. That between Bellevue and Ponsanooth will be first described. BeUevue and Ponsanooth. — Owing to the area being under cultivation and the infrequenoy with which the rock protrudes from the soil, the continuity of the sills cannot be demonstrated. At Bellevue a coarse-grained greenstone is seen, having apparently a width of about 80 yards. This rock is again visible at Lower Treluswell. Between that place and Burnthouse, where it has been quarried, it cannot be traced, but large blocks occur in a field between Treluswell and Burnthouse. Beyond the latter locality it has been quarried at Cosawes Pascoe. Another pit has been opened on this band about half a mile to the north-west, and this is the only quarry at present being worked. The seam appears to die out before reaching Ponsanooth. The coarse greenstone is accompanied by a smaller band of finer texture, which appears on its western side, in close proximity to it, at Lower Treluswell, Burnthouse, and on the main road near Ponsa- nooth, where a corresponding band also occurs on its eastern side. The larger and coarser band is a massive amphibolite, resulting from the alteration of a coarse dolerite or gabbrb. A specimen from near Bellevue (3,367) shows under the microscope large masses of fibrous hornblende, in a matrix of coarse felspar, in which a large number of the crystals are still idiomorphio, while many are broken and crushed. The rock is half a mile distant from the Carnmenellis granite, and it would appear that prior to contact metamorphism by the latter that it was decomposed, and while the original felspar remains, the decomposed pyroxene is re- placed by actinolite. There is a sporadic appearance of actinolite amongst the felspars, probably due to a migration of the decom- position products. Iron ore is present in process of alteration to granular s'phene, as well as fine needles of apatite, some of which are broken and may possibly be original. A specimen obtained from the new quarry near Cosawes Pascoe, and within 300 yards of the granite margin, is essentially the same rock, but under the microscope (3,371) is seen to be slightly sheared, and shows a GREENSTONE. 43 higher degree of granulitisation. It is a massive amphibolite, and the hornblende is more abundant than in the last rock, forming compact masses, very pale green towards their centres, mixed with a little pale brown biotite, the latter probably being a direct result of contact alteration. The felspar is partly in large plates, but occurs mainly in a fine granulitic condition, especially in the shear planes. Some magnetite and apatite are also present. De la Beche* records that this greenstone is traversed at Burnt- house by an el van. At present the quarries at that locality are no longer working, and, being densely overgrown, cannot be satis- factorily inspected. In one of the old greenstone pits on the north side of the inn a few elvan fragments are seen that corre- spond to the description given by De la Beche, but no trace of the rock in situ is now visible. The finer-grained greenstone sill already referred to has been quarried at Lower Treluswell and at Burnthouse. A specimen selected from the latter locality, about 150 yards south of the inn (3,562), shows the rock to be decomposed and sheared. It is full of pale green fibrous hornblende, mostly divergent, and of felspar which is decomposed and sheared. The rock is almost in contact with the granite, and contains a few scales of biotite, probably due to contact metamorphism. The original structure of the rock, however, has been obliterated. The fine-grained greenstone seen in a corresponding position to the amphibolite on the main road leading to Ponsanooth (one- eighth of a mile east of Cosawes) is little more than 100 yards from the granite margin. Fresher specimens are to be obtained than at Burnthouse, one of which (3,569) is seen under the micro- scope to consist of fibrous pale green matted hornblende ; iron ores, surrounded by rims of sphene; felspars, partly simply twinned, partly untwinned, and partly polysynthetic. The latter are fractured, but in many cases their original outline can be detected. In other cases, however, (3,568) the felspar has been entirely decomposed to micaceous aggregates. Another specimen (3,567), which appears to belong to the same mass, shows the igneous rock to be " brecciated and to contain veins of pyroxene and quartz, which may be ascribed to secondary alteration and the meta- morphic action of the adjacent granite. Pengreep and TrevisJcey. — This greenstone, like that of Ponsa- nooth and Bellevue, flanks the Carnmenellis granite, and its junction with the slate can only be approximately defined. It is about 1^ miles in length, and its extreme breadth exceeds a third of a mile. It forms an irregular lenticle, the western portion of which con- tracts more rapidly than the eastern part. In the neighbourhood of Trebowland Vean it is only separated by about 70 yards from the granite. Notwithstanding its extent, the rock is of much finer texture than the mass extending from Bellevue to Ponsa- nooth. While portions are as coarse as in the latter., the greater part of the rock is of fine grain. Moreover, its texture is exceed- ingly variable, as may be seen within the compass of a limited »" Report on the Geology of Cornwall," &c., p. 484. 44 IGNEOUS SOCKS. section. This is well exhibited in the quarry at Devis (half mile S.S.W. of Grwennap) where patches, the crystalline nature of which is easily visible, succeed bands so fine in tiexture that the crystals can only be detected with a lens. Both types, more- over, alternate sharply with zones that are very finely sheared. The mass has evidently undergone considerable compression, the finer, more compact zones and those of coarser texture having been packed and squeezed together, and shearing set up along the latter type. The rock is partially mineralised, with secondary pyritous products, while quartz veins apparently mixed with epidote cross the prevailing banding. Some of the finer cross veins are hornblendic. Under the microscope all these bands are seen to be slightly schistose. Those most foliated consist of fibrous green actinolitic hornblende, arranged to form irregular wavy folia; the crystals are small and in some bands are densely matted, while in others they are scattered through a ground mass of felspar which is finely granular and shows no crystalline form. Epidote is common in very minute grains, and there are comparatively large masses of iron oxides and pyrites (3,443). The two less (schistose bands are rocks of essentially the same type, but contain in addition some fine scaly deep brown biotite, which in all ptobability indicates contact alteration. The eastern portion of the mass near Pengreep is partly of coarser texture, a specimen of which (3,368) bears a strong resem- blance to the rock described from Bellevue (3,367). It consists of large crystals of fibrous hornblende, while the felspar is partly idiomorphic and partly granulitic, and the section shows foliation planes. The iron ores in this rock are well preserved. A finer- grained rock from the same locality resembles the greenstone of Devis Quarry. It shows no sign of crushing beyond traces of shear planes like those in the last specimen. Th* felspar is much weathered, and there is a little brown biotite. This greenstone is pierced at Burncoose by an elvan dyke. It is seen in a quarry amid the adjacent killas, but it is not now visible within the greenstone zone itself, where the land is under culti- vation. De la Beche, however, states that it traverses that rock.* A small mass of greenstone occurs beyond the main band about a mile to the north-east of Burncoose. Its limits, however, cannot be precisely defined, as its presence is only detected by the debris turned up in the soil. In the larger mass quarries have been opened, the principal of which are at Devis and near Gear. Area East of Penetn.— The greenstones of this district occur in a zone from Eestronguet Creek on the north to the neighboui-- hood of Falmouth on the south, and are most strongly developed in Penryn Creek, where they are seen both on the Flushing and the Falmouth shores. They occupy smaller bands than niost of those already described, are usually highly decomposed, but appear to be less sheared and are marked by a more acid composition. * Report previously cited, p. 186. GREENSTONE, 45 The most extensive of these tnaiises is seen at Flushing, tvt the entrance of Penryn Creek, where it has a breadth of about 200 yards ; it ascends the hill for about 350 yards and then disappears. The rock has been extensively quarried, and formerly a silver lead lode was worked along its eastern margin at Wheal Clinton. It occurs at the extreme limits of the metamorphic aureole, and its easterly margins have a knotted appearance. Apart from this, the rock does not appear to have sufifered from contact alteration. It is usually much decomposed, with an occasional tendency to a foliated arrangement. The colour is pale green and the texture is fine, but can be resolved by the naked eye into an admixture of felspar , and a green chloritio mineral. Under the microscope (3,373) it is seen to be largely made up of felspar, very little granulitised, but consisting mainly of large and often idiomorphic individuals, though frequently broken. The hornblende has all decomposed to chlorite, and the iron ores are weathering to leucoxene. The rock is a somewhat basic andeaite that has suffered but little from cataclastic movements. The rock is not visible on the Falmouth shore,* but two out- crops that occur along the same line on the east and south of Penwerris appear to be identical with it in composition. The former has been quarried along a band of white quartz about 8 yards wide, while the latter can only be detected by the detritus among the soil. Where the texture is finest it appears to have been cleaved. The following analyses of these rocks were made by Mr. J. H. Collins.t The first refers to the rock at Flushing, and the second to that east of Penwerris from Beacon Hill : — SiO, Al.Oj Fe,03 FeO CaO MgO K2O Na^O H2O } I. II. 55-45 53-30 25-95 24-48 6-07 12-02 1-26 0-73 2-39 3-75 1-48 trace 4-30 1-27 2-85 4-70 99-76 100-25 , Sp. Gr. - - - 2-66 2-72 * It was apparently noticed, however, both by Mr. Collins, and later by Mr. F. J. Stephens on rhe Falmouth shore south of Green Bank Pier. Trs. E. &.S. Corn., 1896, vol. xii., part ii., p. 51. + Jovrn. Roy. Inxt- Corn., vol. viii., p. 202. In that publication Mr. Collins has included these greenstones with the mica traps. See paper on the plutonic and other intrusive rocks of West Cornwall by J. B. Hill. Tn. R.&.S. Corn., vol. xii., p. 7., 1901. Mr. F. J. Stephens noted its difference from the normal mica traps of the district in a paper on the greenstones of Penryn Creek in 1896, one of which he considered to be an altered asli bed. Trs. Jt. &. 8. Corn^ , vol. xii., part ii., p. 49. 46 IGNEOUS KOCKS. On the south side of Penryn Creek, below Penwerris Church, two greenstones are seen about 55 yards apart. The easterly mass has a width of about 80 yards, but the whole breadth of outcrop is not visible. At its eastern niargin the rock is most massive, enclosing harder and -fresher cores. It is grey in colour, and vesicular, and even in the finer and less massive portions tiny felspars project on the weathered surface. The rock is much decomposed, even where most solid, and the boundary with the slate is not seen. The westerly mass is exposed for about 12 to 14 yards, but it may be larger. It is more decomposed and never solid, but tiny felspars can be detected on the weathered surface. Above high-water mark it is brown and friable. The bed contains similar vesicles, notwithstanding that it is more cleaved than tEe band to the east. Under the microscope a specimen from the latter and more solid mass (3,565) is seen to be a much decomposed, and practically unsheared, porphyritic and vesicular igneous rock which apparently belongs to the trachyte group. It contains abundant phenocrysts of idiomorphic felspar, some of which are untwinned, but most are-simply twinned on the Carlsbad plan ; a few are plagioclase. These lie in a giound mass composed of small felspar crystals, and filled with small scales of secondary mica and chlorite, so that the original structures can no longer be deciphered. The abundant steam cavities are filled with granular quartz, mica, and chlorite. So far as the micro-section shows, this rock is practically unsheared, the porphyrilic felspars are unbroken, and the vesicles retain their original irregular shape, but the hand specimen indicates that it has been subjected to a certain amount of deformation. These bands appear also on the northern shore of the creek west of Flushing, where they are only about 15 yards apart. Here they are much disturbed by interfolding with the slates, and by small faults and thrusts that are often so closely arranged that the truncated cores are reduced to the thickness of a foot. At Mongleath, about a mile to the west of Falmouth Parish Church, a highly decomposed greenstone has been quarried that is probably allied to the rocks last described. It is a lilac grey tine- grained rock in which small felspars are seen in the more solid portions. The boundary with the slate is not seen. Under the microscope (3,564) it is so much altered and decomposed as to entirely lose its original character. It consists principally ot a turbid felspar in very irregular grains, decomposed and obscured by abundant enclosures of biotite, chlorite, and iron ores. Ihese felspars are mostly untwinned, sometimes simply twinned, rarely polysynthetic. They are never idiomorphic, but form niasses of extremely irregular shape. The other minerals form small specks. or tiny flakes. Biotite is the most common ; it is usually irregu- larly scattered, but is in some parts arranged along dehnite curving lines. Irregular black patches of iron ore are frequent, and there is a good deal of disseminated chlorite. There is here and there a very small quantity of quartz, and diffused ferruginous stains are conspicuous in places. Dr. Flett is of opinion that the rock is undoubtedly igneous, that it is both decomposed and GREENSTONE. 47 sheared, and belongs, in consequence, to the greenstone group. It is exceptional in the absence of hornblende, the abundance of felspar^ and the general resemblance it presents to the paler fels- pathic andesites. It may even approach the trachytes, but without detailed chemical analysis its affinities cannot be determined. To revert to the sections along Penryn Creek, a small green- stone mass occurs on the southern shore near Beyers Cellars. It is a grey massive band, fine grained, cleaved, and much decom- posed. It varies in width from 6 feet upwards. The ground is so disturbed by small fractures as to obscure its relations to the slate. It weathers with a yellowish brown crust, and fresh portions are difficult to obtain. It appears to be very felspathic, and is probably related to the greenstones of Penwerris and "Flushing already described. This rock has been considered as a volcanic ash* but there does not appear to be good grounds for separating it from the bands just referred to farther east, the igneous origin of which is clear. Between Penryn Creek and Eestronguet Creek a few greenstones are met with. They can seldom, howeverj be traced for any distance, and are usually highly decomposed, and in most cases seem to be allied to the andesitic greenstone of Flushing. At Carclew one of these bands is sufficiently fresh for microscopic examination (3,563). It contains large patches of chlorite, mixed with granular felspar, a little quartz, and iron ores in large grains. Hornblende is less common, having usually weathered to chlorite. The rock is both decomposed and sheared. A band appears to extend from Sailor's Creek to Woodlands where it has been quarried, both at the latter locality and near Trevissome Farm. On the south side of Eestronguet Creek, about one-third of a mi[e north-west of the quay, there are three exposures of decomposing greenstone, one of which is 30 yards broad. These, like the band last described, have suffered but slight deformation from mechanical stress, and resemble the andesitic greenstone of Flushing. A similar rock is met with on the shore of Carrick Koads, below Great Wood, only 4 or 5 feet in width, in which shearing has proceeded further. The greenstone coloured on the old map to the east of Trevissome Farm was not seen in our survey, but Mr. Collins confirms its existence at that locality.t Camborne and Eedruth District. — The greenstones of this area are distinguished by a basic composition, a fine-grained tex- ture, a more or less uniform shearing, and the presence of veins that are frequently strongly garnetiferous. A broad band extends south-westerly from Camborne to the margin of the map. In a north-easterly direction, from Camborne to Treleigh, the band is apparently discontinuous. It is, moreover, found in isolated bodies in the mine workings of this area, as at South Eos- kear, East Pool, and many other localities. The boundaries * P. J. Stephens. Transi Boy. Geol. Soo. Corn., 1897. t Journ. Hoy. Inst. Corn., vol. viii., p. 194i, AJr, Collins, however, has included this band amongst his njica traps. 48 ' JGNEOirS EOCKS. of this greenstone can only be approximate! j drawn as sections and surface exposures are few. An exeeUenfc section, however, is afforded by the railway cutting west of Camborne Station, where an elvan is seen to traverse it. Two smaller patches of greenstone are dissected by the railway cutting between Cam- borne and Pengegon Coombe. It has also been quarried in the neighbourhood of Tuokingmill. In other localities reliance has to be placed on the rock fragments of the soil and on local information. As this stone has been extensively utilised for the building of hedges and other purposes, and as the blocks employed are often of enormous size, great diflBculty is experienced in dis- criminating the nature of the country rock where sections are scarce, greenstone debris often predominating where slate con- stitutes the bedrock. The railway cutting between the goods shed at Camborne Station and the bridge near Osborne House affords a continuous section of the garnetiferous greenstone for a length of one-third of a mile, and exposes its junction with the slates. The green- stone is of exceedingly fine texture, and is usually very closely banded. It is seldom massive, but is generally rudely fissile and decomposing, with a tendency to cleavage somewhat like the slates. It frequently weathers to an ochreous crust, and is often friable and soft. The rock is not only characterised by an absence of vein quartz, but by the presence of abundant veins of brown garnet. The veins are often two or three inches in thickness, and are at times so closely packed as to occupy half the mass of the rock. They are usually, however, much thinner, and are often represented by mere cores, some of which are of small size. They are parallel to the banding of the rock, in the crumpling of which they share. They are not confined, however, to these planes, which they frequently transgress, and often coalesce. The garnetiferous veining is bounded by a very pale greenish margin, contrasting strongly with the darker green matrix of the rock. Moreover, veins of this nature are common in which the garnet is absent. This mineral occurs both in a massive condition and in well-defined crystals, while the veins fre- quently decompose into ochreous material. The junction with the slate is seen at both ends of the section, but the disturbances which have affected both rocks do not admit of its precise nature being determined. Under the microscope (3,919) the greenstone is seen to consist of small green horn- blendes, arranged in strings and bundles in a matrix of clear granular felspar, so fine grained as to form in some places almost a crypto-crystaliine mosaic. Besides grains of iron oxide occa- sionally converted into sphene, clear brown biotite and chlorite are present, but no garnet. At Weeth Farm, at the spoil heap of Gustavus Mme, a specimen of greenstone of the same general type was veined with green hornblende, quartz, and greenish pyroxene (3,920). Another fragment in a field from the same locality (3,921) is a fine-grained greenstone traversed by one of the pale green veins formerly alluded to, the latter consisting of GREENSTONE. 49 granular pale green or colourfess pyroxene, mixed with micaceous products after felspar. Epidote is rare or absent in the vein, and there is no garnet, but it is cut by another which is filled with colourless fibrous highly-polarising minerals, probably of the zeolite group. In a quarry near Tuckingmill Gasworks a gar- netiferous patch in the greenstone (3,922) consists of pink isotropic garnet, sometimes zonal, frequently intergrown with epidote, and never distinctly idiomorphie, but often in skeleton crystals. It is mixed with pale green pyroxene, colourless epidote, chlorite, granular and crystalline sphene, and colourless micaceous patches which are secondary after plagioclase felspar. Hornblende occurs in the greenstone, but very seldom in the vein. Calcite, although not visible in the slide, occurs in the hand specimen in large patches. There are some fairly large crystals of pyrites and a few scales of chlorite. The greenstone met with in North Pool Mine, presumably from the Daubuz lode, has been brought to the surface at Broad Lane. A specimen shows the rock to be full of parallel bands or veins of the pale green material in which garnets are interspersed. Under the microscope (3,923) it is seen to consist of fibrous horn- blende, epidote, weathered felspar, and chlorite, with pyrites, a few grains of garnet, sphene, a small quantity of carbonates, and occasional traces of pyroxene, but epidote and felspar are the principal constituents. The epidote is pale greenish yellow, and very similar to the pyroxene, though not so green in colour. The hornblende may be partly secondary after pyroxene. The weathered felspar is nearly always untwinned, and may be an orthoclase. The garnet is more conspicuous in the hand specimen than in the slide. The veins in this rock, therefore, are largely made up of epidote with garnet subordinate, which an inspection of the burrow debris suggests. The greenstone exposed in the railway cutting about half a mile north-east of Camborne Station is of the same type, although generally much weathered, but the veins are characterised by an absence of augite. One specimen (3,924) is a sheared greenstone, with finely fibrous or prismatic hornblende disseminated in a matrix of granulitic felspar with iron ores and minute grains of sphene. Small scales of brown biotite are mixed with the horn- blende. A vein of hornblende traverses the section, but this contains no garnet, pyroxene, or epidote. Another specimen (3,925) is a similar rock, but coarser in grain, in which the l^orn- blende is compact instead of fibrous, and the slide contains a little pale epidote, aogite, and sphene. Another part of this mass is a compact fine-grained sheared greenstone, but without veining. This rock (3,926) is conspicuous for the abundance of the secondary augite in its matrix. It occurs as a clear pale green pyroxene in crystals up to a millimetre in diameter, occasionally showing crystalline outline, though as a rule not displaying distinctive form. They contain a few enclosures of granular sphene or felspar, and sometimes of clear green hornblende in small compact crystals, but occasionally fibrous and radiate. These all lie in a matrix of 50 IGNEOUS EOCKS. ' minute felspars, forming a mosaic of small grains mixed with granular sphene. Epidote is scarce, although a thin vein of this mineral traverses the section, but no garnet is observed. The matrix of the rock is very like that of some of the sheared green- stones, but the large pyroxenes have evidently developed after the shearing was complete, and may be ascribed to the contact action ol The adjacent granite, two fine-grained sills of which are seen in the railway cutting to pierce the greenstone. The south-westward extension of the Camborne mass was traced by Mr. Dixon to the edge of the map and; into the adjoining sheet (351). In the latter area the rock is sometimes both un- crushed and unweathered, and constitutes an ophitic diabase, the structure of which often approaches that of a gabbro, so that its intrusive nature may be confidently accepted. To the south of Polstrong, although not deformed, it has experienced mineral reconstruction, hornblende having replaced augite, and the twinning planes of the felspar are obliterated (3,787). On the other hand, according to Mr, Dixon, "spotting" has been confined to sheared zones. A specimen of this nature from the railway cutting west of Penponds Viaduct consists mainly of pulverised felspar, containing parallel streaks of magnetite and- leucoxene, together with spots of sub-radial hornblende, epidote, and chlorite, of square or rhomboidal shape, whose absence of distortion points to their production subsequent to the deformation of the rock (3,785). Another example of " spotting " in which the felspathic constituents have been modified is afforded by the sheared green- stone exposed in a quarry to the north-east of the latter locality (3,784). The crag lying to the south of the same viaduct, on the eastern side of the valley, is formed of sheared greenstone in which the felspar has retained its original structure. Other greenstone outcrops occur at Penhale and south of Trevoole, while a rock resembling this type was noted by Mr. Dixon near Water- gate (lUogan), at a considerable distance from the nearest green- stone horizon (3,646). These peculiar intrusions, therefore, of the Camborne district are characterised by secondary veins infilled with garnet, epidote, augite, hornblende, felspar, and quartz, either singly or in com- bination. Not only are these secondary minerals disposed in veins, but, with the exception of garnet, occur diffused in the matrix of the rock in the same manner as the secondary biotite. These rocks lie within the aureole of contact metamorphism ot the granite, and the presence of those secondary minerals may be confidently attributed to such contact action. It may be noted, however, that where they are in closest proximity to the granite the garnet appears to be absent. Mr. J. A. Phillips* thought it probable that they also contained axinite, and considered them to represent volcanic ash beds. While their fineness of texture might well lead to the supposition that they were the meta- morphosed products of volcanic muds, their matrix frequently * On the so-called greenstones of Western Cornwall, Q.J.G.S., vol. xxxii., 1876 GHEENSTONE. 51 closely resembles that of the normal sheared greenstones, the igneous origin of which is undoubted, and their passage into coarse types that represent gabbros points unmistakably to their in- trusive origin. There is an entire absence, moreover, of clastic structure, and in this connection it may also be remarked that the presence of undoubted ash beds, or even lavas, has not been demonstrated in this part of Oornwall. The following analysis in duplicate of a garnetiferous green- stone from Cam Camborne is taken from the paper of J. A. Phillips, already cited : — Water /bygrometric - ^ combined Silica - - Phosphoric anhydride Alumina . - - Ferric oxide - - - „ persulphide - Ferrous oxide Manganous oxide - Lime . - - . Magnesia Potassa . - . - Soda ... - Specific gravity = 3"03. As pointed out by Mr. Phillips, the composition of this rock closely resembles that of the metamorphosed dolerites in the Penzange district. Moreover, the only rocks in the latter area that were regarded by De la Beche as highly altered ash beds differ widely in chemical composition from the rocks at present under consideration. To the east of Pendarves House, and also at Treslothan, two bands of greenstone occur that belong to the class just described. Their exposures, however, are scanty, and their boundaries have been taken from the old map. In Eosewarne Park an^ in the north-east of Camborne there are two greenstone exposures, each of which is traversed by an el van dyke. In other localities, as at Higher Eosewarne, North Pool, and Broad Lane, where these greenstone bands have been drawn on the map, there are no surface indications, but the position of their outcrops has been approximately drawn by Mr. MacAlister from information aiforded by mine plans. The band that is quarried at Tuckingmill* is of coarse texture and is a fine-grained dark green sheared greenstone in which the characteristic veining of the garnetiferous type is absent. The quarry is extensive, so that the rock can be satisfactorily examined. Under the microscope (3,914) it is seen to consist of •14 •12 •60 •65 4830 48^41 trace trace 17-04 17^02 2-73 2-68 traces traces 9^50 941 trace trace 13^30 13-15 6-18 6^20 •30 •30 2-01 213 100^10 100^07 730 yards north by west of AU Saints' Church. E 2 52 IGNEOUS ROCKS. fibrous subradiate green hornblende, forming irregular bundles and tufted growths, mixed with granulitic felspar, iron oxides, apatite and a little brown biotite. The felspar forms a mosaic of very small grains, which resembles the ground mass of a felsite. South- Western Distkict.— An exposure of greenstone situated in . the south-western corner of the sheet, at Wheal Trannack, in the Cober Valley, and in close proximity to the margin of the Uarnmenellis granite, may be referred to here. This mass is exposed on the hillside forming the eastern banks of the stream, where it has been quarried ; the eastern tongue of the lenticle is seen in the railway cutting above, where it has been pierced by a fine-grained granite. To the west of the Cober Elver the greenstone is at present being quarried. It is a compact rock of normal type, like that already described from near Tuckingmill, but contains much more biotite, due to the close proximity of the granite, this mineral being the only ingredient due- to contact action. A specimen from the railway cutting (3,953) at the thin end of the lenticle shows acicular green hornblende, forming divergent aggregates in a matrix of finely granulitic felspar, scattered masses of iron ores surrounded by borders of sphene, and a few small crystals of apatite and pyrites. A specimen from the quarry on the left bank of the stream from the interior of the rock is coarser in grain, dark green in colour, and with bronzy areas, owing to the develop- ment of numerous fine scales of brown biotite. Under the micro- scope (3,916) it is massive, not schistose, with much pale, clear green amphibole that forms large compact masses with very irregular borders, and, consequently, differs from the aggregates of fine hornblende needles which are usual in the greenstones. This hornblende has only a very slight pleochroism and is generally perfectly fresh. Aclear matrix of fine granular felspar surrounds the hornblende, forming a mosaic of irregular, usually untwinned grains, with occasionally larger individuals, which, however, are never idiomorphic. The biotite is of a dark chestnut brown colour, and occurs in small scales, usually grouped together to form patches of irregular shape, either in the felspar or scattered through the hornblende. Small prisms of hornblende and scales of biotite lie in the felspathic matrix. There is also a little apatite and iron ores, the latter sometimes surrounded by borders of sphene. The abundance of biotite, the compact nature of the hornblende, and the coarseness of the felspar mosaic, all indicate that this rock has been subjected to contact metamorphism. II. Granite. The principal granite mass within this sheet is that of Oarnmenellis, which forms a rudely circular boss extending from BuUer Downs, about one mile south of Eedruth, on the north, to slightly beyond the southern edge of the map. On the east it extends to Budock and Penryn, while its western margin reaches from the vicinity of NancegoUan Station to the west- ward of Crowan and Garnick. To the north of the Carnmenellis GRANITE. 53 boss lie the two adjacent masses of Carn Brea and Cam Marth. Subordinate intrusions flank the Carnmenellis granite near Treluswell and Budocli on the east, and on the south-western margin from the vicinity of Orowan to the valley of the Oober. On the north side of the Carn Brea granite a small sill of aplite or fine-grained granite traverses a greenstone in the railway cutting near Pengegon. Carnmenellis Granite. — The Carnmenellis mass is essentially a muscovite-biotite granite, of acid composition, in which tourma- line is a common constituent, while andalusite is frequently present. Apatite and zircon .sometimes occur, while topaz and pinite are rare. The granite has often undergone great modi- fication, especially in the vicinity of the mineral lodes, and in these cases new minerals have been introduced. The rock is frequently porphyritic by the dispersion of large idiomorphic felspars of orthoclase and plagioclase in a finer-grained base. Such felspars often exceed an inch and, exceptionally, two or three inches in length, but seldom attain the abnormal dimensions that characterise the granites of the Land's End and St. Austell. The texture is, nevertheless, coarse as compared with British granites generally. This rock, while fairly uniform throughout, nevertheless exhibits local deviation, both as regards composition and coarse- ness. Speaking generally, the eastern margin is not only of finer texture, but is perceptibly richer in biotite. These characteristics mark also a greater part of the southern margin. On the south- west and west, however, there is no perceptible difference as regards texture, but it continues to be rich in biotite, almost to the entire exclusion of white mica. It is sometimes veined with pegmatite, especially in the vicinity of Ponsanooth. Con- temporaneous veins of fine-grained granite or aplite are common over the mass. They are less abundant, however, in the eastern portion, but are extremely numerous in the central district, while in the west two areas of fine-grained granite occupy tracts sufficiently extensive to be separated on the map. One of these, exceeding a square mile, occurs between Bolitho and Boswyn, the other forms a protruding lobe, comprising a quarter of a square mile, on the margin of the granite at Praze. The latter is a a fine-grained biotite-tourmaline-granite occurring amongst coarse granite of similar composition, to which its marginal relations are obscure. The mass between Bolitho and Boswyn yields more exposures. Over a large part of its area the fine texture is fairly uniform, often approaching that of an elvan, but veins of coarser granite are of frequent occurrence, while at times the finer type itself may contain idiomorphic felspars an inch in size. The marginal relations are usually obscure, but occasionally the fine granite sends veins into the coarser normal rock. At Crowan Beacon, however, the passage of the normal granite into the fine- grained type is seen. Here the former gives rise to tors with rudely stratiform structure which are absent in the area occupied by the latter. It passes first into a coarsely porphyritic granite, the porphyritic constituents being identical with the individual 54 IGNEOUS ROCKS. crystals of the normal rock, but lying in a ground mass of finer material. The porphyritic individuals, however, both felspar and quartz, are idiomorphic, so that with a sufficiently fine matrix we reach a rock indistinguishable from some of the elvans. iStructurea. — ^The system of jointing pertaining to the Carn- menellis granite bears a definite relation to the crystalline arrangement. There are three well-defined joint planes: one set of vertical joints, having a prevalent direction of north- north-west, is crossed by another vertical set at right angles. These two systems, in conjunction with a third set more or less horizontal, divide the whole rock into a set of rough prismatic segments. The regularity of these joint planes has been an important factor in the development of the granite industry of Cornwall. The planes which trend north-north-west are termed " cleaving-way " joints, those at right angles are the " tough- way " joints, while the horizontal planes are known as " floors " or " quartering-way" joints. The grain of the rock has been found to correspond with the position of the joints, hence their names. The " tough-way " joints, or those which approximate to an east-north-east direction, may sometimes be faults ; instances being common where the horizontal " floors " have been thrown by them as much as 2 feet, or where the joints display slicken- slided surfaces, indicative of relative displacement of the walls. Further, the fin«-grained granite and aplite veins tend to take a course parallel to these same joints, while the elvan dykes undoubtedly follow the same parallelism. The horizontal joints or " floors " producing stratiform weather- ing are characteristic features in the field. De la Beche* considered them as original structures, and the fact of their being faulted by the " tough-way " joints proves them to be older than the movements along those divisional planes. Later joints, however, occur which cannot always be dis- tinguished from the true " floors," into which they appear to merge. The intervals between these horizontal joints or "floors" increase with depth from the surface. In Pelastine quarry the joints are 60 feet apart, while in Polkanuggof quarry the disposi- tion of the joint planes would admit of blocks being raised 120 feet long, 28 feet wide, and 30 feet deep. The rock cleaves most readily along planes parallel to the " floors " or horizontal joints. The next easiest cleaving plane is that parallel to the " cleaving-way " joints, while the rook cleaves most irregularly parallel to the " tough-way " joints. An examination of numerous sections in which this triple jointing is visible appears to show a distinct tendency to orientation along planes parallel to the horizontal " floors," and to the " cleaving- way " joints, although no absolute regularity in this respect has * Report (previously cited), p. 163. This structure was also noted by Dr. Boase.— '! Treatise on Primary Geology," 1834, p. 96. t The quarries are thus designated by Messrs. John Freeman & Co., by whom they are worked. GRA^'ITE. > 55 been observed. While in many instances these planes depart from the normal direction, it is unusual to find more than one joint system deflected in the same exposure. The greatest irregularities in the jointing and' corresponding cleavage occur in the vicinity of the granite veins. The horizontal joints, although often un- dulating, are the most regular of all. The cleaving planes of the rock are not always strictly parallel to the joints^ yet, on the whole, the parallelism between the joints and the directions along which the rock most readily splits is unmistakable. From the evidence of a large number of sections there is reason to conclude that not only is there a close connection between the major joints and the grain of the rock, but that this grain is dependent on the mineral arrangement of the granite, and that all three phenomena are closely related. The crystalline structure appears to consist, 6rst, in a tendency for the mica to lie with its basal planes horizontal ; secondly, in a disposition of the felspars, both as constituents of the matrix and as porphyritic individuals, to rest with their flat sides in a similar position ; and, thirdly, in the orientation of the felspars with their long axes parallel to the " cleaving-way " joints. The first and second of these structures probably explain the proneness to cleave parallel to the horizontal joints, while the third seems to show why the rock tends to cleave in planes parallel to the " cleaving-way " joints. The rock does not differ outwardly in any marked degree from ordinary granite ; yet it has evidently undergone a rude and initial stage of foliation, whereby its component minerals have been forced to rearrange themselves in a definite direction so as to acquire a cleavage. The set of major joints, which trends approximately east-north- east, corresponds to an extensive system of fissures that has been formed in the granites and Palaeozoic rocks of Cornwall by the subterranean disturbances, to which the former owe their origin and the latter their deformation. This system of fracture is parallel with the axis of granitic intrusion, and also with the general trend of the elvan dykes and mineral lodes, both of which have occupied its fissures. These phenomena are well illustrated in the Carnmenellis mass. Within that granite, in the Mabe and Constantine districts, mineral lodes and elvan dykes are practically absent, while the east-north-east system of fissuring is almost entirely confined to the visible joints. In the parish of Wendron, which forms the central belt of that granite, this system of fissuring has been so sensibly increased that the stone, which is raised on a large scale in the two former parishes, can seldom be profitably wrought. With this change elvan dykes make their appearance, likewise an extremely attenuated set of mineral veins that have been worked for tin ; moreover, the granite, which is of coarse texture, is extensively veined by finer-grained material. The east-north-east fissuring is no longer confined to the major joints, but the inter- spaces between them are very closely fractured along parallel planes. Frequently they consist of tiny cracks that sever the various crystals along their course. In the next stage, the cracks have been infilled with quartz, which has been followed by the in- 56 IGNEOUS KOCKS. troduction of schorl as an accompaniment of that mineral, and finally to almost its total exclusion. With the oncoming of wider veins the rock takes on a banded appearance, the black schorlaceous seams standing out in striking contrast to the granite. The schorlaceous veins carry tin, and in some instances it is quite clear that the lode coincides with the east-north-east joint. Over the whole district the schorlaceous bands rarely exceed a few inches in width. When this granite is followed, however, further north, towards the marginal zone, the extent of the elvans and the magnitude of both fissure and lode have reached their maximum. Microscopical Ohxiracter. — Having given a general description of this granite, it will be convenient, before touching on local characteristics, to present a brief relation of its microscopic characters. A fairly typical specimen of the coarser granite representing the interior of the mass was taken from Eathorne, in the parish of Mabe. As a whole the rock is very fresh, and is a muscovite- biotite-granite with accessory tourmaline and andalusite. The felspar is mainly perthitic orthoclase, but there is also some microcline and plagioclase. The biotite is rich brown, with strong pleochroic halos. Muscovite is common, and often occurs in parallel growth with biotite. Numerous small grains and prisms of andalusite lie scattered through the section. They are some- times nearly colourless, but others exhibit marked pleochroism, which ranges from rose pink to colourless. There are one or two irregular grains of deep brown tourmaline, and apatite is common in unusually large crystals. Zircon is present in considerable quantity, especially in the biotite. The quartz contains numerous large fluid cavities with mobile bubbles. In parts of the section the felspar is decomposed, and the biotite has passed into chlorite (3,.'i56). To the north of the latter locality, in the vicinity of Long- downs, a specimen was obtained at the junction of the normal granite with one of the finer-grained veins. Here the coarse rock is a biotite granite containing andalusite, while the finer-grained vein is a tourmaline granite (3,356). At Chywoon the fine-grained granite that occurs amongst the coarser and more normal type is a tourmaline-muscovite-granite (3,357). On the other hand, a fine-grained granite from Trevales is a muscovite-biotite-granite containing both andalusite and tourmaline. The felspar is largely perthitic orthoclase, but there is also an early generation of well-crystallised plagioclase. The biotite is deep brown, with strong halos. Muscovite is abundant, and andalusite occurs in small grains with characteristic pleo- chroism. There are a few small grains of brown tourmaline, and apatite is common (3,557). The preceding specimens, taken from the eastern region ot the granite, represent its normal condition in an area free from brecciation and mineral veins. It has been mentioned that two fairly large tracts of fine- grained granite have been mapped in the west, in the parish of GRANITE. 57 Crowan. A specimen from the more westerly mass, and near the granite margin from Trethannas, shows a fine-grained tourmaline granite with a little chlorite after biotite, and much muscovite. Perthitic orthoclase occurs in small porphyritic crystals (3,933). The corresponding granite extending from Bolitho to Boswyn shows a passage to quartz porphyry, and the quartz is often idiomorphic. A specimen fiom Crowan Beacon may be described as a fine-grained porphyritic muscovite-biotite-granite with topaz. Both quartz and felspar occur as porphyritic constituents. The biotite is clear brown and weathering to chlorite* Topaz is fairly common, but never idiomorphic. Muscovite is less frequent than usual. The ground mass is micro-granitic, and in places some- what poikilitic. Tourmaline is rare and occurs only in one or two small crystals (3,853). A specimen from the northern part of the mass, obtained from a locality a quarter of a mile south-east of Croft Michell, is really a quartz porphyry with porphyritic quartz and turbid felspars. These are often surrounded by coarsely graphic halos, but the main part of the ground-mass is micro- granitic. Chlorite is common, probably after biotite. Muscovite is mainly secondary in the felspars. There are many large rough apatites, but only a few grains of tourmaline are visible. Dr. Flett observes that the amount of micro-pegmatite in this rock is exceptionally large for a Cornish granite (3,851). A sample from the same locality, but in which mineral alteration and silicification is developing, is a porphyritic granite, with mus- covite, tourmaline, and biotite. The biotite is weathering into chlorite with strong black pleochroic halos. The tourmaline is in small ill-shaped prisms and always of a brown colour. Apatite is common. Muscovite is both primary and secondary. There is not much evidence of secondary quartz-tourmaline infiltration, although some of the felspars of the ground mass have been partly replaced by quartz and muscovite ; the porphyritic crystals, how- ever, are unaffected (3,852). Besides the normal condition of the granite, in which the original mineral constitution is still intact save for a few un- important decomposition products, there are large areas in the parish of Wendron and on the western border where planes of fracture closely traverse the granite, and in which infiltration of quartz and tourmaline has modified the character of the rock. The bands and veins of quartz and tourmaline have already been alluded to, but in addition to these secondary veins the granite itself has been converted into greisen, and the various stages of alteration can be followed from the unaltered granite into a normal greisen. Sometimes this complete change has been eff'ected within the limits of a few inches. The veins have frequently been subjected to movement and breccias produced ; moreover, by the introduction of stanniferous material into the latter, we reach the stage of a mineral vein. The lateral transition from such mineral veins into normal granite can be favourably studied in the district of Wendron. Besides the decomposition of the felspar and its replacement by quartz and schorl, the biotite has been converted into chlorite ; the tourmaline, which in the normal 58 IGNEOUS HOCKS. ' granite is usually brown, is often either entirely blue or edged by blue borders. The succeeding examples will illustrate the pro- cesses of alteration. The following specimen (3,850), taken from East "Wheal Lovell, about half a mile east by north of Hendra, represents a fine- grained granite which passes gradually into the coarse normal type. The fine granite becomes progressively studded with porphyritic felspar crystals until finally the matrix is insignificant and the felspars exceed a square inch in size. The fine-grained specimen is a muscovite-tourmaline-granite without biotite. The felspar is orthoclase with a small amount of plagioelase. The tourmaline occurs in irregular zonal brown prisms, sometimes edged with blue, and often with blue pleochroic halos, but never fibrous and rarely idiomorphic, Muscovite is common in large idiomorphic tablets, and also as small secondary scales in the felspars. Large irregular apatites are numerous, and the quartz is full of fluid cavities. The next specimen (3,854), from a locality three-quarters of a mile north-east of Hendra, is a granite which, although showing mineralisation in the field, yet in the slide only exhibits the earliest changes in the form of conversion of the felspars into micaceous aggregates. It is a muscovite-biotite-granite with tourmaline. The rock is fairly coarse in grain, and shows pink felspars, which, at a distance of rather more than an inch from the joint face are fairly fresh and have their characteristic twinning and micro- structure, but nearer the joint become dark grey and are changed into aggregates of pale shimmering mica. Silioification is not conspicuous. Muscovite and biotite are both present in well- formed crystals. The latter is decomposing into dark green chlorite. Brown tourmaline occurs in scattered grains and in spongy masses which prove to be in graphic intergrowth with quartz. It is only rarely blue upon its edges. In the next rock (3,864), from Medlyn Moor Mine, the granite is passing laterally into a quartzose modification or schorlaceous greisen. In the granite there is a little brown schorl and much muscovite, chlorite probably after biotite, and large crystals of perthitic orthoclase. In the greisen quartz preponderates, the brown tourmaline has well-marked blue borders, the felspar has disappeared, and its place is taken by aggregates of quartz, fine muscovite, green chlorite in small subradiate scales, and occasional needles of pale blue tourmaline. The original muscovite, in large stout crvstals, remains unchanged. The slide shows the various stages of alteration of the felspar, which can be clearly followed in a distance of less than a quarter of an inch measured at right angles to the surface of the fissure. In another specimen from the same locality (3,855) the felspar has practically entirely disappeared, having been replaced by quartz and muscovite. There are a few prisms of tourmaline, brown in their centres and blue on their surfaces. Apatite and chlorite are also present. This is a granite that has been con- verted into greisen. The granite is often traversed, as already described, by quartz- GRANITE. 59 tourmaline veins. A specimen was sliced from Kama Common (3,856). In the vein the quartz is granular, and the tourmaline is blue and prismatic. The granite is rich in muscovite and in chlorite after biotite, some of this chlorite being vermicular. Tourmaline is found in the granite in large brown crystals edged with blue, and apatite is rather common. The felspar is much altered and rarely shows its characteristic micro-structure, being largely converted into muscovite, quartz, and kaolin. A quartz-tourmaline vein in the granite half a mile north-west of White Alice (3,862) is filled with alternating layers of dark blue tourmaline peach, and quartz with a smaller amount of tourmaline. Some of the quartz veins are comby, but there is little or no brecciation. The next stage is represented by the brecciation of the vein- stone. A specimen from East Wheal Lovell illustrates this type (3,863). It consists of fragments of white milky quartz, with many fluid cavities, and filled with small tourmaline crystals. These are surrounded by fine dark bluish green peach, and some large crystals of brown tourmaline are also present in the slide, with their cracks and borders often fringed with blue needles. This tourmaline is frequently broken, and is probably of the same age as the early milky quartz. A few thin later quartz veins cut the whole mass. The blue tourmaline, therefore, is clearly later than the brown crystals, having filled its cracks. The following specimen from Porkellis Moor (3,857) illustrates still more clearly the progressive products of infiltration. This is a brecciated quartz-tourmaline vein, in which white fragments of quartz are lying in a dark blue matrix of tourmaline peach. This quartz is white, milky, and contains vast numbers of fluid cavities, but little tourmaline. It is surrounded by a cementing material of finely granular quartz filled with blue or bluish green needles of tourmaline, aad the whole mass is cut by later veins of clear quartz with small indigo-blue tints. The earlier quartz fragments are often crushed and give undulatory extinction ; the quartz of the later veins is granular and uncrushed. There are thus three periods of infiltration, viz. : — 1. Quartz. 2. Peach, 3. Quartz with tourmaline. Local foliation. — ^Besides the rude orientation of the granite to which attention has already been drawn, a more pronounced foliation has been occasionally set up both in the main mass and in some of the smaller sills that fringe its border. In the neighbourhood of Kennal Vale, near Ponsanooth, the granite is very distinctly foliated for a distance of about half a mile from its margin. The orientation set up is very obvious, having a strike of about north-north-west, which corresponds to the trend of the " cleaving-way " joints. Here the orientation is no longer restricted to the parallelism or a number of the elongated minerals (porphyritic felspars) producing the "grain," but there 60 IGNEOUS EOCKS. are definite planes in the rock which dip steeply towards the margin of the granite, and the mass is sometimes so foliated that its schistose character can be detected in a hand specimen. The foliation agrees in its trend and general hade with the correspond- ing planes in the slates which flank its margin, A specimen obtained one-sixth of a mile north-east of the Powder Mills, near Ponsanooth, is seen under the microscope (3,558) to be a sheared muscovite granite. The rock is pale coloured and contains very little biotite. The felspar is mainly perthitic orthoclase, much weathered with the production of secondary muscovite. Primary muscovite is common, and there are one or two grains of tourma- line, bat no andalusite. In many places the rock shows cataclastic structures. The quartz is often broken up into a mosaic of interlocking grains. The amount of crushing varies in different parts of the section and is most pronounced in certain narrow undulating bands, along which there is often a layer of parallel scales of muscovite.' About 200 yards north-north-west of Lower Tretharrup, in the district of Lanner, a fine-grained granite has been quarried. Ifc occurs within the normal granite, and is in the nature of a con- temporaneous vein. It is about 15 yards in width, but thins in a south-westerly direction. It behaves somewhat like an elvau, and hades steeply to the south-east. The normal, coarse- textured granite is rich in biotite. This mineral, however, is absent in the vein, a specimen of which, seen under the micro- scope (3,872), is a fine-grained muscovite granite, with a few crystals of brown and green tourmaline. The rock is very rich in muscovite, but contains neither biotite nor chlorite. For the following analyses of the Carnmenellis granite we are indebted to Messrs. John Freeman & Co. : — Silica - Alumina - Ferric oxide - Ferrous oxide - Lime Magnesia Sodium oxide - Potassium oxide Moisture and loss Smaller Intrusions Flanking the Carnmenellis Granite.- The smaller granite intrusions which fringe the CarnmeneHis massTre mainly confined to that P<>f io\« ,"V^f ^-^"o ^°t! situated between Crowan and the vaUey o the Cober On ho east two small examples occur near Budock, and another m tne neiehbourhood of Treluswell. . , With the exception of the bosses near Budock, these marginal intrusions usually take the form of small sill-like masses parallel Pemryn. Carnsew. 72-84 72-05 16-25 15-83 •14 -39 1-49 1-50 1-10 1-14 •55 -51 2-25 2-65 5-19 4-79 -63' -64 100-44 99-50 GRANITE. 61 to the granite border. They are marked by a texture finer than that of the main mass, and differ in mineral composition, owing to the presence or absence of tourmaline or of biotite. Some are true aplites, while in other cases the rock more properly falls under the category of greisen. Moreover, their structure shows an equal variation, some exhibiting cataclastic characters, and even foliation. An example of the latter is afforded by two sills that flank the granite margin at Treluswell, near Penryn. In the railway cutting these foliated sills are interposed between the slates, and appear to have participated in some of the stresses to which the latter have been subjected. They are about 30 yards distant from the granite j auction, and share in the hade of the slates, which dip away from the main granite. Their foliation planes correspond with the cleavage planes of the slate between which they are intercalated. Microscopic examination (3,364), shows them to be fine-grained granite, cataclastic, and distinctly foliated. The quartz is all crushed, and in addition to felspar the rock contains both muscovite and biotite. The evidence favours their modification by pressure before final consolidation, the repeated intercalation with the slate that marks their upper junctions suggesting folding. It is possible, however, that the irregularities of the junctions may represent the original in- trusion, and that the foliation may have been induced after solidification. Between Trannack and Praze, sills of granite, often closely contiguous, are exposed in the cuttings of the railway. The absence of good sections in this district precludes a satisfactory examination of the granite margin, and it is probable that the sills drawn on the map, and which are almost entirely confined to the railway cuttings, quite inadequately represent the minor granite intrusions of this tract of country. The largest mass noted is seen in the railway cutting above Wheal Trannack, at a distance of about 200 yards from the edge of the main granite. Although of variable texture, this marginal intrusion is chiefly of fine grain, often recalling the finer veins of the Carnmenellis granite. It is frequently studded, however, with porphyritic felspars, some of which attain an inch in length, but their occurrence is attended with great variation. Biotite is often very plentiful, and tourmaline is sometimes present. It differs from the main granite mass in its immediate vicinity, which is of coarse and uniform texture as far as its margin. On the valley slope, where a quarry has been opened, it is interbanded with the slate. A small sill, a quarter of a mile west of Truthall, is seen under the microscope (3,934) to be a rather fine-grained schorlaceous greisen, which has been sheared, so that the quartz and felspar are often granulitic, the quartz showing undulatory extinction, and forming an interlocking granulitic mosaic. The muscovite is bent and dragged out. The shearing, however, is not visible in the hand specimen. Another sill, occurring about half a mile west of Tregathennan, is a highly quartzose rock, containing very little felspar, and is' 62 IGNEOUS KOCKS. almost a schorlaceous greisen. It is fine-grained, with primary and secondary musoovite, orthoclase, plagioclase, and apatite (3,935). A sill situated one-third of a mile east of Chynhale is a fine aplite (3,936), with decomposed felspar and quartz in a mosaic of very irregular interlocking grains. In the hand specimen a few blebs of quartz are visible. There is no tourmaline or biotite. Cakn Brea Granite. — This granite forms a lenticular mass, trending north-east and south-west for a length of about four miles between Redruth and Pendarves. It is clearly an extension of the Carnmenellis granite, being separated from the latter by a strip of killas with an average width of little more than half a mile, while in the neighbourhood of the Condurrow and Grrenville mines the two granites more closely approach one another, the intervening killas occupying about one-eighth of a mile. The subterranean connection between the two masses is demon- strated by mining operations. This granite forms the rugged and picturesque hill of Cam Brea, where its rude prismatic jointing and coarsely stratiform structure are admirably displayed. (Plate VII.) To the north- east, after crossing Church Coombe, it contracts to a thin tongue, which extends as far as Eedruth, about half a mile distant from the western margin of the Cam Marth granite. On the south- west, from Camborne Beacon to the neighbourhood of Bottetoe Bridge, it occurs as a narrow strip, converging to a point. For the latter part of its course, however, within the grounds of Pendarves, it does not protrude at the surface, and its boundaries can only be approximately drawn. It is a tourmaline-muscovite-biotite-granite like that of Carn- menellis, and conforming to the same system of jointing, and in- cludes a similar assemblage of contemporaneous veins of fine- grained granite or aplite. On the slopes of Cam Brea it is of coarse texture, but at The Rocks, between Camborne Beacon and Pendarves, where it contracts to less than 300 yards in width, the texture is finer, but it still contains porphyritic felspars up to an inch in length. , t> i i In a quarry about a quarter of a mile north-east of Bosleake the granite exhibits a singular regularity in the arrangement of the finer-grained aplite veins. The normal rock is of coarse texture, the felspars exceeding an inch in size. Tourmaline is scarce. ' Biotite is abundant, and also white mica, the latter often a lithia mica and occurring in large plates with pinkish hues. The aplite veins are marked by a strict parallelism with a dip of 30 deg. to the south-east, and are sometimes studded with large felspars identical with those in the adjoining granite. These finer veins vary in width from six inches to one inch. Moreover, there is a subordinate system of jointing parallel to them. The « cleaving-way " joints of the granite are N. 65 deg. W with the larger felspars orientated in a like direction. The " tough-way " joints are about N. 45 deg. E. There is also a vertical system of Assuring parallel to the " tough-way " joints, which cut GRANITE. 63 through the aplites and contaiD tourmaline. The aplites are moreover disturbed by the subordinate system of parallel jointing already alluded to. The coarse granite in this quarry contains some fluorspar. A quarry on the western border of the granite, about a quarter of a mile west- south-west of Camborne Beacon, shows a mixture of fine-grained biotite-granite and pegmatite. Amongst the granite large individuals of white felspar, of irregular shapes, and reaching a size of five or six inches, are abundantly interspersed. The margin of the granite is exposed along the railway cutting between Brea and" Penhellick, and a specimen obtained at the railway cutting near Cook's Kitchen Mine shows an unusual amount of mechanical deformation. Under the microscope (3,931) it is seen to be a granulitic fine-grained muscovite granite. The quartz is much crushed, and everywhere shows cataclastic structures, and the felspar is mainly replaced by aggregates of quartz and muscovite. There are a few grains of sphene and of brown tourmaline. The muscovite is often much puckered and bent. About half a mile north-east of Camborne Station, and rather over 200 yards from the granite margin, a small dyke of fine- grained granite traverses a greenstone. It is a tourmaline granite, containing also a little biotite but no primary muscovite. Plagio- clase is common in well-formed crystals, but the orthoclase and quartz are quite irregular. The following analysis of the Cam Brea granite was made by Mr. J. A. Phillips*:-^ Water -(^yg':°.'"«^"° " '34 l^combmed - . . .gg Silica - - - - - - 74-69 Alumina - - - - 1621 Ferrous oxide - - - 1'16 Ferric oxide - - - - trace Manganous oxide - - - -58 Lime ----- .gg Magnesia - - '48 Potassa ----- 3.54 Soda - - - . 1.18 Lithia - - _ - _ .^q 99-55 Specific gravity - - 2-64 Caen Makth Gkanite.— The Carn Marth granite forms an irregular boss between two and three square miles in size. It ex- tends from the eastern side of Redruth to St. Day, and from the vicinity of Mount Ambrose on the north to the southern slopes of Carn Marth on the south. Its southern margin approaches within * Q.J,0,S.;Yoi. xxxi., 1875, p, 339, 64 IGNEOUS EOCKS. about 130 yards of the Carnmenellis granite, in the neighbourhood of Pennance, while mining operations show that below the surface these granites still further approach one another, even if -they are not actually contiguous Its boss-like shape, however rather suggests an independent intrusion than an outlier of the Carn- menellis granite. Moreover, in spite of its general petrological relationship to the latter, its textural arrangement appears to be somewhat dififerent, while tourmaline is also probably of more con- stant occurrence. The textural character of this granite is marked by the slenderness of the porphyritic felspars, a feature which appears to give it a distinct individuality as compared with the granites of Carnmenellis and Cam Brea, and it possibly represents an independent intrusion from the same magma basin. This rock is likewise characterised by an excess of biotite, the muscovite being usually subordinate. In some cases, how- ever, the two micas are more equally apportioned. It is rare however, to find a section in which either tourmaline or biotite' are not prominent constituents, and in this respect the granite markedly differs from that of Carnmenellis. In the quarries at Carn Marth the texture is often somewhat coarse, some of the felspars measuring 1^ inches by 1 inch. In a quarry about 70 yards north-west of Carn Marth it is sub- ject to considerable differentiation and banding is common, the rock being as a whole of somewhat coarse texture, but inter- mixed with a fine-grained biotite granite, which sometimes con- tains porphyritic felspars. This fine-grained porphyritic type may occur along the horizontal floors, or as irregular veins, and sometimes in large nodular forms. In some of this granite there are concentric selvages. In one instance a coie of coarse dark granite three feet in diameter is bounded by a thin ring of schorl ; this is succeeded by a zone one to two inches wide of felspar, that passes outwards into granite very rich in tourmaline, parts of which are highly felspathic. In another instance the successive rings of schorlaceous and felspathic material contain felspars with a uniform orientation in- dependent of the concentric structure. In some cases the core is of fine-grained schorlaceous granite, surrounded by rings of coarser normal granite. The interbanding and concentric structures are not constant, but the various segre- gatory types are sometimes imperfectly mixed. A few of the vertical bands that coincide in direction with the " tough-way " joints contain porphyritic felspars two to three inches in size. III. Elvan. Elvan dykes are abundantly distributed in the districts of Camborne, Eedrutb, Grwennap, and Chacewater. To the east of Truro and the Carrick Eoads they have not been detected, and they are likewise absent in the belt of country that fringes the north coast. In the remaining area, lying approximately south of Carnmenellis, their occurrence is sporadic. The tract in which the elvans are conspicuous, extending approximately from Camborne ELVAN. 65 to Baldhu, also represents the principal metalliferous region. Moreover, the trend of the elvans (about east-north-east) corre- sponds with the general direction of the mineral lodes. Elvan dykes occasionally trend in other directions, but this is far from common. While some can undoubtedly be traced for two or three miles, the bulk of these dykes are continuous for only very short distances, and it is probable that the map somewhat exaggerates their general continuity. They vary from a few feet to many yards in thickness, while in some instances they attain great dimensions. They are usually very steep, and the hade in the majority of cases is to the north-west. A considerable number traverse the granite and a few cut the greenstones. No instances, however, have been observed during the progress of. the survey where the elvans and mica traps are in juxtaposition, and their relative ages, therefore, cannot be definitely fixed.* Their petrological relationship to the granite is so obvious that there can be little doubt that they represent its dyke phase. They exhibit, however, considerable variation both as regards texture and mineral composition. In their resistance to weather- ing they differ considerably, some affording excellent building stone, while others have so decomposed as to be worked for clay. Their colour ranges from pale grey to pink, while some are dark and of a greenish hue. They are frequently bounded by a finer- grained fielvage, and in exceptional cases the rock is somewhat banded. So far as this districtt is concerned, they are character- ised by a micro-granitic ground mass, which varies in texture from fine to fairly coarse. In this matrix phenocrysts are usually scattered, and they are often idiomorphic, and consist of quartz, felspar, generally perthitic orthoelase, sometimes pjagioclase, biotite, and occasionally muscovite. The porphyritic constituents may all be present, or be represented by one or two of these minerals only, but quartz is seldom absent, while occasionally no porphyritic minerals are enclosed. The porphyritic quartz is often corroded at its edges, while the felspars are frequently wholly or partially decomposed, with production of secondary white mica, and the biotite frequently passes into chlorite. Original white mica is not common as a porphyritic constituent. The minerals of the groundmass are quartz, felspar, usually ortho- elase, white mica, biotite, and apatite. Finite is rare, but tourmaline is often present, sometimes as an original con- stituent, but generally as a secondary infiltration product. The groundmass often contains micropegmatite and is occa- sionally micropoikilitic. Very frequently its felspar has been more or less completely replaced by a fine-grained mixture of muscovite and quartz. Most of the elvans are. granite-porphyries or micro-granites, and some are aplites, while others belong to the granophyres. The schorlaceous varieties are mainly confined to _ * Mr. Collins, however, has described a junction that will he referred to m the aescription of the mica traps. ^J^^- .•^: '^• Phillips has described the general petrographical characters of the Cornish elvans. Q.J. G.S., vol. xxxi., 1875, p. 334. ^6 IGNEOUS EOCKS, the great belt in which the mineral veins are situated. Tour- maline, when original, is usually of the ordinary brown colour, while the blue varieties are more commonly found as secondary infiltration products, the latter tint either pervading the entire EQineral or forming a border around the brown individuals. In the process of mineral alteration by impregnation with silica and schorl, the felspar of the rock has often entirely disappeared, and biotite has been wholly or partially replaced by chlorite. In some mineralised elvans, however, the biotite has not been attacked, and apatite has also offered considerable resistance to decom- position. As these dykes are so numerous, only a few of the more important will be described. A typical elvan is quarried at I^ansavallan Wood, about a mile to the south-west of Truro, This dyke, which hades steeply to the west, is probably at least from 25 to 30 feet thick. It is a granite porphyry, with por- phyritic felspar, quartz, and biotite. These felspars attain an inch in length, while occasionally the biotites are equally large. The quartz occurs in bleb-like forms, which sometimes exceed a quarter of an inch. The groundmass of the rock is rather coarse. For several feet from the edge of the dyke the porphyritic crystals are absent, and this portion of the rock is sometimes banded (3,358). The elvan that is quarried at Enys is of similar type, but finer in texture, and hades about 70 deg. to the east-south-east. A dyke traverses the granite for over a mile between Town- tanna and Trevales — on the old map it has been drawn for a mile farther in a south-west direction, but no evidence is at present available for such extension. At the quarry at Towntanna it occurs as a medium-grained grey elvan, 25 to 30 feet in thickness, with porphyritic felspars up to half an inch in size. It is irregularly jointed, with the prominent joint planes oblique to the horizontal. Under the microscope (3,360) it is seen to be much decomposed, with many small phenocrysts, and only a little ground- mass. This dyke, where it is quarried near Trevales, is more regularly jointed, some of the " quartering-way " joints (" floors ") of the granite being continuous into the elvan. Moreover, one of the main joints of the latter corresponds with the "cleaving- way " joint of the granite. The more horizontal joints, however, of the elvan are uneven, and cut one another obliquely. The dyke is more or less vertical, with a junction not quite regular. Its margin is veined with hssmatite, which partially stains the dyke, imparting a red colour. It is here about 18 yards in width, and its face is slicken-sided. There are some large individuals of porphyritic felspar and some quartz blebs, but the biotites are small. Under the microscope (3,361) the ground- mass is seen to be micro-granitic. An elvan which attains abnormal dimensions extends from Greensplat to Lanner Moor. From Greensplat it follows a westerly direction by Frogpool, PuUa Cross, and Grvrennap. It passes to the south of Trevince, and soon after curves round in a west-south-west direction to Lanner Moor. It varies in ELVAN. 67 width from 150 to at least 300 yards. This dyke conforms to the normal type, and contains porphyritic crystals of quartz and turbid orthoclase in a microgranitic groundmass of quartz, felspar, and secondary muscovite. Many of the felspars are entirely replaced by white mica (3,834). At Frogpool the phenocrysts are quartz, felspar, and biotite, and the matrix is micropoikilitic (3,442). To what extent the width of outcrop represents its thickness cannot be ascertained, as its hade is uncertain. The porphyritic felspars are sometimes of one-half to one inch in size, and the quartz is frequently idiomorphic. A good section is afforded by the road cutting in the hill above Comford. On its eastern boundary, two smaller dykes in the neighbourhood of Coldwind may possibly represent branches, but the evidence is insufficient to connect them with the large mass, and a like obscurity attends its western limits at Lanner Moor. The elvan dykes between St. Day and Perranwell are extremely difficult to trace. Information from mine plans has been utilised where available, but as many bands encountered underground do not appear at the surface, this source of information is far from reliable. A few of the dykes from this area will now be described. A band that can be followed from the vicinity of the large Grwennap elvan, from Grreensplat to Greenwith, and which is possibly identical with the elvan extending from Higher Carnon to Killiow, is seen at the quarry near Pencoose to hade 30 deg. to the north-west. It is about 20 to 30 yards in width, and contains porphyritic felspars an inch in length, with smaller quartz blebs and mica in a fine-grained grey matrix. It is traversed by strong splitting planes hading 60 deg. to the south- east. In the quarry near G-reenwith the rock is somewhat fresher, while under the microscope (3,441) it is seen to contain phenocrysts of corroded quartz, weathered felspar, and decomposed biotite, in a groundmass which is granular crystalline, composed of quartz and felspar, with secondary muscovite, chlorite, and calcite. Many of the elvans of this district occurring in the metalliferous area have been modified by mineral infiltration. A dyke at "Wheal Maid is a scTiorlaceous quartz-porphyry, containing small, slightly corroded blebs of quartz, with plates of perfectly colourless musco- vite, in a matrix which is a micro-granitic aggregate of quartz and untwinned felspar filled with scaly secondary muscovite. Tourmaline occurs throughout the rock in fairly large prisms, which in their centres are brown, but at their edges are blue with strongly-marked pleochroic halos, giving colours ranging from pale yellow to dark blue. Smaller prisms also occur, mostly bliie, and in some instances a brown tourmaline is enclosed in a quartz phenocryst, but blue borders are then absent. Grains of zinc- blende are also scattered through the rock (3,836). A dyke near Sparry Bottom has undergone considerable silicifi- cation. It is a dark coloured schorlaceous quartz-porphyry (3,842) containing porphyritic crystals of quartz which are not highly idiomorphic. The groundmass is chiefly quartz and muscovite, felspar being almost entirely removed, a change comparable to that r 2 68 IQNEOUS BOCES. taking place in the formation of greisen. Tourmaline is not abundant ; it occurs mostly in small irregular prisms of yellow- brown colour, rarely bluish, and never fibrous. A specimen taken from another part of the dyke shows yet further alteration (3,841), but contains abundant blebs of the original quartz pheno- crysts. The whole rock has been filled with bluish tourmaline, which forms veins and irregular patches, and it is, moreover, fractured and distinctly brecciated. Areas of granular quartz are frequently developed in the groundmass, the remainder consisting of an aggregate of fine mica and minute quartz grains, while no felspar appears to be left. The tourmaline, in very fine needles mixed with quartz, resembles the " peach " of the veinstones, but the section shows no tinstone. Another elvan from near the same locality (3,845) is more thoroughly silicified, but contains a few conspicuous quartz crystals, one of which is an idiomorphic double pyramid. It consists of a fine mosaic of quartz, chlorite, and muscovite, with iron ores, pyrites, and limonite, and was probably originally a fine-grained non-porphyritic elvan. These rocks bear the same relation to the normal elvans as do the greisens and schorlaceous greisens to the granite. In the Chacewater district, lying immediately to the north, a well-known elvan has long been quarried at Saveock Water. This rock is characterised by schorlaceous nests and patches which sometimes attain an inch in size. The dyke hades north-west, and the quarry is traversed by a cross course. The porphyritic con- stituents are felspar, which are about a quarter of an inch in size, and quartz blebs. Under the microscope (3,833) the phenocrysts of quartz and orthoclase are seen to be idiomorphic, the quartz showing few signs of corrosion and filled with large fluid cavities with mobile bubbles. Many of these cavities are negative crystals, and some contain small transparent cubes. The por- phyritic felspars are much decomposed, but are mainly perthitic orthoclase, although some are possibly oligoclase. A curious feature is the presence of porphyritic groups of coarser micro- pegmatite. Some of the porphyritic quartz is surrounded by an m-defined narrow halo of smaller quartz grains in optical con- tinuity The matrix is a microgranitic aggregate of quartz, cloudy untwinned felspar, and fine scales of muscovite. Chlorite is also present, often in radiate bundles, fairly dichroic. Ihe tourmaline is practically confined to the rounded patches seen in the hand specimen. It forms small irregular grains, highly pleochroic, in shades of blue, bluish green, and pink, and appears to fill up the interstices between the grains of quartz, which constitute the remainder of the aggregates. It never yields perfect crystals and occasionally forms radiate groups. 'J^l^e/tructure of these patches is not poikilitic, but in some parts of the section Sere are small poikilitic areas. Larger crystals of quartz occur in them, evidently phenocrysts, and lead to the conclusion that these rounded spots are due to local toijrmahnisation. Another well- marked dyke traverses Kerling Downs, where it has been quarriea. This is a greenish elvan, rather fine grained, and dipping about 40 deg to the north-west, and sometimes decomposes to a ncU ELVAN. 69 orange colour. Under the microscope (3,848) this rock retains no igneous structure, except, perhaps, the chloritic pseudomorphs after idiomorphio biotite. It consists entirely of irregular grains of quartz with highly sinuous borders, turbid with innum- erable enclosures of miisoovite and of chlorite in small scales, sometimes radiate, but mainly quite irregularly dispersed. Felspar is absent, but some of the apatite remains, and the original quartz grains may occasionally be traced, surrounded by an extensive growth of newly-deposited silica, with which it is in optical con- tinuity. Pyrites and limonite are present in small quantity. This rock furnishes a good instance of silicification by post-volcanic processes. A silicified elvan that is quarried about half a mile south-west of Chacewater has been a fine-grained non-porphyritic pinitiferous biotite granite. It is about 5 or 6 yards wide and apparently hades to the north. It contains black scales of biotite, which under the microscope (3,835) are seen to be weathering to chlorite and rutile. One large pseudomorph, consisting of scaly muscovite and chlorite, belongs to the pinite group. The mass of the rock consists of irregular grains of quartz, the felspar being almost completely replaced by silicification. Veins of granular quartz traverse the section, and in places this mineral forms nests which contain small needles of tourmaline. A peculiar clear green chlorite occurs in circular patches consisting of radiate bladed crystals, usually closely related to the infiltrated quartz and tour- maline, so that it may be regarded as a mineral of subsequent aqueous deposition, and is very similar to the chlorite of the tin -bearing veins. Another good example of a silicified elvan occurs in the same locality. Under the microscope (3,844) it shows many corroded quartz phenocrysts, and patches of scaly brown biotite absolutely fresh, some pyrites, apatite, and iron oxides. The matrix of the rock is a mosaic of rather large irregular quartz grains, which are filled with fine flakes of secondary muscovite, and no felspar is present. The secondary quartz of the groundmass surrounds the original quartz phenocrysts, usually in the form of a broad border in optical continuity with the central crystal, but easily distinguished from it by its turbidity and by the large number of enclosures which it contains. It is clear that the whole ground- mass has been reconstructed under the action of percolating siliceous solutions. Between Chacewater and the Camborne district there are numerous elvans that can be more continuously traced than usual. They lie mainly on the north side of the Cam Brea granite, and are most conspicuous in the tract between Pool and the western edge of the map, in the vicinity of Penhale Moor. To the east of Higher Cardew, near Eedrufch, a band is quarried on the margin of the Cam Marth granite, which it pierces. It is a porphyritic pinitiferous elvan (3,837), the phenocrysts being orthoclase and biotite, the latter decomposed into chlorite, together with pinite in well-formed idiomorphic small six-sided prisms. The band which cuts the granite further to the east^ and which has been 7n '" IGNEOXIS EOCKS. quarried close to the main road, is possibly a continuation of the dyke last described. It has, however, suflfered a great deal of alteration from mineral impregnation. It is a schorlaceous quartz porphyry, containing a considerable amount of orthoclase with quartz, muscovite, tourmaline, and chlorite. The rock has been porphyritic, with a rather coarse-grained quartzo-felspathic ground- mass, but this has sufifered largely from silicification, and has be- come impregnated with quartz, tourmaline, and chlorite. The tourmahne is mainly brown, but sometimes bluish yellow, grey or colourlesf . The chlorite is of the grey-green variety with high polarisation colours characteristic of the tin veins (3,846). iv.'V^^'^^ ^^'^^ pferces the Carn Brea granite, a little to the east of the Castle, is unusually coarse in texture, owing to the large number of phenocrysts. This is a granite-porphyry in which porphyritic crystals of quartz, orthoclase, and chloritised biotite are lying in a microgranitic groundmass of quartz, felspar, and scaly musco- vite. This elvan is about 12 yards wide, and nearly vertical, bome of the porphyritic felspars exceed an inch in length, and there are schorlaceous patches 2 or 3 inches in size. On either sidei;here is a chilled margin against the coarse granite about 2 or 3 feet wide, but in this fine marginal portion porphyritic fel- spars are occa.sionally scattered. At Tuckingmill a pinitiferous elvan contains rounded nodules of quartz and blue tourmaline. The phenocrysts are quartz, ortho- clase, and pinite, and the groundmass is micro-granitic with scaly muscovite (3,941). An elvan from Higher Eosewarne of the silicified type is seen under the microscope (3,942) to contain small phenocrysts of orthoclase, quartz, and chloritised biotite, in a turbid and flinty- looking groundmass, which, between crossed nicols, breaks up into irregular rounded patches of quartz, with intervening areas of fine decomposed products. The railway cutting west of Camborne Station affords an excellent example of an elvan intersecting a greenstone. The dyke which hades to the north is the usual type of granite porphyry. Phenocrysts of quartz, perthitic orthoclase, and chloritised biotite lie in a fine microgranitic groundmass, which in places is micro- poikiiitic, and apatite is common (3,939). The north-easterly continuation of this band in the direction of Camborne is obscure, but to the south-west it appears to run for some distance through^ Higher Penponds and Barripper. Another elvan traverses the greenstone for a considerable dis- tance between Weeth and the railway cutting near the western edge of the sheet. Other localities where these dykes cut the green- stone are in the grounds of Eosewarne, and on the mineral rail- way track a little to the east of the latter locality. The elvans occurring to the south of Camborne between Beacon Hill and Gear. Farm cannot be satisfactorily connected, owing to the paucity of the sections and the somewhat conflicting evidence obtained from the mining plans. On the east side of Beacon Hill a large quarry has been formerly worked, in which an elvan, about 30 yards wide, ELVAN. 71 appears to underlie north. The rock, where seen, is fine grained, but this texture may possibly represent its margin ; otherwise if this is the same dyke that occupies the railway cutting at Pengegon Coombe, just beyond the granite margin, it would appear to have undergone a considerable change in texture. It there underlies north, and is so coarse in grain that its decomposed portions might readily be mistaken for granite, the felspars often reaching three-quarters of an inch in size. The dykes that pierce the Carnmenellis granite are most abundant along its northern margin, especially at Buller Downs, Four Lanes, and Croft Michell. Between Troon and Bolenowe Crofts a grey elvan occurs, with the usual northerly hade, and contains porphyritic felspars up to an inch in size, with some tourmaline. A very coarse-textured band runs from Bolenowe Moor to Croft MicheU. It is a granite porphyry, 30 to 40 yards in width, hades steeply to the south, and presents chilled margins to the granite. A little to the east of Trebowland an elvan has been traced through Tredeague as far to the south-west as Treweege. It varies in texture from coarse to fine grain, and contains tourmaline in varying proportions, while in the coarser zones the porphyritic felspars reach three-quarters of an inch in size. Under the microscope (3,838), this rock is a schorlaceous granite porphyry, with porphyritic quartz, orthoclase, and biotite, in a rather coarse groundmass of miorogranitic quartz and untwinned felspar. There is a little brown tourmaline, and blue needles of that mineral form occasional radiating bunches. A somewhat similar rock occurs a little to the south between Angear and Treskewes, a specimen from which (3,849) is a brecciated coarse elvan with tourmaline and muscovite, and traversed by veins of quartz and tourmaline. Short rough prisms of brown tourmaline are common, but the blue variety is rare, except in the quartz veins. The groundmass is coarsely miorogranitic ; most of the muscovite and tourmaline are primary, and large irregular apatites are rather frequent. An elvan which rfccurs about three-quarters of a mile south-west of Carnmenellis somewhat resembles the dyke just described from Trebowland. Although not traced in the intervening area, which exceeds a distance of two miles, it seems to be on the same line. It is grey to pink in colour, contains porphyritic felspars up to three-quarters of an inch, porphyritic quartz, and much tourmaline, forming nests of stellate individuals as in the Trewbowland dyke. Under the microscope the rock is a schorlaceous granite porphyry (3,840), with numerous crystals of idiomorphic quartz and orthoclase, the latter having sometimes plagioclase at their centres. Biotite occurs also in large crystals, but is not common, and the presence of piniteis doubtful. The groundmass is microgranitic, and is filled with small musco- vites, while blue tourmaline with quartz forms certain rounded patches. Tourmaline is often radiate, but is usually granular, and the pleochroism of some crystals ranges from pale pink to dark indigo blue. Sometimes this mineral occurs in the interior of felspar crystals, but it is mainly confined to the groundmass. '^ IGNEOUS ROCKS. A fine-texfcured grey elvan, belonging to the aplite ^roup, occurs at Tresevern Croft, where it appears to extend for at least half a mile. After bei'ng lost sight of for a mile, it again appears at Polmarth, and can be followed for about three-quarters of a mile in the direction of White Alice. Whether the dyke is really continuous with that at Tresevern is uncertain. It is of precisely similar character, however, and is on the same line. Moreover, in neither locality would its presence have been detected were it not for the quarries and the assistance of local information. As in the quarry at Tresevern it pinches out entirely at its southern end, it is probable that the dyke reaches the surface in discontinuous strips. In this quarry it is about 15 yards wide. At the northern end it deflects to the east, and becomes intermixed with the granite, but there is always a sharp distinction between the two rocks, and pieces of granite are often enclosed in the dyke. Tl^e horizontal joints of the adjacent granite are continued through the elvan. The dyke is fine grained and of a pale grey colour, with a few small phenocrysts of clear quartz, while porphyritic felspars are rare and always small. Under the microscope (3,831) the rock has the structure of an aplite, and consists of small irregular crystals of untwinned felspar and of quartz, the felspar occasionally showing rudimentary crystalline form. Much muscovite is scattered through the slide in small scales, apparently secondary ; but there are also occasionally idiomorphic plates, which are, perhaps, primary. Plagioclase is practically absent. There are one or two small porphyritic crystals of quartz and felspar, the former not strongly idiomorphic, the latter well formed, but much de- composed. The rock is a very fair example of an aplite. In the quarry at Polmarth the elvan is precisely similar in appearance, and, like the rock at Tresevern Croft, pinches out to the south- west, after which it again widens. It is about 12 to 15 yards in breadth, and hades very steeply to the north-west. The adjacent granite is partly mineralised, due to secondary infiltration, the vertical joint separating the granite and elva;n forming a marked line of mineralisation. To the north-west of White Alice this dyke is again exposed in a small quarry with a similar hade, where it is about 12 feet wide. It may be considered as a type of elvan in which the felspar was especially abundant, but has been extensively replaced by secondary quartz and white mica (3,832). About half a mile south of Tregolls a fine-textured grey elvan occurs, in which porphyritic felspars are rare, and, as seen in the field, bears a strong resemblance to the dyke just described. Under the microscope (3,847), irregular phenocrysts of orthoclase and quartz are seen in a groundmass of quartz, felspar, muscovite, and chlorite, some of the latter being after biotite, and much of the muscovite is also secondary. Tourmaline is only represented by a few small grains, but apatite is fairly abundant. Nearly two miles further to the south-west, but along the same line, this dyke apparently reappears between Wheal Enys and Bodilly Veor. It has been quarried about one-third of a mile north-north-west of ELVAN. 73 Crelly, where the width is about 20 to 25 yards, and the hade is steep to the north-west. Under the microscope it is seen to be a fine-grained, pale grey aplite, consisting of quartz and felspar in small irregular granules, mixed with minute scales of muscovite. There are one or two large idiomorphic felspars, and here and there an idiomorphic crystal of muscovite. At Polcrebo an elvan about 16 yards in width crosses the railway. It is porphyritic, with a microgranitic groundmass of quartz, felspar, and Scaly muscovite. In this lie phenocrysts of quarts, perthitic orthoclase, graphic intergrowths of quartz and felspar, and biotite weathered into chlorite. A few of the pheno- crysts are plagioclase, and there i.s one micaceous aggregate), suggesting pinite (3,938). An elvan which in the field resembles a very fine-grained granite is quarried at Praze Station. It is grey in colour and of very even texture, but occasionally a porphyritic felspar of larger size is seen. This dyke, which is from 15 to 20 yards in width, hades to the north. It has not been observed within the granite which is closely adjacent, but it extends in a south-westerly direc- tion to the margin of the map at Little Drym. Its passage through the park at Clowance can be followed by the line of pits from which stone has been formerly raised. It has also been quarried between Clowance Wood and Wheal Sarah. Under the microscope (3,946) it is seen to contain many small phenocrysts of felspar and of quartz, in a groundmass which is partly micro- graphic and partly microgranitic. Both biotite and muscovite are present. Dr. Flett observes that micropegmatite is unusually common in this rock for a Cornish elvan, and generally forms well-developed halos around the smaller irregular phenocrysts. This rock belongs to the granophyre group. The elvan that is quarried near the roadside between Trevoole and Trenoweth closely resembles the dyke at Praze Station in outward appear- ance, but contains in addition small nests of tourmaline. In the railway cutting, about one hundred yards south-east of Praze Station, an elvan appears to pierce a fine-grained tourmaline granite. This dyke (3,944) is the usual type of granite porphyry, in which the quartz phenocrysts are slightly corroded. One or two crystals of tourmaline occur enclosed within porphyritic felspar. In the region bordering the north coast two elvans have been traced for considerable distances, one passing through Menagissey, and the other extending from Treswithian Downs to Mawla. They both hade to the north-west, and sometimes, in the- case of the latter, at a very low angle, as may be seen atlUogan. In these dykes the original orthoclase phenocrysts have frequently dis- appeared. Under the microscope the original quartz phenocrysts are bounded by a secondary outgrowth in optical continuity, while the felspars occasionally exhibit a similar structure (3,803, 3,804). Another group of dykes, extending from near Camborne to the western edge of the sheet, resembles the former, but according to Mr. Dixon their northerly hade is less, their felspars are less prone to alteration, and the outgrowths of the quartz phenocrysts are not constant. A further group occurs to the south of the latter, 74 IGNEOUS ROCKS. to which it is oblique, having a trenri more approaching east and west, and in some cases hading to the south. Mr. Dixon observes that their matrix is generally coarser, that phenocrysts are rare, and that greisen and kaolin hare been developed associated with tinstone. One of the latter type intersects a dyke of the pre- ceding group, and this evidence of posterior age, together with their pneumatolytic alteration, has led Mr. Dixon to the conclusion that the groups represent two successive periods of intrusion, the interval between which was possibly greater than that separating the latter injections from the metalliferous impregnations with, which they were subsequently charged. Elvan branches occupying north-north-west fractures occur in the cuttings west of Two Barrows, and north-west of Coswinsawsin^ The following analysis of the elvan from Newham Quarry, near Truro, was made by Mr. J. H. Collins, who describes it as a re- markably tine-grained elvan, showing almost no porphjritic character* : — Water (hygroscopic) - - - "24 „ combined . - - 2*04 Silica ... - 72-88 Alumina - - - - 14-47 Ferric oxide - - - 2-45 Manganous oxide . - - -82 Lime- ... - - -10 Magnesia . . - - trace Potash ) 7. 15 Soda j Lithia \ _ . . trace Fluorine J 100-15 IV. Mica Traps. Genekal Description and Lithological Characters.— The mica traps of this area were formerly included amongst the elvan group, but De la Beche refers to them as greenstone ; one of this type was described as an elvan from Trelissick by Mr -I. A. Phillips.t Later the mica traps of Cornwall were described by Mr. J, H Collins + who states that Mr. A. K. Barnett was the first to draw attention to this class of dyke in the Truro Eiver Subse- quently the mica traps of this particular area have been described by the author.§ The course of some of these bands is shown on the old map by faint dotted lines. In this sheet they appear to be entirely confined to the mmette • Jmr^K Hoy. Inst. Cam., vol. vi., p. 419. t C.^.fi'.-S.,vol. xxxi.,1875,p.337. ... t J(mm. Hoy. Jmt. Com., part 11., vol. vm., 1S84. § J B. Hill! Tram. Boy. Qeol. Soc. Com., vol. sn., part vu., 1902. MICA TRAPS. 75 family, that is to say, the two principal ingredients are orthoclase felspar and biotite, while apatite, quartz, and carbonates form the principal accessories. Augite has been rarely detected, and in these cases the rock is more correctly designated as augite minette. Owing to their advanced state of decomposition the felspars are not always sufficiently well preserved for identifi- cation, and it is possible that kersantites may be included in the group. In their field behaviour they bear a close resemblance to the lamprophyres of the Scottish Highlands, especially in their irregular sill-like characters and in their in- clusions. In Cornwall, however, they are far more decomposed, but this character is shared in common with Cornish rocks generally. These rocks are similar in composition, state of pre- servation, geological age, and mode of occurrence to the lampro- phyres of Giimbel, which occur as small dykes (usually running N. and S.) in the Palaeozoic strata of the Fiehtelgebirge, Thiiringer Wald and Voigtland, that occur in strata as high as the Culm measures.* In the South of Scotland and the North of England they pierce Lower Palaeozoic rocks, while in the Scottish Highlands they are allied to the newer granites, and may possibly be of Lower Old" Eed Sandstone age. In Cornwall Mr. J. H. CoUinst considers them to be anterior to the granites, an opinion that finds some support in their having undoubtedly shared to some degree in the stresses that have affected the district, as will be shown later. On the other hand, rocks of this class in Devonshire have been found by Mr. Ussher to pierce the Permian. The minettes do not occur within the granite aureole, nor do they exhibit metamorphism other than that resulting from atmospheric decomposition. They are never granulitised, but there are instances in which the micas have been bent and contorted. The biotite is sometimes bleached to a pale white colour, and in some instances this mineral has been entirely replaced by chlorite. They present a rusty brown aspect in the field, and are so weathered that fresh specimens are obtained with difficulty. They occur as sills and dykes that can be followed for very short distances among the slates, on which they have effected a limited amount of contact alteration, confined to the induration of the marginal slate for a width of six or nine inches. Their intrusive character is apparent ; the same mass which lies between the strata as a sill may suddenly divert its course and behave as a dyke, while small veins penetrate the adjoining strata. They vary from a foot in width to fifty yards, but the latter does not correspond to the thickness of the sill, which is probably consider- ably less. They frequently display spheroidal weathering, the more solid cores being encircled by concentric outer layers of exfoliating material. Flow structure is not uncommon, especially in the finer- grained marginal portions. In some rocks exhibiting fluxion * Teal], " British Petrography, "_p. 351. + Jomn. Boy. Imt. Corn., vol. xiii., p. 203. Mr. Collins considers the mica traps to have been injected " about the close of the Devonian period." 76 IGNEOTTS ROCKS. the spheroidal cores are elongated in the direction of flow, while rounded qaartz inclusions lie with their long axes in a corresponding position. Notwithstanding their decomposition, the mineral constitution of these rocks can generally be recognised as a medium-grained admixture of biotite and felspar, while in- clusions of quartz and crystalline felspathic rock are characteristic, and slate fragments are frequently seen. The inclusions both of quartz and felspar are of rounded, angular, or even of rectangular shape. Notwithstanding the abundance of quartz inclusions, this mineral does not appear to enter largely into the composition of the matrix. They vary considerably in the' distribution and abundance of felspar, some of the fresher parts appearing to be made up almost entirely of this mineral. They differ likewise in texture, some corresponding to coarse-grained dolerites, while others assume the texture of basalt. In the coarser sills the biotite plates retain their normal dimensions in the fine-textured marginal portions. They appear to have been intruded after the slates had beep cleaved, but before the cessation of the stresses. This may to some extent account for their occurrence in discontinuous patches. Some of their joint planes are parallel to the movement planes in the adjoining slates, and there is a tendency to a parallel structure and orientation corresponding to the latter. The minor faults in the adjacent killas have often affected the mica traps and heaved them. They do not penetrate the cross courses (N.N.W. faults) and are almost certainly older than those fissures. Distribution and Field Relations. — The mica traps are of sporadic distribution in a narrow belt of country running approxi- mately north and south across the map, on the horizon of the Carrick Roads and the continuation of the Fal estuary as far as Truro. In that tract these rocks occur at the following localities, viz., Pendennis Point, Penryn, on the coast of Carrick Roads below Messack ; on the River Fal at Channals Creek, and on the coast below Pill Farm (south of Trelissick), and at the entrance of Oowlands Creek and of Lamouth Creek; at Higher Trelease and PenpoU, at the western mouth of Lambe Creek, and on the shore below PenpoU Wood. To the north-west of Truro they occur near Gloweth, Boscolleth, and at Shortlane End. Of these various exposures those occurring on the coast are alone susceptible of critical study, the inland localities yielding only the decomposing surfaces of their outer crusts. One of these mica traps, originally noticed by Mr. A. K. Barnett * was analysed by Mr. J. A. Phillips,t and subsequently by Mr. J. H. Collins.J The following analysis and description of this rock is taken from Mr. Phillips' analysis of the rock from Trellissick Creek, north of Carrick Roads : — * Btport Minert' Assoc, of Oornmall and Devon, 1873 t Q.J. O.S., vol. xxxi., 1875, p: 335. + Trans. Rvy. Geol. Soc. Comrvall, vol.ix.,p. 221 MICA TRAPS. Water /bygrometric (^ combined - _ _ •34 . . 6-11 Silica - - . 47-35 Alumina - - . . _ 20-60 Ferrous oxide - . - 1-60 Ferric oxide - ^ - 3-10 Manganous oxide - - - trace Lime . . - - - 4-72 Magnesium oxide - - 6-12 Potash - - - 6-29 Soda - - 3-58 Fluorine trace 99-81 Specific gravity - 2-70 7-7 Mr. Phillips remarks that this elvan belongs to the north and south class. The width is about 30 feet, " and its colour varies from yellow or bufif to a dark chocolate-brown, in accordance with the less or greater degree to which the iron present has become peroxidised. Its general appearance is that of a rock composed of a large quantity of mica, with a little felspar, enclosing occasional crystalline fragments of quartz." " Under the microscope thin sections are seen to consist of a nearly equal mixture of quartz, felspar, and brown mica, enclosed in a felspafchic base. The felspar is monoclinic, and the quartz contains a few small gas-cavities ; but no well-defined fluid- cavities containing bubbles were observed." Dr. Teall* records that a section in the British Museum, pre- pared from a rock in the same locality, contains a nearly colourless augite, abundant apatite, and octahedra of magnetite, in addition to the constituents mentioned by Mr. Phillips, and that the rock is a typical augite minette. The dyke described by Mr. Phillips is in all probability the mass that strikes the coast about half a mile S.S.W. of Trelissick. It is here about 50 yards in width and cuts the killas at low angles. Its southern junction is dipping at an angle of 10 deg., ' while its northern wall hades at an angle of 30 deg. in the opposite direction. The latter margin is highly disturbed, and some of the mica trap is seen abutting against the slate at a distance of 12 yards from the main junction, which is apparently marked by a small thrust. The rock is much decomposed and displays spheroidal weathering. The matrix is an admixture of biotite and felspar, but it contains quartz inclusions two or three inches in size and pegmatite veins an inch in width. The quartz inclusions are often rounded and sometimes brecciated. Some of the spheroids are bound by material showing fluxion structure. It has a narrow selvage of finer-grained material confined to a few inches in width, in which the biotite flakes, however, are still of * " British Petrography," pp. 353 and 365. 18 IGNEOUS aocKS. large size. It indurates the adjoining slate for a distance of eight or nine inches. The parallelism of its joints to those of the adjoining slates, the brecciation of some of its quartz inclusions, and the character of its northern junction, points to its having shared in some of the disturbances that have affect ed the killas. A specimen examined under the microscope (3,365) shows a large quantity of biotite in long broad laths, some of which are bent, and variations from striated laths, greenish to brown in colour, to dark brownish decomposed masses devoid of structure. Apatite in elongated prismatic and in transverse sections is ver}' aljnndant and forms a striking characteristic of this rock. Turbid felspar without striation, probably orthoclase, seems to behave as a ground- mass, together with calcite and quartz ; sphene is also present. It contains likewise a green decomposition mineral, in which faint cleavage traces are discernible, as a pseudomorph, that may possibly represent angite. Two small sills are seen further south along the coast, one to two feet in thickness, about 150 and 560 yards distant respectively, the former of which has been split by earth move- ments, while about 70 yards north of the large intrusion a sill 6 feet in width has been involved in the faulting of the slate. It is probable that the resistance offered by the dyke has given rise to the fracture along its junction. At its base the rupture is slight, but its tipper junction is accompanied by much dislocation and contortion of the slate, while the sill itself has suffered from the disturbance. On the north side of Channals Creek, in the immediate vicinity, a 4-foot sill is seen 60 yards east of the Fish Pond, and about 8 yards farther east another about 2 feet in thickness, while yet another about 4 feet wide occurs about 200 yards east of the same locality. The last three dykes are highly decomposed, and these, together with those previously described, are intruded in the Falmouth series. On the south side of Channals Creek these rocks are not at present visible, although, according to Mr. Collins, four distinct bands were seen by him in 1878,* which are probably now concealed beneath the mud. , . ri • i A good example is furnished on the east side of the Carrick Eoads, about 1,000 yards north of Messack Point, which also occurs within the Falmouth series, and varies in width from 3 to 5 feet Its intrusive character is obvious, as veins extend into the adjoining slate. The sill exhibits fluxion structure, more especially on its margin, and both the spheroids and the majority of the rounded quartz inclusions that occur up to 2 inches in size he with their long axes parallel to its walls. The mica trap at Pendennis Point, near Falmouth, skirts the coast for a considerable distance below high-water mark, so that its relations to the adjoining Portscatho beds are exceptionally clear. This band, with an average width of about 6 feet, after behaving for some distance as a sill, suddenly deflects to the north and cuts transversely across the strata as a dyke. It has been * Joum, Roy. Inst. Cornwall, vol. viii., p. 194- MICA TRAPS. 79 heaved slightly by one of the numerous small faults that traverse the slates, and its veins penetrate the adjoining strata. The rock is highly decomposed, and the biotite has been bleached to a pale white colour resembling muscovite. A marked characteristic of this rock is its pronounced veining and the abundant inclusions of quartz, felspar, and pegmatite. The pegmatites form rounded cores, and some of the quartz fragments are likewise rounded, while others are angular and even of rectangular shape. The very fine-grained veins not only contain quartz fragments similar to those in the body of the rock, but in many instances rectangular felspar fragments are so abundant as to monopolise the greater portion of the veins, which vary from an inch to a foot in width. In the narrowest of these the individual felspathic fragments occupy the entire breadth of the vein. Mica trap occurs on both shores forming the entrance to Cow- land and Lamouth Creeks, to the south of Halwyn. It is about 15 feet thick and is lying at a very low angle, while the exposure on the southern shore shows the sill as strictly conforming to the bedding of the Portscatho beds. They are characterised by numerous quartz inclusions, both angular and sub-angular, one of which is 8 or 9 inches in size. The band is visible at Higher Trelease following the same direction about a quarter of a mile further north. According to Mr. Collins mica trap also occurs in Cowland Greek, in a faulted condition, which he has figured.* At Penpoll, west of Lambe Creek, a decomposing mica trap has a width of 6 or 8 yards. It is also seen on the shore below Penpoll Wood, forming a series of disconnected patches and lying nearly flat amongst highly disturbed Portscatho beds. It shares in the dislocations of the slate, and is in one instance divided by a slide plane containing slate along the line of fissure. Seeing, however, that the rock is intrusive, the slate seam may be in its natural position, and it thus served as a plane of weakness. On the opposite shore, at Victoria Point, Mr. Collins bas figuredf two mica trap dykes, 2 feet and 8 feet thick respectively, in close proximity, that share in an abrupt contortion of the killas. Un- fortunately, at the time of the survey, these rocks were not visible on account of the muddy condition of the shore, so that we are unable to confirm Mr. Collins' description. A 2-foot sill^ however is seen in the immediate vicinity (170 yards N.N.W. of Victoria Point) in a quarry, conforming strictly to the bedding of the Portscatho strata, and showing no disturbance. To the north-west of Truro these rocks are seen in the vicinity of Shortlane End, Gloweth, and Boscolleth. At the former locality they are marked by a line of pits on the farm of Car- vinack, the buildings of which have largely been constructed of this stone. At G-loweth a mica trap has been wrought, and an old quarry that formerly existed north of the road in the same locality doubtless marks a continuation of the same band. Two exposures * Jowm. Boy. Inst. Corn., vol, viii., p, 195. ■f O^, Pit., p. m, *''«^ -^ 80 IGNEOUS ROCKS. are seen nearly a quarter of a mile north of Boscolleth. Mr. Collins states* that this band is intersected at Treliske by an elvan. We were unable to discover its junction in the course of the survey, nor has another instance been recorded in the West of England of an intersection of a mica trap and elvan. Mr. Collins' statement, however, is important, as if he has correctly interpreted the nature of the intersection the relative ages of the mica traps and elvans are defined. It must be confessed that the fractured condition of the mica traps sup- ports their greater antiquity, as already pointed out by us.f Their probable association, however, with the Permian volcanic rocks, and the Carboniferous age of the elvans have naturally led to the opinion that the mica traps are of later age ; and until a section can be laid bare showing unequivocally the intersection of the two rocks the question is an open one. As Mr. Collins has not de- scribed the section showing their junction, we have no means of judging whether the evidence was sufficiently clear as to be abso- lutely decisive. According to Mr. Collins, a mica trap showing spheroidal struc- ture occurs in a quarry at Ashfield, between Falmouth and Pen- rynf , and another occurs at Penryn.§ There are doubtless other bands that have been exposed which we have been unable to trace, through the infilling of the pits from which the material was formerly raised, either as stone, or for manurial purposes. * Jowm.Roy. Inst. Corn., vol. viii.,pp. 197 and 202. + Tram. Roy. Geol. Soc. Cornwall, vol. xii., part vii., 1901. On the pm- tonic and other igneous rocks of West Cornwall, by J . B. Hill. + Journ. Roy. Inst. Com., vol. viii., p. 193. This q^uarry is at present over- grown and largely inaccessible. ' § At the back of Messrs. Fox's timber yard. We were unable to inspect the section, as it was blocked by timber. Mr. Howard Fox described the rock and noted its spheroidal structure in a paper read before the Miners Associa- tion of Cornwall in 1873. 81 CHAPTER VII. CONTACT METAMORPHISM EFFECTED BY THE GRANITE. The granite' masses of Carnmenellis, Cam Brea, and Cara Marth are in such close proximity that their metamorphic aureoles overlap. It will be convenient, therefore, to describe their contact alteration on the surrounding Jjillas without reference to these individual masses, but rather to regard the granite as a unit. Moreover, as already remarked, it has been demonstrated that the granites of Carnmenellis and Carn Brea are connected beneath the surface. The killas into which it has been intruded is con- fined to one division, viz., the Mylor series, and where it flanks the granite has been considerably altered by contact action, so that we have an encircling metamorphic aureole, the width of which exhibits great variation. While the extent of the aureole depends on the subterranean contour of the granite, the degree of metamorphism, notwith- standing a general decrease from the granite margin outwards, is by no means uniform. While this is to some extent connected with the diverse chemical composition of the killas, it can- not be doubted that the structural features must likewise con- tribute to this result. The sediments were folded, fractured, and cleaved prior to the irruption of the granite. Moreover, the compression to which they owe their deformation has taken place at depths suflSciently shallow to lie well within the zone of frac- ture. Consequently, the folds are rarely of great amplitude, as re- lief from strain has been readily afforded by actual disruption. In some instances plication is altogether absent, and fault planes have been directly produced unaccompanied by folding. More frequently, however, plication and fracture accompany one another. As a result the rock mass is divided into a series of irregular segments that may be compared to a regional breccia. The fracture planes have but slight displacement and the con- tinuity of the general dip is not seriously affected. This breccia- tion has in some cases been carried so far as to permeate the in- terstitial portion of the rock mass, so that crush breccias and pseudo-conglomerates have been extensively developed. As the ultimate result of these mechanical changes the killas is on the large scale singularly incohesive. The intrusion of the granite, in spite of the concomitant disturbances necessitated by its injection, has to some extent restored the solidity of the killas ; the contact alteration to which it has been subjected being comparable to a process of rock welding, so that within the metamorphic aureole the beds are more massive than beyond it. The heterogeneous nature of the killas due to these structural changes alone, doubt- less played an important part in controlling the chemical changes set up during the cooling of the granite. Not only must the Q 82 CONTACT METAMORPHISM EFFECTED BY THE GRANITE. rock have exhibited great variation as a conductor of heat, but the unequal cohesion would have afifected the outward passage of the thermal currents. The varying widths of the contact aureole have been already described in Chapter I. in connection with the hade at which the granite plunges beneath the surface. The differentiation of the various degrees of mineral alteration within the aureole is in this area unfortunately impossible. A study, moreover, of a series of specimens taken at progressive distances from the granite margin, leads to the conclusion that such zonal division could not have been accomplished if all difficulties in connection with the obscurity of the sections were removed. Throughout the contact zone the dominant feature is the development of spots or knots forming " spotted slates " or knot- enschiefer, which are especially marked in the argillaceous members of the killas. This peculiar aggregation of material that charac- terises the earlier stages of thermal metamorphism is, so far as the outer portion of the aureole is concerned, the sole product of alteration. It is, however, also strongly developed among the more highly modified products of the inner zone. As the rocks are mainly argillaceous, the contact minerals formed are chiefly aluminous silicates, the most characteristic of which are andalusite, muscovite, and biotite. These minerals occupy the inner zone, Andalusite is distributed for a distance of about 150 yards from the granite. Secondary white mica and biotite are especially conspicuous in the inner zone, the biotite perhaps occupying a wider range than the muscovite. Both micas, however, closely aggregated, occur generally in very tiny scales, the biotite being of the characteristic reddish brown colour of the contact type. In some areas hornfels has been produced in which the spotted structure is absent. Pyroxene and garnet have only been exceptionally noted in the contact zone, and usually in association with the greenstones. The knots exhibit various forms ; they are sometimes aggregations of carbonaceous matter, in others they represent andalusite in an imperfect state of crystallisation, while again they may be aggregates of mica and quartz. Tourmaline is occasionally present, but in this area it is not often a common mineral in the contact zone. It has been already remarked that the killas is frequently divided by shear planes that impart the mechanical structure of a schist. Con- sequently, in the inner zone of alteration mica schists have been developed, the crystallisation of which has been the result of contact metamorphism. Microscopic Characters of the Metamorphic Zone. — A description, however, of some of the micro-slides will better illus- trate the phenomena of the contact zone. At Tregarne Mill, a specimen taken from close to the junction of the killas with the granite is an andalusite slate, with large crystals of colourless andalusite, which is only rarely pleochroic, in a matrix of biotite and quartz (3,385). A specimen about 80 yards distant from the granite margin, near Penryn, is a knotted andalusite slate, showing an advanced stage of contact alteration. The mass of the MICROSCOPIC CHARACTERS OF THE METAMOHPHIC ZONE. 83 slate consists of biotite, muscovite, and qaartz, and these fornv winding, irregular, sinuous, interrupted folia. There are large paler knots, consisting principally of quartz and biotite, and others which are mainly muscovite and biotite. Many large crystals of andalusite are scattered through the rock; they are occasionally pleochroic, but are usually nearly colourless. The enclosures are biotite, naagnetite, and dark matter, apparently graphitic, and as they are sometimes arranged to form a rude cross the mineral approaches chiastolite. The folia curve around and never pass through them (3,434). About 100 yards from the granite junction, at Treviades, a knotted andalusite slate is composed principally of quartz, biotite, and muscovite. The quartz forms strongly-marked parallel bands running along the foliation. The biotite is deep brown, and is partly weathered ilito chlorite and limonite. Andalusite is abundant, although the crystals are not large, but tend rather to form aggregates of small grains. In this rock knotting is neither conspicuous in the hand specimen nor in the slide (3,435). At Penwarne, at a distance of 120 yards from the granite, the rock is essentially similar. It is roughly foliated and rather nodular, but the knotted character is not very pro- nounced (3,436). At Polwheveral, about 135 yards from the granite, a specimen shows on its surface pale, divergent, sheaf-like masses, resembling those of the garbenschiefer. Under the microscope (3,437) it consists of biotite, muscovite, quartz, andalusite with a small amount of tourmaline, magnetite, and chlorite. The andalusite is often fall of biotite, but never resembles chiastolite in the arrange- ment of its enclosures. The foliation of the rock is rude and imperfect. Specimens obtained at greater distances from the granite, where the rock is more in the condition of typical spotted slate, were also examined under the microscope by Dr. Flett. One obtained at Roscarrack, about 500 yards from the granite, is a sheared decomposed killas, that is contact altered. It consists principally of pale muscovite and quartz, with spots of clustered biotite. There is a little tourmaline, but no andalusite. The rock is a good deal sheared, and fractures pasS* through it in curved branch- ing lines that are well defined by a deposit of limonite. The contact alteration is principally displayed in this rook by the spotting (3,438). A specimen from the outer margin of the aureole, about 900 yards from the granite junction, is a grey slate much spotted on the surface (3,439). In Penryn Creek the aureole of metamorphism suddenly diverts to the eastward, forming a narrow loop extending as far as Flushing, Whether this feature, whereby the contact zone is locally enlarged to the width of a mile and three-quarters, is the result of unevenness in the subterranean contour of the granite, or to crustal movements, is not apparent. On the coast below Trevissome, in Penryn Creek, a specimen of a silky slate or phyllite, that is knotted, is seen under the microscope to be crushed, and crossed by quartz veins that are distinctly granu- q2 84 CONTACT METAMOEPHISM EFFECTED BY THE GRANITE. litic in character, and are broken and interrupted. Lines of fracture cross the cleavage, and along them the laminse of the rock are faulted, forming a sort of auawewhwngadivage. The knots are obscure, being filled with limonite, and largely com posed of mica (3,576). A little further up the creek, about a quarter of a mile south-east of St. Gluvias Church, the rock is a fine shale with prominent quartz veins. Under the microscope it consists of small plates of mica mixed with fine angular quartz There are a few rounded knots containing small crystals of biotite and quartz (3,577). At Treluswell, within 300 yards of the granite, a pyroxene homfels occurs. The sections here are very obscure, but greenstone is probably in close proximity. The shale therefore, had probably been modified by the latter before the granite intrusion. The rock is crumpled with dark wavy lines, suggesting that it was originally an argillaceous sediment,' but it is very rich in clear, shapeless crystals of colourless pyroxene, which are developed in rounded patches and along certain belts. The intervening matrix is a fine mosaic of quartz, and perhaps felspar, filled with dark opaque granules. Although having the appearance of an altered calcareous shale it is probable that the lime has been derived from the adiacent green- stone (3,380). At Ponsanooth, on the eastern side of the stream, the Mylor series is very siliceous, containing very fine-grained quartzose bands, some of which are 4 feet in thickness. A specimen selected from the latter about 100 yards from the granite junction was determined under the microscope to be a contact- altered sheared grit. It consists of a mosaic of quartz grains, which have largely lost their rounded clastic form as the result of horcfelsing. A reddish brown biotite forms wavy streaks and irregular clusters, and is apparently a product of contact alteration. Zircon, iron ores, and garnet are the principal accessories (3,447). A contact-altered shale from the same district and equally distant from the granite, one-eighth of a mile east of Cosawes, shows under the microscope the lamination and slate structure well preserved. There is no knotting, but the specimen is crosseid with veins of granular quartz. The rock consists of small angular quartz grains, with biotite and muscovite. The biotite is dark brown, quite firesh and very abundant, and its parallel scales impart to the rock a distinctly schistose appear- ance. In the hand specimen it resembles an indurated homfels (3,578). In the district of Eedruth a very coarse type of andalusite hom- fels was noticed amongst the mine burrows, about 170 yards west of Grambler. The andalusite occurs in needles, nearly half an inch in length, and somewhat pink in colour in the hand specimen. Under the microscope (3,861) it is often colourless, or shows a dichroism from colourless to pale pink. The remainder of the slide consists of muscovite, biotite, and quartz, with a few grains of brown tourmaline. The rock is an andalusite biotite MICRO-STRUCTURES — CHEMICAL ANALYSIS. 85 hornfels, in a highly crystalline condition, that has been much deconaposed. In the south-west portion of the map the actual junction of the granite and killas is seen in the railway cutting, one- sixth of a mile south by west of Trannack. Under the micro- scope the Mylor slate is seen to consist of alternating layers of grit and shale, much altered by contact metamorphism. The gritty bands are changed into a mosaic of quartz grains filled with small scales of chlorite and brown biotite, while the argillaceous layers are represented by chlorite and muscovite, with iron ores, and occasionally a little biotite. The chlorite has probably all resulted from the decomposition of the original biotite, so that the rook is a decomposed biotite hornfels. The contact structures in the grit bands are well developed, but andalusite was not found in the slide (3,951). A hornfels occurring in the railway cutting 100 yards south-east of Praze Station is likewise of the chloritic type. The biotite is replaced by chlorite, and it contains also muscovite, quartz, iron oxides, together with a little tourmaline in small brown prisms, and the rock is indistinctly spotted (3,952), To the west of Crowan the aureole of metamorphism reaches beyond Clowance to the western edge of the map, near Penhale Moor. According to Mr. Dixon, the altered belt extends thence to the north coast and connects this aureole with the metamorphic region north of Grwinear. The outer limit of the sporadic spotting has been traced by Mr. Dixon to lUogan, from which it extends to Forth Towan on one side and to Crane Islands on the other ; and be remarks that some of the spots are rhombohedral, and composed of carbonates. 4 Mr. J. Arthur Phillips, in his description of the rocks oi the mining districts of Cornwall,* gives two chemical analyses from the metamorphic aureole of this area, as follows : — Water i bygrometric ^^^^^ \ combined Silica Phosphoric anhydride Titanic anhydride Alumina anhydride Ferrous oxide Ferric oxide Ferric persulphide Manganous oxide Lime - - - Magnesia Potash Soda - - - Specific gravity - - 271 JJ"73 * Q.J.6.S., vol. xxxi., 1875, p. 322. •48 •94 ■67 2-18 67-32 67-82 •13 _ 20^85 9^56 1-66 5-02 2-83 trace . •68 1-20 2-03 2-58 trace 3-42 ■60 2-37 3-37 4^32 99-94 10009 86 CONTACT METAMORPHISM EFFECTED BY THE GRANITE. The analysis in the first column was taken from killas in the 215-fathom level of the Dolcoath Mine, while the other refers to a specimen taken from Huel Seton, Camborne, at the 160-fathom level. From the author's description the latter has apparently been more metamorphosed than the former. It will be noted that although the percentage of silica in the two rocks is almost identical, there is a marked reduction of alumina in the latter, together with an excess of iron and potassium, while man- ganese and magnesia are present in appreciable quantities. Mr. Phillips remarks that the amount of magnesia in the rock bounding the great cross course at Huel Seton, " which is tra- versed by the modified sea-water constituting the well-known lithia spring, is twice as large as in the normal killas of the locality. The magnesium of the sea-water has in this case almost entirely disappeared." Mr. J. H. Collins has described some contact-altered killas from Penryn as gneiss. The Mylor slates there, in the vicinity of the granite, have been highly metamorphosed and may be accurately designated as mica schists, Mr. Collins made an analysis, as follows* : — Combined water - - - '90 Silica - - - 76-85 Alumina - - - - 15'05 Ferric oxide - - 0-50 Ferrous oxide - - - 1"80 Lime - ... - 0-10 Magnesia - - - - 0-10 Potash ------ 1-39 Soda - - . - - 2-33 Loss - - - 0-98 100-00 Specific gravity .... 2-587 A specimen was examined by Professor Judd, who detected the presence of minute garnets. Although portions of the altered killas may contain transitional stages between mica schist and gneiss, the rock as a whole does not approach the latter category.f * Joum. Boy. Inst. Corn., vol. viii., p. 82. t The occurrence of gneiss at Penryn was contested by Mr. A. Soinevvail. Joum. Boy. Inst. Corn,, vol. vii. p. 264. 87 CHAPTER VIII. FAULTS. In Chapter III., dealing with the structure of the killas, it has been pointed out that the Palaeozoic earth movements which pre- ceded the granite intrusions resulted in a system of rock flexure and fracture that were directly related. Under the influence of compression the crust was broken up into rock segments so closely aggregated as to present on a large scale the character of a regional breccia. These pre-granitic fractures are individually of slight displacement, and their profusion is such that they cannot be delineated on a small scale map. The rock deformation in mass, which not only effected that regional breccia but evolved pseudo-conglomerates on a large scale, was brought to a close by the granite intrusions towards the close of the Carboniferous period. That volcanic phase was ac- companied by a system of rock fracture parallel to the belt of intrusions represented both by granite and elvan. These fractures have a trend of about E.N.E., and agreeing with the main trend of the sediments they form strike faults which are not readily detected. Many of them, however, occur in the mineral areas, where they form the home of the lodes. Although their average trend is E.N.B. many follow directions oblique to that course. There is another set of faults with a N.N.W. direction that are of later age, and not only cut the E.N.E. group but also the elvans, and their transverse course both to these and to the normal strike of the sediments renders them more conspicuous than the former group of faults. Many of them are known to the miner as cross courses, some of which heave the E.N.E. lodes, a de- scription of which is given in Chapter XV. These faults are especially prominent along the belt occupied by the Carnon Valley, and extending to the north coast on the one hand, and to Eestronguet Creek on the other. This system of fracture has originated since the formation of the tin and copper lodes, and their close parallelism with the Assuring produced Ijy the volcanic eruptions of early Tertiary times render it extremely probable that they should be referred to that period. , Although these two prominent types of dislocation are the products of the later Carboniferous and the early Tertiary periods respectively,' it is not implied that fractures can be rigidly assigned from their directions alone to those two phases of dislocation. Doubtless, fissures following either trend have been produced over the extended period that has elapsed since Carboniferous times. 88 CHAPTEE rX. PLIOCENE DEPOSITS. POLCEEBO GrBAVELS. A deposit of quartz gravel at Blue Pool, in Crowan, has been <*f8cnbed by Mr. W. Tyack.* As it occurs at an elevation of about 500 feet, and as remarked by Mr. Tyack does not appear to have any connection with the alluvia of the district, there are some grounds for the opinion that it represents a patch of the Pliocene deposits that formerly spread over the killas platform of this area, and the only other representatives of which are found at St. Erth, St. Agnes, and Gronsa Downs, in the adjacent maps. The deposit occurs on a common near Polcrebo, in the heart of the granite district. Mr. Tyack describes the bed as consisting of quartz pebbles, evidently akin to the spar of the district, and varying both in structure and colour. They are more waterworn than the stream deposits of the Cober Eiver, but in his opinion have been subjected to less attrition than the pebbles in the marine beaches at Loe Bar and Perrannthnoe. " They are of all sizes, from boulders as large as a pumpkin to pebbles as small as hazel-nuts; the larger ones are few in number and generally found most deeply bedded in the soft clay on which the greater part of the pebbles lie ; they are also the smoothest. The small ones are most numerous, and are generally on, or very near, the surface. Most of the pebbles are about the size of a hen's egg ; the very small ones are but slightly more waterworn than those of any river-bed pebbles in the district." The deposit occupies an area less than half a mile in length and about a quarter of a mile in breadth, and thins away towards the margin. Mr. Tyack also states that it overlies a substratum of olay, derived from the decomposition of the granite, in which some of the larger pebbles have sunk to various depths ; the subsoil being soft and saturated with water in the winter months. The gravel has been worked for tin, but it was never rich. Similar pebbles are seen about a mile distant in the valley below, at an old abandoned stream-work, at Velanhausen, but whether they were carted, or brought down by the stream, is uncertain. Mr. Tyack was of opinion that the pebbles were derived from quartz veins in a killas district, but drew attention to the fact that they occurred at a greater elevation than the killas in their vicinity ; and that, moreover, they could not have reached their position by stream deposit in the present surface configuration of the area. He attributed their origin, nevertheless, to an ancient river the traces of which have been removed by a vast amount of * Trans. Soy. Geol. Sua, Cbm., -vol. ix., pp. 177—181. POLCEEBO GRAVELS. 89 denudation that has obliterated all traces of the valley in which the river flowed. According to that observer, the few granite fragments with which the quartz pebbles are mixed are rough and angular, so that we may conclude that they were not embedded in the original gravel deposit, but represent detached fragments from the under- lying granite. Mr. Tyack was evidently of the same opinion, as he lays such great stress on the deposit having originated in a killas area. As we are unable to conceive of a river whose volume per- mitted of the transportation and attrition of the large boulders described flowing over a bedrock of granite, without the in- corporation of that material in its alluvia, the origin of these Polcrebo gravels must be sought elsewhere. As the deposit accords approximately in elevation with the old Pliocene shore-line, it is probably a relic of the marine accumula- tions that lined the floor of the Pliocene sea ; and Mr. Clement Beid, who has recently examined the deposit, agrees with this opinion.* The association of gravel and bedrock, sharply con- trasted in their lithology, may be readily accounted for by the shore deposits being swept forward by the currents to such portions of the rocky bottom as were beyond the destructive action of the breakers. * See also lemiu-ka by C. Reid, in " Summary of Progress " for 190), p. 31. 90 CHAPTER X. PLEISTOCENE DEPOSITS. I. Raised Beaches, With the exception of the Polcrebo gravels, this area affords no evidence of stratified deposits from the PalsBozoic period until the Pleistocene, the latter being represented by the raised beaches underlying the Head, which is probably n product of the glacial age. These ancient beaches* that were laid down in the Pleistocene seas, form ledges which fringe the coast seldom more than a few feet above the present sea level. The raised beaches, composed of material identical with that of their modern counter- parts, are sometimes cemented by oxide of iron that has con- solidated them into a condition of durability. In this state they offer great resistance to wave action, as is well seen in Grerrans Bay on the beach of Pendower. In some instances the ancient caves of the Pleistocene coast have been partially preserved by the- old beach floor being sufficiently consolidated to form the roof of modern caverns that have been excavated in a lower portion of the same cleft, examples of which are seen in Falmouth Bay. Ei^en on the coast-line, where beaches are absent, a tiny fringe of gravel is often visible. It may be observed along some of the steeper cliffs, where its preservation is obviously due to the durability of the cementing material, which has not only held the particles together, but has firmly bound the gravel to the rock on which it rests. Every gradation is seen between well-defined beaches and mere shreds of gravel, either cemented or incoherent, that occur in isolated strips above the present high-water mark, the degrada- tion of which causes the commingling on the modern beach of the Pleistocene pebbles with those of recent origin. The beaches of either age contain, in addition to fragmental material repre- senting the detritus of the adjacent rock formations, numerous foreign pebbles, mainly chalk flints and cherts, which in some situations are profusely distributed; They have either been swept around the coast by current action, or have been derived from a deposit more ancient than the raised beach which may fringe the coast beneath the level of the sea.t In some instances the recent rock shelf, planed by wave action, has been shaped from the more ancient Pleistocene platform. This is well seen at Sunny Cove, in Falmouth Bay, where the older platform, standing but 5 or 6 feet above the present eroded * These raised beaches were described by local geologists prior to the survey by De la Beche. See also W. A. E. Ussher on " The Recent GeoloCT of Cornwall " (articles reprinted from the Oeol. Mag.), 1879 ; and " The Post- Tertiary Geology of Cornwall " (printed for private circulation), 1879. i- Thel - - - ..... largely ( Eocene Survey), by George "Barrow. RAISED BEACHES. 91 shelf, is fringed along the coastal notch by the innermost edges of the raised beach, averaging but a foot or so in thickness, that has escaped destruction. (Plate VIII.) Notwithstanding the close juxtaposition of these Pleistocene and Eecent formations, the interval which separates them has been mariied b}' consider- able vertical oscillations of the coast-line, the evidence of which will be given later. The final results of such crustal movements have been that the relative level of land and sea more closely approximates to the old Pleistocene coast-line than in the periods that have intervened. The appearance of the ancient ledges along the present cliff faces would at first suggest that the coastal erosion due to wave action had been slight since Pleistocene times, but the explanation is to be found in the oscillations of level that Lave taken place in the interval, so that the erosion of the modern coastal shelf has been restricted to the period that has succeeded the submergence of the forest beds. Between Grerrans Bay and the Zoze Point there are three examples of the Pleistocene beach, one of which occurs at Pendower, along the north front of Gerrans Bay ; another lines the inner portion of the small bay at Portscatho ; while the last is similarly situated in the bay fronting Towan beach. The raised beach of Pendower is a magnificent example, and owes its preservation to a very thick deposit of Head, which has acted as a protective covering. It is resting on a killas floor, a very few feet above the level of high-water mark: the base consists of coarse fragments of slate and quartz with which pebbly beds of the same nature are mixed, while the upper portions consist of red and brown sandstone and sand, bound together by a cementing material of oxide of iron. It sometimes attains a thickness of 8 to 10 feet, but is often much less, and the deposit is not always continuous. This beach has been described and figured with its relations to the under- lying rocky base and the overlying Head by Mr. Howard Fox.* At Portscatho it is represented by an insignificant shelf of gravel and rusty sand, that follows the coastal shelf below the Head, a little above high-water mark. At Towan beach, how- ever, there is a more extensive exposure of Head, and the under- lying beach is consequently well preserved. On the southern edge of the deposit there is a thickness of about 15 feet of Head that overlies about 2 or 3 feet of sand and gravel, some of which is compacted by iron oxide, as at Pendower, while in other parts it is a friable deposit of gravel and sand. Continued further north, the beach deposit, as at Pendojjier, is seen to be discontinuous, and in some places appears to be represented by a gravelly clay. The raised beach here, together with the overlying Head, has been trenched by a small channel connecting Towan beach with Porth Creek, the seaward portion of which has been covered by a deposit of blown sand. In Falmouth Bayf the raised beach is also seen in a corre- , * Trans. Royal Gebl. Soo. Corrmall, 1896, p. 9. t In 1832, R. W. Fox drew attention to the raised bfeaches of Falmouth Bav. Phil, Mag., vol. i,, December, 1832, p. 471. ^2 PLEISTOCENE DEPOSITS. sponding position at the base of the Head, between Swan Pool and the Falmouth Hotel. It consists of gravel, partly cemented in which quartz is usually the chief constituent, and its base stands a very few feet above high-water mark. A little to the north of Pennance Point there is a small deposit of Head, from 20 to 25 feet in thickness, beneath which there is a layer of com- pact stratified sand from 1| feet to 2 feet in depth, the shelf being only three or four feet above high-water mark. Between Pennance Point and Maen Porth a deposit of Head lines the coast in the neighbourhood of Sunny Cove, and rests on a rock shelf a few feet above high-water mark ; moreover, as remarked earlier, this platform stands about five or six feet above another which marks the modern shore-line. In Sunny Cove the ancient beach, about three or four feet in thickness is dissected by the cleft which forms the cove, and consists of gravel, often stained yellow, and even black, and frequently very compact, while angular blocks of slate are also enclosed, especially towards its base. Between Newporth Head and Maen- Porth a small portion of the old beach is adhering to the cliff face at a height of from twelve to fifteen feet above high-water mark. Traces of this raised beach are also seen along the coast of the Can-ick Koads and the harbours of St. Mawes and Falmouth. In St. Mawes Harbour, on the coast north-east of Carricknath Point, a deposit of white quartz gravel, well rounded, and about a foot in thickness, is overlain by Head. The gravel contains also some blocks of slate, while some of the quartz pebbles are six inches in length. The deposit is only three or four feet above high-water mark, and appears to be slightly distorted from the creep of the overlying Head. Between Castle Point (St. Mawes) and St. Just the coast is lined more or less continuously with a narrow ledge of Head, at the base of which there is a deposit of quartz gravel about a foot in thickness. A little to the south of St. Just the raised beach, about a foot thick, consists of sand and gravel ; the band is not horizontal, but slightly undulating. In the upper part of the Carrick Eoads it has not been observed, although the Head is sometimes present. North of a line drawn between Mjlor and St. Just the only example is on the coast to the south of Weir Point, where a bed of quartz fragments about a foot thick is seen below a thin covering of Head. Between Penarrow Point and Trefusis Point the deposit, however, is almost continuous at the base of the Head. It averages about a foot in thickness, and consists of white quartz gravel, usually incohesive, but sometimes cemented firmly together. It is often very coarse, with blocks up to six inches in size that are more or less rounded, but at times angular. On the north side of Falmouth Harbour, notwith- standing an extensive deposit of Head that fringes the coast, the ' raised beach is almost entirely absent; a small ledge, however, underlies the Head, to the east of Wheal Clinton. Traces of the platform are met with in the cliffs arid islets along the north coast, while at Portreath and Kerriack Cove HEAD, 93 patches of the Pleistocene shingle are found firmly cemented to it by manganese dioxide. II. Head. This deposit forms an irregular accumulation, in which stony material preponderates, often reaching great depths on the coast, and overlying the raised beaches and the killas. The Head is sometimes almost identical with the subsoil, into which it frequently merges. In fact, this abnormal deposit may be looked upon largely as subsoil that has been transported to lower levels. It is sometimes stratified, and may even contain beds of sand and fairly rounded gravel ; more often, however, ifc presents an irregular accumulation of stones, niostly angular, and occasionally subangular. This formation is probably of glacial age. While nowhere on the mainli-ind of Cornwall* is there evidence of glacial action, its proximity to the icefield that lay to the north nece,ssarily entailed the rigours of an Arctic climate, under which the land was incapable of supporting any but the sparsest vegetation. The melting of the winter snows and the ice which bound the frozen .soil, acting on a surface unchecked by vegetation, probably involved the sweeping of material down the slopes that would amply account for the abnormal nature of the deposit. In its downward course it has filled the hollows on the coast-line, and covered the shelf of the ancient beach, to which it has afforded a protection, so that the thickest deposits of Head are found in the smaller bays, by the infilling of which the shore-line has been modified. Some writers have considered the Head to have been formed beneath the sea, but the phenomena which it presents can be more satis- factorily accounted for on the above hypothesis. The Head which covers the raised beach at Pendower in Gerrans Bay forms a cliff from 20 to 50 feet in height. Mr. Howard Fox described it as " composed of loam and sand, and containing occasional angular fragments of quartz, chert, and shale,"t This deposit also extends from Pendower to Creek Stephen Point ; and about a quarter of a mile before reaching the latter locality it is fully a hundred feet fleep ; this section contains also some sandy material. At Creek Stephen Point, where it is only fifteen feet thick, the basal portion consists of stratified brown sand. As the upper surface merges into the hill slope, its inland limits can rarely be ascertained, but the strip is usually very narrow. Another shelf skirts the cliff between Portscatho and Porthcurnick, and overlies the raised beach, but that coast- * In 1843 Sir R. I. Murchison, in his address to the Geological Society of London, expressed the opinion that the search in Cornwall for the evidence of ancient glaciers would be unsuccessful. The principal exponent of the theory of glacial action in Cornwall has been Mr. Nicholas Whitley. "We have failed, however, to detect any indications of glacial phenomena although some blocks herein described are of the nature of erratics that have slid to lower levels over a frozen surface. In the Soilly Isles Mr, Barrow has recently described a glacial deposit, with ice-scratched stones, that over- lies the Head, and which is attributed to the action of ice-floes Sea pp. 21-28, " Geology of the Isles of Scilly " (Mem. Geol. Survey) + Trms. Boy. Geol, Soe, Corn., 1896, p. 9. 94 PLEISTOCENE DEPOSITS. line is rapidly receding, from the effect of landslips : south of Pencabe the section is about twenty feet thick. Another exten sive deposit forms a cliff fronting Towan beach, and is in nart sandy and rudely stratified : towards the north its upper part consists of sandy material and fine gravel mixed with soil for a depth of a foot or eighteen inches. The cliff at Falmouth front nig the bay affords a good section of Head overlying the raised beach, where it is frequentlysandy and stratified, 'A thick deposit also reposes on the raised beach at Sunny Cove. Within the Falmouth estuary ledges of Head frequently line the coast. Opposite St. Mawes a deposit of this nature overlies the raised beach north-west of Carricknath Point Be- tween St. Mawes Point and St. Just Pool a similar ledge is almost continuously exposed, occasionally from 15 to 20 feet in thickness, and frequently iinderlain by the ancient beach. On the coast, rather more than half a mile south of Messack ipoint the Head is from 8 to 10 feet in depth, rudely stratified, and capped by a thin layer of loose gravel. Ou the north side of the Carrick Eeads a deposit lines the coast from Pill to within a short distance of Eestronguet (Point. Between the entrances to Eestronguet Creek and Mylor Creek are two smaller patches; one, south of Weir Point, is about 4 or 5 feet in depth, and rests' on the raised beach; the other, south of Great Wood, is 12 feet thick, and reposes directly on the rock platform of the modern shore. From Penarrow Point to Flushing it forms a well. marked ledge, sloping to the coast, and underlain almost con- tinuously by the raised beach. Another conspicuous deposit of this type fronts the shore of Pendennis Peninsula froin Middle Point to the Docks, where it has been quarried : the pit section exhibits at the base fine sand that is overlain by about 12 feet of more typical Head, which, however, is stratified; the slate fragments, instead of being irregularly disposed, lie with their flat sides parallel with the dip, which is towards the sea. Although this is a well-marked ledge, the landward boundary cannot be accurately drawn, as it merges gradually into the hill slope.* In the valleys and estuaries which converge to the Carrick Roads, deposits of Head are less frequent. There is, moreover, in the interior a difiSculty in distinguishing it from the subsoil, especially where the latter is of great thickness. Some of the inland accumulations, however, which are in the nature of drift, may have been formed contemporaneously and under the same general conditions. In the district of Bissoe, for instance, between Wheal Baddon and Wheal Clifford, the slopes are covered with debris for a depth of several feet. In the vicinity of Pennance, below Carn Marth, the slopes are strewn with granite detritus far below the granite margin. Moreover, the size of some of the blocks and the general nature of the ground preclude the possibility of the phenomena being due to the downward creep of the surface debris under the conditions that prevail at the * A characteristic of the Head that reposes on the Pleistocene platform is its smooth surface, which from a distance recalls the features of the Raised Beaches of the West of Scotland. This is especially noticeable within the Falmouth estuary, (See Plate II,) STREAM TIN. .95 present day. A more striking instance still of the transport of material from a distance is seen on the northern flank of the Carn Brea granite. A section along the railway cutting, between Carn Brea Mine and Barncoose, exposes a deposit of granite detritus, several feet in thickness, resting upon killas. In the finer material blocks of granite are incorporated, some of which attain a size of 5 or 6 feet. The granite margin is probably about 70 yards distant at the west end of the section, and about 180 yards at the eastern portion. If the ground were steep, this deposit at such a short distance from the granite would not be unusual, but as a matter of fact the land here is comparatively flat, the angle of slope being only from 1? to 2° while the declivity from the base of Carn Brea hill extending to a distance of 500 yards only averages 4". It is clear, therefore, that the larger granite blocks could only have reached their present situation under abnormal conditions, and in all probability they were detached from the summit of Carn Brea while its slopes were covered with frozen snow, over which they slid to their present position. III. Stream Tin and Submerged Valley Deposits. Stream Tin. — The stream tin industry in Cornwall is now a matter of the past, the valleys and basins in which these deposits occurred having been repeatedly worked over, and their sites now remain as tumbled and disordered ground, much of which from an agricultural standpoint is a waste. While we are unfortu- nately precluded from the examination of these deposits in their natural condition, they present interesting questions of post- Tertiary geology that cannot be overlooked. As will be seen later, at Eestronguet Creek, where the section is below the level of the sea, the stream tin deposit immediately overlies the rock shelf. This relative position of the rocky floor and stream tin, according to all accounts, holds good wherever these deposits have been worked. As observed by De la Beche,* while the submerged stream tin deposits were being covered by marine or estuarine accumulations, " the stanniferous gravel strewed down the higher parts of the valleys became simply covered by ordinary river alluvium, mingled with trees and vegetable matter ; in flat places, such as may have constituted marshy ground or shallow lakes, peat accumulating intermingled with the waste of gravels, sands, and clays, from the adjoining higher lands, in the same manner as now takes place commonly in peat -countries." The peculiar association of the stream tin with the subjacent rock, instead of being interstratified with the alluvial deposits, was ascribed by the earlier geologists to the efifects of a sweeping denudation having passed over the land, and in the words of Mr. Carne,t " the efiects produced by which have never been repeated by any subsequent flood." Moreover, the fact that the more ex- tensive deposits of stream tin occurred in the valleys that opened to the south, notwithstanding that the richer tin veins were situated in the northern region, was considered to indicate that * " Report on the Geology of Cornwall, Devon, and West Somerset," p. 406. f. Trams. Boy, Geol, Soa. Corrmall, vol. iv., p. 55. 06 PLEISTOCENE DEPOSITS. the current of the deluge* swept from the north.t This theory was apparently countenanced by De la Beche, who suggested that a great body of water crossing the Bristol Channel from South Wales carried forward the disintegrated material of the rocks that opposed it on this side of the Channel, " transporting them into the chief inequalities, and carrying them down the principal valleys, according to the directions of the minor currents pro- duced by the inequalities of the land beneath.''^ Although we have failed to detect evidence of glaciation in this part of Cornwall, it is known that glaciers reached the Bristol Channel, and its proximity to the Welsh icefield must have entailed an Arctic climate during the period of maximum glaciation. Not only does the highly decomposed condition of the surface rocks discountenance the idea of glaciaL action, but further confirmation is afforded by the absence of rock striae, and erratics from the north. As already premised, in treating of the origin of the Head, in glacial times the ground must have been covered with snow, and it is probable that the more elevated tracts lay permanently above; the snow-line. The melting of the winter snows and the ice that bound the frozen soil must have been productive of floods that swept the valley floors with a volume and velocity altogether incomparable with the insignificant and sluggish streams that water the valleys at the present day. Under such conditions, it can be readily understood that only the denser detrital matter could find a resting place along their channels. No doubt pre- vious to this period the bottoms of the valleys were not bare, but assuming that they were lined with alluvia no thicker than that which obtains at present, its removal by such torrential floods would be a simple process. It is unnecessary to assume that the occurrence of stream tin adjacent to the bedrock, without occupying higher positions between the overlying alluvia, im- plies a simple and continuous sequence of deposit with the heavier material at the base. In all probability the intervals between the periodical floods were marked by the deposition of normal alluvia. With the renewal, however, of torrential condi- tions, these lighter deposits would be swept away, just as we suppose the alluvia that originally lined the valley floor was dis- persed. No doubt these periodical scourings of the river basins succeeded in carrying to the sea much of the stream tin itself. At the close of this period, when the severity of its climatal conditions had passed away, the deposit of stream tin lying on the bedrock was the sole relic of a long period of deposition, extend- ing not only over the era which evolved such deposit, but over the period which preceded it. To put the case succinctly, the condi- tions which permitted of the formation of the stream tm mvolved the destruction of normal alluvial deposits, both older and con- temporaneous. . , i, , The explanation suggested herein to account for the phenomena • Trtmt. Oeol. Soc. Corrmall, vol. iv., p. 55. t Ihid. p. no. I Report previously cited, p. 401. STREAM TIN, 97 presented by the stream tin supports the theories advanced by the earlier observers, to the extent that both hypotheses invoke torrential conditions. Whilst their view of a general diluvial immersion and the advance of a large body of water from north to south cannot be sustained, yet the facts on which it is based are substantially correct, although admitting of a simpler interpreta- tion. That, so far as this area is concerned, the stream tin was principally located in the valleys opening on the south coast, and that the more important tin lodes lie in the northern tracts, may be admitted. These phenomena, however, appear to be in harmony with the physical features of the district. The watershed is not only nearer to the north coast, but the rivers which drain that area are shorter, and therefore of greater declivity ; consequently, more of the stream tin proportionately reached the sea. Now the rivers emptying on the south are not only of lower gradient but traverse a larger area, and also more frequently become confluent, so that their lower portions have received the deposits brought down by numerous tributaries. This is illus- trated by the river which discharges into Restronguet Creek, and contains the celebrated tin stream works of Carnon. This river system attains a total length of about 45 miles, 25 miles of which are situated in the metalliferous districts of Ohacewater, Scorrier^ St. Day, Grwennap, Baldhu, and Bissoe. Although it is true that the individual lodes of this central area are not so rich as those situated in the northern tract of Camborne and Redruth, yet the amount of stanniferous detritus spread over the surface and susceptible of denudation may quite well have equalled or even exceeded the tin-bearing detritus of the northern area, in spite of greater mineral concentration in the latter. Moreover, when it is considered that the stream tin of the northern region has been distributed by numerous rivers, whereas the drainage system of the district which culminates in the Carnon Valley converges to a single channel, the more extensive alluvial deposits of the latter are readily accounted for. Submerged Valley DEPOSiTS.-^The submergence of the land which the forest beds imply is further supported by the evidence of the deposits that will now be described. The search for stream tin has been the means of dissecting these accumulations at Restronguet below the level of the sea, where remains of a forest growth in its natural position are buried beneath deposits exceed- ing 50 feet in thickness that overhe the stream tin. The following is a section of the Carnon stream-works by Mr. Hen wood* : — ft. in. 1. Sand and mud ; the river wash n in 2. Silt and shells— three successive beds - - - - 2 „ 3. Sand and shells ,o « 4. SUt— three beds - oxfl! 5. Sand and shells - - - - " " " -oto4:0 6." Silt mixed with shells in large quantities - - ' ,„ , 1? ^ 7. Silt, in some places containing stones - - - - 18 to ii.J * Trara. Hoy, Qeol. See. Cornwall, vol. iv., p. 58. 98 PLEISTOCENE DEPOSITS. 8. Wood, moss, leaves, nuts, &c., all of a dark colour, much ft. in. resembling what has been charred ; a few oyster shells ; animal remains, those of the deer being most abundant ; and some human skulls --.. .. 16 Towards the sea the bed 8 entirely disappears, giving place to 7, which reposes on 9. The tin-ground, which consists of rounded masses of tin- ore, in some cases unmixed with any other substance, in others in a matrix of quartz, and quartz and schorl, with rounded pieces of slate, granite, and quartz, varying in thickness from a few inches to - - - - - 12 The following section was supplied by Edward Smith in 1807 * As pointed out by De la Beche, the name " Carnon Streams " has been given to a long line of works down the valley, bo that ihe section is subject to variations: — ft. 1. Mud and sand - ..... .. 7 2. Granite gravel, intermingled with small pieces of a substance resembling charcoal, and a few shells - ... 4 3. Fine gravel, mud, and shells - - - - - 12 About this depth are several irregular strata of oysters, about 4 or 5 feet in thickness, extending irregularly to within 4 or 5 feet of the tin ground. 4. Closer mud, intermingled with shells ... - 19 In this stratum have been found several branches and trunks of trees, some of which had evident marks of being cut with an axe or other sharp instrument ; antlers and bones of stags, likewise human skulls. 5. Tin-ground, varying from - - - - - - -lto2 De la Beche states that the shells from these sections which he had examined, corresponded with the species still found in the Falmouth estuary.t At the time when De la Beche wrote, the higher Carnon Works had been " abandoned, the search for stream tin in the same valley being confined to the bottom of Eestronguet Creek, beneath the tidal waters of the estuary, on the south of Daniell's Point."J These submarine operations, however, have long since ceased. Beyond the area of the present sheet a very similar section has been described at Pentuan, where human skulls are stated to have been found 40 feet below the surface, mingled with the remains of deer, oxen, hogs, and whales. Assuming these facts to be correct, then, as De la Beche remarks, " a considerable change took place in the relative levels of sea and land since man inhabited Cornwall, allowing estuary or marine deposits to be effected in creeks upon a surface that previously permitted the growth of terrestrial vegetation, the remains of the marine creatures entombed in the mud, silt, or sand showing that these creatures were of the same species as those which now exist in the adjoining sea."§ As these submerged valley deposits have only been brought to light by the search for tin, their occurrence can only m these instances be demonstrated. It cannot be doubted, however, that similar evidence exists in other valleys which extend seaward as tidal estuaries. • Trans. Oeol. Soc, vol. iv., 1817, p. 404. + Report previously cited, p. 404. j Report previously cited, pp. 404 and 405, § " Report on Cornwall, Devpn, and Wes West Somerset," p. 407. 99 CHAPTER XI. RECENT DEPOSITS. I. Submerged Forests. "While the raised beaches demonstrate the elevation of the coast- line, the presence of forest beds beneath the level of the sea point just as clearly to its subsidence. The existence of the submarine forest fronting the valley at Maen Porth has long been known. It can, however, rarely be observed, being buried beneath sand and shingle. Portions of it are, nevertheless, occasionally laid bare after heavy gales, during the lowest tides. It has been described by the Rev. Canon Rogers,* who observed the stump of an oak in its position of growth, with peaty material enclosing its roots, and containing the remains of the common yeUow flag (Iris pseudo- corus) still flourishing in the adjoining swamp. In 1895, after a succession of easterly gales, the overlying shingle was removed, and part of this submarine forest was exposed. It was described by Mr. S. Roberts,! who found the jawbone of a small horse that has been doubtfully referred to an extinct species. On the same occasion an antler of a deer was obtained by a work- man. J The mould was excavated to a depth of 3 feet by Mr. Eoberts without reaching the bottom. It emitted a noxious odour of sulphuretted hydrogen, and contained the " remains of aquatic plants, the impress of the leaves, stems, rootlets, and flags being very marked. Hazel-nut shells, hazel twig with the bark on, as well as fir cones partially deprived of their seeds, were abundant. These were so compacted together that, when removed, their prints were well-defined in the mould." The mould contained a number of trees lying in various positions, some of them from 12 to 20 feet in length, the largest reaching a diameter of 2 feet, and all yielded readily to the touch. Mr. Roberts states that some of the timber was nearly black, and some of a reddish colour, and considered that .it was represented by oak, pine, alder, willow and hazel. The jawbone was found close to a large^ pros-: trate tree trunk. "It was about 1 foot in length, and set in it in perfect order were five large teeth — the whole set — all molars, well preserved with labyrinthine crowns." In 1871 a submarine forest was laid bare at Market Strand^ Falmouth, and described by Mr. H. M. Whitley.§ The forest bed was about 7 feet thick, and its surface about the level of low-water mark, and buried beneath a bed of sand about 2 feet in. thickness, while it was separated from the underlying rock by about 4 feet of gravel. It consisted of compact peat containing the remains of flags, ferns, and trees, few of which exceeded 12 inches in diameter, * Trs. M.ff.S. Corn., vol. iv., p. 481. t Fi-a. M.G.S. Corn., vol. xii., part ii., p. 58. J Both the antler and the jawbone are in the possession of Mr. Robert Fox, of Grove Hill, Falmouth. § Joivrn. Roy. Inst. Com., 1872, No. 13, p. 77. h2 100 RECENT DEPOSITS. chiefly of hazel, oak, and fir, but beech and birch were also abun- dant. The forest bed is continuous for some distance inland along the valley known as the Moor,* while another portion of the forest was exposed during excavations at the Bar pools. In Gerrans Bay a submerged forest was observed some years ago at Porthcurnick by Mr. H. G. Handsombody, who saw tree stumps projecting from the sand at low tide. In 1898 we observed a large root at Pendower beach that had evidently been detached from the forest bed at the mouth of the valley at Pendower, which was seen quite recently by Mr. Clement Reid. At Portreath, on the north coast, peat was encountered beneath the sand in a dock excavation. While the beginning of the submergence in which these forest beds are involved may have followed closely on the termination of the glacial period, there are some grounds for the opinion that it Doay have continued to historic times. II. Marine Alluvia. Numerous beaches of sand and shingle have accumulated in the various bays along the seaboard, the most extensive of which on the south coast occur at Pendower, Porthcurnick, Towan, Falmouth, and Maen Porth. The beach at Swanpool that fronts the mouth of a valley, has acted as a natural dam and ponded back a coQsiderable freshwater lake, while in other localities the free egress of the streams has been so far checked as to produce swamps at the valley mouths, as at Gryllyngvase and Maen Porth. The deposits, however, that line the estuaries, and which are laid bare at low tide, are of far greater extent than the accumula- tions which have collected in the more sheltered situations along the seafront. The mud discharged by the streams into these estuaries is gradually filling them. At Restronguet, ships could ride at anchor considerably farther up the Creek than at present, within the memory of the present generation ; while the mud-flats of the River Fal, below Ardevora, are creeping rapidly seaward at a rate that is readily detected. Tradition avers that Tregoney was an important Roman settlement accessible to shipping, and there is historic evidence that the tidal waters reached that place in the sixteenth century. The Fal estuary is of especial interest, as the tidal flats, instead of forming banks of dark mud derived from the decomposition of the killas, consist of pale tenacious clay, brought down from the surface of the western portion of the St. Austell granite mass. That rock, being in a highlv decomposed condition, is eroded more rapidly than the kiSas'so that the material deposited in the estuary consists largely of impure kaolin from that district, considerably augmented by the drainage of the waste water from the china clay works. An instructive paper on the silting up of the creeks of Fal- mouth Haven was communicated by Mr. H. M. Whitley m 1881 to the Royal Institution of Cornwall.T The comparison between • The lower part of this vaUey was formerly the site of a tidal inlet that has since been artificially reclaimed. t Jimm., vol. vii., pp. 12—17 ; also pp. 50—52. ALLUVIA. 101 the ancient and modern charts affords conclusive evidence of the serious nature of the shoaling, and to some extent of the rate at which the mud banks are accumulating. Between the years 1698 and 1855 the bottom has risen 12 feet at Tolvern Point, and 18 feet at Trego thn an boathouse. The most extensive silting appears to have taken place in Devoran Creek, being considerably augmented there by the mining operations along the Carnon Valley. Mr. Richard Thomas, in his history of Falmouth, states that the channel opposite PenpoU has silted up 10 feet since the Admiralty survey of 1698, and at Restronguet Pool, at the higher end, where in 1698 there was a depth of 42 feet at low water, was in 1855 dry at the same period, and at the lower end there was a growth of 12 feet in the same interval ; whilst the bank between the main channel of the Haven and Restronguet " has shoaled during the same period from 12 to 3 feet at low water." Although the creeks are shoaling more rapidly than the main harbour, Mr. Thomas calculated that the silt brought down into the harbour would form a layer 1 foot thick in about 43 years, supposing it uniformly distributed through- out the haven and its branches. III. Freshwater Alluvia. Notwithstanding the extensive valley system that prevails over the area, the alluvial deposits that line its floors are comparatively meagre, while the streams that water them are proportionately insignificant. Age of the Valleys. — From what has been already said, it will be understood that these deposits have been laid down since the stream tin, even in those localities where the latter is absent, for it is evident that the cleaning out of the valleys was universal over the district. The evidence, moreover, of the submarine valley section at Restronguet, shows that these deposits which overlie the stream tin belong to the Recent period. While the age of the valleys cannot be demonstrated, they may probably be referred to the later Pliocene period. Subsequent to the emergence of the Pliocene sea floor, more ancient valleys, however, may have been sealed' beneath Pliocene deposits, the evidence of which has been lost by the removal of the material that filled them. That the valleys were enlarged in the Pleistocene epoch is very evident, as the raised beach which lines the coast of the lower portion of the Carrick Roads is not met with in the estuaries that diverge from that inlet. Moreover, the deposits of Head along the valleys and estuaries are insignificant. We may conclude, therefore, that both deposits were removed by the torrential conditions attending the formation of the stream tin. Notwithstanding their great depth, some of the valleys have very narrow floors, probably due to their being deepened rapidly in the glacial epoch, when they must have presented the appearance of narrow gorges. Nature of the Alluvia. — The alluvium of the killas districts consists of a muddy silt in which sand and gravel deposits are rare, except where the higher portions of the streams have traversed 102 E.ECENT DEPOSITS.. granite areas, when detritus from that rock has been brought down in the form of gravel, the grains of which are unrounded. In granite districts the alluvia is mainly of the latter description. In some situations, where the declivity is slight, clay has been formed, more especially in the upland basins. River terraces, marking different stages of deposit, are rare : moreover, the alluvial flat itself, which lines the valley floor, occasionally presents difficulties in its demarcation. Not only does it often merge insensibly into the dfebris of the valley slopes, but the streams frequently originate in broad, open basins, and the tracing of the alluvia along these hollows is attended with much uncertainty. This is especially the case in granite areas, as the debris formed by the decomposi- tion of this rock is practfcally indistinguishable from the granitic alluvia. In valleys that have been worked for stream tin, or which have been used for treatment of the ores raised from the mines, the alluvial margins have often been obliterated, and along some of the hollows the ground is so disordered that it is uncer- tain to what extent they were lined with alluvia. The stream tin valley of Porkellis, in the parish of Wendron, may be instanced as an example. Moreover, this valley is fringed by gentle slopes, in which the underlying granite is completely hidden by a soil cap made up of its debris, and corresponding precisely with the granite alluvia which floors the valley, and the one shades imperceptibly into the other. The uplands occupied by the granite present numerous instances of alluvial basins in which the original flat is gradually being modified by the soil creep from the slopes. Some of the moors which so frequently occur at the beads of the valleys have thus been formed. The want of fall renders drainage difficult, and their clay bottoms are frequently lined with marshes. The Valley Systems.— The valleys are disposed in three prevalent directions that are common to the whole district, but each type predominates in certain areas. On the eastern portion of the sheet the principal valleys trend from north-east to north- north-east. On the horizon of Truro and Falmouth there is a strong tendency for the larger hollows to run north and south, while west of that belt the majority of the streams lie in valleys trending from north-west to north-north- west. The north and south system is in all probability the oldest, as it appears to have no relation to the structural features of the geological formations which make up tbe existing land surface. The north-north-east system approximates to the general strike of the killas and to the system of fracture produced by the volcanic disturbances of the newer Palsozoic period; while the north-north-west system coincides with the direction of fracture that probably originated in early Tertiary times. To what extent the valleys coincide with faults there is seldom evidence to show, but tne straightness of some of them, and in other cases their parallelism, suggests that their course has frequently been determined by lines of dislocation or well-marked joints. Moreover, two valleys divided by a ridge are often in perfect alignment as it their course bad been determined by a single line of fissure. BLOWN SAND. 103 Eate of G-rowth of the Alluvial Deposits.— The Fal is the largest river within the region, but only its lower reaches enter this area. As that part of the river was, however, in historic times, a tidal estuary, the age of the alluvium "can be approxi- mately ascertained. In the description of the marine alluvia the seaward growth of the valleys and their encroachment on the tidal estuaries is referred to. There is evidence to show that the alluvial flat above Lamorran and Euan Lanihorne has been formed since the sixteentl^ century, and Mr. H. M. Whitley has estimated that it has been silted up at the rate of 1 foot in about thirty years.* The deposits lining the Carnon Valley have been still more rapidly accumulated, mainly as the result of the extensive mining operations that formerly prevailed. In 1620 the tide flowed beyond Lower Oarnon, and, according to tradition, it even once flowed above Bissoe Bridget It has been calculated that at the height of mining activity — in the 21 years between 1821 and 1842 — deposition was at the rate of 1 foot in five years. Accord- ing to the late Mr. W, J. Henwood,J the surface of the valley at Higher Carnon was raised between the years 1820 and 1867 at the rate of about 1 foot in ten years. IV. Blown Sand. Sand dunes and towans are seldom developed in this area. These aeolian deposits are mainly composed of finely comminuted sea shells, such as form the shelly beaches, and have been largely utilised in Cornwall for enriching the soil by the lime contained in their composition. On the north coast there is an extensive developmcHt of blown sand at Forth Towan, from which the name has evidently been derived. On the south coast sand dunes occur at Pendower and at the mouth of the hollow a quarter of a mile east-south-east of Gwendra. At Porthcurnick blown sand occurs, but not to any appreciable extent, Further south, in the parish of St. Anthony, a tract of blown sand fronts Towan beach below Porth Farm, and has succeeded in choking an old channel con- necting the estuary with the open sea that formerly constituted the present peninsula of St. Anthony an island. * Journal Roy'. Insti Corwrnall, vol. vii., p. 12. t About 1§ miles above the point now reached by ordinary tides. t Presidential Address, Roy. Inst. Cornwall, 1870.' 104 CHAPTEE XII. ECONOMIC RESOURCES, EXCLUDING THE ORES.* Soils and Vegetation. — The fertility of the district is subject to great variation. While the larger part of the area yields a generous soil susceptible of a high degree of cultivation, there are large tracts occupied by gorse and heath that are comparatively barren. Not only do these fluctuations depend on the character of the underlying rock, but an important influence has been exercised by physical situation. Among the latter, such conditions as elevation, proximity to the north or south coast, the shelter afforded by valleys, and the varying declivities of the slopes have materially contributed. The geological conditions are very pro- nounced in areas occupied by granite as compared wRh districts characterised by killas. There is a further marked distinction in the metalliferous areas and the districts that bound them ; in much of the former the mineral alteration and excess of quartz has materially impoverished the soil, while in some cases the extensive mining operations and stream washings have devastated large tracts that would otherwise have been susceptible of cultivation. The eastern area is very fertile and is given over entirely to agriculture. The district lying within the basin of the Fal and its extensive tributary system is in a high state of cultivation, and includes the parishes of Probus, St, Erme, St. Clement, Kenwyn, Kea, Feock, Merther, Lamorran, Cornelly, St. Michael- Penkevil, Euan Lanihorne, and Philleigh. The peninsula south of Philleigh, embracing the parishes of St. Just, Gerrans, and St. Anthony, is almost equally fertile. West of the Carrick Roads and Falmouth Bay, the tract extending inland as far as the granite produces good agricultural land in the parishes of Mylor, Penryn, Falmouth, and Budock. The killas which enters into the geology of the eastern area is mainly confined to the Portscatho division, but the Falmouth and Mylor groups are also represented. There is no very marked difference in the lithological typesof these divisions,so that the soils resulting from their disintegration present no striking contrasts. On the whole, perhaps, the Falmouth group furnishes the best soil, especially when represented by the sandy friable type that so readily decomposes. This is well illustrated by the rich lands of Ardevora, in the parish of Ruan Lanihorne. In the area occupied by the Portscatho group it has been observed that the soil is lighter and of a higher agricultural value where the sandy types prevail. The extensive valley system, into which the eastern area tas been trenched, has produced marked variations in the agricultural * Mining eoonomios are treated in Part II. SOILS AND VEGETATION. 105 value of the land. In some parts of the region the valleys are so closely adjacent that the intervening ground affords little or no fiat land. In fact, it may be claimed generally that in this area level ground is almost entirely restricted to the valley floors, and that the difference between one tract and another is that characterised by the relative declivities of their slopes : some valleys being broad and open, while others are narrow and steep. In the former the soil is deep, while in the latter the covering is so thin that the rock often protrudes at the surface. The wash of the soil from steep slopes to their base is counteracted by the farmer, who periodically respreads it on the higher land to preserve its fertility. The great mineral area between Camborne and Baldhu con- sists largely of killas. The extensive mining operations have laid waste large tracts, especially in the districts between Baldhu and Scorrier. Besides this cause, the soil is often materially im- poverished by the large amount of quartz detritus, derived from the disintegration of the siliceous veins. Apart, however, from these considerations, the belt of country fringing the north coast, and in which mineralisation is not conspicuous, is markedly less fertile than the killas on the south, and there are large tracts which are out of cultivation.* These northern slopes not only suffer from their bleaker aspect, but the district is not so ex- tensively trenched by valleys as the south, and is consequently more exposed to the winds. This is particularly brought out by the comparative absence of woodland in the northern district, whereas the southern tract sustains flourishing plantations, and exotics from warmer climes thrive in its gardens. The killas area on the extreme western portion of the sheet, between Camborne and Carnmeal Downs, is fertile and almost entirely under cultivation, while the timber at Clowance flourishes in a degree altogether unusual in the district, comparing favour- ably with the woods of the Fal basin. The granite district exhibits marked variations in its agri- cultural value. While over large tracts the rock is buried beneath a soil cap through which it rarely protrudes, these areas are often suddenly replaced by rocky wastes that are sterile, while in other situations good arable land is broken by extensive protrusions of rock. "Whereas the differences in elevation over the granite areas partly accounts for these variations, this cause does not altogether explain the phenomena. Fertile tracts and barren areas are frequently closely adjacent, and although resulting doubtless from chemical distinctions in the granite that have affected the nature of its decomposition, these mineralogical variations in the field are not always to be detected. The Carnmenellis granite reaches a height of 819 feet. Its northern margin has an average elevation of about 500 feet, while the eastern portion descends to the 300-ft, level and sometimes * Much of the Downs has been reclaimed comparatively recently, thick dressings of " marl " being applied, the material of which has been mainly derived from greenstone. 106 ECONOMICS. lower. The western portion is higher than tBe eastern, and succeeds the killas between SOO and 400 feet above sea level. The most fertile areas are the eastern and southern slopes in the parishes of Stithians, St. Gluvias, Budock, Mabe, and Oonstantine. On the other hand the most elevated region at Carnmenellis, and including Nine Maidens, Calvadnaek and from thenoe to Cannebone, is the most barren part of the tract, little of which is under cultivation, the remainder consisting of rocky wastes covered with gorse and heath. The land also lying between East Wheal Lovell and Wendron is an abandoned mining district, the agricultural value of which is poor. The whole of the western region of Crowan, and including Polcrebo, contains large tracts of ubcultivated downs. On the north, about Carwynnen, there is also a large area out of cultivation. As already remarked, there is a great discordance in the depth of the granitic soils apart from differences in elevation. In some districts the granite is decomposed for a considerable depth from the surface, as is seen in the neighbourhood of Kame Common, and extending to Menerdue on the north and to Butteriss Downs on the south. While in this district the granite disintegrates to a friable soil which is light to work, it frequen|;ly yields a stiff clay. Indeed, over the granite area generally, the soil is cold as compared to the killas, and crops are later. Although some portions of the granite region include lands that are highly pro- ductive, the killas areas are the most fertile, irrespective of the factor of their being more low lying. This is exemplified on the granite margin, where there are sharp differences in fertility at its junction with the killas, the area occupied by the latter being markedly superior. The summit of Cam Brea reaches an elevation of 740 feet in the granite region named after that peak. This rugged country is replaced near Bosleake by cultivated lands that occupy the remainder of the granite area in its course to the south-west, the continuity of which is occasionally broken by rock as at Cam Arthen, and further west at The Rocks, near Croft Danger. The Cam Marth granite area is mainly under cultivation, except in the southern and most elevated tract, culminating in its summit at an elevation of 771 feet. The decomposition of the greenstones yields a rich soil, but these rocks occupy an insignificant portion of the area. The mica traps, while still more sparsely distributed, disintegrate readier and possess a manurial value from the phosphoric acid which they contain. The Stone Industry.— This area furnishes a large proportion of the granite that forms the well-known Cornish granite industry, the rock being mainly raised from the Carnmenellis mass. The headquarters of this industry is situated at Penryn, where the stone is dressed, and from which port it is shipped Ihe granite raised, liowever, in the more southern districts of Mabe and Oonstantine is shipped at Porthnavis. The stone is mainly wrought in a belt of country lying to the west of Penryn, extend- ing from the south of Stithians to Long Downs and Burnthouse, THE STONE INDUSTRY. ]07 Eathorne, and Brill. In this tract quarrifes are both numerous and extensive. Beyond this region granite is wrought along the Cober Valley, south-west of Wendron, and at Carwynnen, about two miles south of Camborne. Besides these localities, quarries on a smaller scale, many of which are no longer working, occur on the eastern margin of the Carnmenellis granite near Pencoose, at Kennal Vale, Ponsanooth, Penryn, Budock, and Penwarne. In the western area the principal localities where the stone has been raised are at Croft Michell, Praze, Crowan, Bognio, Nancegollan, and Prospidnick. Quarries have been worked also at Lower Tretharrup, near Carrannel, Tretheague, Halabezack, Tolearne, and at other localities which need not be enumerated. The granite is grey in colour, and its principal mineral con- stituents are felspar, quartz, and two micas, viz., muscovite and biotite, while tourmaline is commonly present as an accessory mineral. In texture there are two varieties, known com- mercially as "fine grit" and " coarse grit." The former, which usually occupies the outer belt for an average width of about a mile, although the superior stone, is not so extensively worked as the "coarse grit," on account of its being more expensive to dress. It is not only finer in texture, but is darker in colour, containing more biotite, and has a higher specific gravity (about 1 per cent.). A good example of this stone is seen at the quarries at Carusew, about one mile "west of Penryn. The "coarse grit" is a more attractive stone, and is studded with porphyritic felspars that reach an inch or more in size, some of the most beautiful varieties of which occur in the parish of Mabe. As remarked in a former chapter, the granite is divided by a threefold set of joint planes, one of which is horizontal and the others vertical, the latter intersecting one another approximately at right angles. Moreover, the joints are sufficiently far apart to adnait of the extraction of immense blocks. In fact, the favour- able disposition of the jointing is one of the most important factors in contributing to the success of the Cornish granite in- dustry. (Plate IX.) The principal quarries are confined to the eastern portion of the Carnmenellis mass, where the rook is little disturbed, and in which elvans are rare. In the central and north-western area the granite has been subject to much Assuring and disturbance, in connection with the oncoming of the mineral veins, and in these districts the_stone has only been raised for local purposes. Not only so, but the rock is frequently less uniform from the abundance of finer-grained granite and aplite veins with which the normal rock is mixed. These differences in texture cause irregularities in the joint planes, which renders its working un- profitable. Even in the granite belt which forms the heart of the industry these veins are of too frequent occurrence, and are often the cause of the quarry being abandoned. These finer-grained granites or aplites are rarely, however, sufficiently large to be independently quarried, and in some in- stances they are not easily distinguished from the elvans. In 108 ECONOMICS. fact, the term elvan as used by the quarryinen includes these finer varieties. A quarry of this nature occurs at Lower Tretharrup, near Lanner. The Cam Brea granite is of similar texture to that of Carn- menellis, and has been raised in various places between Cam Brea and Cam Arthen. At Bosleake a quarry has been opened on one of the finer-grained veins. The Carn Marth granite is of somewhat similar texture to the "fine grit" stone of the Carnmenellis granite, but the felspars are usually porphyritic, and of a slender habit. It is quarried ex- tensively on the hiU of Carn Marth. It is frequently, however, mixed with veins, and is inferior commercially to the granite of Mabe and Constantine. It has supplied the principal building stone of the town of Redruth. The following table, for which we are indebted to Messrs. John Freeman & Co., Penryn, illustrates the crushing strength of the Carnmenellis granite, as determined by Mr. David Kircaldy in May, 1904 :— Dimensions. Inches. 3-92 3-96x3-95 4-00 3-98x3-97 3-98 3-98x3-98 Mean 3-96 3-96x3-96 3-96 3-96x3-96 3-97 3-96x3-96 Mean Base Area. Crushed. Locality. Stress. per sq. in. per sq. ft, Tresahoe (Parish of Constantine) sq. ins. 15-64 15-80 15-84 lbs. 314,200 335,700 269,500 lbs. 20,090 21,247 17,014 tons. 1,292-0 1,366-4 1,094-1 15-76 306,467 19,450 1,250-8 Carnsew (Parish of Mabe) 15-68 15-68 15-68 398,500 357,400 294,800 25,415 22,793 18,801 1,634-4 1,465-8 1,209-1 15'C8 350,233 22,336 1,436-4 At the present time the granite industry is undergoing a period of depression consequent on its inability to compete with Norway, where the conditions of labour, the ease with which the rock is dressed, and its presence on the seaboard, facilitate its importa- tion at a cost below that at which the stone can be remuneratively wrought in this country. The decline of the industry is being severely felt in the district of Penryn, whence some of the skilled workmen are emigrating to America.* • Some idea of the extent of the granite trade in this part of Cornwall during recent years may be gathered from a perusal of the following table, which represents the supply of dressed stones by Messrs. J. Freeman & Co. or dock and harbour works, bridges, and lighthouse alone : — THE STONE INDUSTRY. 109 The elvans afford some of the best building stones of the district, and have been extensively utilised. The harder varieties are extremely durable, but in many instances those in which a certain amount of decomposition has set in have been selected on account of the freedom with which they are dressed, and to which the term freestone has often been applied. Of this type are the elvans of Newham.t near Truro, at PorkelliSj near Wendron, at Kerling Downs, near Chacewater, and many others. These rocks have been so extensively quarried that it is unneces- sary to enumerate the localities. The stone now being raised for building purposes to the south of Nine Maidens is of excellent quality, coarse in texture, and grey to pinkish in colour, and studded with dark nests of tourmaline. The well-known elvan at Saveock Water, to the east of Chacewater, is a somewhat similar stone, in which the tourmaline nests are exceptionally well developed. At Enys a fine-textured grey dyke has been quarried, which is exceedingly fresh. The stone wrought at Towntanna, and at Trevales, is often of a reddish colour. A very fine-grained light grey elvan is quarried at Tresevern Croft, and at Calvadnack ; while a similar rock is wrought adjoining the high road to the north of Crelly, and between Little Trewince and TregoUs. The elvan that is worked at Grreenwith and Pencoose is porphyritic, with a fine grey matrix ; at the former locality it is fresh, but at Pencoose incipient decomposition has set in. At Lower Carnon another large dyke has been ex- tensively quarried. The elvan at Kea, near Truro, is greyish green in colour, and is beginning to decompose. At Nansavallan, near Truro, a band is wrought of the. porphyritic type. Near Redruth a dyke is quarried at Higher Garde w, and on the east of Cam Brea Castle a coarse-grained stone is being worked. On the northern flanks of Cam Brea a fine-textured grey elvan has * Dock and Harbour Works. Gibraltar, 1899 to 1904 Keyham, 1897 to 1905 Cardiff, 1899 to 1904 - Portsmouth, 1894 to 1896 Fc>lkestone, 1897 to 1904 Dover Harbour Board, 1892 to 1901 - . . . Barry, 1892 to 1898 - Total Order, OuMe Feet. 1,250,000 1,891,400 142,000 606,000 142,000 118,162 162,218 Bridges. Kew, 1899 to 1902 - Kutherglen, 1893 to 1895 Tower Bridge, 1887 to 1889 Supplied by Messrs. Freeman. OiiMc Feet. 900,000 945,000 142,000 606,000 142,000 118,162 162,218 149,000 90,643 139,000 LlGHTHOUSB. Fastnet, 1898 to 1902 69,000 + Mr. Collins states that a large portion of the city of Truro was built from this stone. Trams. Roy. Geol.Sgc, Oarymafl. vo}. ix., p. 226. 110 ECONOMICS. been quarried. Grood stone is also being raised from the quarries at Bolenowe Crofts and Bolenowe Moor, to the east of Troon. The dyke which runs through Gregwartha is fine-grained, soft and locally known as freestone; it is at present being quarried half a mile to the north-east of that locality. A hard durable stone is raised at Creegbrose, near Chacewater. At Praze Station there is a large quarry of a greyish green elvan of a very fine-grained, even texture, and a somewhat similar rosk is wrought near Trevoole. The greenstones and mica traps have only been exceptionally used for building purposes, the former on account of their tousrh- ness and cost of working, and the latter from their decomposition. In spite, however, of their general unsuitability, the mica traps have occasionally been utilised in preference to the killas amongst which they occur. When not too decomposed they are readily dressed, and are said to be durable. The green- stone has been quarried at Flushing, Bissom, Treluswell, Devis, Tuckingmill, and Wheal Trannack. At Camborne it has beea extensively used for walls, in which huge blocks have been laid. Notwithstanding the superabundance of excellent building stone in the district, the more massive beds of the killas have been employed where superior stone is not immediately available. Although situated within two miles of the Carnmenellis granite, the town of Falmouth is mainly built of killas, and that stone, especially the crush conglomerate, is stiU largely utilised for building material. EoAD Metal. — The stone mainly employed for road metal is elvan, the finer varieties of which produce an excellent surface. Grreenstone is also made use of to some extent, but notwith- standing its excellence this rock is frequently exceedingly tough to break, as at Treluswell and Ponsanooth ; nevertheless, at this latter locality it is at present being worked. Granite forms an inferior road metal, but is often used in the granite areas. The harder sandy beds in the killas, especially the siliceous grits of the Lower Devonian area, are likewise wrought. Veinstone from the mine heaps is occasionally utilised. Stone is also imported, as the Plymouth limestone, and hornblende schist from the Meneage peninsula. These are mainly used, however, in the eastern district, where igneous rocks are rare, and where the tidaj estuaries have favoured water carriage. The hornblende schist produces a greasy surface, and is, therefore, not so suitable as the greenstone. One of the latter type, locally known as " blue elvan," is at present being worked at Porthoustock by Messrs. Freeman & Co., and yields an excellent road metal.* Clays.— China clay, into which some of the Cornish granites decompose, is rare in this district. At Lower Kergilliack, how- ever, near Penryn, the granite yields an inferior china stone, which is mixed with imported china stone from the St. Austell • Samples of thig rock submittod to attrition tests yield dust to the low percentage of 4'61. The specific gravity of tlie stone is 2-91. CLAY — WATER SUPPLY. Ill district, and worked at Penryn. China clay works of small extent formerly existed in Porkellis Moor, in the parish of Wendron. Near St. Day the decomposing granite is utilised for the manufacture of bricks, and the factory turns out over a million annually. The granite is decomposed for a depth of about 50 feet, and was formerly used for china clay, but was unable to compete with the superior clays of the St. Austell district. On account of the gritty nature of the clay the individual bricks are cut by hand. Those produced from this decomposing granite have smooth faces, but their edges are imperfect. Some of the decomposed elvans have also been worked com- mercially for their clay products. Between Carharrack and Lanner clay pits have been formerly opened on an elvan for china clay and bricks. Similar dykes have also been worked as clay pits at Sparry Bottom, in the parish of Gwennap, at Carnon Downs, and at Wheal Baddon. The upper part of the Fal estuary is lined with a deposit of grey clay brought down by the drainage of the china clay district of St. Austell. This clay, which is of a whitish and pale yellow- grey colour, is not only used at Trelonck for the manufacture of bricks, but works have also been established forthe production of the coarser varieties of earthenware. The following analysis of this clay was made by Dr. Pollard* from a sample taken at the ford between Ruan Lanihorne and Lamorran : — SiO, TiO. AlA CaO MnO MgO K,0 NajO Li,0 Air-driea ! Sample. 49-67 CI •19 HjO 105° 33-43 HjO above 105" 1-92 + Some organic Trace Trace ■37 Less for CI ... 3-32 ■29 Trace ■07 matter) •37 130 9^64 100 ■s? ■17 100-40 The chlorine and sulphuric acid are due to sea water. The soluble salts amounted to "83 per cent., the sand + acid silicates to 24^7 per cent. Water Supply. — The granite and killas, which almost entirely make up the geology of the area, both hold water. The experience of miners leads to the conclusion that the killas contains more water than the granite, which is doubtless due to the excess of Assuring and shattering in the slaty rocks. The granite, however, appears to furnish the largest springs, and it is from this source that the principal towns of the district, viz., Falmouth, Penryn, Eedruth, and Camborne, draw their water supply. Truro, on the other band, obtains its water from the killas in the vicinity. Although there is no lack of water in the slate, the absence of large springs is often a serious difficulty in dealing with the water supply of the smaller villages that are unable to bear the expense * " Summary of Progress of Geological Survey " for 1899, p. 175. 112 ECONOMICS. connected with storage reservoirs. The average water level is perhaps, about 40 fathonas, but this is subject to great fluctua- tion. At Wheal Vor, for instance, it varied as much as from 30 fathoms in winter to 45 fathoms in summer. The public water supply of St. Agnes and Mount Hawke is obtained from the adit of an old mine east of the latter locality. Smelting, Arsenic, and Ochre Works. — Tin smelting works are in operation at Point in Restronguet Creek. Further up the valley, at Bissoe, are two arsenic factories, one, situated about a quarter of a mile west of Bissoe bridge, employed in 1902 about 8 men in addition to carters. The crude arsenic calcined at the mines is sent there for refinement. Ochre works exist in tae same locality, which at the time of our survey in 1902 were said to have been in continuous operation for over 40 years. The oxide of iron carried in suspension, in the waters that discharge from the main adit into the Carnon stream, is caught in small pools, after which it is pulverized and washed. It is then dried into a fine brown ochre, in winter by fires, and in summer by the sun. The works are small, and there is no continuous market for the product. 113 PART II. MINING. BY D. A. MacALISTER. CHAPTER Xlir. GEOLOGY OF THE MINERAL AREA. The rock formations, together with their tectonics, have been described by Mr. Hill in the preceding pages. The mineral lodes of this district are almost entirely confined to those divisions of the killas which have been assigned to the Lower Palaeozoic system, and to the granite, which invaded the killas about the close of the Carboniferous period. As the metalliferous minerals are very largely concentrated in the mutual marginal zone of the granite and kiUas, and as the lodes are frequently influenced by their association with igneous sheets and dykes, the following .details in connection with the sub- terranean occurrence of granite, elvan, and greenstone will elucidate the underground geology of the metalliferous region, so far as mining operations have revealed it : — Svhterranea/n Features of the Granite. In a geological map constructed by Bichard Thomas and published about the year 1819, the Redruth (or Cam Marth) granite mass is shown by a sea level contour of its junction with the overlying killas to be con- tiiinous with the Carnmenellis mass. The Carn Brea granite is connected with the Carnmenellis mass under- ground, a fact confirmed both by the subterranean dips of the granite and from information obtained from the mines. It is, moreover, of identical lithological character, as described in Part I. It is possible that the three masses of granite are connected, but this conclusion requires verification. Note. — In the ensuing pages the following publications are so frequently re- ferred to that for the saEe of brevity the author's surname alone willbe quoted in the footnotes : — W. J. Henwood, " On Metalliferous Deposits of Cornwall andDevon." Tr. B.O.S. Corn., vol. v., 1843. Richard Thomas, " Report on a Survey of the Mining District from Chacewater to Camborne," 1819. DelaBeche, "Geological Report of Cornwall, Devon, and West Somerset," 1839. Josepb Carne, " On the Veins of Cornwall." Tr. B.O.S. Com., 1822, vol. ii. Clement le Neve Faster, " On the Great FlatLode." Q.J. G.S., 1878, vol. xxxiv. John Garby, " On some Cornish Mineral Localities."" Tr. R. G.S. Corn., vol. vii., 1847. 1]4 GEOIiOGY OF THE MINESAL AHEA. Its petrologloal character and mode of occurrence, as already pointed out by Mr. Hill, suggests the Cam Marth mass to be an independent intrusion, but it may nevertheless be in juxtaposition below the surface with the adjacent granite of Carnmenellis.* The following table gives the dipsj of the junction of the granite and killas : — . 1 Mine. From Point, In direction. Angle with horizon (near surface Remarks., Carn Brea Grcmite. Deg, Deg. Camborne Vean South of Engine shaft N.50W. 58 Becomes flatter in depth and is thrown up into a ridge Dolcoath ... South of Stray Park shaft N. 20 W. 72 Ditto. Ditto North of Wil- liam's New shaft N. 22 W. 40 Becomes steeper until it meets with Dolcoath Main lode at about 140 fathoms from surface, when it is thrown up into a ridge Ditto OnCaunter lode W. 5N. 72 — Ditto On Main lode near Eastern shaft W. 32 S. 23 Becomes steeper and then flattens Cook's Kitchen South of Dun- kin's shaft N. 37 W. 30 Gets flatter and is thrown up into a ridge Cam Brea ... Providence shaft N. 11 W. 30 Ditto. Ditto Near Tregajop- rau N. 48 W. 30 ~ Ditto Druid shaft (on east) North slope of N 30 Ditto. East Cam N. 24 W. 34 — Brea tongue of granite Wheal Uny ... Southern slope S. 24 E. 40 Becomes flatter and of tongue of (approx) continues into granite the Carnmenellis mass North Wheal S. 30 E. 35 Becomes flatter and Frances continues into the Carnmenellis granite South Dolcoath — S. 42 E. 18 Ditto. South Con- Near King's S.45E. 17 Ditto. durrow shaft South Tol- Near Taylor's S. 10 Tending to become carne shaft steeper in depth * J. B. Hill. " Summary of Progress of the Geological Survey for 19(53," p. 26. t The angle of dip is measured from the horizontal. SUBTERRANEAN FEATURES OF THE GRANITE. 115 Mine. From Point. Eeraarks. Redruth (or Cam Marth) Granite. Deg. Deg. Pedn an Drea Bast of Bragg's W. a few 18 At 75 fathoms from '' shaft deg.N. surface it is ver- tical for 30 fathoms below Street shaft. Then dips 32 deg. in the same direc- tion Ditto South of Tre- vena's shaft ]S'.15(?)W, • 23 — Wheal Beau- — 40to50i — champ Ting Tang ... North of Eoach's shaft S. 40 E, 473 ~— West Poldice B. 30 N. 30' Same dip in Poldice Treskerby ... — — 22^ — Ca^nmenellis Gra/nite. Tresavean — B. 40 N. 36« Belowthe 60-fathom Mine level the junction of the granite and killas is irregular and almost per- pendicular in - some places Wheal Beau — N.E. 60^ — champ Wheal Buller Point near ... N. 24 W. 58 — - Wheal Basset South of Mar- N. 57 Gets flatter and riott's shaft * then steep again Wheal Gren- South of King's N.45B. 30 — ville shaft From the foregoing data it is possible to form an idea of the shape of the granite surface concealed by the overlying slates (see Fig. 2). The ■western portion of the northern margin of the Carn Brea granite dips ' Henwood, p. 71. ^ Thomas, p. 10, gives the dip of the granite and kiUas junction from Wheal Damsel to Carharraok as 10 deg. and in a direction S.E. towards Ting Tang Mine as 18 deg. Henwood, p. 71, gives the dip from East Wheal Damsel east- wards as 14 deg. to 16 deg. ; and at Ting Tang in a S.E. direction as 40 deg. to 45 deg. ^ Op. cU., p. 10, gives dip at Wheal Gorland to Wheal Unity as 20 deg. * Op. cit., p. 10, gives dip as 26 deg. ' Op. cit., p. 10. Henwood gives the dip as 40 deg., p. 71- * Henwood, Table Iviii. i2 116 GEOLOGY OF THE MINERAL AREA. SUBTERRANEAN FEATURES OF THE GRANITE. 117 under the slates at a high angle (72 deg.), but in going eastwards it gradually flattens out, and in Cook's Kitchen Mine the dip is only 30 deg. Further east, near JRedruth, it is inclined to the horizontal at 24 deg. The dip in the western portion of the southern margin is, at South Tolcarne Mine, only 10 deg., but in going eastwards the angle of dip increases until at North Wheal Frances it is 35 deg. ; and further east still, in Wheal Uny, near Redruth, the angle is 40 deg. from the hori- zontal. The elongate, somewhat curved shape of this mass is perhaps its most peculiar feature, as it is, correctly speaking, a ridge rather than a dome. On the east this peculiarity is strongly pronounced. The Redruth (or Carn Marth) granite presents the form of a more even dome, since not only is the exposed surface more nearly circular^ but the dips around its margin do not vary to such extent. The northern and western slopes dip beneath the killas at angles varying from 1 8 deg. to 23 deg. The eastern margin is steeper, and its slope beneath the killas varies from 30 deg. to 47 deg., the highest angle of dip being towards the south. The southern slope appears to have a maximum dip of about 50 deg. The killas which lies in the subterranean basin formed by these three granite masses probably exceeds 1,200 feet in thickness in the vicinity of East Wheal Basset. Proceeding from thence westwards in a direction W. 35 deg. S., between the two granite hills (of the Carn Brea and Carnmenellis granites), the killas thins out rapidly, until at South Con- durrow it is, at most, 300 feet in thickness, after which it dips away west- wards at an unknown angle. Underground exploration in the mines has to a certain extent revealed the character of the upper surface of the granite concealed by the killas. It appears to be undulating, but on the north of the Carn Brea mass there are two well-marked subterranean ridges^ of granite striking in the same direction as the cleavage of the killas. The granite plunges northwards beneath the killas, and after reaching a certain depth it rises in the form of an irregular wave trending B. 30 deg. N. This subterranean ridge varies in height to a maximum of 40 fathoms, and has been identified in Camborne Vean Mine, Dolcoath, New Cook's Kitchen, Tincroft, and East Pool. About 150 fathoms further north there is a second but smaller ridge, of a maximum height of 30 fathoms, trending in the same direction, but only encountered in depth in South Crofty and East Pool.' In this locality there are also a number of intrusive sheets protruding from the main mass of granite which penetrate the killas on the north of the Carn Brea granite. To the list of such intrusive offshoots encountered in mining operations, the particulars of which have been published,* may be added those which were met with in the adit level at Kellivose Mine,* and the tongue of granite which was driven through for several fathoms in Wheal Uny. At the 10-fathom level in Williams' shaft, in South Con- dnrrow Mine, the junction of the granite and killas can be observed, where small veins of granite penetrate the killas. The 70-fathom cross- cut, in Wheal Basset, is driven northwards from the North Basset lode ^ H. C. Salmon. Mmmg and Smelting Magazine, 1862, p. 385. ^ There is dif&culty in accurately tracing these ridges, and it may be that the former really trends from Camborne Vean, through Dolcoath, New Cook's Kitchen, and South Crofty to East Pool. s W. Phillips, "On the Veins of Cornwall." Tr. Geol. Soc, vol. il., 1814, p. 152, and plate 7. Thomas ; Henwood ; Joseph Came, ' ' On the Veins of Cornwall." Tr. JR.G.S. Com., vol. ii., 1822. Veins, tongues, or intrusive sheets of granite occurred in Kellivose, Dolcoath, Cook's Kitchen, Tincroft, Cam Brea, South Condurrow, Wheal Uny, Herland Mine, Wheal Basset, Pedn an Drea, East Wheal Sparnon, Wheal Beauchamp, Ting Tang, Wheal Damsel, Wheal Gorland, Poldioe, Wheel Peevor, Cardrew Down Mine, Wheal Unity, Wheal BuUer, Tresavean, Wheal Trannack, Carleen Mine, Wheal Vor, * From an old report, Pendarves Estate OfBce, Camborne. Obtained through the courtesy of Mr. Vercoe. 118 GEOLOGY OF THE MINEEAL AKEA. towards South Cam Brea Miae and passes alternately, in some places, through granite and killas. The deeper parts of the more important mines situated in the killas on the north o£ Carn Brea have reached the granite. In Wheal Agar the granite is encountered at a depth of from 140 to 150 fathoms. In East Piiol it is about the 135-fathom level ; in South Crotty it is met with at a depth of from 140 to 160 fathoms, but getting deeper westwards ; in New Cook's Kitchen from 120 to 136 fathoms. In Wheal Tehidy, on the east granite was not met with in the mine, but it is probably about 120 fathoms below surface. The granite was never reached in the Boskear or Seton Mines. Finally, in no case have the workings of any mine, when once fairly into the main mass of the granite, been known to pass through it. Svhtefranean Occurremce of Elvan} Mining operations have revealed the presence of a greater nimiber of elvans, both in the granite and killas, than can ever be discovered at surface ; but the available information is scanty, owing to the fact that the miners have no interest in recording their occurrence, and conse- quently each discovery is soon forgotten. It is only in a, few cases that all the particulars can be forthcoming, since it is only here and there that elvans are intersected during the development of the mine. This may partly accoant for the statement so commonly heard from miners that elvans occur in patches ; but it is also certain that such intrusions are sometimes split up into branches. At Wheal Beauchamp an elvan throws off several branches into the slates.' Several irregalar " spots " of elvan occurred in the western part of Wheal Unity.' The elvans in the killas in Barncoose, Wheal Druid, and Wheal Basset are greatly branched.* At Wheal Clifford the elvans are considerably branched in depth. Elvans sometimes show considerable change in width witliin short dis- tances ; thus at Wheal Beauchamp the elvan at the 29-fathom level is 3 fathoms in width, but at the 69 it is 30 fathoms in width.^ In Wheal Unity an elvan varies in width from 6 feet to 60 fathoms.^ " The elvan courses are from two or tliree to twenty or thirty fathoms in breadth, some of them larger.'" The following are a few selected examples of the widths of elvans as discovered in the mines :— In Wheal Beauchamp the width of the elvan is as much as 40 fathoms in some places.^ In Wheal Buller an elvan is 25 fathoms in width.'' In Consolidated Mines'" there is an elvan 16 to 20 fathoms in width. In Cook's Kitchen an elvan is 17 fathoms wide ;" another is 20 feet wide.'^ In Chacewater Mine an elvan is 6 fathoms in width.'' In Ci-enver and Wheal Abraham, 1 to 3 fathoms in width." In East Wheal Crofty (South Crofty) an elvan is 6 fathoms wide." In Cardrew, 8 or 10 fathoms.'" In Creegbrose, 4 feet to 5 fathoms." In Wheal Unity, 5 fathoms.'^ In Wheal Vor there are two elvans, one 8 fathoms and the other 2 feet in width." In Carn Brea an elvan is 7 fathoms wide, and another one less than this ;^ at the 300-fathom level ' The angle of underlie is measured from the vertical. ^ Kenwood, p. 81. " Thomas, p. 66. * 3. Maynard, "Remarks on two Cross Sections.'' ilst Rep. Moy. Corn. Poly. Soc, 1871. ^ Henwood, p. 81. " J. Carne, " On the Veins of Cornwall," Tr. M. G.S. Corn., 1822, vol. ii., 1>. 93. ' Thomas, p. 16. " Op. eit., p. 50. " Henwood, p. 81. '" Op. cit., p. 83. " Op. cit., p. 63. "^ W. H. Argall, " On Elvan Courses." Miners' Assoc, 1875. " J. Carne, " On the Veins of Cornwall." 2K Ii.6f.S. Corn., vol. ii., 1822, p. 79. " Op. cit., p. 82. " Henwood, p. 62. " Op. eit., p. 80. '■' Thomas, p. 34. '^ Op. cit., p. 65. '" Henwood, p. 52. *> Op. cit., p. 63. SUBTERRANEAN OCCURRENCE OF ELY AN. 119 there is an elvan 10 fathoms in width. In South Roskear there are elvans from 5 to 9 fathoms in width.i In Ting Tang an elvan is 24 fathoms wide." In Tincroft, 6 fathoms wide.' In Wheal Grenville an elvan was penetrated for 40 fathoms without cutting through it. Very few of the elvans underlie south. There are two south underlying elvans in the section of ground between South Wheal Basset and South Dolcoath Mine ; and at the present time elvans which underlie south can be seen in the deep workings of Dolcoath and Wheal Grenville. Hen- wood (p. 80) gives two other examples. Elvans sometimes change their underlie in depth. In Dolcoath there is an elvan which in the upper part of the mine has an underlie north of about 45 deg. In depth, where the "country rock" is granite, it is almost perpendicular, underlying slightly south. At Clifford Amalgamated Mines an elvan, outcropping between Garland and Hawke's shafts, starts from surface with a northerly underlie of 70 deg. as far as the 75-fathom level, after which its underlie is 35 deg. N. In the Gwinear district there are two series of elvans : one series strikes approximately B. 30 deg. N., and the other series striking nearly B. and W.* Now, although two series cannot be identified in this district, there appears to be one elvan about 40 feet in width, which strikes nearly B. and W. between Camborne and Dolcoath.^ At the 400-fathom in Dolcoath Mine, about 40 fathoms west of the Old Sump shaft, there is an elvan striking nearly B. and W. and underlying N. 35 deg. All the other elvans have a strike approximately B. 30 deg. N. In the Camborne district it is particularly noticeable that the elvans in the killas, on the north of the Cam Brea Hill, are much more highly inclined to the vertical than those on the south, situated entirely in granite. The information concerning this can be generalised as follows : — The elvans cropping out on the north of North Wheal Crofty and striking westwards (W. 30 deg. S.) towards the Seton Mines vary in underlie (angle from vertical) from 47 deg. to 60 deg. N. The elvans are slightly steeper on the west than on the east. An elvan passing through South Crofty Mine underlies N. 45 deg. The elvans of West Stray Patk, Carn Camborne, Dolcoath, Cook's Kitchen, Tincroft, Cam Brea, and Wheal Druid (eastern part of Carn Brea), situated along the northern margin of the Carn Brea granite, vary in underlie from 30 deg. to 45 deg. In Cook's Kitchen an elvan underlies N. 54 deg. In Wheal Druid there are two elvans ; the more northerly underlies N. 37 deg. and the more southerly N. 15 deg. An elvan in South Dolcoath Mine and West Wheal Basset underlies S. 18 deg. to S. 40 deg. The elvans in Wheal Basset are in killas, and are perpendicular or inclining north. An elvan between South Wheal Basset and Carn Kie underlies S. 8 deg. The particulars of the underlies of the elvans between Scorrier Gate and the United Mines in a similar manner may be generalised as follows : — At Little North Downs Mine an elvan underlies N. 47 deg. At New Treleigh Consols an elvan underlies N. 38 deg. From Treskerby to Great Wheal Busy the elvans underlie N. from 28 deg. to 47 deg. lu Killifreth the main lode accompanied by an elvan underlies N. 58 deg. In Wheal Unity an elvan underlies N. 10 deg." In the Consolidated Mines the elvans vary in underlie from 30 deg. to 60 deg. N. Prom Ting Tang through the United Mines, Wheal Clifford and Nangiles to Wheal Jane the elvans underlie N. 35 deg. to 65 deg. (65 deg. in Wheal Jane). In Wheal Clifford the elvans becomes steeper in depth. Throughout the whole district most of the elvans underlie north — a few only (in the granite) underlying south. The following table gives the underlies of elvans in various mines : — I » Thomas, p. 42 ; W. H. Argall, "On Elvan Courses." Tr. R.G.S. Corn., Miners' Attoc, 1875. 2 Kenwood, p. 71. ^ Op. cit., p. 63. * Ernest Dixon (H.M. Geological Survey) Summary of Progress, 1901, p. 25. Mr. Dixon considers the latter series to be more recent than the former. ■ " Henwood (p. 160) quotes from a paper by Professor Sedgewick. Camb. Phil. Tram. I., p. 129. ' Thomas, p. 65. 120 GEOLOUy 01' TllK MINEKAL AREA. Mine. Barucoose Basset, Wheal Bell Mine BuUer, Wheal Baddern, Wheal Underlie of Elvan. Rema/rks. Deg. N. 15 N. 37 N. 46 Nearly vertical N. 45 to 50 N.59 Outcropping about 120 fathoms south of the Great Western Railway. Two el vans outcropping about 60 fathoms south of the Great Western Railway. They are greatly branched near the surface. Between Miner's shaft and Wheal TeUdy (about 180 fathoms north of the Great West- ern Railway). Two elvans, a large and a small one. They probably unite in depth. Intersected in the mine 40 fathoms from sur- face. Tin occurs in it. (A. K. Barnett " On Elvan Courses," Boy. Com. Poly. Sac., 1873, p. 18.) 25 fathoms in width. (Henwood, p. 81.) 170 fathoms south of Hillbrother's shaft. A smaller elvan 15 fathoms north underlies in the same direction. (Fig. 3.) Fig. 3. — Great Wheal Baddern. Bosleake Busy, Great Wheal Consolidated Mines Cook's Kitchen Cbacewater Mine S. (?) N. 35 N. 45 to (iO N. 40 N. 60 N. 47 Pig. 4. In Wheal Fortune at 160 to 200 fathoms below adit, 16 to 20 fathoms in width. (Kenwood, p. 84.) 20 feet wide. (W. H. Argall "On Elvan Couises," Miners' Assoc, 1875.) Another elvan. Part of Great Wheal Busy. Elvan lies between "Winter's" and " Chacewater " lodes. 6 fathoms in width. Came states that there are two elvans uniting in depth. (" On Elvan Courses," Tr. R.G.S. Corn., vol. i., 1818, p. 104.) SUBTERRANEAN OCCURRENCE OF ELVAN. 121 Underlie Mine. of Elvan. Remarks. Crenvep and Deg. N. 45 to 1 to 3 fathoms in width. (J. Came " On the Wheal 75 Veins of Cornwall," Tr. B.G S. Corn., 1822, Abraham vol. ii., p. 82.) Crotty, Wheal N. 52 Clifford Amal- N. 70 Outcrops near Garland shaft. At the 75- gamated fathom level it is directly under Deeble's Mines shaft and underlies N. 35 deg. N.57 Crops out near Moor shaf b on the south of the sett. Copper Hill - N.38 Cam Brea S. 40 100 fathoms south of the Monument. Monument • K. 15 North of the Monument. (J. Maynard, " lie- marks on Two Cross-Sections," 41st Bep. Roy. Corn. Poly. Soc, 1871.) Oarn Cam- N.30 [n depth it is vertical. borne Cardrew Mine N. 30 to Near South lode. 8 or 9 fathoms in width. 40 (Henwood, Table Ixviii.) Carn Brea Slightly At the 300-fathom level it is 10 fathoms in Mine North width in granite. N. 20 N.40 [•Seen in upper levels. (Henwood, p. 63.) Fig, 4. — Great Wheal Busy, 150 TV^Lcvel . Dolcoatb - East Pool - Emily Hen- rietta, Wheal Jane, Wheal - Little North Downs New Cook's Kitchen N. N. N. N. 44 60 65 47 N.44 See Bemarks on Elvaus in Dolcoath, in Sec- tion on Mines, p. 217. Crops out between South and Pearce's shaft. Two elvans in south part of mine about 30 fathoms apart. (Maynard's "Cross-Sec- tions," 4:l«t Bep. Corn. Poly. Soc, 1871.) Elvan in the hanging wall of the lode. 122 GEOLOGY OF THE MINERAL AREA. Mvne. Underlie of Elvan. RemarJea, Nangiles North BuUer- New Treleigh Consols New Wheal Seton South Dolcoath South Wheal Seton (Gilly Mine) Sithney Carn- meal Mine Deg. N. 50 N. 50 N. 10 N.38 N.47 S. 22 N. 25 N. 45 S. 60 Near Wheal Clifford lode. Crops out between Gardner's and Carp's shafts. South of Providence lode. Crops out 100 fathoms south of the Engine lode. (Pig. 5.) Fig. 5. — Sithney and Cammeal Mine. N. S Sputh Roskear South Crofty- Seton, Wheal Squire, Wheal Ting Tang Mine Tin croft Treskerby Tehidy, Wheal Union, Wheal S. 10 N. 45 N. 50 N.45 N.40 N. 20 to N. 30 N. 30 N. 30 N. 30 N. 61 N.45 (W. H. Argall " On Elvan Courses," Rep. Roy. Corn. Poly. Soc, 1875.) South of Bickford's shaft. Crops out 60 fathoms south of Tilly's shaft. Elvans so nearly horizontal that they were called " Floors " by the miners. (J. Carne " On the Veins of Cornwall," Tr. R.G.S. Corn., vol. ii., 1822.) 24 fathoms in width. Worked for tin ore at Poldory and Ale and Cakes Mine. It sends out branches into killas. (A. K. Barnett " On Elvan Courses," Boy. Gam. Poly. Soc, 1873, p. 15.) Crops out between Highburrow and Dunkin 3 shafts. 6 fathoms in width. (Henwood, p. 63.) A branch from it is perpendicular up to the Crops out 30 fathoms north of Moyle's shaft. Crops out south of Wheal Union. _ Elvan further north than last. (Maynards Cross-Sections, 41st Sep. Corn. Poly. Soc, 1871.) SUBTERRANEAN OCCUBRENCE OF "GREENSTONE. 123- Mine. United Mines Unity, Wheal Vor, Wheal West Wheal Basset Underlie of Elvan. Deg. N.60 N. 10 S.(?) N. 50 to 57 N. 20 to 30 Vertical to S. 18 Remarks. Two elvans north of Chapel's shaft. Irregular underlie. 25 feet wide, and con- tinues into Creegbrose. (A. K. Barnett " On Elvan Courses," Eep. Corii. Poly. Soc, 1873, p. 12.) 20 feet wide. Another elvan. (Op. cit., p. 14.) Two elvans. The larger 8 fathoms in width. (J. Carne "On Elvan Courses," Tr. B.G.S. Com., vol. i., 1818, p. 103.) Another elvan 2 feet wide. (Henwood, p. 52 ) Vertical near surface. Fig. 6. — West Stray Park Mine. West Stray N.35 Fig. 6, Park Wentworth, N. 53 Wheal West Seton N. 58 SubterraTiean Occurrence of Greenstone {Irestone, Ironstone, Iron Killas). Pryce^ is the first to have mentioned the occurrence of greenstone as encountered in mining operations, and states that " it often keeps a course east and west like a lode but is commonly very wide .... it is very tedious and chargeable where an adit must be driven through it." Charles Thomas,^ who was a prominent mine captain in the Camborne district, asserts that greenstone never behaves like the elvan courses but occurs in " embedded masses." Some of the following facts lack confirmation, but they illustrate the subterranean extent of this rock, which is the oldest of the igneous rocks. ' Mmeralogia Comubieniis, 1778, p. 75. ' "Kemarks on Mines in Cornwall." Hep. Corn. Poly. Soc, 18S4. 124 GEOLOGY OF THE MINERAL AREA, At iloskear, on the nortti o£ Camborne, a sill o£ greenstone, 20 fathoms in width, was penetrated at the deep adit level (30 fathoms from surface) at about 120 fathoms south of the South Boskear lode.' Another sill was encountered in the. workings of the South Roskear lode from the 107 to the 139-fathom levels at least.^ In North Roskear Mine greenstone was met with about the main lode from a depth of 30 fathoms from sarface (deep adit) to 100 fathoms.' An old unpublished report states that the Doctor's shaft was sunk through greenstone from the 30-fathom level to the 80, after which it was in killas until greenstone was again encountered at a depth of 150 fathoms. Greenstone was encountered in Wheal Seton between the 130 and 140- fathom levels at Tilly's shaft, which is sunk on the North Gaunter lode.* Greenstone with a westerly dip of 12 deg. to 16 deg. occurred at the 108-fathom level in Stray Park, Wheal Gous, and Camborne Vean.° In the western part Cam Camborne Mine the workings were in greenstone from the 20-fathom level (or adit) to the 50 ; at West Condnrrow Mine (or Kellivose) greenstone was encountered when sinking was commenced on the North lode. In South Crofty Mine a cross-cut driven north from Pryoe's lode near Bickford's shaft at the 120-fathom level (near a granite ridge) encountered greenstone in the killas.^ In the same mine a greenstone sill, about 100 leet thick, was passed through in Robinson's shaft above the 60-fathom level.'' A little further west in the same mine the Caunter lode passes through greenstone at about the 70-fathom level, and the Copper Tankard lode was in greenstone at about the same level. Other lodes encountered greenstone in different parts of the mine from the [30 to the 75-fathom levels.® In East Pool Mine there are two small sills of greenstone about the Engine shaft at the 48-fathom level. They have a northerly underlie. At North Pool there is a sill of considerable thickness, outcropping about 60 fathoms south of the main shaft and underlying north at about 54 d^. from the vertical." A greenstone sill 20 fathoms in -width was found in the npper part of Tincroft Mine.'" Further east there appears to be a sill of greenstone at about the 20-fathom level in Barncoose Mine. At Wheal Union, near Redruth, greenstone is said to have been encountered at about the 80-fathom level. In Trevaskus Mine, Gwinear, greenstone occurs in the walls of the lodes at the ^, 51, 66 and 71-fathom levels." In the killas, on the north of the Carn Brea granite, there appears to be two prominent but irregular sills of greenstone. The sill seen in North Pool Mine may be the same as that seen in North Roskear and Wheal Seton. The other appears to extend from Barncoose through East Pool, South Crofty, to South Roskear, and the sill observed in Tincroft Mine probably represents that intrusion. ' Thomas, p. 18. ^ Henwood, Table liv. ' M. L. Moissenet, " Filons de Coinouailles," 1874. ■■ H. C. Salmon, Mining and Smelting Magazine, 1862, vol. ii., p. 282. ' Henwood, Table xlix. " J. Maynaid, " Remarks on Two Cross Sections." Jiep. Com. Poly, boc, 1871. Thomas, p. 18. ^ -r, a ■' Information from John Penhall, luanager of South Crofty, Cam Brea, and Tincroft Mines. " Henwood, Table Ivi. " See " Cross Sections," by J. Maynard (op. cit.) '" J. Carne, " On the Veins of Cornwall." ZV. R.e.8. Corn,, vol. u., 1822, p. 61. '' Henwood, Table xxxv. 125 CHAPTER XIV. NATUEAL HISTORY OF THE LODES. I. DiSTBIBUTION OF THE LODES. The lodes of the area are almost entirely confined to the western district, and are mainly restricted to the neighbourhood of the 8 o ■J? I 1 nJH-^ §5^ i =9 o GQ O 5S eg =9 Em * s 126 NATURAL HISTORY OF THE LODES. granite, and more especially near its margin ; but they continue to occur for a distance of 4 miles eastward of the granite. Thus the country lying between Baldhu (on the east) and Camborne (on the west) and extending for a few miles north to a few miles south of Redruth includes the principal mining area of this map. (See Fig. 1.) S 03 d 60 o ^V-i QQ For simplicity this.district can be roughly divided npintomineralised areas without separating the lodes genetically. Thus, the margin of the Carn Brea granite is the site of a remarkable series of tin and copper lodes (striking N.E. xE., approximately parallel to the granite margin), extending from Camborne to Eedruth. The DISTRIBUTION OF THE LORES. 127 lodes of this mineral belt which are situated but little more than three-quarters of a mile north of the granite margin, are of no great value. Near the margin, however, the lodes have been enormously productive in tin and copper ores for a distance of at a CQ ^ast 3 miles along their strike. The lodes on the north of the Eedruth (or Cam Marth) granite may be considered as beine m the eastern extension of the same belt. Between the Cam Brea and Carnmenellis granites there occurs 128 NATURAL HISTORY OF THE LODES. ^ 8 I I r— I (5S < ■"*l t 8 I 8 l-l -Ol DISTRIBUTION OF THE LODES. 129 a .»5 ^ J I I "fe-S % ^ r S S o CO s ^ l: §11 fes :ft :o * v->^ <;; I-H _ S"^ t^ • •-* ^■^t i U4 " a? (U -ys- ' 99 d> ' -^ ", v~ in •"''' ■i_ h v . & ISO NATtJHAL HISTOEY OF THE LODES. a prominent series of lodes, of which the G-reat Flat lode is the largest member. The series extends from the west of South Condurrow Mine to Cam Marth (on the east) — a distance of 3i miles. (See cross sections, Figs. 7 to 16.) On the west of the Carnmenellis granite is the mining district of Grwinear and Crowan, Here and there, around the same granite mass and in the more elevated portions of the interior, from Wendron to Halabezack, are lodes containing both tin and copper ores. Finally, there is the Forth Towan group of lodes near the sea coast on the north of this map. II. GrEOLOGICAL AgE OF THE LoDES. In discussing the ages of the lodes, it should not be assumed that the mineralisation of a fissure commenced immediately after its formation. Game's classification* of the lodes into six systems appears to imply that movements operated successively for the production of fissure systems, and that each movement was accompanied not only by a series of fissures, but by a distinct period of mineralisation. The fissures of a single zone of Assur- ing, or of a whole fissure system such as either of those referred to on p. 205, may be assumed to have had a common mode of origin. The process which produced the fissures should be regarded as a progressive or long-continued one, so that the fissures first formed should not be separated from the last. In speaking of the age of the lodes, therefore, a period is implied during which two operations may have gone on hand in hand — (1) fissuring, (2) mineralisation. Eeference will be made else- where to the order in which the minerals arrived, but it may be mentioned incidentally that it appears to be this which accounts to a certain extent for the confusion that has arisen regarding the relative ages of the lodes. The tin and copper lodes may be broadly described as of post-Carboniferous but pre-Triassic age.f In Cornwall and Devon this epoch is characterised by an intrusion of granite, which in fact appears to have been the culminating effect of great earth movements. The direction assumed by the lode fissures formed after the consolidation of the granite appears to have depended upon the structures produced by these pre- granitic movements. Indeed, lines of weakiiess so formed do not appear to have become fissures capable of the reception of minerals until after the intrusion of the elvans. The process by which the fissures were mineralised was probably long-continued. III. Relative Age of the Tin-Copper and Silver- Lead Lodes. Besides tin and copper, other minerals occur in the lodes, and of these the ores of silver and lead are among the more impor- * Tr. B.O.a. Corn., 1822, vol. ii., p. 49. t See De la Beche, p. 283. STRUCTURE OF THE LODES. 131 tant. G-eographically, the distribution of the ores of lead and silver in the district is comparatively wide, but their economic importance under present conditions is small. They occur in districts outside the great tin and copper centres, but they are also found in lodes containing tin and copper. The arrival of the silver-lead ores appears to have been delayed to a late period in the history of the metalliferous veins of the district, since although they occur in a number of east and west lodes, they continued to arrive after the lodes of tin and copper had been completely formed; and, indeed, these ores were still being deposited during the later phase of movement, which re- sulted in the production of cross courses (or cross faults). Many of these cross courses contain ores of silver and lead and other minerals of less economic importance. Tin and copper ores had entirely ceased to arrive during the formation of the cross courses. IV, Structure of the Lod'es. Many lodes have been formed intermittently by operations extending over a lengthened period, with the result that they frequently display a variety of structures. The veinstones of the lodes show that they have originated in one or more of three modes of production : — 1 . Infilling of a Sssure or series of close parallel fissures by minerals derived from a distant source. 2. Alteration and impregnation of the country rock in the vicinity of a fissure or fissures by minerals derived from the fissure. 3. Alteration and impregnation of a friction breccia contained in a fissure (modification of 1 and 2). (Plates X. and XI.) The simplest structure which a lode can have is the comby or platy structure. Here the lode is built up of layers parallel to the walls, each layer representing a period of deposition and also, possibly, a widening of the fissure. In the "tin-copper" lodes the comby structure is not rare, but is mainly seen as the linings of actual cavities, particularly in the upper parts of lodes. In some fissures completely filled with quartz the " combs " are clearly seen interlocking in the middle of the vein. The Cathedral Mine, near Eedruth, shows successive depositions of quartz, fluorspar, and copper pyrites in the lode ; and at Wheal Julia, near Binner Downs, the layers consist of quartz, blende, and copper pyrites.* At Wheal Tolgus a specimen shows the order : quartz, blende, and iron pyrites. A table prepared by Henwoodf shows that a definite order of mineralisation can be made out in the lodes of many mines. The mineral which occurs most frequently against the walls of lodes is quartz ; and in tin lodes tin is also in this position. When wolfram occurs it is likewise here. The next appears to be principally sulphides of copper, with occasionally galena, and sometimes iron and man- • De la Beche, p. 340. + p. 2H. 92 132 NATXTRAI. HISTORY OF THE LODES. ganese minerals and arsenical ores with blende, associated with quartz, fluorspar, chlorite, and other veinstones. Another form of banded structure is that produced by the infilled fissure and the country rock, which for a short distance on each side has been altered into *' capel." This alteration in the walls is characteristic of the tin lodes, and in some cases the country rock in the vicinity of the fissure is worth breaking down for the tin ore it contains. Thus the stanniferous deposits of East Wheal Lovell consist of altered granite, in the neighbour- hood of fissures, impregnated with tin ore.* In some eases the lode has a banded appearance, the origin of which is interesting. The lode may consist of a series of narrow parallel cracks or joints, through which at one time mineralising solutions were passing, with the result that the lode consists of a series of narrow strings, containing cassiterite or wolfram, quartz, &c., enclosed by bands of altered country rock.-j- In other instances the original character of the fissures is obscure, as sometimes the cracks or joints are so close together that the intervoning layers of country rock are completely altered, while at the same time the fissures have been obliterated. ' Sometimes, where the lode appears to be massive, minute lines of rifting can nevertheless be seen, through which, no doubt, the changes in the walls of the lode were efiFected.j A microscopic degree of fineness, in which the lines are so closely packed that the rock appears homogeneous, is sometimes discernible. Modifications of these structures are very interesting, as accounting for the presence of strings of chloritic material, or for veins and plates of " peach " (fine-grained schorl rock) which not infrequently occur in the lodes in both granite and killas. Some of these cases may be explained as follows : — The first fissure in- filling firmly cemented itself to the walls of the fissure, but when the fissure re-opened at a later time it did so along a plane of weakness parallel to the lode, but in the band of altered country rock alongside the original fissure infilling. In this manner a plate of altered country rock became detached and enclosed in the lode between old and new infillings. In some cases, especially in killas, where the lode is parallel to the cleavage, this has happened again and again, so that each fresh re-opening of the fissure took place on the outside of a thin sheet of country rock, which re- mained firmly attached to the lode. A similar explanation may be applicable in many cases to the presence of more irregular masses in the lodes {e.g., horses), and to go a step further is to arrive at a structure which resembles a breccia. Breccias in lodes are not rare, but they also originated in a variety of other ways. * C. Le Neve Foster, " Remarks on the Tin Deposits of East Wheal Lovell.'' l!r, J«.6'.(S. Com., 1876, vol. ix. + Illustrations of similar structures are to be found in " Mineralogisehen Geographie," by J. F. W. Charpentier, 1778. t An excellent account of the connections of ore deposits with joints will be found in " Ore Deposits of Monte Christo, Washington," J. E. Spurr. V.8. Oeol. Survey 22nd Ann. Rep., 1900-1901. Instructive examples ot the struc- ture of lodes will be found in the various publications of the U.S. Geol. Sur- vey by such authors as Ransome, Adams, and Spencer. ,. ■ STRUCTURE OF THE LODES. 133 Locally, the breccias were again brecciated by movements taking place in the plane of the lode.* In other places the lode cracked, and the walls slid over each other, so that the vein materials were sheared out and crushed. Phillips says that " in many instances the original opening would appear to have been a mere comminuted fracture of the rock in a given general direction, between the several planes of which a deposit of mineral substance has sub- sequently taken place through chemical agency. The final re- sult in such a case will be a brecciated veinstone of thB kind so constantly met with in mineral districts."! The structure of lodes in the killas is, on the whole, more varied than of those in granite. Some lodes are of enormous width, and consist of zones of crushed and dragged-out fragments of killas, filled with granite and metalliferous minerals. In the Dowgas Mine (St. Austell), for instance, the " Goffin " lode iu some places attains 50 feet in width, and it is difficult to say exactly where the lode ends and the country rock begins. In the neighbourhood of Ventonwyn Mine (St. Austell), the cleavage of slates is nearly horizontal, or dip gently northwards, but in the vicinity of the main lode of that mine the dip of the slates is greatly increased until it becomes parallel to the lode which underlies steeply northwards. In this case the slates were bent, dragged out, and broken by the sliding downwards of the hanging (or north) wall of the lode. Slickensides are common. In other cases the killas in the vicinity of the lode is contorted and gnarled, and traversed by irregular lenticular quartz veins, and in appearance very like some of the structure depicted in the Kingsbridge and Salcombe MeTnoir.X Instances of gnarling in the vicinity of the lode have been noticed in the St. Agnes district.^ Another kind of lode structure is that which depends upon the infilling of the interstitial spaces, and the alteration and impreg- nation of the crushed material of friction breccias. In the Camborne district this type of veinstone is extremely common, and many modifications of it are represented. Thus the lode may consist of an interlacing network of stanniferous and quartz veins, enclosing fragments of altered country rock. This breccia may be brecciated again and again, and each time sealed up by infiltrated minerals. Thus at Wheal Basset a specimen of veinstone shows at least four successive operations of crushing and healing up. The lodes of Dolcoath, South Crofty, and East Pool also typify this sort of structure. Lodes in killas generally contain a great amount of that material, either as large broken masses or small fragments. In granite the lodes very frequently ' J. H. Collins, "Cornish Tin Stones and Tin Capels." Mm. Mag., 1882, p. 15. J. S. Flett (H.M. Geological Suirvey), " Notes e i Some Brecciated Stanniferous Veinstones from Cornwall." Summary of Prtgreit, 1902, p. 154. "Petrography of West Cornwall." Summary of ProgreSc, 190S, p. 158, t J. A. Phillips, " Lodes of the Mining Districts of Cornwall." Q.J.G.S., vol. xxxi., 1876, p. 341. t By W. A. E. Ussher, 1904, see pp. 7 and 8, and Fig. 3. § C. Le Neve Foster. Tr.M.ff.S. Cormvall, 1871. " Remarks on Some Tin Lodes." 134 NATURAL HISTORY OF THE LODES. have what is known as a " granitic structure." In this way the lodes vary in composition according to the nature of the country they traverse. The formation of crush conglomerates is locally characteristic of some of the lodes. In South Wheal Frances, at the 82-fathom level, or 105 fathoms from surface, near the middle of the copper lode, rounded stones (granite) were found, all of them apparently moved away from the places originally occupied by them by dis- turbances in the lode. Some of them were embedded in copper ore. Pieces of granite the size of the palm of a man's hand were found embedded in the lode in the eastern part of Cam Brea Mine,t where the lode was disturbed by a cross course. The occurrence of conglomerate in the lodes of the adjacent mineral district of Gwinear was more common. At East Kelistian pebbles cemented by copper ore and iron pyrites occurred. The infinite variety of structures presented by some of the great lodes of the Camborne district almost defies deseription. The enormous excavations alone remain in many cases as mute witnesses of the size and value attained by the deposits of this district. In some cases, as for instance in East Pool Mine, the country rock for a great distance on either side is highly altered by silicification, &c., and, indeed, it is a matter of difficulty to see a really fresh piece of granite, except at con- siderable distance from the lodes. Alteration of the country rock in the vicinity of the lodes is exhibited on a large scale in other mines, as for instance Dolcoath, Wheal Grenville, &c. Observation in Dolcoath Mine shows that this extensive altera- - tion of the country rock does not take place from a single fissure. It sometimes happens that the lode consists of two or three or more cracks or fissures, along which the solutions have flowed at the time the lode was being formed ; they may be more or less parallel, but very often it appears that the country rock is sn shattered near the lode that the mass would be better described as a breccia. The country on either side of these cracks has been completely changed, so that no fresh, unaltered rock remains in the space between the cracks. Thus at the 412-fathom level in Dolcoath Mine, between the Eastern and New Sump shafts, the lode contains two or three parallel fissures which are only discerned with difficulty, since they are very narrow and cemented up. The lode here, for several feet in width, is a dark, hard, schorl rock containing tin in certain parts. The country granite near the lode has been taken away for the tin it contains, which is generally in the form of strings. At the 375-fathom level very numerous small, irregular strings penetrate from the main lode into the country rock, and the tin contained iiT them and their neighbourhood has warranted the excavation of a considerable piece of ground. These generally are regarded by the miners * John Kule, " Notice of the Discovery of Several Rounded Stones in the Lode at South Wheal Frances." Tr. R. 6f.S. Com., 1847-65, vol. vii., p. 161. t W. H. Argall, " On tlie Elvans of Cornwall," Miners' Assoc, 1875, STRUCTURE OF THE LODES. 135 as droppers or feeders, since they are supposed to feed or enrich the lode. At the 375Tfathom level the noain lode is clearly seen in a stope on the west of the Eastern shaft. At this point the lode consists of a small band of soft, light blue peach, on the north or foot wall of which the granite is altered for several feet into tough schorl rock (" peach "). On the south or hanging wall the granite is altered, but not to schorl rock. On the south there is a dropper (or off-set) underlying north, consisting of schorl rock. The wedge of ground between the dropper and the main lode at this place has been worked away for tin ore. On a much larger scale the granite between the South lode and the north part of the main lode has been excavated to a great extent. The South lode, and the north part of the main lode between the New Sump shaft and the Eastern shaft converge in depth and unite at the 400-fathom level. Both these lodes and the country rock between them from above the 375-fathom level downwards have been worked to an enormous extent, and the size of the immense caverns formed by the sfcoping away of this rich tin ground for many fathoms in breadth and height is but faintly appreciated by the dim light of the miners' candles. The country rook between the lodes above mentioned is traversed through and through by small strings, so that the mass is really a breccia on a large scale containing tin ore. It may happen that the initial fissure in which the lode was produced has left some trace of its original form in the occurrence of a persistent tin, quartz, or schorl rock vein. In such cases these features may act as indicators, or leaders, to guide the miner in driving and opening up the lodes. Leaders are, however, generally of more recent origin. A smooth wall, a clay flucan, or parting filled with clay, quartz, fluorspar, chalybite, &c., may also act as leaders. The leader at Wheal Uny is in one part 18 inches wide, consisting of a mass of fragments of more or less altered killas (capel), with some tin oxide, and it soon dwindles down to a mere flucan, or vein of clay, with a little quartz, only 2 inches wide. The sides (walls) are very smooth, presenting numerous slickeusides ; in fact, the leader has all the appearance of being a mere crack, filled, iu the main, mechanically, by fragments of the sides reduced in places to a clay by the attrition of the walls."* At South Cam Brea Mine this leader becomes a copper lode 2 to 4 feet wide, and in West Wheal Basset the leader of the same lode was frequently reduced to a mere ferruginous joint. At West Wheal Frances (on the west) the leader becomes a quartz vein 2 or more feet wide, but it is generally poor in tin.f In Wheal Grenville the leader sometimes consists of a very hard, fine-grained schorl rock, of the usual lode type, varying in thickness about a foot or so, but occasionally dwindling down until it disappears altogether, or changes its character to a ferruginous clay or quartz vein. * Foster, p. 641. t Op, dt. 136 NATUBAL HISTORY 03? THE LODES. At Great North Wheal Seton a flucari, or clay parting with some vein quartz, occurred in the lode. The North Tincroft lode in Cook's Kitchen Mine is 3 to 6 feet in width and consists of quartz and soft killas. The leader is a vein of crushed fluorspar (" can ") 3 inches in width. In East Wheal Lovell the lodes are very narrow, " sometimes a mere joint or line of division in the rock, but occasionally a couple of inches thick; they consist of quartz, a little clay, and red oxide of iron, and per se are utterly valueless." These are regarded as the leaders, the valuable ore occurring as impregnations of the countrj rock.* A few common types of veinstone or altered country rock neat the lodes have received special names, as Gapel, Peach, Prian, and Scovan. Capel.— The following is from Pryce's old bookt :— " The Scovan lode, whea in decay for tin, will commonly degenerate into a caple, which, in fact, is mostly o£ the nature of a scovan lode's walls, or that enclosing stratum, which it is in contact with ; thence called the caples or walls ot the lode. But there is really such a thing as an original caple lode, properly so called ; which abounds with a very stiff, hard stone, some- thing like a limestone, except the colour, wherein the tin is sometimes veined, and other times very small and disseminated. A primary caple lode is promising for tin, though but seldom for copper, unless there is a branch of copper ore or gossan that veins downwards in the lode." In the glossary of terms in the same book, Pryce says : — Capel is " a sort of stone something like limestone, but will not burn. The walls of most lodes are of this kind of stone, therefore it is common to call the walls of a lode by the name of its caple. Also some veins which abound in this stone are termed caples, or caple lodes." William Phillips^: says that " a vein is termed a caple lode when consisting of a hard, compact and unpromising substance which seems principally to be quartz intermixed with minute portions of chlorite, giving a greenish or brownish-green tinge to the mass. Tin is often found in it, copper rarely. But if a branch of copper ore, or a gossan be found to take its course down the vein, it commonly makes a durable copper mine." " Of this word it is almost impossible to give a definition, as it refers rather to situation than to substance."§ " The word capel refers rather to situation than substance, but it generally appears to be a hard homo- geneous stone, of a grey or bluish grey, with no structural peculiarities."]! Phillips states that the hard quartzose altered country material in the vicinity of the lode, if not carrying tin, is called " capel." Under the microscope it is quartz and chlorite, or quartz and tourmaline with unaltered country rock.^ " Capels are most frequently composed of a quartzose base through which crystals of schorl are very thickly disseminated either in the form of spheroidal aggregations radiating from various centres, or as acicular crystals crossing one another in all directions. Sometimes, particularly when they occur in slates, capels are a mixture of quartz and chlorite ; in others, both chlorite and tourmaline are present. They also often contain innumerable fragments of the country rock, and are traversed by narrow strings of quartz into which project hair-like crystals of schorl, which are generally attached to the sides of the enclosing , Assure. In addition to the foregoing, * Le Nieve Foster, "The tin Deposits of East Wheal Lovell." Tr. JR.0.S, Corn., 1876, vol.' ix., p. 4. t Min. Comub., 1778, p. 90. X Fr. Oeol. Soc., vol. ii., 1814, p. 119. " On the Veins of Cornwall." § J. Came, " On Elvan Courses." Tr. R.Q.S. Corn., vol.. i., 1818. II Thomas, p. 19. H J. A. Phillips and Henry Louis. " A Treatise on Ore Deposits," 1896. STRUCTUEE OF THE LODES. 137 capels frequently enclose crystals and crystalline groups of quartz (traversed by belonites of schorl), which, sometimes appear to have been broken by contraction or otherwise, and afterwards repaired by a growth of schorlaceous matter within the crack."* Poster, speaking of Penhall's Mine (St. Agnes), says that " the word capel is applied to a rock which appears to me to be simply a highly altered killas— a killas which has been greatly acted on by mineral solutions, and changed from a soft, slaty rock into a hard, dark-coloured compact mass of quartz and schorl, these minerals being arranged in streaks following the original lines of stratification of the killas. In addition, the capel is generally full of short lenticular veins of quartz, and is intersected by numerous little strings of cassiterite and chlorite."* In Wheal Uny, situated on the Great Flat lode, the lode lies between granite and killas in one place. Here the leader " is 18 inches wide, consisting of a mass of fragments of more or less altered killas (capel), with some tin oxide," while the term "greyback" is reserved for the altered granite which is found below the lode, consisting of " schorl rock with large grains of quartz in a compact black matrix.":}: In the part of Wheal Uny, where the lode is entirely in granite, the word capel has a different meaning. The capel here is found in the granite below the lode and is a " compact " schorl rock, with spots and veins of quartz, containing a very little tin, 2 feet thick." The " grey- back " lies just beyond, and consists of a " schorl rock with large grains of quartz in a compact black matrix." This shades off into " country " granite.§ In South Cam Brea Mine there is formed in the granite, below the copper lode, a "more or less stanniferous schorl rock, i.e., lode or capel," while above the copper lode, in killas, the capel consists of " schorl rock derived from killas." In West Wheal Basset the tin lode is entirely in granite. Here the stanniferous lode shades off into slightly or non-stanniferous schorl rock. In South Condurrow the same lode is entirely in granite and has a capel consisting of compact schorl rock above and below the lode ; that " above the lode is much veined with quartz and contains little or no tin." At Wheal Grenville the capel for about 2 feet on each side contains 1'6 per cent, of tin ore (36 lbs. of black tin per ton), whilst the capels left standing contain -j to 1 per cent, of tin ore. II Mr. Collins states that " capels are the silicified walls of fissures, they occur more especially in tin mines, and often, indeed, contain enough tin to pay for working, but they are known also in lodes yielding copper, lead, zinc and iron."1[ " Tiie substance known in Cornwall and Devon as capels may be described as highly altered and usually silicified bands of country rock, bordering a more or less distinct fissure or fissure-filling. The term is sometimes applied to a silicified or mineralised band at the side of a fissure traversing granite or even elvan, but most well-marked capels occur in killas. Tin capels contain particles of tin oxide in notable proportions, though not always in quantities sufiicient to pay for working."** Peach. — Prycejf states that " a peach, or peachy lode, takes its name from a kind of stone, which principally abounds in the lode, and is generally of a spongy texture, and of a greenish or dark green olive colour. It is better for tin than copper ; but is not a desirable lode for either, especially the latter, which is always of a poor quality and value when found in a peachy lode." * J. Arthur Phillips, "Eocks of the Mining Districts of Cornwall." Q.J.G.S., 1874, vol. xxxi., p. 341. t " Remarks on Some Tin Lodes in the St. Agnes District." Tr. B.G.S, Corn., 1877, vol. ix. J Foster, p. 642. § Op. cit. || Op. cit, IT J. H. Collins, " Origin and Development of Ore Deposits." Journ. Rov. Inst, Corn., 1892, p. 86, " ** Op. cit., p. 157. tt Min. Qornuh., 1778, p. 90. 138 NATURAL UlSXOIiy OF THE LODES. Williain Phillips* says that " a vein that contains a great proportion of chlorite is termed a peachy lode." Carne writes that peach is chlorite ; or mica if it is tinged with green.f Professor Foster remarks that the "green peach of the Cornish tin mines is undoubtedly chlorite, but the so-called ' blue peach,' which is so large a constituent of the tin lodes of such mines as Dolcoath, Cook's Kitchen, Cam Brea, West Basset, &c., is a bluish grey variety of tourmaline.":]: Specimens of peach from Dolcoath and Wheal Basset, examined by Dr. Flett, show it to be fine grained and dark green or bluish green in colour and " while in some cases it is so fine as to be crypto- cryatalline in appearance, in others it is visibly composed of little acioular needles." Light-coloured peach from Dolcoath shows under the microscope many aggregates of pale mica, which appear to be altered remains of felspar, no doubt derived from the country rock," and " owing to the abundance of finely-divided chlorite " was green in eolout, " while tourmaline was present only in small quantity." The blue or dark blue varieties from Dolcoath and Wheal Basset are rich in tour- maline."§ Pbian. — "A vein is said to be a pryany lode when the tin or copper ore does not occur in a compact state, but when the stones containing either of them are found mixed with other substances such as gossan or fluccan." II A term applied to a vein material of tin and copper lodes which consists of loose, crumbling ferruginous mixture of clay and quartz grains, and sometimes mica. The clay by itself would be called fluccan, while a ferruginous loose quartzose vein infilling is known as a " gossany " or "sparry" veinstone. ScovAN. — Pryce^ says that a " scovan lode is formed of a hard compact crystalline stone either of a brown or black hue, according to the colour of the tin with which it is mixed. The ore is often rich, ponderous and solid in this stone, and when it is worth one half for metal they call it scove." William Phillips states that " when tin ore is intimately mingled with quartz and chlorite the Vein is termed a scovan lode, which is of a dark brown or of a greenish hue, but not very hard or compact. It sometimes occurs in a vein the contents of which are not solid, thence by the miners termed a sucked stone."** This substance is a "hard blackish stony matter."! I Hunt describes it as tin ore mingled with quartz and chlorite of a dark brown or dirty green hue, generally loose textured.:]:! Cavities or " Vugs " in Lodes, &c. — In the Dolcoath main lode, at a depth of 175 fathoms from surface, a large cavity was discovered about the year 1814. It measured 18 to 20 fathoms in length, 3 fathoms in height, and from 4 to 9 feet in width. Carbon dioxide was present in quantity sufficient to extinguish a candle flame.§§ At the 352-fathom level in the main lode the granite is soft and the lode " vuggy."||]| At the 462-fathom level in the same lode there are several vugs. One of them is an irregular cavity of about 12 feet in length, 6 feet in height, and 4 feet in width. The ground in which it is enclosed is very rotten. * " On the Veins of Cornwall." Tr. Geol. Soe., vol. ii. , 1814, p. 118. t " On Elvan Courses." Tr. R. G.S. Corn,, vol. i., 1888, J "New Mineral Localities." Min. Mag,, 1877, No. 3. § J, S. Flett, "Stanniferous Veinstones of Cornwall." Summary of Fro- gres) of Oeol. Survey, 1902, p. 155. II W, Phillips, "On the Veins of Cornwall." 2r. Geol. ;Soc., vol. u., 18H, p. 119. IT Mvn, Comub,, 1778, p. 90. ** " On the Veins of Cornwall," Tr. Geol. Soc, vol.r., 181*, p. 118. f\ Thomas, p. 34. tt Bobert Hunt, Sritish'Mining, 1884. §§ John Rule, " Cavern in Dolcoath Mine." Tr. H. GiS, Corn., 1818, vol. i., P- 225. III! K. J. Frecheville, "Notes on the Great Main Lods of Dolcoath." Tr. M. G.K Corn., 1883, \ol. x;, p. 147. VUGS — HORSES— WALLS OF LODES. 139 A vug containing phosphate and arsenate of lead with quartz occurred in the lode at Wheal Rose, in the parish of Sithney * At the Consols Mine (Gwennap) a " great cavity or vug was found, many fathoms in length and height," at the bottom of which a mass of brecciated copper ore was met with, some of which had evidently fallen from the upper part of the cavity .f At Great Gondurrow Mine a vug was encountered in the main lode at the 155-fathom level ; the length is 36 feet, height 12 feet, width 2 or 3 feet. Horses. — Large pieces of the country rock, which are entirely surrounded by lode matter (that is, round which the lode has formed), are called " horses." In Dolcoath Mine there are at least three " horses " of granite in the main lode. The largest is at the 425-fathom level, and measures 40 fathoms in length and 15 fathoms in thickness. In depth it has not yet been proved. Other " horses " occur at the 210-fathom level, between the Old and New Sump shafts, and at the 352-fathom level on the east of the New East shaft. "Horses" were encountered in Binner Downs Mine, Cook's Kitchen, and other mines.f Walls of Lodes. — The transition between the payable lode and altered country rock is often gradual, and it is probable that the grinding of the walls upon one anotherj together with the corroding or altering action of solutions traversing the fissures, have obliterated the original walls in many cases. Thus the Great Flat lode has no sharp bounding walls, and, except for many faces or joints in the lode running in the same direction, the lode gradually dies out laterally in the country rock. Many parts of the Dolcoath main lode show similar characteristics. In Cook's Kitchen Mine, at the 145-fathom level on the Highburrow lode, the lode is 10 feet wide. The granite walls are more or less ragged or rough in appearance, and on close inspection the wall rock is seen to cleave most readily along irregular planes rudely parallel to the walls. These are sometimes narrow cracks filled with lode material. The country is occasionally so shattered as to be really a mass of impregnated rock,» enclosing a number of irregular open or closed fissures, situated near to one another. In the country rock of the Highburrow lode in Tincroft Mine there is occasionally a fairly well-defined cleavage or jointing, which strikes more or less in the direction of the lode, but is inclined more towards the vertical than the south underlying Highburrow' lode. These joints do not appear to traverse the lode, and are mineralised to a very slight extent with a little tourmaline or quartz, or they are simple clean cracks. On the other hand, many of the lodes are bounded by sharply-defined walls. The North Entral lode at Dolcoath shows clean bounding walls in many places, but the walls are nevertheless considerably altered. * Hugh Stephens, " Mineral Phenomena of Wheal Rose." Sep Corn, Poly, Soo., 1871, p. 77. t De la BeGhe, p. 324. J Kenwood, p. 176. 140 NATUBAL HISTOHY OF THE LODES. V. Caumter Lodes. " Cornish miners always give the name of a contra-lode, or caunter, to those veins which do not hold the directions of their main lodes, and therefore what may be termed a contra-lode in one district coincides in direction with the normal lodes of another ; thus the lodes of the southern part of the St. Austell district coincide with many contra-lodes in Grwennap, Camborne, &c., and the direction of some of the contra-lodes in the former coincides with the true lodes of Grwennap, &c."* Prycef states that Caunter lodes frequently cut through all lodes except the cross gossans (cross courses), but points out that lodes which intersect are caunters with respect to one another. Eichatd Thomas^ states that the general course of the lodes in the Cam- borne and Eedruth districts is from E. 20 deg. to E. 40 deg. N., and that the Caunter lodes vary in direction from this course from 30 deg. to 40 deg. Joseph Carne§ says that the contra-lodes are metalliferous veins, whose direction is from E. 30 deg. S. to E. 40 deg. S., but that some run in an opposite direction. The following relates to the Dolcoath Caunter lodes : — The North or Valley Caunter Lodb branches off from the main lode near the Gossan shaft and strikes E. 60 deg. N. for some distance until it eneonnters the South Entral lode. It is really a branch of the main lode. With a southerly underlie of 5 deg. it yielded immense quantities of copper ore to the 130-fathom level. The Dolcoath Caunter Lodk — Henwoodll states that the Caunter lode faults Harriett's lode (which has bearing E. 30 deg. N.) at the 56 and 76-fathom levels but at the 96 and 116-fathom levels Harriett's lode faults the caunter. The Caunter lode passes from killas into granite. It has an underlie of 15 deg. S. and a bearing E. 4 deg. S.f This lode produced con- siderable quantities of copper ore to the 125-fathom level ; but recently it was intersected in the granite by the 220-fathom cross cut driven south from the Old Sump shaft and at that depth is tin bearing. Particulars of other Caunter lodes are given in the following table : — Mine, Cook's Kitchen Caunter Lode. South Caunter Middle Engine lode Deg. E. 20 N. E. 5N. Deg. 40 S. 15 N. to 40 N. Remarks. Contained tin and probably copper ore. Branched from Chapel's lode at the deep adit and was productive in copper ore uiitil it changed its under- lie to 40 deg. N. at the52-tathomlevel. • De la Beohe. p. 363. + Min. Comuh., 1778. X p. 19. § V-^ II Table L., Kenwood quotes the authority of R. W. Fox. Phil. Tn, IS^''- 11 Henwood, Table L., states that the bearing la E, 11 deg. b. GAUNTER LODES. 141 Mine. Gaunter Lode. Bearing. Vnderlie. Bemarks. Deg. Deg. Cam Brea Druid Gaunter E. 20 S. Nearly vertical An ore-bearing lode from adit to 50- fathom level. Vigur's lode E. 20 S. Nearly vertical South of Druid lode, to which it is con- nected by short branches. Con- tained copper ore to the 105-fathom level and then tin ore. Camborne Vean E. and W. S. Probably copper. West Roskear ? ? Gaunter branched from main lode at about 12-fathom level. Both lodes contain lead, blende, copper and iron pyrites, and tin. Great North Branched off from Seton the main lode at the70-fathomlevel. South Wheal E. and W. 15 N. Branched off from Seton 1 main lode in deep levels. Wheal Seton - North Gaunter lode B. and W. Worked upon in North Roskear and East Wheal Seton. It contains copper and iron pyrites. (Harry Tilly, "Particulars of a Thermal Spring at Wheal Seton." Miners' Assoc, 1873.) South Gaunter 45 N. Contains some tin lode ore. North • Wheal A Gaunter lode in Crofty ;,,j It. west end of mine of no value. South Crofty - Reeves' Gaunter lode B.3S. 10 N. Contained copper ore to the 90-f athom level. Recognised in North Roskear and Wheal Seton. Longclose E. 30 S. Nearly Vertical to the 35- Gaunter vertical to N. 13. fathom level. Cop- per ore abundant to the 115-fathom level. (Henwood, Table Ivi.) , Copper Tank- B.24S. Contains copper. ard lode zinc ores, and iron pyrites. , Trevenson E.2S, 14to40N Yielded copper ore. ibde (Henwood, Table Ivi.) 142 NATURAL HISTORY OF THE LODES, Wheal Crofty - Gustavus Wheal Tehidy East Pool Park an Bowan (Boskeamoweth) Wheal Harriet Great Condur- row West Basset - Wheal Basset - Wheal Gorland South Wheal Hawk East Wheal Chance Wheal Basset and Grylls Crenver (and Wh. Abraham) Deg. E. 25 S. E. a few degs. N. E. and W, E. 24S. Middle lode Gaunter E. 24 S. B. and W, E. 20 S. Deg. 8 to 25 S, N. S. 20 N 2or3N « 2or3N. Contains copper lead and zinc ores,' and iron pyrites. (Henwood, Table Iv.) Copper and iron pyrites. Branched off from the south of Pryce's lode. A Gaunter at the 170- tathom level in granite is abreo- ciated lode, coa- tains tin and other ininerals,with later vein of chalybite. This lode is being worked. Copper to the 70- fathom level. (Part of North Boskear) contains copper and zinc ores. Copper ores. This mine is in granite. Gaunter at 10- fathom level ec- tained copper ore. Contains copper and tin. It intersects Williams' lode. Paulti the Great Flat lode. Lodes counter to one another. Contains copper. It intersects the South Wheal Hawk copper lode. (Thomas, p. 43.) The Caanter lode intersects the main lode which underlies south and faults it 12 feet. Both eon- tain copper. (Thomas, p. 37.) A Gaunter lode 5 feet wide con- taining tin ore. A Caunter lode intersected and heaved by the Great lode 70 fathoms. (Oarne, p. 98.) INTERSECTION OF LODES. 143 Mine. Gaunter Lode. Bearing. Underlie. Bemarles, Deg. Deg. Herland - Fancy Gaunter lode E. 35 S. 8 to 18 S. (Kenwood, Table xxiv.) North Downs - E. 28 N. 7 to 10 N. Contains copper pyrites. Forms a junction with the Tenpnnny lode and is with" it for 8 fathoms. (Hen- wood, Table Ixix.) United Mines - Bawden's South lode S. 10 to 24 Two lodes have an east and west bear- NichoUs' Branch S. 12 to 30 ing but are not called Gaunters. Both contain cop- per ores. (Hen- wood, Table Ixi.) Gaunter lode N.B. (Game). Killifreth E. 34 N. The main lode has a nearly E. and W. bearing and the Gaunter branches ofl from it on the north side. The foregoing list is far from complete, and there are probably errors in the few details which it has been possible to collect. On the whole the Gaunter lodes are far more common in the killas than in granite, and although some of them contain tin ore, they more generally contain copper or other ores. As a whole Kenwood's statement that "Gaunter lodes have no distinctive character but that of direction " is true. VI. Intersection of Lodes. The question here concerned is largely that dealing with fault- ing, and whether or not there is any justification for the view that the lode fissures were formed successi«vely by distinct epochs of movement. The information of the precise mineral phenomena of the intersections of lodes is very meagre, but in view of the diverse opinions of different writers* the ease requires a very careful examination of the facts. The question is complicated by the probable processes of secondary concentration of some of the ores in the lodes, their unequal mineralisation^ and by the move- ments that have taken place in the lodes long after they were formed. The facts recorded by early writers must sometimes be treated with caution ; thus there are somewhat disturbing state- » In. 1778 Pfyce classified the lodes under twelve heads IMmeraloaia Conmiurms, p. 88). In 1822 Came divided the fissures into eigllt successive epochs of formation {Trans. Geol. Soc. of Corrmatt, vol. ii., pp. 85-119) In 1SQ7 Mr. Collins classified Dhe lodes under nine heads, each representing a distinct epoch of movement {Journal Roif, fnst^ gor-^mU.l^^T, p. J95). ^ I'siincii 144 NATUEAL HISTORY OF THE LODES. ments in one of Game's papers, in which it is said that " in some copper lodes tin is so plentiful in some parts as to give them, for a short space, the appearance of tin lodes."* And, again, " it is con- sidered a favourable symptom to find, on the back (of the ' oldest east and west lodes') tin ore/'f Came states that " it appears probable that previous to about A.D. 1700, the copper ore produced in Cornwall was principally, if not wholly, from tin mines, or at least from mines originally wrought for tin."$ Eichard Thomas says that the " Chacewater lode at "Wheal Daniell is called a tin lode ; at Chacewater Mine, a tin and copper lode ; and at Treskerby a copper lode."§ Phillips states that the old miners frequently worked a lode for copper, entirely ignoring the presence of tin ore considering it to be not worth working, or else thinking the lode was of no more value after the copper ore had been extracted.! There are many cases where a number of lodes are proved in depth or in their direction of strike to be really branches of one lode, although each is treated by the miners as a separate lode and called by a special name. In the following are a few particulars of the intersections with one another of what appear to be inde- pendent fissures : — Cook's Kitchen Mine. — The Great lode, which has a southerly under- lie, intersects and heaves Toy's lode, which underlies north, to the extent of 18 fathoms at a depth of about 105 fathoms below adit. Above this place the Great lode was only copper bearing, but the part of the lode between the intersected portions of Toy's lode contains both copper and tin. Below the intersection the Great lode only contained tin ore. Thus it contained no tin above the intersection and no copper below. ^f The Great lode is that which is known at the present time as Dunkin's lode. Exploration in the deeper parts of the lodes since Came made the above observations shows that copper occurred in Dunkin's lode to the 222- fathom level. Thomas states that Toy's lode contains both tin and copper ores and that it crosses the Great lode at the 90-fathom level.** Henwood says that the junction consisted of " a mass of earthy red iron ore, quartz and vitreous copper ore 10 feet wide. They continue nixed on the line of Dunkin's lode for 9 fathoms " after which there is black and vitreous copper ore, crystallised red oxide of copper, and some tin ore.|| Wheal Basset.— The intersection of the Great Flat lode by the numerous more or less perpendicular lodes which heave it is characterised by a great widening of the Flat lode near these places. The lodes which fault the Great Flat lode contain mainly copper ore, but copper ore also occurred in the upper part of the Great Flat lode itself, while some was also only recently taken from it at the 250-fathom level in Wheal Basset. The tin ores in this mine are mainly obtained from the Great Flat lode, but tin also occurs in smaller quantities in the lodes which intersect it. The lines of intersection are not distinct, but in West Wheal Frances (further west) a copper lode containing some tin ore is stated to have actually passed through the Flat lode as a distinct vein. North Eoskbab and Whkal Ceoftt. — The Engine lode is possibly traversed by the Gaunter lode which underlies south. The intersection * Came, p. 103. t Op. eit., p. 93. $ "Copper Mining in Cornwall." Tr. R. 6. S. Cornwall, vol. iil., 1828, p. 44. § Thomas, p. 20. II "On the Veins of Cornwall." Tr. Geol. Soc, vol. ii., 1814, p. 122. IT Carne. »* Thomas, p. 33. t+ Henwood, Table h. INTERSECTION OF LODES. 145 of the Canntep lode with the South lode, which has a variable undej^lie, is simply a confused lode, and at a lower level these lodes are together for 7 fathoms with no sign of a heave. They all carry copper.* South Condtjekow. — The Engine, Middle and West Basset lodes, which are more or less vertical, all heave the Great Flat lode. All of them con- tain tin and copper, but the Great Flat contains very little copper and the other lodes not much tin. South Feancks Mine. — The Basset lode and two other lodes heave the Great Flat lode between the 134 and 205-fathom levels. The Basset lode underlying north intersects one of the copper lodes which underlies south. They all contain tin and copper ores. The Great Flat contains but little copper, while the other lodes contain more copper than tin. South CHOFTY.^The Middle lode drops from the south wall of Pryce's lode into the North lode. The lodes cannot be distinguished at the junctions and are of similar composition, containing tin and copper ores. Tkkskebby. — The Flat North underlying copper lode crosses the north underlying Chacewater lode at the 60-fathom level. The Chacewater lode in Chacewater Mine contains tin and copper ; in Wheal Daniell it is called a tin lode.t United Mines.— The South lode and the Great lode (in the Ale and Cakes part of the mine) intersect each other at the 170-fathom level. Both underlie north and contain copper.| ' The Mundic lode underlying north intersects, but does not heave Bawden's lode, which underlies south. Both lodes contain tin and copper.§ The Cargruel lode, containing both tin and copper, traverses the Eapsey copper lode. || Wheal Gorland. — Dennis's lode, which is a vertical copper lode, inter- sects Green's lode, which underlies north and contains tin and copper.^ Whkal Unity.— The Solid tin lode underlies north and forms a junc- tion with Francis copper lode, which underlies south. The lode so formed carries both tin and copper, and . is known as Green's lode in Wheal Gorland.** Oaezisb Mine. — The Caunter lode joins the Carzise lode and they continue as one lode for 20 fathoms and then separate. Both carry tin and copper and underlie south.! j East Wheal Chance.— See p. 226. POLDICE. — The Great ore lode underlying north and containing copper intersects and heaves to the extent of .about two fathoms the Poldice tin lode and the Bissoe tin lode, which underlie south.|:|: SooKRiBB Mine.— Two copper lodes underlying north are intersected by a Caunter lode underlying north and eonfaining copper. The Caunter is the same as that seen in East Wheal Chance.§§ Wheal Hawke.— The Wheal Hawke copper lode underlying south intersects the tin lode which underlies north. Similarly, the'Pendarves copper lode crosses a south underlying tin lode in Wheal Messar.|| 1| Nangilbs. — Two copper lodes heave a tin lode.^^ Dolooath.— See p. 140. East Wheal Ceoety.— The Longclose main lode intersects the Long- close Caunter lode at the 30-fathom level. At the 54 and 65-fathom levels the main lode heaves the Caunter lode 3"5 and 5-5 fathoms respectively. Both lodes underlie north and both contain copper and zinc.*** * Henwood, Table Iv. + Thomas, p. 20. + Op. dU, p. 49. § Henwood, Table Ix'. 11 Came. If Thomas, p, 56. ** Thomas, p. 65. tt Henwood, Table xli. JJ Thomai, p 40 §§ Opicit., p. 42. nil Oy. cit., p. 57. iriT Came, p. 88. *•• Henwood. Table Ivi. ^ 146 NATLTBAI, HISTORY OP THE I.ODES. Ting Tang.— The itiiddle lode unites with the main lode -westwards and forms one lode with it. Both lodes contain copper and underlie north.* CoNSOi^iDATBD Mines. — Glover's and Kitto's lodes both underlie south and intersect Paul's lode which underlies north ; all contain copper. Taylor's and Tregonning's lodes unite eastwards.t South Wheal Towan.— The Slide lode is thrown up 25 fathoms by the South lode. Both are copper lodes.:]: The above list, together with that of the Gaunter lodes, includes the cases upon which systems of classification according to the different ages of lodes have been based. It appears that in these instances the intersecting lodes do not differ from each other, except in a few cases, in the actual minerals they contain. In some lodes, however, copper predominates, while in other lodes tin ore is more abundant than copper. The case at Cook's Kitchen Mine (page 144) shows how easy it is to be misled as to the pre- cise meaning of these intersections. In Poldice it appears that a tin lode is heaved by a copper lode. On the whole those lodes containing much more copper than tin sometimes intersect those containing more tin than copper. Joseph Carne§ endeavoured to classify the lodes into distinct systems, but the data upon which he based his classification were incomplete. Thus he refers to the Dolcoath lode as being one of the " oldest east and west copper lodes," whereas it is known at the present time that in depth it is an exceedingly fine tin lode with no copper in it. Before the lodes can be classified in this manner it must be shown that there are two or more distinct fissure systems, each of which contains characteristic minerals, separating it in some way from the others. The formation or re-opening of a fissure giving rise to a lode is not necessarily followed immediately by infilling of minerals. VII. Faulting by Lodes. De la Beche pointed out long ago that most of the lodes are faults. The evidences of faulting are based upon direct observa- tion, which can be classed under three heads : (1) Dislocation of the walls of the lode ; (2) Form of the fissure ; (3) Brecciation of the walls of the fissure. On account of the similarity in dip and strike of the lodes and elvans it is only in a few cases that the elvans are clearly seen to be faulted by the lodes which cross them. At Herland Mine (Gwinear) an elvan is heaved six feet by a Gaunter lode.|| Another elvan in the same mine is thrown some fathoms by a lode (op. cit). At Duffield Mine there is a similar instance.1I The Great Flat lode, south of Camborne, is faulted by ' several more or less vertical lodes in South Condurrow, South Frances, West Basset, and Wheal Basset, At Wheal Basset the * Henwood, Table Ix. t Op. cit., Table Ixii. t Op. cit., Table Ixxli. I Carne. i| HenwoOd, Table xxxiv. IT Op. otY., Table xxxvii, FAULTING BY LODES. 147 Flat lode is heaved 20 fathoms by the Old lode.* In Camborne Vean Mine the granite is heaved 20 fathoms by the lode, and in Dolcoath the hanging wall of the Gaunter lode is lower than the footwall. At South Crofty Mine the granite is faulted down southwards by Pryce's lode to the extent of 9 fathoms. The sheet-like intrusions from the granite in Cook's Kitchen Mine and Tincroft are dislocated by the Highburrow and other lodes.t The granite is faulted (10 fathoms) at Wheal Beauchamp by a lode,| and at Tresavean§ and Wheal Trannack.|| Cases where one lode faults another are common. At South Wheal Towian the south under- lying lodes are dislocated by the north underlying lodes to the extent of 25 fathoms (see page 146). The form of the fissure frequently shows that faulting has taken place, as the infilUng is often made up of alternate wide and narrow parts produced by the movement of the walls of an irregular crack along one another. Any of the larger lodes exemplify this, Brecciation of the lode materials indicates crushing by move- ment of the walls either during dislocation or by vibration, such as those arising from earthquake shocks. " Fragments of slate cemented by quartz and yellow copper ore " were obtained from the principal lode of the Consols Mine, Gwennap. Angular pieces of slate cemented by yellow copper ore were found at the United Mines, Gwennap. At Wheal Jane (Helston) similar veinstones occur. At Binner Downs Mine (Crowan) angular portions of slate, yellow copper, and zinc blende cemented by pearl spar or carbonate of iron occurred.iy Brecciated veinstones from the deep levels of the lodes can be identified in East Pool, South Crofty, Dolcoath, and Wheal Basset. Slickensides occurring in a lode already supposed to be a fault are confirmatory evidence. " Slickensides " may, however, be produced by the squeezing of a soft substance such as moist clay between hard walls, or by a vibratory move- ment of the walls upon one another, or it has been suggested that etching of the walls by corrosive gases may produce the appear- ance of a slickenside. In Cook's Kitchen Mine the footwall of the Highburrow lode at the 270-fathom level is a hard granite scratched up and down for several fathoms. At the 210-fathom level in the main lode of Dolcoath, on the west of the North Valley shaft, there are horizontal striations. Numerous slicken- sides occur also in Wheal Uny.** Slickensides on iron and copper pyrites occurred in the walls of lodes in Great Wheal Fortune, South Crofty, and Consolidated Mines. ft In conclusion, it may be stated that movements appear to have taken place in the plane of the lode both before and after mineralisation, and of those lodes * J. Maynard, " Remarks on Two Cross Sections. ' Rep. Corn. Poly. Soo 187L t Thomas, p. 43. Henwood, Table li. and p. 60. t Henwood, p. 199. § Op. cit., p. 7L || Op. cit., p. 197. f De la Beche, p. 323. ** R. H. Thomas, " Some Observations on the Great Flat Lode in Wheal Uny." Sep. Corn. Poly. Soc, 1886, p. 184. tt Henwood, p. 181. i2 148 NATUEAX niSTOHT OP THE TjODES. in which both can be shown to have occurred the principal are found at the margin of the granite, which is a position of structural weakness, and may be described as the focus of the metalliferous area. It is a position very favourable to the produc- tion of breccias. It is more than probable that the largest ore lodes are generally to be found at the edge of the granite where the lodes are parallel to the granite margin. Lodes in which the Faulting is InsignificaM. — Mr. Hill states* that in the parish of Wendron there is "an extremely attenuated set of mineral veins which have been extensively worked for tin." He traces a connection between these fissures and tbe E.N.E. system of joints (toughway joints of the granite), and concludes that they originated in the continued operation of the same stress with wbiei the intrusion of the granite is connected. It is not improbable that the tin deposits of Wheal Lovell and East Wheal Lovell and many other mines afford some instances of this nature.f In many cases the lodes of this region each consist of a series of close parallel cracks. The intervening layers of country rock have been so completely changed, and the fissures themselves so obliterated by the action of the vapours which once traversed them, that the original structure of the bde is altogether lost, and may have the appearance of a massive fissure infilling. Sometimes there are two or more systems of cracks intersecting each other at a narrow angle, and seeming to form conjugated systems such as those lererred to by Daubree. "But," as Mr. Hill points out, "when the granite is followed into the districts of Eedruth and Camborne, the magnitude of the fissure lodes and elvans have reached their maximum, and the marginal zones of the granite constitute the heart of the mineral area."t With regard to the origin of the jointing in its relation to lode fissures, Professor Crosby's hypothesis that parallel jointing is due to earthquake movements is one worthy of consideration.§ VIII. Tkknd of the Lodes. The metalliferous fissure veins or lodes in any particular part of this district, in common with the elvan dykes (and " toughway " joints of the granite), have a certain more or less definite bearing which varies slightly for each locality from the bearing common to the whole. .Henwood|| states that the mean strike of the lodes in the Camborne district is E. 20 deg. N., and that in the Eedruth district it is E. 22 deg. N. The mean strike of all the lodes in any particular locality is, however, not the same as the mean strike of the principal lodes ; in Camborne, for instance, the mean bearing of * J. B. Hill, R.N. (H.M. Geol. Survey), Summary of Progress, 1903, p. 31. t See " Tin Deposits of East Wheal Lovell," by C. Le Neve Foster. Tr. M.a.S. Cornwall, vol. ix., 1876. J 8fnm/marry of Progress, 1902, p. 31. § W. O. Crosby, Proo. Boston Nat. Hist. Boo., 1882, vol. xxii. The American Geologist, vol. xii., 1893. II p. 250. TREND OF THE LODES. 149 the principal lodes is E. 30 deg. N. There are, bherefore, certain lodes which have a bearing differing from that of the majority; and in Camborne there is a marked series of lodes having a bearing nearly E. and W. called Gaunter lodes. These lodes " have no distinctive character but that of direction/'* and are comparatively few in number. __ The following tabular statement is an attempt to give for each locality the mean bearings of those lodes that have the same general trend : — Lodes. Camborne Distnct. — Dolcoath, &c.,and the lodes on the north. Lodes in the granite on the south of above, excludmg the Great Flat lode. Redruth District. — Bound the margin of the Bedruth granite. District on the north of the Bedruth granite. Carnmenellis granite. Bound the N, and N.B. margin. Gwannap District. — Between St. Day and Twelve Heads. District between Twelve Heads and Newbridge. Wendron Dis'rict. — Southern part of Carn- menellis granite Perth Towan lodes. Beabing. B. 30 deg. N. B. 32 deg. N. B. 22^deg.N, E. 21^ deg. N, B. 30 deg. N. E. 20 deg. N. B. 34 deg. N. B.36deg. N, Bemabes. B. 20deg. N. Lodes along the margin and on the north of the Cam Brea granite* excluding Catlnter lodes. Great Flat lode. (Prom South Condurrow to West Frances "E. 31 deg. N. From West Frances to South Carn Brea E. 35 deg. N. From Wheal Uny eastwards 18 deg. N.) The lodes on the northern margin have a bearing greater than this number ; those on the south less. Some have a nearly B. and W. bearing. The bearings vary from E. 15 deg. N. to E. 35 deg. N. Some lodes run nearly E. and W., and are not included. The bearings vary from B. 16 deg. N. to E. 36 deg. N. the latter being the Tresavean main lode, the former those lodes on the north and north-west of Tresavean. Some of the lodes not included bear nearly E. and W. ; others bear E, 30 deg. N. to B. 40 deg. N. One lode, at least, has an E. and W. bearing, and is not included. Lead lodes not included. The lodes vary in direction from E. 15 deg. N. to B. 53 deg. N. The latter are round Garlidna and Halabezack district. There appear to be several series of lodes corresponding with directions E. 5 deg., 17 deg., 28 deg., 35 deg., and 48 deg. N. Some lodes not included strike nearly E. and W. IX. Underlie of the Lodes. As a rule, the principal lodes underlie north, and in this their behaviour is similar to that of the elvans. * Henwood, p, 253. 150 NATURAL HISTOSY OF THE I.ODES. Taking the Camborne district first, and traversiBg the district from north to south, the following general average underlie of the principal lodes is obtained. The most northerly series of lodes in the Camborne district is that extending from Wheal Tolgus (on the east) through West Wheal Tolgus westwards. Situated entirely in the killas, the average underlie is from 26 deg. to 30 deg. N. The next series, on the south, includes the lodes of the Seton Mines through to North Pool and South Wheal Tolgus ; the average underlie is 40 deg. N., but the lodes on the west are flatter than those on the east. The next series includes the lodes of the Roskear Mines, South Crofty, East Pool, and Wheal Tehidy. In South Crofty and Bast Pool the lodes pass into granite in depth. The average underlie is from 20 deg. N. to perpendicular, but some lodes underlie south. A single lode lying between the last series and the next is known in Dolcoath as the North Entral lode, and eastwards as the North Tincroft lode. It underlies N. 34 deg. (average). The next series is that situated along the margin of the Cam Brea granite, and extends from West Stray Park, through Dolcoath, Cook's Kitchen, Tincroft, and Carn Brea. The lodes vary from vertical to S. 18 deg.; but in the deep levels of Dolcoath, over 300 fathoms in the granite, the underlie is S. 45 deg. Numerous lodes in the upper levels of these mines underlie north. South of this series is a lode situated in granite extending from Carn Camborne to Wheal Providence, and it underlies a few degrees north to vertical. The lodes from Great Condurrow to South Dolcoath Mine underlie a few degrees S. Along the southern margin of the Carn Brea granite is a series of lodes situated mainly in granite extending from South Tolcarne through South Condurrow, West Francis, West Basset, and Wheal Basset (in killas). These lodes are more or less vertical, hut some underlie north and others south. The Great Flat lode, which belongs to this series, is exceptional, and has an average southerly underlie of 51 deg., but is steeper on the east and flatter on the west. There are a few lodes extending from Grillis to South Wheal Basset, situated in granite. The underlie is a few degrees to the north. The district from Scorrier Gate to the United Mines in Gwennap can be dealt with in a similar manner as follows : — The lodes of Wheal Mary and Little North Downs intersect each other, some lodes underlying south and others underlying north. They appear to follow no particular direction as regards underlie. Some of the lodes of New Treleigh Consols, Wheal Peevor, and North Downs underlie north at about 19 deg., but some underlie south or are vertical. The main lodes of Treskerby and Great Wheal Busy (Chacewater Mine) underlie north from 34 deg. to 40 deg., but some lodes underlie south. The lodes of Killifreth underlie north at 58 deg; or less. The Unity Wood series underlies north. The Wheal Gorland lodes underlie north or are perpendicular. The lodes from West Wheal Damsel to the Consolidated Mines underlie north from 20 deg. to 25 deg. There are numerous south underlying branches in the Consolidated Mines. The lodes from Ting Tang, through the United Mines, Wheal Clifford, and NangUes to Wheal Jane underlie north from 20 deg. to 65 deg. A few lodes in Nangiles are nearly perpendicular. " Flat " * Lodes. — There are many cases of lodes underlying at about 45 deg., but in a few cases the lodes approach more nearly to a horizontal than to a vertical position. The following examples indicate those of low hade : — At West Wheal Seton (on the north of Camborne) the underlie of the lode (which is accompanied by an elvan) is 58 deg. N. At Wheal Jane the main lode underlies north at about 65 deg. (Fig. 17.) At Killifreth the middle lode underlies north at 58 deg. (Fig. 18.) The Great Flat lode * The term " Flat Lode " is commonly applied in Cornwall to a lode with a characteiistic low hade. UNDERLIE OF THE LODES. 151 (along the southern margin of the Carn Brea S'^'^'t^l f *'^^ ^^ HlO underlying Flat lode. At South Tolcarne its underlie is 80 ^eg. b. ju S fcom the horizontal), but eastwards the lode ^'eoomes gradual y s^e^er^until at Wheal Uny it is 45 deg. S. There are several Placesm which the lode is almost vertical, but only for f »'*,;?i«t^^fi;„^^* JS Sauire the Flat lode underlies N. 54 deg.* At Wheal Peevor the llat loTe underlies north at 53 deg. There are also Flat lodes in Wheal Music, United Hills, Wheal Busy, &c. Fm. n.— Wheal Jaw. The Eelative Underlie of Lodes and Elvans.— There _ are a great many cases in which the lodes underlie in the same direc- tion as the elvans in their vicinity. The flat, north underlying lode in the Seton Mines, on the north of Camborne, is contiguous to an el van. The lodes of Dolcoath Mine m the deep workings are associated with elvans. Some parts of the Great H lat lode in Wheal Basset are mineralised elvan, which underlies south at about the same angle as the lode. At Wheal Wentworth (near Redruth) an elvan underlies in the same direction as the lode. At North Wheal Crofty a Fig 18. — KUlifreth Mine. north underlying elvan is intersected by north underlying lodes which are slightly steeper. In the ClifEord Amalgamated Mines two north under- lying elvans are intersected by slightly steeper north underlying lodes ; and in Nangiles, Treslserby, Wheal, Busy, Killifreth, and Wheal Jane the lodes and elvans are more or less parallel or occupy the same fissure. At Copper Hill an elvan underlies north with the lode. At Wheal Moyle Ting Tang, an elvan underlies northwards towards the granite, and is intersected by north underlying lodes which are slightly steeper. At Wheal Jennings (Parbola-Gwinear), Bissoe Bridge (near the United Mines * J. Carne, "On the Veins of Cornwall." Tr, B.G.8. Corn.,\o\.\\., 1822, p. 98. 152 NATURAL HISTORY OF THE LODES. Gwennap), Chacewater Tin and Copper Mine* and Wheal Unity,! much ot lode material is only mineralised elvan. Thus, many of the lodes miderlie in the same direction as the elvans, and either at the same angle or more steeply. The angular difference between the amount of underlie of the lodes and elvans occurring in the same mine in a few selected cases is as follows : — In West Stray Park Mine the difference in underlie of the elvan and lode is about 25 deg., in Wheal Clifford from 35 deg. to 50 deg., in the United Mines about 30 deg., in Ting Tang Mine about 20 deg., in Wheal Emily Henrietta (near Tolvaddon) about 25 deg. ; in all these cases the elvans and lodes underlie towards the north and are in killas, and in no case is the elvan steeper than the lode. Similar differences are observed in the granite, but where, as in Dolcoath, the lodes and elvans are south underlying, the elvan is steeper than the lode or is parallel to it. Cases in which lodes underlie in a direction opposite to tliat of the elvans are not so numerous or striking. The Engine lode at East Pool Mine is a steep south underlying lode, and intersects an elvan which underlies north. Similarly, in Cook's Kitchen Mine the main lode (Highburrow) underlies southwards into the granite, and intersects an elvan which underlies northwards. Finally, there are numerous cases where the lodes of a mine underlie in different directions and, consequently, intersect each other. Thus : at Little North Downs Mine, one set of lodes underlies north in the same direction as an elvan, while another set underlies south. Similarly, at Chacewater Mine, the ore-bearing, north underlying, elvan is intersected by south under- lying lodes. X. Length of the Lodes. The length of a lode is the length of a more or less continuous fracture which may be subject to the irregularities of ordinary faults. Most of the lodes have nob as a rule been completely explored from end to end, owing to their poverty or other causes; but the lodes of one mine can be frequently identified in a neigh- bouring mine into which they pass. " Whether explored hori- zontally or as they descend in depth, they are seen often to be wavy and irregular, to go off from and return to their usual direction, and to present so many anomalies, that whilst on a map we may be obliged to take a straight line as an average, the real course is usually such as not only to complicate the workings but to make us slow to accept some of the brilliant theories which have connected lines of fissures with actual dates asserted to be discoverable in the elevation of mountain chains."! In a general way, however, the important lodes, whether as single fissures or mineralised zones, have been traced for considerable distances across the country. The Great Plat lode extends continuously from South Tolcarne, through South Condurrow, West Francis, West Basset, South Carn Brea, and Wheal Uny to Cal Downs (on the western margin of the Redruth Granite), a distance of 3^ miles. It becomes steeper as it goes eastwards, and so loses its chief peculiarity, making it a matter of difficulty to identify « m that direction. The Dolcoath main lode extends from Cam Brea Mme, * J. Carne, "On Elvan Courses." Tr. B.G.8. Com., 1818, vol. i.. p. 104. t Brenton Symons. "A Sketch of the Geology of Cornwall," 1884. _ t Warington Smyth, F.E.S., " Physical Phenomena connected with the Mines of Cornwall and Devon." British Assoc, Sep., Plymouth, 1877. BREADTH OF THE LODES. 153 where it is known as the Highbuprow lode, through Tinorott, Cook's Kitchen, Dolooath, Camborne Vean and West Stray Park, to near Bams- gate. Total length nearly 3^ miles. The Cam Camborne main lode extends from Kellivose through Carn Camborne and Wheal Providence to Wheal Druid, a distance of over 2^ miles. The Wheal Briggan main lode extends from Wheal Mary, on the west, through North Downs and Wheal Briggan to East Downs. Distance 2^ miles.* The Great Wheal Busy lode has been traced from Wheal Daniell (on the east) through Great Wheal Busy, Seorrier Old Mine, Treskerby to Cardrewf and possibly runs into Treleighwood Mine. In the United Mines the old lode has been traced from Camborne Parish through Oarnkie to Baldhu, a distance of 7 miles.| No information is forthcoming of the way in which a lode dies out in the direction of strike, since if the lode is poor it has been abandoned ; and, as William Phillips states, " the most experienced miner never satisfactorily witnessed the termination of a vein either on the east or west."§ Where a lode in killas is coincident with the cleavage, it probably dies out gradually along these planes. Mineralised joints in granite will die out into a mere line of rifting. XI. Breadth of the Lodes. The breadth of a lode includes the width of the infilled fissure and the altered rock on each side of it. As both these factors are Jiable to considerable variation it is almost impossible to determine what is the true width of any single lode. But by means of a number of measurements, Henwood|| found the mean width of the lodes in the Camborne district to be 3'68 feet, and in Bedruth 3-36 feet ; and generally that the width of the lodes in slate is greater than that in granite. He also noted that, on the whole, the lode containing both tin and copper ores are wider than those containing copper only. Since Henwood's time the workings have been carried to a much greater depth, and the information so obtained casts considerable doubt on the conclusions he arrived at, more especially since many of the lodes are not single fissures. A few examples will illustrate the difficulties in the wav of any attempt to calculate an average for the width of the lodes' Dolooath.— The lodes where principally worked va;ry in width from a mere parting to 20 feet, but the average is 3 or 4 feetf^ The widest parts of lodes occur principally where there is an abrupt change in the strike of Jnl,°^ft% P'"?! tlie 200 to the 300-fathora level (in granite) the lode varies n width from 1 to 9 feet. At the bottom of the mine, near the 490-fathom level, nearly 300 fathoms in the granite, the lode consists of a hard breccia, utfj^^^l The junction formed by the Main and South Entral lodes IS 60 f^t wide. The South lode-which is a branch of the main lode- vanes from 6 inches to 2 feet in the upper levels. The Silver lode is about 2 feet wide. The Caunter lode varies from 6 inches to a ?oo . The Great Plat LoDE.-The part of the lode left standing in Wheal Granville is 1 foot to 8 feet in thickness, and in South Condirfow the t?n- laoZfJfJ''^ 5 or 6 feet in breadth, but the total width ofThe lode includii^ the barren oapel in either wall, is 12 to 20 feet. In West Wheal Basset the lode and altered country rock at the 140-fathom level are * Thomas, p. 30. + Op. cit., p. 32. f«r«.?®v9'» tile Veins of Cornwall." lr.B,0,S. Con ,mo\ H „ 9fi f, *^o"lo*^* ^^'"* "* Csrnwall." Ir, Q. Soc, voh ii., 1814, p! U3. ' ^' IT Josiah Thomas. Jown. Boy, Imt, Corn., 1868, vol. ill., p. 192. 1 54 NATURAT, HISTORY OF THE LODES. together 40 to 50 feet in thickness* In Wheal Uny the same lode varies from 4 to 10 feet in thickness, and in one place near a cross course is 72 feet wide.t Miscellaneous Lodes.— In Tincroffc Mine, on the north of the Cam Brea granite, some parts of the Highburrow lode are 3 or 4 feet wide, while other parts are 30 to 40 feet. The Engine lode at North Eoskear varies from 1^ to 18 feet. In Wheal Vor the main lode varies from 3 to ^ * f +■ f ^°^ ^°^^ '" Polladras Downs Mine varies from 1 inch to 4 feet.J In Nangiles the main lode reached a maximum width of 30 feet. Observations on the Width of Lodes.— If the original fissure in which a lode is formed is irregular, the relative displacement of its walls by faulting results in the formation of open and closed parts as was shown by De la Beche,§ Le Neve Foster,|| and other writers. During the act of dislocation the walls of the fissure are crushed or ground together so that the original walls are obliterated. In this manner the fissure becomes largely filled with breccia. These breccias may also originate in' the swift vibratory move- ments accompanying earthquake shocks, or may result from, direct pressure without faulting. Again, the width of lode is largely determined by the extent of the alteration in the vicinity of the fissure by active agents con- tained in solutions traversing the fissure. It will be seen, then, that in nearly all cases where the width of a lode is given it much exceeds the amount of opening in the original fissure. In this way the walls of those parts of a fissure which have afforded a passage for mineral solutions for a lengthened time must (other conditions being equal) be altered more completely, and for a greater distance on either side than in a case where access of solutions was only limited. Finally, every movement, which is not one of shearing under great lateral pressure, serves to further increase the width of the fissure, so that in this manner a lode is always tending to increase in size. Where, as is often the case, the lode consists of a series of close parallel joints or cracks, the width of the lode varies con- siderably, according to the number and proximity of the cracks. XII. Veinstone of the Lodes. In hand specimens the veinstones in any particular lode are considerably varied. Broadly speaking, the miner recognises certain types to which special names are given (see page 136). The miners' terminology, although rough and ready, is expressive enough. The characteristic veinstones of any part of the lode area vary almost imperceptibly in passing from one place to another, owing to the preponderance of different minerals over one another in different parts of the district. Certain types ot • C. Le Neve Foster, "On the Great Flat Lode." QJ.G.S., 1878, ""t'R^ILTLmts; "Some Observations on the Great Flat Lode." i?«p. Com. ± Henwood. p. 240. § Geological- Report previously cited.. H " ReraKpon the Tin Deposfts of East Wfieal Lovell." Trans. A.Q.S. Corn., vol. ix., 1876. VEINSTONE OF THE LODES. 155 veinstone are regarded as good or bad signs of the value of the lodes. A soft or " plumb " Inde containing quartz and chlorite, or a little clay or prian is supposed to be a good lode. The hard blue-black rock (schorl rock) which is commonly met with, especially in the deeper parts of the lodes, is a good sign, par- • ticularly if it is brecciated, although tin ore may only occur in it in small quantities. The schorl rock of a somewhat lighter blue colour, frequently modified by the presence of kaolin, rendering the rock more or less pulverulent, and especially if associated with chlorite, is an excellent indication of a good lode. The presence of oxide of iron, or the existence of cavities or vugs, are sup- posed to be indications of a good lode. A quartz (sparry) vein, unless accompanied by other minerals such as peach, chlorite, &c., is considered valueless as an indication of the presence of ore. William Phillips* makes mention of the miners' saying that " Black Jack rides a big horse," from the fact that a lode con- taining blende in the upper part is often rich in copper in depth ; an instance of this being Wheal Towan. Microscopic Structures of some Tin Stones. (Plate XII.) The microscopic structure of the veinstones of the Camborne area, from material collected at Dolcoath, Wheal Basset, South Crofty and Cam Brea, was described by Dr. Flett in the Summary of Progress of the Geological Survey for 1902 (pp. 154-159). The descriptions that follow illustrate the micro-photographs depicted on Plate XII. : — Fig. 1. — Veinstone from Carn Brea Mine. The material is a breccia consisting mainly of quartz, tourmaline, and cassiterite. In the tissue sketch over the plate the cassiterite is represented by (1), cassiterite and tourmaline needles by (2), quartz by (3). (E. 3,601). Fig. ^,— Carn Brea Mine, 300-fathom level. The slide shows large crystals of tin ("Zinngrauper,") with usual zonary banding, set in a matrix of quartz and chlorite with abundant oxide of iron (haematite) which occurs among the chlorite. The part of the figure marked (1) represents cassiterite, (2) is chlorite and oxide of iron largely interstitial, (3) is quartz. (B. 3,603). Fig. 3.— South Crofty Mine. The figure shows cassiterite (1), radiate green chlorite (2) which are intimately associated, and quartz (3), also quartz crowded with tourmaline needles C4). (E. 3,604). ^ ' Fig. .^.— South Crofty Mine. The figure shows a veinstone consisting of cassiterite and chlorite traversed by a vein of fluor- spar. In another part of the slide there is a quartz tourmaline vein. (1) consists of cassiterite with a little chlorite, (2) of chlorite, (3) of fluorspar, and (4) of quartz. (E. 3,605). Fig. 5.— Wheal Enys. A brecciated veinstone. The fragments • " On the Veins of Cornwall." Tr. Geol. Soc, Vol, ii,, 1814, p. 121. 156 NATURAL HISTORY OF THE LODES. in the slide consist of cassiterite, which in some places, owing to its yellow colour, appears almost black in the photograph, and some quartz. The whole mass is traversed by veins of quartz in which topaz occurs. (1) consists of brecciated cassiterite, (2) quartz frequently crowded with tourmaline needles, particularly where near the cassiterite. Rows of inclusions and of grains of oxide of iron show a zonal arrangement in the quartz. (E. 3,858). Fig. 6. — ^Dolcoath Mine, 475-fathom level. The slide shows several periods of disturbance of the brecciated lode. (1) consists of quartz-tonrmaline veinstone, and is possibly itself a breccia. (2) infilling consisting of cassiterite, quartz, chlorite, and dusty nnddermined inclusions, (3) cassiterite, (4) quartz. (E. 4,278). 157 CHAPTEE XV. CEOSS-COURSES, CROSS-FLUCANS AND SLIDES. The lodes are intersected by a system of fissures probably pro- duced in Tertiary time?. These fissures traverse the district in a direction approximately at right angles to the lodes, from which fact the term " cross-course " is no doubt derived. Although the cross-courses are frequently faults, sometimes sufficiently large to affect mining operations, they have no important effect on the geological structure of the district. Excepting those cases cited in the section dealing with the general distribution of the ores, the cross-courses are unproductive from the miners' point of view. It is impossible to separate them geologically, however, from similar fissures which in some parts of Cornwall have yielded so much iron and silver-lead ore. In 1778 Pryce defined a cross-course (cross bar, cross gossan, cross lode) to be " either a vein of a metallick nature, a cross gossan, or else a soft earth, clay or flookan like a vein, which un- heads and intersects the true lode."* Elsewhere in the same work •' flookan " is defined to be " an earth or clay of a slimy glutinous consistence, in colour, for the most part blue or white, or compounded of both." The same word is now used loosely where the term " cross-flookan " should be employed. According to Pryce, "a cross-flooken runs across through a lode, unheads it and throws it on one side out of its place. There are flookan s also which run parallel with metallic lodes and take the name of course-flookans." When clay occurs throughout an, ordinary lode it is called a flookan lode, A slide is defined as being " a course-flookan or course-gossan, that either inclines faster or in direct opposition to a metallick lode." There is here no attempt at classification as regards age. Eichard Thomas, however, stated that cross-courses and cross-flookan s appear to be more recent than lodes or slides, and pass through them without interruption.f He called a cross-course which contains clay a " fluccan." In 1822, Carne distinguished two kinds of cross-courses, the difiference between them being both in bearing and underlie. Most of those which have a bearing E. of N. underlie west, and those with bearing W. of N. underlie east.f With regard to slides, he states that they traverse every other kind of vein— a statement directly contradicting that of Eichard Thomas. The slides, although generally parallel with lodes, may run in any direction. Henwood does not make any statement on the relative ages of the cross-courses and slides, but he remarks that the slides never contain metalliferous minerals, and that they never occur in granite, " Their whole substance consists of soft * Mm. Oorntib., p. 319. t Survey, 1819, p. 21. $ J.iCarne, " On the Veins of Cornwall." Tr. E.G.S. Com., vol. ii,, 1822. 6 6 4 158 CROSS-COUKSES, CROSS-FLTTCANS ANll SLIDES. clay, similar in mineral composition to the rocks which thev traverse. So close, indeed, is this resemblance, that even the lammation of the slate is often as perfect in them as in the con tiguous rock," and "the softijess of the slide is frequently the" "country/"* ' ^■^^'"g'^i^bing it from the ndghbouring The slides are few in number, seldom exceed a foot in width and their average underlie is about 45 deg. or 50 deg. Slides are said to occur in Treskerby, Wheal Squire, Wheal Vor,wt^l FrTendshb &c. In the districts of Camborne and Redruth the dSons S the principal cross-courses and cross-flucans, with their average TeSTfoUot":!!'' "^ ''""°°'^' '^' *^^ -"^'« ^^y b« P- _ . Number. N.toNToo^w. ^n°™" ^r'" N. 10° to 20° W. ... _ o N. 20° to 30° W. ..4 N. 30°to40»W. ... 2 ' N. 40° to 50" W. ... 1 N. 50° to 60° W. ... 1 _ N. 60° to 70" W. ... — 1 W. 20° to 30° S. ... — 1 W. 50° to 60° S, ... — 1 W. 60° to 70° S. ... — 4 W. 70° to 80° S. ... 2 — W.80»S. toS. ... — 2 Average bearing ... N. 34"? W. W. 35° N. Average width ... 1-48 feet. 1-62 feet. Henwood says that the material principally fillingthe cross- veins consists of quartz and clay, and according as one or other of these constituents predominates they are called cross-courses or cross-flucans, and it is owing to the impervious nature of these flucans that they are sometimes selected as the boundaries between different mines.f The Great cross-course, which can be seen in the adit between Cook's Kitchen and Dolcoath Mines, is a case of an impervious barrier between two mines. The structure of cross-courses is variable,but they have, as pointed out by Mr.Hill, an intimate connection with the " cleaving way " jointing of the granite.| They are not characterised by the presence of breccias as a rule ; are generally more or less vertical, and are not infre- quently faults of considerable magnitude. The larger of them contain quartz with fragments of country rock, while the smaller are mere cracks, that may or may not contain quartz, but along which there has generally been a little faulting. Henwood stalTes that some cross-courses consist of several parallel cracks filled with quartz or other materials. The tabular statements contained in his book have much detailed information concerning the cross- courses in the mines. Mr.'Carne says that there is no connection between the size of cross-courses and the amount of faulting they produce,§ and gives p. 282. t Henwood, p. 258. Trans. Boy. Qeol, Soo. Corn., vol. xii., part vii., 1901, ' On fciie Veins of Cornwall," 1822, p. 117. CBOSS-COTJHSES, CROSS-FLTTCANS AND SLIDES, 159 set'eral examples of considerable faulting by cross-courses which are comparatively narrow, and vice-versd. In Wheal Virgin (Consoli- dated Mines) a cross-course 2 feet wide heaves the lode 6 fathoms j in Wheal Peevor another of the same width heaves the lode 18 fathoms ; at Sparnon a cross-course 8 feet wide heaves the lode only 2 fathoms. In Wheal Unity a flucan 18 inches wide heaves the lode 5 fathoms. In Wheal Squire a flucan 2 feet wide heaves the lode 18 fathoms. A small flucan in Wheal Daniell heaves the lode 14 fathoms, while lodes in the United Mines are heaved only 1 fathom by a flucan over 2 feet wide. The principal cross-courses and cross-flucans of the Camborne and Eedruth district are indicated on the map published by Eiehard Thomas in 1819. The facts relating to a few of the principal cross-courses of this district may be briefly stated as follows : — The Great or County cross-course has been referred to by Berger, Thomas, Carne, and Henwood. Thomas says that it starts from Tolben rock, near Forth Towan, 2^ miles N.E. of Portreath, and goes through to Wheal Jewell. From here southwards it is divided into four branches, each of which is a fault of about 20 fathoms. Although Berger* states that this cross-course continues its way southwards to Pedn Boar Point, the statement is not proven. Carne remarks that there are two cross-courses seen at some distance from each other in the cliff at Porth Towan, and that they intersect and heave all lodes as far as Wheal Peevor, at which place they run into one another. The eastern one heaves the lodes 54 fathoms and the western one 18 fathoms to the right hand. From Wheal Peevor to Wheal Jewell the heave is 74 fathoms, but further south still, at Wheal Damsel, it runs into confused ground, and heaves the lodes only 16 fathoms. Henwood appears to disagree with both views, and says that although there are several flucans in Wheal Damsel, Wheal Squire, and Poldory, none of them can be shown to run into the Great cross-course, while the only considerable heave north of Wheal Peevor is in Cliff Down (western part of Wheal Towan), where the heave is to the left hand. Another important cross-course is that which separates Cook's Kitchen from Dolcoath Mine, and is known to dislocate the main lode to the extent of 74 fathoms. Northwards, it passes between North Koskear and East Wheal Crofty, and is the same as that exposed in the cliffs near Samphire Island. At the present time it can be seen in the adit between Dolcoath and Cook's Kitchen, where it is of a clayey or flucany nature, while at Samphire Island it is a quartz vein. Some cross-courses have, on account of their special interest, received notice from several writers. A north and south cross- course called Skewes flucan, with a slight heave to the left, traverses the mines of Ting Tang, Wheal Damsel, Wheal Jewell, and Wheal Gorland. Between Wheal Jewell and Wheal Damsel it passes through t^e Great cross-course. A cross-course, designated the Gaunter cross-course, separates Wheal Prussia and Wheal Boys, and southwards passes through Wheal Derrick, In Wheal * Geol, Trans., vol. i., p. 165. 160 CROSS-COUBSES, CROSS-FLUCANS AND SLIDES. Prussia it is traversed by Butcher's cross-course, and in Wheal Derrick by Wheal Boys' cross-course, both of which are parallel with the County cross-course, the Gaunter cross-course bearing about W. 40 deg. N. Tiddy'scross-course contained some ores of copper. It passes from Poldory (Uni( ed Mines) through Wheal Virgin (Consolidated Mines) and Poldiee, where it is called Trussal's cross-course. At the Garras Mine (Gwarnick) there is a silver-lead lode striking approximately north and south. It is 2| feet wide, and is heaved twice by two slides, each to the extent of about 6 fathoms.* In the south-western part of the map some remarkable cross- veins have been noticed. Woolf's cross-course, at Great Wheal Vor, consists of quartz. It intersects the old Wheal Vor and the Wheal Metal lodes, and is considered to be the same as that which yielded grey copper ore in the Grodolphin Bridge Mine, and lead ore, with oxide of iron, in Wheal Eose.f • J. Carne, "On the Discovery of Silver in Cornwall." Tr. R.G.S. Corn., vol. i., 1818, p. 120. + H. Stephens, Rep. Corn. Poly. Soc, 1871, p. 77, " Mineral Phenomena of Wheal Kose." See also K. Hancock, "On the Mineral Deposits of the Old Wheal Vor." Hep. Roy. Poly. 8oe. Com., 1870, p. 101. 161 CHAPTER XVI. NATUIiAL HISTORY OF THE ORES. I. The Ore Bodies. The profitable parts of the lodes (containing anything over 1 per cent, of tin) alternate with poor or barren parts. That the ores do not occur uniformly disseminated throughout the lodes is a point which cannot be too strongly emphasised. Generally speaking, the conditions affecting the shape of the ore bodies depended upon (1) the shape of the cavity or breceiated mass in which the ore was deposited, and (2) the nature and jointing (or Assuring) of the country rock in the neighbourhood of the lode. In this district there is no evidence for differentiating the origin of the more remarkably-shaped ore bodies from that assigned to those of ordinary lodes, since all the deposits are connected with fissures. Impregnated masses formed in the open parts of an irregular fault-fissure^ or in a friction breccia of a fissure, together with the metalliferous altered country rock in their vicinity, are known as bunches or pipes. A succession of such bunches makes up a " chute " or " course " of ore. The word " chute " refers to a succession of bunches in more or less vertical arrangement. A " course " refers to a succession of bunches in a more or less horizontal direction. The lodes of the trwinear district were termed " bunchy " by the miners, but used in that sense tbe word means that the bunches were un- certain in occurrence. A "pipe" is an elongate bunch within the lode, with its longer axis lying in the direction of underlie of the lode, or " pitching " slightly to one side or the other ; or it may be the infilled line of junction of intersecting lodes, or the line of bifurcation of a branching lode. The dis- tinction between the terms "chute," "course," and "bunch" is not very definite, and the use of the terms is a matter of con- venience only. " The masses or shoots of ore in any given lode have, generally speaking, a prevailing dip (pitch), and whether they occur in granite or in slate, whether on the eastern or western side of granite tract, this inclination is invariably towards the great body of the slate."* In Wheal Uny the oi-e bunches pitch westwards.! The lode is very large, and yielded great quantities of low-grade tin ore t In Wheal Grenyille the ore pipes in the lode pitch slightly eastwards. The three chutes of ore in Dolcoath Mine and the chute of ore in Cook's ?^^?®'' J^"'.^'.?^*?""?? ^^™°^* vertical, have a slight easterly pitch in depth The individual bunches of which these shoots are composed are lU-deflned. In .Great Wheal Fortune and Great Wheal Vor the shoots incline in the direction of the granite and killas junction, or where associated with elvans they follow the dip of the latter.§ * Henwood,p. 195. Uny/> X^'TcJrlm^. 5«r' "" '''' '"^''' ^'** ^"^^ - Wheal J H. C. Salmon. Mining and Svieltiiiq Mcujaavne. l&&i n ^l« i Op. cit., 1862, vol. ii., p. 14. ■> y > ^oo^, p. di». 162 NA-TTTEAL HISTOHY OF THE OUES, < m z < 8 s Z u. O cc o z :S I- Auvp unoff tjrtrns stC3A.mff '8 o J e z lU X t z CO ^ o o o iCnyprunog -- o o CQ liJ a o ■£, -J I— t ■i ^ £ < o o _l o o v^S" *""«• mo V^Vi" s""???? V^VM %/mig suoQ imniM. THE ORE BODIES. 16 In Dolcoath, the main lode can be divided vertically into three chutes- (Pig. 19.) The lode regarded as the main lode strikes from the western boundary of the mine to Harriett's shaft at E. 30 deg. N. Thence to the Old Sump shaft it strikes E. 50 deg. N. (at the !90-fathom level near the junction of the granite and killas). Thence to the Gossan shaft, in the eastern part of the mine, the strike is B. 30 deg.N'. The lode then splits into two branches known as the Valley lode and the Valley Gaunter lode. The main chute of ore is situated between the Gossan shaft and the Old Sump shaft. This chnte is made up of more or less connected bunches which have been worked for copper down to the 190-fathom level, and (after passing through a zone of mixed copper and tin ores) for tin, down to the deepest point of the present workings, which are 490 fathoms below adit, or over 500 fathoms from surface. The width of the bunches varied from a few feet to 60 feet. Thus, the junction of the main lode and South Entral lode is 60 feet wide. From the 150-fathom level to the 200-fa thorn level the lode varied in width from 7 to 12 feet, and from the 200 to the 300-fathom levels from 1 to 5 feet. At the 338-fathom level the lode was from 6 to 9 feet wide, and at the 485-fathom level the width o£ the lode, including the altered country rock, is 42 feet in width, carrying 25 lbs. of black tin per ton of stuff. Another chute of ore occurs in the same lode in the section of ground between Harriett's shaft and Wheal Killas shaft (on the west). This chute is made up of disconnected bunches of ore, showing the same change in mineral contents in depth as that of the chute just described, but has only been explored to the 338-fathom level. In the western part of the mine there is another chute of less importance. The section of ground between Harriett's and Old Sump shaft,striking E. 50 deg.N,,is almost barren,and the lode here is wrung up between the first and second chutes above described. The lode was extremely rich in tin ore above, and on the eastern slope of ' the large " horse " of granite, occurring about the 425-fathom level. (See page 139.) Tin ore also occurs in small strings and veins in parts of tha " horse " itself. In Cook's Kitchen Mine the chute of ore is in the continuation of the same lode as that worked upon in Dolcoath, but is here known as the Highburrow lode. The chute is made up of connected bunches, and has been worked upon from surface to the 430-fathom level. The width of the bunches varied from 6 to 20 feet ; at the 400-fathom level the lode is 30 feet wide, and at the 450-fathom level is 66 feet wide. The width of the bunches is always greatest where the lode was branched. Further east an important chute of ore was shared by both Tincroft and Cam Brea Mines. This chute was worked from surface to the 330-fathom level. In the eastern part of Carn Brea Mine the lode is split up into branches. On the south of the Carn Brea granite is situated the Great Plat lode, which affords some interesting examples of ore bunches. Thus, at Wheal Grenville, the lode underlies 60 deg. S.* (dip 30 deg. S.), and the ore occurs chiefly in pipes separated from each other by intervening portions of poor lode. Observation shows that this lode undulates very gently in the direc- tion of its strike, so that the levels driven along the lode zig-zag slightly from left to right. In West Wheal Frances a chute of tin ore was worked °? *^^f "•« l°*e. In West Wheal Basset, between Granville's and Pascoe's Shalt, there was a chute of tin ore extending to great depth. Part of this chute was known as Pascoe's pipe. Further east in the same mine Thomas s shaft was sunk through a chute. In Wheal Basset some parts of the Great Flat lode are as much as 150 feet wide, but these are at noints of intersection of the bunches of the Great Flat lode with other lodes thr'SiOT?^^™'^"''*''"'"* ^'^'"^^^"''^ °^ """^ °^ ellipsoidal shape at grSuTb^i^Sy *'" '"•«°''«^>-sin pipes pitching west, the intervening * Foster, p. 640. t Information from Captain W. James, manager of Wheal Basset. Vn/- ne-p^^X:^7y''s:rS' "" '''' «"** ^'''' ^«<^« '''Wheal ii9 164 NATTTRAL HISTOET OF THE ORES. Irkegular Bunches or Masses.— An abnormal development of the lode may form an irregular bunch or mass. In some cases ore bodies occur which bear some resemblance to carbunas. The carbonas of the St. Ives district have, however, given to this terra a special meaning. In that region the carbonas are irregular, more or less horizontal " pipes,'' passing into the country rock along cracks, making a large angle with the lode. Typically, they contain a large amount of schorl. The term " Carbona " as used in the Camborne district does not appear to have received recognition. In Wheal Basski the carbonas are impregnations of the country rock in the Ticinity of small flssares which ran " counter " to the lodes and so sometimes connect them. These deposits are somewhat irregular and of a soft or " plumb " nature (decomposed granite). As a rule they are uncertain, widening out into a body 6 feet across, or narrowing down to a small string iu a short distance. The largest occurred at the 115- fathom level on the west of Camkie shaft, and contained from 14 to 28 lbs. of black tin per ton of stuff. The veinstone is chloritic and highly ferruginous. The manager of Wheal Basset* considers these bodies to be branches from some of the nine or ten more or less vertical lodes which traverse the mine. Where these branches cross each other the line of intersection contains tin or copper ores, and the pipe-like deposits so formed are more or less horizontal. The carbonas occur mainly in the neighbourhood of Carnkie shaft. The carbonas on the west of the shaft produced mainly copper ores, and those on the east mainly tin ores. Both the lodes and carbonas were richest above the 130-fathom level. In PoiJ)icE Mink, in Gwennap, a fissure branched off in a south-westerly direction from Singer's tin and copper lode. The body of ore associated with it was known as a carbona. Balmtnheeb Mine (Wendron). -The deposit consists of a large irregular mass of stanniferous altered granite. A vein or slide about 6 inches in thickness, consisting of white clay and a little quartz and mica, underlies N. 60 deg., and bears B. 32 deg. N. Below the slide the irregular mass of tin-bearing rock varies in thickness from 30 to 50 feet, and underlies in the same direction as the slide. Between this mass and the granite there is no regular plane of separation. Occasionally there is some tin ore above the slide. This mass, which consists of qjnartz, chlorite, gilbertite, iron pyrites, zincblende, and tin ore, and occasionally a little wolfram, extends tor 36 fathoms along the strike of the slide, the lowest workings being at 30 fathoms from surface,! In 1S76, 2,200 tons of tin ore were stamped 1,-ielding over 1 per cent, of black tin per ton. Hai-abez-Vck Farm (Wendron).— There is a vein of clay about 2 feet wide which underlies N. 26 deg. A mass of granite about this vein has been worked as an open quarry for the tin ore it contains. The breadth of the deposit is possibly 20 fathoms. In addition to the tin ore there was micaceous iron ore and iron pyrites.^ The produce varied from 10 to 56 lbs. of black tin per ton of ore. SoTJTH Wendron Mine.— The deposit here is a very irregular cylindroid of stanniferous rock, merging gradually on all sides into granite, with its axis dipping at 49 deg. from the horizon in a direction N. 25 deg. W. The lono^r axis of the oval section of the pipe varies from 20 to 60 feet In length, while the shorter is about 10 feet. The mass consists of quartz, mi<», gilbertite, a little iron pyrites, and tinstone, and is traversed by a few irregular joints ; the stuff is cavernous or honeycombed, and in little cavities there are fine acioular crystals of tourmaline.§ * Captain W. James. + foster, p. 648. t Charles Fox, "A Deposit of Tin in Wendron," Miners' Ame, Corn, and . Devon, 1868, p. 47. § Foster, p. 650, THE.OEte iBODIES. 165 LovELL MtNE. — The South lode is traversed by numerous joints. The principal joints dip and strike with the lode. On one or both sides of the lode there is an altered band of " country " rook, 6 to 12 inches thick, con- sisting of quartz, mica, gilbertite, chlorite, icon pyrites, copper pyrites, and a little schorl. The lode itself is a dark mixture of quartz, gilbertite, mica, zincblende, chlorite, iron pyrites, and a little copper pyrites, fluor- spar, and tinstone. When one of the aforementioned joints diverges from the lode it carries "lodey stuff " with it. The North lode, which is very " bunchy," is 10 to 15 feet wide, and consists of quartz, gilbertite, some iron pyrites, tourmaline, and tinstone.* East Wheal IiOYEll (Wendron). — The main " chute " of ore in this mine " is in the shape of a long irregular cylindroid or cylinder with an elliptical base generally from 12 to 15 feet long by 7 feet wide." This chute has been followed down from the 40-fathom level to the 110-fathom level as one continuous pipe. There were several other pipes and bunches of similar character. " The East Wheal Lovell pipes and bunches resemble in their mode of occurrence some of the carbonas of St. Ives, but differ in the absence of tourmaline, which is so very abundant at St. Ives."! Pedn an Dkea. — A curious deposit of tin ore, called a " carbona," occurred in the killas not far from its junction with the granite, at the 68-fathom level. It consisted of a mass of small veins penetrating the killas. These veins branched off from a lode 4 fathoms in thickness. The mass so formed was 25 fathoms long and 11 fathoms wide, the richest portion being in the country rock between the Engine and Martin's lodes.| Wheal Vtvian. — The deposit has the " character of an enormous granitic lode, bearing 20 to 30 deg. S. of W.," and dipping N. 40 to 55 deg. It is 5 to 10 fathoms wide, or even more in some places, and the composi- tion is similar to that of the country rook. " The whole substance of the lode is thinly interspersed with tin ore, copper pyrites, and also spots of iron pyrites," &c., but these minerals occurred chiefly in small veins and strings running in the same direction as the lode and having a northerly underlie. " The joints of the rook seem to coincide with the veins both in bearing and dip, and where there are crevices in them their faces are commonly coated with fine crystals of tin ore."§ Wheal Music (St. Agnes).— The lodes which had been worked for many years were at length " split up Into minute strings and branches, none of Fig. 2Q.—Whml Mudc. which were, singly, worth pursuit. The whole rook was then removed and the copper ores extracted. An excavation of an Irregular elliptical form of about an acre in area and 25 fathoms in depth " was left.|| (Fig. 20.) * Foster, p. 649.' ta^c ^® Neve Foster, ''The Tin Deposits of East Wheal Lovell." Tr R.Q.S. Corn., vol. ix.', 1876. X M. H. C. Salmon. " p. 143. § Henwoodi P' 72. and Op. ait., p. ■aziner vol. ii., 1862, 166 NATXJUAL iaiSTORT OF THE OfeES. Chacewatee Tin and Copper Mine. — The elvan in this mine is "full of small strings of copper ore which cross the elvan at 45 deg." The ore does not enter the klUas at all. There are also small unconnected beds of " red elvan " called " floors " by the miners, which, although quite dis- tinct from the other, are intersected by the copper veins in the same manner.* CoNBOus Mine (Gwennap).— Near Frances' shaft at the 135-fathom level " for more than 25 fathoms in length and 15 fathoms in height, the lode vas from 8 to 12 feet wide, and foil of fragments of copper ore, some of the fragments of slate weighing several tons, and occurring, as to the position of their lamiiue, in all directions." " Many of these masses and smaller stones had the appearance of having been washed by a flow of water. Above this mixed mass, and in the level above, a great cavity or vug was found many fathoms in length and height, from whence it was conjectured the fragments beneath had faUen.''^ Wheal Vob. — ^The lode produced ore in killas, but was riclier in elvan. The lode was 2 feet wide, bnt in elvan was 5 feei^ and [in some places branched into it so as to impregnate the whole elvan and render it profit- able for 20 feet in width.! " Unconnected " masses of tin ore occurred in the elvan as small veins and irregular bodies.§ At tlie 180-fiitfaom level, the lode from being 2 feet wide suddenly broadened to 6 feet, and consisted of cfaloritic products and tin ore, either separately s^r^ated or more or less "mixed." Wood tin ore occurred in scattered grains, in small isolated masses, or in very fine veins, often no thicker than paper, bnt always with the fibrous stmcture.|| At East R>ol Mine there was a somewhat remarkable occurrence at the jnnction of the granite and killas, a position highly &vourable for the production of irregular deposit& The ^gine lode underlies south 13 deg. to 27 d^., and strikes the granite at about the 135-fathom level. At this place there is a ridge in the granite some 35 fathoms in height, which trends in much the same direction as the lode (see page 117). The Engine lode c(»iiing down from surface follows down the southern flank of this ridge and enters the granite near the foot On the other flank (northern side of the ridge) the Great Wolfram lode, over 12 feet in width, under- lyins north, emerges from the granite in its upward course and following the junction of the granite and killas on the northern flank of the ridge bends over it at its apex, and finally joins the Engine lode. The ore in the Wolfram lode, near the junction of the granite and killas, consisted of mundir, copper, tin, and wolfram.* A solid branch of wolfram ore 4 feet in width Tras found in the lode bdow the 140-fathom level. Floor?.— In the Cambome district the term " Floor " is applied to a more or less horizontal ronghly-sheeted deposit, branching off from the lode into the country rock Thus, a deposit in a " bed- ding plane " or horizontal crack in the granite would be regarded as a floor. The term is loosely applied and refers to the general shape of the body, bnt it is not used for stockwork deposits. PhiUips r^ards " Floors " or " Carbonas " as stockwork deposits.** The " tin floors," in the parish of Madron, were made tip of small fissures or veins containing tin ore, which follow the inclination of the strata and appear to be branches from a central body.jt * J. Came, "On Elvan Conrses.' Tr. Ii.6f.S., vol. i., 1818, p. 104. t De la Beche, p. 324. „. „ ^ , ^ i • icio „ oaa 5 J. Carne, " Oh Eh-»n Courses.' Tr. Jl. G-S. Om., vol. i., 1818, p. 238. f W.^A^l.^^'-On'the Occurrence of Wood Tin." Jwm. Soy. Imt. Com., vol. iv., 1873, p. 255 , . „ • ,oco „ 90= ir H. C. Salmon, mning and Smeltxng Magazine, 1862, p. 385. ^ •* J. A. Phillips and H. Louis, "A Treatise on Ore Deposits, 189b, ^tt John Hawkins, "On Tin Floors, &c." Tr. ii.ff.S. Com,, vol. ii., J822. p. 36. GENESIS OP THE ORfiS. 167 In Wheal Vor floors containing tin ore, and ot a composition similar to that of the lode, branched off from the lode nearly horizontally into the killas * In South Crofty Mine the main lode in the killas, near the junc- tion ot the granite and killas, branched off into floors. The killas was greatly disturbed and mineralised. At the 50-fathom level m West Eoskear Mine, the divisional planes of the adjacent slates were infilled with copper pyrites and mundio, thus forming floor deposits as branches from the main lode. II. Genesis of the Ores. The limited number of types of ore deposit in the region Tinder consideration enables the discussion of their genesis to be confined to a mode of origin the explanation of which was first suggested by Elie de Beaumontf and Daubree.f Daubree's results were based largely on experimental researches carried out by him in 1849, although the principle was first sug- gested by him in 1841.§ In reference to the tin lodes of Cornwall, the works of the late Sir Clement le Neve Foster stand pre-eminent for the examples brought forward by him, which have become classic, as illus- trating the connection of the tin deposits with lines of greisen action ; a fact entirely supported by Mr. J. H. Collins, author of many well-known works relating to the geology of Cornwall. Although the tin and copper deposits are without doubt con- nected with the granite, yet since they occur in fissures, gener- ally about the peripheral portions of the granite masses, they should not be regarded as being immediately connected with the country rock in which they are enclosed. The ores are now sup- posed to have originated by " extraction " of metalliferous solu- tions emanated during the final phase of consolidation of the acid magma from which the granite was formed. The secretion of the ores depends upon the principle known as " magmatic extraction," by which is meant the extraction in solution of metalliferous minerals from a still completely fluid or partially consolidated magma, by means of other materials which combined with them, and may be termed " carriers." The precise chemical and physical phenomena are still only vaguely known, but the ex- planations offered by Professor Vogt, of Kristiania, form a land- mark in the field of ore deposits of the kind here considered, and the conclusions arrived at by him are the most satisfactory hitherto formed.|| Professor Vogt has clearly stated his views in an ingenious argument, in which is shown how tin veins in granite may be compared with rutile-apatite veins in gabbro.** * Henwood, Table xlv t "Note sur les Emanations Volcanique et Metallif^res." Bull, de la Soc. ffeol. de France, 2e Serie, Tome iv., 1846, p. 1255. X " Etude Synfchetlqne de Geologie Experimentale," 1879, p. 29 § " Memoire sur le Gisement, la Constitution et I'Origine des Amas de Mineral d'etain. ATm. det Mines, 3e Serie, Tome xx., 1841, p 65 11 J.H. L. Vogt, Zeit. f PraU. Qeol., 1894-95-98-99. See also Professor Kemp s paper, " The K61e of the Igneous Rocks in the Formation of Veins " Tr. Am,. Inst. Mm. Eng., igoi, which is a recent valuable contribution to the science. . Op. eit., 1895,' pp. 447, 474. »» ^68 NATtriLAL HISTOBY OF THE ORES. In both cases the extraction process is mainly dependent on the nature of the compounds formed with halogens present in thfi magma. Both magnaas contain phosphoric acid, which forms compounds readily soluble in acids, but it is present in larger quantity .jn gabbro than m granite. The metds forming eom- pounds with the halogens (fluoride and chlorine) are able to pfssTnTo fissures along with phosphoric and bydrofluosilicic acid The STranU? T''"''"-f gabbro, but only accessory in he cas and so^P ST" """'"u '''^^ Pb°«Phates, possibly a little silica thiiT thi earths, are concentrated in fissures mainly through the agency of chlorine in the case of gabbro. ll granite, cass.ten e, wolfram and silica, together with! little phos- riv V, "^.^^ i'^f ^"^ P°^^'^' ^'^ ^^t^acted by Muorine. Each Pxjlr ^f''*!"'^'°^^^''^'^^°° P'^«'^'^°ts; and possibly they ex sted as dissolved gases, which on relief of pressure at anj point, as by a fissure in the consolidated crust, were permitted to vapounse and escape. It is this assumption that gases and not liquids formed the mam part of the emanations that prompted the use of the terms " pneumatolytic " and "fumarole." This implies that gas was the principal agent in the secretion of tin ores at least. The only difference in the meaning of these words 18 that "pneumatolysis" refers to the action of gases above cntica] temperature (and hence generally of deep-seated origin in connection with bulky igneous intrusions), while " fumarole " refers to gases considerably below their critical temperature. The whole history of the actions which finally resulted in the deposition of the metalliferous minerals of the cassiterite veins is very complex, but the elements which took part in these opera- tions are discovered in the secondary minerals, which commonly occur in the altered country rock, in the vicinity of the fissures which form parts of the lodes. The minerals of the " tin-copper " lodes of Cornwall can be broadly divided into two classes, corre- s|)onding with the minerals of the infilled Cssures and those of the altered country rock. To the former class belong such minerals as cassiterite, wolfram, scheelite, mispickel, copper pyrites (and other sulphides), mundic, arsenical pyrites, and other metalliferous minerals, together with quartz, apatite, schorl, chlorite, fluorspar (occasionally in great quantity), &c. These have been introduced into the lodes by gases or solutions traversing them. To the second class belong tourmaline, axinite, topaz, garnet, and various secondary micas, chlorite, &c. These minerals have been formed by the action of valours on the country rock, e.g., tourmaline in granite, and axinite in lime-bearing ro«;k by^ addition of boric acid ; garnet veins in greenstone by addition of silica during metamorphism by granite. To these may also be added iron pyrites, which results in many cases from alteration of oxide of iron in the country rock by sulphur vapours. As a whole, then, the materials brought up in solution were composed of the elements — tin, wolfram, arsenic, copper, iron, &c,, silicon, chlorine, fluorine, boron, phosphorus, oxygen sulphur, hydrogen, and carbon, together with lead, silver, zinc, nickel, cobalt, manganese, &e., which, as Yogt points ont^ may or GENESIS OF THE OKES. 169 may not be present but often are, in small quantities, charac- teristic of cassiterite veins. The early history of the metalliferous minerals is intimately bound up with the more general petrological problems concern- ing rock magmas. In all probability the metallic elements were diffused uniformly throughout the magma when it was intruded. As the mass cooled the basic materials of the magma crystaliised out first, while the more siliceous material (which resulted from their withdrawal), as crystallisation proceeded, drove out the active gases, gradually concentrating them in a siliceous "residual magma." It is in the latter that the gases and the metals extracted by them are concentrated, but " so long as they remain in the magma, they must be regarded as belonging to it and playing their part along with the other constituents in producing the final result."* Fluorine, chlorine, boron, phosphorus, and steam are common characteristic constituents of granite magmas, and assist in keep- ing some of the free silica fluid to a late stage in the history of the consolidation, and possibly even decompose the first formed minerals, with, for instance, the production of tourmaline from ferro-magnesian minerals, &c. In this manner they are concen- trated in the fluid part of the consolidating mass and carry with them tin, wolfram, and other metals, and in fact it is possible that the extraction of these compounds does not take place until the magma is actually consolidating. The silica or silicic acid combined with fluorine is carried up into the veins as SiF^ (silicon fluoride), or hydrofluosilicic acid, from which quartz is derived by decomposition in contact with water. Fluorine, and possibly also chlorine in the same way extract lithium, potash, &c., which go to form secondary mica. Most of the other bases are also attacked in the same way by fluorine, with which in all cases steam co-operates powerfully. The reaction in the case of tin may be represented by the equation— SnF, -I- 2Efi = SnOj + 4 HF. The fluoride of silicon may be supposed to be decomposed in the same way. In the case of the iron and titanium of basic rocks, each re- action IS represented by a similar equation in which, instead of fluorme, chloriiie is the carrier.. While tin is a characteristic accessory of granite, it has been E T- n^ ''°';t ^^^* ^'^PP^'' frequently occurs in cassiterite vems, and in Cornwall the association of stanniferous and cupri- ferous minerals is so striking that the term "tin-copper" veins applied to the lodes i, quite appropriate. They are cassiterite mSLf? ^ presence of copper sulphide and tour- vol. ml; ^'7?*"' " ^'^ ^^°^"*'<"» of Petrological Ideas." Q.J. G s., 1901, '" NATtrUAL HISTORY OF THE ORES. The general relations of the deposits of copper to those of tin have already been pointed out. It will be seen that both are associaed with minerals derived -from the granite. Dalmer has shown that in the Erzgebirge, the sulphide zinc and lead deposits are, in common with the tin lodes, connected with the consolida- tion of the granite, but while the tin ores were deposited in or near the granite, the zinc and lead ores were only deposited at a distance from the granite.* A similar peculiarity is noticeable in the relations of the tin and copper deposits of this region. Dalmer, in reference to the Altenberg, supposes that the tin ores were extracted and deposited while the interior of the magma was still fluid ; and with regard to the position of the deposits in reference to the granite he states that the zone-like arrangement cannot be regarded as accidental. It seems probable that part at least of the sulpho- compounds in the lodes were extracted at the same time as the tin, but whether through the action of fluorine or not is uncer- tain. In addition to the mineralisers already mentioned, there are boric acid, sulphuretted hydrogen, carbon dioxide, &o. The part which the boron plays in the extraction of the metals is at present unknown. The simplest explanation is that sulphuretted hydrogen helped largely in the actual secretion of copper and other sulphide ores; but it is not improbable that fluorine, and even boron, had something to do with their extraction from the magma. In acid magmas sulphur is not generally present in such quantities as in basic magmas. In the later stages of the con- solidation of the acid magma the sulphur compounds are driven out and play their part in the secretion of copper and ether metals. The reactions connected with the extraction of cassiterite and wolfram took place at high temperature and pressure. Those connected with the extraction of copper and the other sulphides took place under the same conditions, but the ores continued to be deposited in the lodes after the deposition of tin and wolfram had practically ceased. The connection of the lead and silver ores with those of tin and copper is obscure ; but from their general distribution and relations to the tin and copper deposits it seems probable that some, at least, were derived from the granite in a manner similar to, but at a later date than, the copper ores. Unlike copper and tin, the ores of lead and silver have not been found in lodes in granite, but, on the other hand, the greatest lead lodes in Cornwall occur in the killas, and have a strike similar to that of the cross-courses of the district in which they occur. The minerals so characteristic of the " tin-copper " lodes are gener- ally wanting in the " lead-silver " lodes, except in those cases where the lead and silver occur in the ordinary cassiterite lodes. In the latter the lead and silver is generally accompanied by zinc, copper, and cobalt ores, iron pyrites, or mispickel, and carbonates. In two instances in the Camborne district lead occurs in cross- * K. Dalraet, "Der Altenberg-Graupener Zinnerz lagerstatten District," Zeit. f. PraU. ffeol, 1894, p. 321. DISTRIBUTION OF THE ORES. 171 courses. In one case it is associated with silver, and in the other with copper and antimony. The facts point to the conclusion that the ores of lead and silver arrived at a late period in the history of the lodes, but not so late as in some cases to pre- clude their extraction in the later stages of the actions connected with the deposition of tin and copper ores. Their deposition con- tinued to take place for some time after the processes connected with the extraction of tin ore and the bulk of the copper ore had ceased. The chemico-physical aspect has been worked out by Svante Arrhenius,* who shows Low metals such as tin, copper, lead, zinc, and iron can exist together as sulpho-salts in an aqueous extract, while their behaviour is mutually independent of one another. In the aqueous extract are also sulphuretted hydrogen, hydro- chloric, hydrofluoric, boric and carbonic acid^, and silica. Hence it 'appears that at high temperatures the liberation of the active compounds of tin and tungsten, <6c., with fluoric and silicic acids and copper, &c., takes place ; and it is only at low temperatures that the more soluble, less active lead, zinc, &c. compounds are liberated, so that their deposition as sulphides does not occur until a late stage. It is also possible that some of the materials were even brought up as solid particles, mechanically suspended in water. III. Distribution of the Ores. The general distribution of the lodes has already been described. In this section the general distribution of the ores, together with a more detailed statement of their vertical arrangement in the lode, will be considered. Between Camborne and Truro the lodes and elvans have a similar geological occurrence and geographical range. With respect to the granite, the richest mines are those situated along the granite margins and in the altered killas beyond. It has already been seen, however, that the granite had consolidated to a considerable depth, and, indeed, the elvans were intruded before mineralisation of the lode fissures began. The peri- pheral portions of the granite itself, therefore, were' very favourably situated for the formation of important ore bodies in it. Speak- ing generally, the more important tin deposits of this district have occurred within the granite margin, and not infrequently in the altered killas beyond, particularly where the lodes are parallel to the granite margin. In some instances the chutes of tin extend to considerable depths in the granite, as for example in Dolcoath Mine, where but little tin ore of value was encountered until the granite was struck; but after this, for 300 fathoms within the granite (down to the -igO-fatbom level), the lode has yielded enormous quantities of tin ore. At the bottom of the mine the lode is 42 feet in width, and contains 25 lbs. of black tin per ton of stuff (1-008 per cent). On the other hand, there are many deposits of tin occurring in close proximity to granite but which * " Zur Phyaik des Vulkanismus." Geol. Foreningms, 1900, p. 415. ^'2 NATUKAL HISTOEY OF THE ORES. are not actually in that rock. That is to say, the lode, although passing from the killas into the granite, was only worth working in the part enclosed by the killas. In the parish of Breage, for instance, there are two mines situated near one another which show remarkable and instructive differences. The lodes of Wheal Vor were of enormous value while in the killas, but in granite were utterly worthless. Great Work Mine, not far distant from VVtieal Vor, appears to have been very rich in granite but poor in the killas. The great ore chutes of both mines plunge away eastwards approximately parallel to the subterranean surface of the granite.* Similarly, the principal courses of tin ore in Pedn an Drea Mine plunged westwards with the granite margin. At the St. Day United Mines the ores occurred principally in the killas, but near the granite, which here plunges eastwards. The ores of copper and tin occurred in a course of ore extending in the direction of strike of the lode for over 700 fathoms, from surface 'to the 130-fathom level. Below this, and roughly parallel to it, was a course of tin ore which was worked to a depth of 205 fathoms below adit. In West Poldice and Unity Wood Mines, a course of tin and copper ores extends from the granite margin into the killas for about 300 fathoms to a depth of 125 fathoms below adit. Similar instances are not lacking from other districts, as for instance at St. Just, where the richest mines are situated round the granite margin. This apparent selection of horizon is brought out forcibly when the case is viewed on a larger scale. Thus, instead of taking a single great ore chute, a succession of them may be selected in any single series of lodes traversing the district. For example, the series of lodes upon which are situated Camborne Vean, Dol- coath, Cook's Kitchen, Tincroft, and Carn Brea Mines, have been of enormous value for a length of two miles. Some of these mines are already exhausted in depth, and under any circum- stances it would be improbable that these lodes should be as rich for a depth of two miles as they have been for a length of two miles in the direction of strike. There appears to be an explana- tion for this. The continuation of some of the larger lodes in depth is a matter of certainty, but that they will prove as rich at gre^at depths within the granite is another question. Supposing that at the time the lode was being formed the solutions contain- ing, tin were rising through the fissure. A little tin ore was deposited regularly in the fissure at points from the greatest depths reached by the fissure to the higher levels. At any par- ticular -place, however, say the margin of the granite, the con- ditions might have been such that the whole of the tin still remaining in solution arriving there was deposited. In fact, it is unlikely that the tin could be carried in solution much further, owing to the low temperature at the margin of the granite. This explanation does not suggest that it is impossible for the tin ore to be deposited at great depths, and all it points out is that at certain * Hen wood, p. 54. DISTRIBUTION OF THE 0R15S. 173 horizons, such for instance as the granite margin, the ore bodies of greatest commercial value are likely to be formed. With different conditions, such as a greater depth of cooling, of the granite before the arrival of tin, the horizon at which the great ore bodies will be formed will also be different. There appears to be some analogy to the tin deposits of the Altenberg (Erzgebirge). In these deposits the tin ore began to be deposited shortly after the intrusion of the granite ; the peripheral portions of the granite were scarcely consolidated before Assuring commenced. The tin deposits were formed mainly in the over- lying rocks or in the portions of the granite which were the first to solidify and crack. As the crust grew thicker, Assuring in the deeper portions took place less easily, and was not so readily accessible by " tin-bearing superheated gases of the magma."* With regard to the copper ores it appears that similar observa- tions might apply, with this exception, that the copper ore was arriving after the arrival of tin ore had ceased ; and, again, copper ores are liable to reconcentration by being dissolved and re- deposited. Copper ore as a rule has been more abundant in the parts of the lodes in killas than in granite. Thus there are the upper portions of the lodes in Dolcoath, Cook's Kitchen, &c. ; South Crofty, South Eoskear, East Pool, &c. ; the United Mines, Consolidated Mines,, and other places in Grwennap, and the lodes in Wheal Basset. In all these mines the copper ore occurred in great quantities in the killas, but in granite were much poorer. There is an important exception in the once magnificent ore chute at Tresavean Mine. Tresavean Mine is situated on the margin of the granite. The lode has an east and west strike, and is nearly vertical. The copper ores occurred from surface in an immense chute within, but parallel to, the subterranean surface of the granite, which here plunges eastwards below the slates. This chute, in the part of the lode in granite from surface to the 310- fethom level, was of great value, but in the killas the lode was not worth working. Trethellan Mine, situated entirely in the granite on the west of Tresavean Mine, worked the upper part of this chute. Treviskey Mine, situated in killas on the east of Tresavean Mine, did not strike the chute except at^ great depths. Certain areas, on account of the ores for which they were par- ticularly celebrated, have come to be regarded as tin districts or copper districts. Thus Grwennap ts regarded as a copper district ; Wendron and Porkellis as tin districts ; Camborne and Kedruth as tin and copper districts. Broadly speaking, the districts situated entirely in the granite have produced mainly tin ore ; those entirely in killas mainly copper ore ; and the marginal areas have, as far as this district is concerned, yielded both tin and copper ores. In describing the general distribution of the ores it is convenient to speak of them in their relation to the granite masses. The less common ores will be treated of elsewhere. (See Fig. 1.) * KarlDalmer, " Altenberg-GraupenerZinnerzLagerstatten," Zeit.f. Prakt, nd Flander's lodes was rich in tin ore. In West Wheal Damsel the intersection of the New North lode with Tremayne's lode was rich in the deeper parts of the mine. At Wheal Basset the junctions formed by the intersection of the Gr^t Flat lode by the nearly vertical lodes, which cut through and heave it, were generally productive in tin ore. The nearly vertical lodes do not themselves contain much tin, while below their intersection with the Great Plat lode they are generally very poor. The Dolcoath main lode at the junction with the South Entral lode ia 60 feet wide, and was very rich in that place. The junction of the Gaunter lode and the main lode in the same mine was also rich. Conditions wheke Lodes aee of Irregular Bearing.— If a lode changes its bearing slightly in different parts, it is generally found that the richest parts have a common bearing. The relative movement of the walls of an irregular or wavy fissure result in the production of open parts, having a common bearing, which have been filled with veinstone. The closed parts have a common * Henwood, p, 224. ; t De la Beche, p. 337. < ' t Pryce. Mm. CormbiensU, i77S,p, 75, § De la Beche, p. 334. DECOMPOSITION AND REDISTRIBUTION OF THE ORES. 187 but slightly different bearing. Dolcoath main lode affords an instance of this,* and the Great Flat lode may be taken as another instance. Moissenet endeavoured to form an estimate of the amount of movement that had taken place in the walls of the fissure necessary for the formation of- the open parts of the lodes in which the ores were deposited. The form of the fissure he re- garded as being intimately connected with the hardness of the rocks through which the fissure passed. Taking Henwood's data and basing his calculations on the relations which existed between the angle of general uhderlie of the lode and the angle of underlie of that irregular part which contained the ore (open part), Moissenet arrived at the conclusion that for most of the lodes of Cornwall a fall of 275 to 3*75 metres would produce an opening in the lodes of one metre. It should be remembered, however, that many of the Cornish lodes are the result of in-filling and alteration in the vicinity of a series of close parallel cracks, so that the width of an ore body does not necessarily represent the width of the original open part of a fissure. VI. Decomposition and Eedistribution of the Qres. Since tin districts are connected with plutonic rocks, it follows that tin-mining districts are situated as a rule only in extensively denuded areas. As a rule also, tin alluvial deposits nearly always occur where there are tin lodes. Simultaneously with the re- moval of the surface deposits the upper parts of the lodes are being greatly affected by the action of water containing various dissolved substances, such as oxygen, carbon dioxide, and organic acids. The surface water, percolating the crust, penetrates cracks in the lodes and attacks the sulphides and other oxidisable or soluble materials, so that not only is the lode considerably changed in appearance and composition, but redistribution of certain of the minerals takes place. It is upon this principle, taken in conjunction with the assumption that water is able to descend through interstitial spaces and capillary openings in porous rocks to great depths, and reascend through larger cracks or other channels, that various theories have been advanced accounting for the secretion of ores in fissures by the leaching out of metalliferous minerals from the surrounding rocks. In great mining regions this process is supposed to have been particularly stimulated by association with plutonic intrusions, and conse- quently was mainly active in the contact rocks of the meta- morphic aureole. Some excellent treatises dealing with the origin of certain ore deposits of America have been written from this point of view by American geologists.| Posepny'sj: view is, that from surface to ground water level, there is an active circulation of waters, called the vadose or shallow-under-- ground circulation, resulting from the descent of rain or surface water through the rocks. Below this is the , deep-underground circulation pro- * K. Hunt. "British Mining," 1884, p. 439. + e.g, C. R. Van Hise, " Preliminary lieport on the Lead and Zinc Deposits of the Ozark Region." ^nd Aim. Rep. U.S. Geol. Swvey, 1900-1901. t "The Genesis of Ore Deposits." 2r, Am. Inst. Min, Mnq, (Chicago Meeting), 1893. 188 NATUEAL HISTORY OF THE ORES. moted by difierences of temperature in the iipper and lower rocks through, which it passes. The water, as it descends through capillary openings in the rocks, is gradually warmed, and is able to ascend through other channels. Daubrfe* actually supposed that steam emitted from natural vents was produced by actions analogous to those in an experiment carried out by him showing the behaviour of water in passing through a slab of porous material (sandstone), one side of which was heated. Water was able to flow continuously from the cool to the warm part, where it was vaporised. In nature the subterranean water was supposed to find its way down and come in contact withlarge heated rock masses — intrusive or other- wise. Van Hisej has elaborated the arguments favouring the view that " the greater number of ore deposits are the result of the work of under- ground waters." Crenerally speaking, the distribution of the underground water has constantly changed with the elevation or depression of the district and with denudation. Locally, the arrangement or structure of the rocks, their porosity or -imperviougness, and also the extent of Assuring, has a great deal to do with the distribution and circulation of the water, and hence, in all probability, upon the distribution or position of some of the secondarily concentrated minerals.. In Cornwall the circumstances do not permit of any extensive application of the principle of circulating waters in regard to the origin of the ores, but it does apply in the case where soluble metalliferous minerals already present in the lode have been dissolved and redeposited in other parts of the lode. The upper parts of lodes, and especially those lodes containing copper ores, are characterised by the presence of oxide of iron, which is the main constituent of the "Iron Hat" or Gossan, a term by which the weathered ferruginous upper portion of the lode is designated. The iron oxide is derived from copper and iron pyrites by oxidation. ..Emmons was one of the first to show how sulphides decomposed in this way are dissolved, carried down the fissures, and regenerated ; and, indeed, he states that the " native metals and their oxides and. chlorides (except, perhaps, gold, tin, and the platinum group of metals) " are generally the result of secondary alteration from sulphides.^ The general vertical distri- bution of the ores has been referred to, but in addition to this it will be observed that there is a vertical arrangement of the metalliferous minerals brought about by the action of water, a fact known to miners from early times. § t Emmons distinguishes three zones in the part of the lode affected by percolating waters. An upper zone, near the surface, of recently oxidised ores, gossan, in which may occur some residual masses of sulphide not yet oxidised. Below this is a second zone in which carbonates, oxides, or native metals occur ; these are the less soluble or more readily precipi- tated compounds. Below this is the zone of sulphide-enrichment in which minerals brought in solution are deposited as sulphides. Here occur sulphides, sulph-arsenides, sulph-antimonides, or native metals, in contact with original sulphides of the lodes which have not yet been altered. * "Geologie Experimentale," vol. i., 1879, p. 241. + C. B. VanHise, "Some Principles Controlling the Deposition of Ores." Tr. Am. Inst. Min. Enq., 1900. $ S. F. Emmons, " The Secondary Enrichment of Ore Deposits." Tr, Am, Inst. Min. ^?i?. (Washington Meeting), 1900. % eg. See Pryce, Min, Cormib., 1778, p. 6. DECOMPOSITION AND REDISTRIBUTION OF THE ORES. 189 Van Hise states* that there are three zones. Above the level of ground water there is a belt composed largely of oxidei, carbonates, chlorides, and associated products which may contain enriched sulphides. Above and below ground water level is a transition belt, consisting of sulphides rich in valuable metals, such as gold, silver, copper, lead, and zinc, and some oxides. Below this are the '"lean sulphides," containing small amounts of valuable sulphurets commonly passing into sulphide of iron. De Launayf says that near the surface there is a zone of oxides or carbonates, sometimes chlorides. Below this is a zone of argentiferous grey copper with copper glance and native copper. Still lower there is copper pyrites. VogtJ has shown that in the San Domingo Mine, in Southern Spain, the amount of copper in the pyrites of these deposits diminishes with depth. He also distinguishes three zones : (1) the oxidised zone, gossan ; (2) the small zone containing gold and silver ; and (3) below this the principal sulphide zone in which the percentage of copper diminishes with depth. Penrose§ states that in Arizona the upper parts of copper deposits con- sist of black and brown ferruginous masses with oxidised copper minerals, such as cuprite, malachite, azurite, chrysocoUa, &e, ; while at depths vary- ing from a few feet to several hundred feet the deposits are a mixture of copper and iron sulphide in which the latter is in excess. Penrose has also noticed that the decomposition of country rocks in the vicinity of ore deposits is more extensive than in similar rocks in which ore deposits do not occur, " The explanation is, doubtless, in many cases, that the rock has decayed under the influence of the same waters that originally con- centrated the ore. When subsequently the ore body is aSected by surface influences, sulphuric acid is liberated from sulphide, and carbonic acid from carbonates, as well as other acids from other minerals, and all these materials have an active effect on most rocks." || The relation of the underground water to the distribution of the ores has recently received the attention of Mr. Pinch,^ who distinguishes three important zones. Zone I. includes " all depths near the surface in which water is accumulated and conducted to a saturated zone. If there is no saturated zone it terminates with the cessation of downward percola- tion. It is the 'belt of weathering.'" Zone II. is the zone of discharge. It is the upper part of the belt of saturation of Van Hise, and " embraces that part of the belt of saturation, in any region, which has a means of horizontal escape and discharge. The upper part of Zone II. is very variable. The bottom of Zone II. is the lowest limit of notable movement of water, and is controlled by lowest limit of discharge. If impervious "barriers intervene the bottom of the zone may be the crest of the barrier and much-higher than the line of lowest escape." Zone IH. The transitory or static zone. "The movement of the water found below the level of the lowest point of discharge is for normal conditions in- finitesimal," but convection currents may be set up by heat. Finch believes that Zone III. is rarely extensive,except where there are deep open fissures ; and that rocks below 1,000 or 1,500 feet are commonly dry. He divides the upper part of a vein in which secondary enrichment has taken place into two zones : (o) the upper is the zone of oxidation, in which are oxides, sulphates, chlorides, bromides, carbonates, silicates, native metals and loose open veinstone materials ; and (b) the lower zone (zone of reduc^ tion), in which are sulphides, arsenides, antimonides, &c., tunestates molybdates, &e., and dense veinstone material. ' 190o" ^"355 ^"''''^P^®^ Controlling Deposition of Ores." 2r. Am. Inst. Mm. Eng., lifLS" ^Zhrt 233°' ^"''^'''^' " '^'""^ ^^^ ^^^^ mn&v^n^ et Mdtal- PoU?a" ^"A^^^Slf liST^r '^"^ -^«--den theile von Gli^oLii™?.^'''"'' "®''P«'^fi'''^l Al-«'-*"<«iof Ore Deposits." Jc^n. II Op.'c4Y.,'p.'295. ' 1 J/' Y' "™'''^' "Mieous Solutions and Lode Ores." Proc. Col 8ci Sob 1904, vol. vii. , , • *"''• '""'•' 190 NATUEAL HISTOKY 03? THE ORES. These general results have been supported recently by Mr, Hill in regard to Cornwall, who asserts that " before the upper por- tion (of a lode) shares in the disintegration and denudation that are going on at the surface, it has already parted with its metal- liferous contents, which have gone to enrich the lode below. Con- sequently, according to this view, the enrichment of lodes must be descending at a corresponding rate with surface denudation."* As early as 1778 this general principle was recognised by Pryce, who wrote at some length on the subject. With regard to the occurrence of cassiterite in the upper por- tions of lodes, it has occasionally occurred in the gossans of mines wrought for copper in such quantity as to make the outcrop of the lode worth treating for cassiterite. Thus, some of the " backs " of the lodes in the Grwennap district, as well as those near Cam Urea and other places, are typical cases, e.g., Cook's Kitchen, Wheal Unity.f Wheal Daniell, Wheal Spinster, &e. Cassiterite is so insoluble under ordinary conditions that this occurrence is not remarkable, and is explained by the fact that the more readily decomposed minerals have been washed away from a matrix originally carrying cassiterite and decomposable sulphide ores. De la BecheJ says " it has been found that the percentage of cases is considerable where an iron ochreous sub- stance, named gossan, prevails and copper ore is connected with it, and it may be said that the instances are very rare where copper ore is found in fair quantity in a lode without gossan having been discovered on the ' back.' This gossan is generally mixed with quartz and other mineral substances, among which the oxide of tin frequently occurs." Henwood states that the greatest number of rare and curious minerals are found if the upper parts of lodes, and particulaily where gossan is pientiful.§ In Henwood's great work on Cornwall the term " earthy brown iron ore" is very commonly used in the descriptions of the metalliferous contents of the lodes. This no doubt refers to the iron oxides resulting from the decomposition of pyrites. This observer found that in the " superficial " portions of the lodes much iron pyrites (mundic) occurs in East Wheal Crofty, Pennance, United Mines, and Baldhu. Blende occurred in the upper portions of the lodes in the United and Consolidated Mines, Baldhu, Wheal Hope, &c., and that the shallower portions of the lodes yielded earthy black copper ore in gossan in Wheal Jewell and the Consolidated Mines. Native copper and red oxide of copper, with carbonates and arseniates, were also found in Dolcoath, Wheal BuUer, Penstruthal, Ting Tang, Wheal Gorland, Wheal Unity, and Wheal Charlotte. Where the lode has a gossan the ferruginous ingredients diminish with depth, while the * J B Hill, K N. (H,M. Geol. Survey), " The Plutonic and ot)her Intrusive Kocks of West Cornwall in their Kelation to the Mineral Ores." Tr. Soyal Geol. 8oe. Cornmall, vol. xii., part vii., 1901, p. 586. + W. Phillips, S'On the Veins of Cornwall." Tr. Geol. fifoc, vol. ii., 1814, p. 122 % p. 326. § p. 204. DECOMPOSITION AND REDISTRIBUTION OF THE ORES. 191 copper becomes more abundant.* The table of the metalliferous contents of the lodes given on page 195 includes those minerals which have been deposited long after the arrival of the ores in the lodes. Of particular interest in this connection are the Cornish pseudomorphs described by Professor Miers. Evidence of the work of meteoric water is plentifully seen in the upper parts of lodes at the present time. Incrustations of basic copper car- bonate, carbonate of iron, and pigotitef occur in the drivages of the Entral lode of Dolcoath Mine, to some distance below adit level. These deposits are comparatively recent, as the drivages were made little more than 150 years ago. In the deeper levels the incrustations are not so plentiful, the levels are drier, and the lodes generally cease to bear much oxide of iron. In North Eoskear chalcedony occurs as replacement of calc-spar. Observa- tions in Cook's Kitchen Mine confirm the generaf results as to the dying out of the oxides in depth, although this mine is an old one and the working places have been exposed to the oxidising influence of air and moisture. Chappie's lode, in Cook's Kitchen Mine, consists in the upper parts largely of red oxide of iron, clay, and chlorite, stained by iron oxide. The granite down to below the 100-fathom level is considerably decomposed. Cracks and vugs in it are filled with oxide of iron and clay. Chalybite occurs in small crystals on the sides of the levels, and there are stalactites of pigotite and oxide of iron in the levels about 72 fathoms below adit. The oxide of iron staining diminishes with depth, until at about the 190-fathom level it is only in small quantity. Copper carbonate occasionally occurs as thin incrusta- tions. From the 85-fathom level to the 258-fathom level the lode is traversed by small veins of quartz here and there. From above the 200 to the 345- fathom level, below which the mine was filled with water at the time these observations were made, the lode consists mainly of peach, chlorite, and quartz (orcapel), with a little kaolin. Most of the ore of value has, of course, been extracted from the working places, but old reports state that the ores of copper were principally . chalcocite and copper pyrites, which were abundant to below the 160-fathom level. The minerals occurring in the upper parts of lodes which may be regarded as being derived by alteration of pre-existing minerals are cuprite, melaconite, native copper, malachite, chrysocolla chalcopyrite, Redruthite, erubescite, chalybite, limonite, &c., and even mispickel, iron pyrites, copper pyrites, vitreous copper ores and other minerals: although some of them are not necessarily derived by alteration but may represent original deposit. The chemistry of the actions by which these compounds are derived has received attention from various writers, who have shown in the form of chemical equations the reactions involved in their production. Iron * W. Phillips, "On the Veins of Cornwall." Tr. Qeol. Soo., vol. ii,, 1814 p. 207. • ' ' t A compound of mudeseous acid and alumina. See paper by J. K. Creichton "On the Occurrence of Pigotite." Geol. Mag.,l%u, p. 223. Also JoEnson "On the Constitution of Pigotite." PUl. Mag., 1840, p. 382; and A A Julien " On the Part Played by Humous Acids in Ore Deposits, Wall Rn^t' Gossan, &c," Proc. Am, Assoc. Adv. 8ei., 1879, p. 382. ' ^^^> 192 NATURAL HISTORY OF THE ORES. pyrites ia the presence o£ oxygen and water is converted, to sulphide of iroQ and sulphuric acid, which react with the production of ferrous sulphate and sulphuretted hydrogen : — FeSa + O3 + H,0 = FeS + H2SO.1 = FeSO^ + H,8. Iron pyrites is likewise acted upon by the sulphuretted hydrogen of this reaction as follows : — FeS, + Oa + 2HjS = FeS + 2Hfi + 3 S but by further oxidation sulphuric acid is formed, which acts upon iron pyrites ; — S + O3 + H2O = HaSOi.* By reaction between ferrous sulphate, sulphuric acid, and oxygen, the ferric sulphate is obtained : — 2 FeSOi + O + H,SO^ = FeaCSOJg + H^O which may react with sulphide of iron with the production of ferrous sul- phate again : — FeS + Fea(S04)a == 3 FeSO^ + S. By reacting with the oxygen of the air and water sulphuric acid is pro- duced, which is capable of converting ferrous sulphate into ferric sul- phate. It was shown by Emmons that the sulphides written in the follow- ing order represent the order of the ease with which their decomposition is effected by ferric sulphate : — Iron pyrites (FeSj) pyrrhotite (FeuSij), copper pyrites (CuaFCaSj), bornite (CuoFeSa), millerite (NiS), copper glance (Cu^S), galena (PbS), and zincblende (ZnS). If copper pyrites or bornite are present the part of the compound con- sisting of iron sulphide is attacked by ferric sulphate, "leaving OujS. as an amorphous, sooty matprial."t The copper sulphide molecule is next attacked by ferric sulphate, with the production of copper and ferrous sulphate, as follows : — OU2S + 2 Fe,(SOJa = 2 OuSO,j + 4 FeSO^ + S.J The copper sulphate is soluble, and is carried down the lode until it is decomposed by meeting with iron pyrites, pyrrhotite, or copper pyrites, as follows : — 4 CuSOi + 3 FeS, + 4 H,0 = 2 Cu^S + 3 FeSO^ + 3 H^SO^ + HjS 2 CuSO^ + 2 FeS = Cu,S + 2 PeS04 + S 2 CUSO4 + OujSFejSs + H.SO* = 2 Ou^S + 3 FeSO, + HaS.g * W. H. Weed, " Enrichment of Mineral Veins by Later Metallic Sulphides." Bull, Oeol. 800. America, vol. ii., 1900, p. 184. + Op. cit. t W. H. Weed gives a formula Cu^S + SFetSOi), + 4H,0 = 2 CUSO4 + 10 FeSOi + 4 H2SO4. ' ' Enrichment of Gold and Silver Veins. " Tr. Am.. Inst. Min. Eng., 1900, p. 478. § According to van Hisethe reactions involved in the regeneration of copper pyrites may be represented as follows : — CuSOi + 2 FeS = CuFeS, + FeSO^ or CUSO4 + 2 FeS, + O4 = CuFeS, + FeSO^ + 2 SO,. In passing up from lowest level at which copper pyrites occurs it becon-.es more abundant until bornite becomes an important mineral, thus : — CujSO* + CuS04 + 3 FeS = CujFeSs + 2 FeSO^ Cu,S04 + CuSO^ + 3 FeS, + 0„ = CusFeS. + 2FeS04 + 3 SO, or CuFeS, + CuSO.. + O^ = CuaFeSj + FeSO* + SO, At a still higher level copper glance may be produced as follows : — Cu, SO4 + FeS = Cu,S + FeS04 or Cu,SO« + FeS, + O, = Cu,S + FeSO* + SO,, or according to the equations — CuFeS, + CUSO4 + 0,= Cn„S + FeSO* + S0„ CusFeSa + CuSOi + O, = 2Cu,S + FeSOi + SO,. At still higher levels come oxides and carbonates. DECOMPOSITION AND REDISTRIBUTION OF THE ORES. 193 lu these reactions copper g;lance is produced owing to the greater affinity of the copper than the iron for sulphur. Sulphates of lead and zinc may also be produced by similar reactions, and may be precipitated in the same way as sulphides. The carbonates produced in the upper parts of lodes are capable of reduction by contact with sulphides of iron, and Van Hise represents this reaction as follows : — PbCOs + PeS = PbS + PeCOs or PbCOs + PeSo + 0^ = PbS + PeCOa + SOj. Similar equations represent the reactions forming zinc sulphide. He shows also that zinc sulphide itself is capable of reacting with the sul- phate and carbonate of lead, with the formation of lead sulphide and zinc sulphate or carbonate thus : — PbSO* + ZnS = PbS + ZaSOi. PbOOs + ZnS = PbS + ZnCOa. . With regard to the production of carbonates, oxides, or hydrates from metallic sulphides. Dr. Evans states that free carbonic acid gas is unable to effect this change directly, and as a rule the formation of such com- pounds from sulphides is accomplished by carbonates.* This is probably owing to the fact that carbonates would be decomposed in the presence of the free acid which would result from this reaction if it were possible. The production of basic copper carbonate, for instance, above the ground water level, is probably effected by some such compound as ammonium, sodium, or calcium carbonate, thus : — 2 CUSO4 + 2 OaCOs + H3O = Cu(H0)jCuC03 + 2 CaSO^ + CO,. The oxide of copper and native copper are produced above ground water level by reactions similar to those represented in the following equa- tions : — 2 CuSO, + 2 CaCOa ^z 2 CuO + 2 CaSOi + 2 CO,. The CuO is reduced to OujO, and may be acted upon either by ferrous sulphate or free sulphuric acid : — Cu^O + H2SO4 = Cu + CuSOj + HjO 3 CU2O + 6 PeSOa = 6 Cu + Pe^^Os + 2 Pe, (&Ot)a or 3 CujO + 2 PeSOi = 4 Cu + PeA + 2 CuSO^. The oxidation of the iron salt is carried out by abstraction of the oxygen from the copper oxide, which is reduced in consequence, and, as pointed out by Penrose, this reaction may take place at comparatively considerable depths below the oxidised zone in the lodes. In the oxidised zone the production of oxides of iron which characterises the gossan takes place according to the equations : — 12 PeSOi +6 + 2H,0 = 4Pe2(S04)s + 2 Fe^OsH^O or to limonite (2 PejOa 3 H^O). Ferric sulphate may also be oxidised .to limonite and free acid. The reactions involved in the decomposition and regeneration of the rarer metals are capable of expression in the form of equations. The question of secondary deposition of silver has received attention from Vogt,| who shows how native silver is a secondary product derived from silver glance. Weed shows how silver sulphate acting upon copper sulphide results in the production of silver sulphide and copper sulphate. Similarly, pyrites decomposes impure pyrites containing antimony, arsenic, and silver, with the production of antimony sulphide. Native silver may result from the action of ferrous sulphate on silver sulphate, thus : — • AgSOi + 2 FeS04 = Ag,Fe,(S0,)8. According to BischoS, silver sulphide acted upon by steam yields native silver : — 4 AgjS + 4 HoO = 8 Ag + H2SO4 + 3 H^S * J. W. Evans, Min. Mag., vol. xii., 1898-1900, p. 377. t " Ueber die Bildung.des gediegenen Silbera, durch secundar prooesse aus Silberglanz undanderenSilbererzen." Zeit. f. PraU. QeoL, 1899, p. 113. 194 KATtlRAL HISTOEY OF THK ORES. The reaction represented by this equation is, however, not an accom- paniment of surface action.* The presence of gold in gossan, in rather larger quantity than is found 'at greater depths in the lodes, is accounted for by the action of ferric and ferrous sulphates. The gold is dissolved by ferric sulphate and precipi- tated by ferious sulphate, a sulphide, a native metal, or by organic matter. Many sulphides contain gold in the form of a mechanical mixture of free gold and the sulphide. The decomposition of the sulphide results in the formation of oxide of iron, in which the gold remains. The variety of ores in the upper parts of the lodes is accounted for by the complicated set of reactions resulting from the eflfect of surface water containing a few simple substances in solution. The depth to which these effects extend in the Cornish mines cannot be stated with accuracy. With regard to the gossan, the tabulated statements of the lodes in the different mines of Corn- wall show that oxidising influences in the Camborne region have been at work from surface to a depth of at least ] ,000 feet, and in all probability below this. The distribution of this oxidised zone is by no means regular, so that no definite assertions can be made. VII. Minerals of the Ores. Cassiterite. — (SnOg) in the lodes presents a variety of struc- tures and modifications, occurring in minute embedded grains (Zinn-zwitter), or in small or large crystals either embedded or encrusting (Zinn-grauper), and as the fibrous variety known as wood — or Toad's-eye tin. Wood-tin occurred in some abun- dance in the Metal lode in Wheal Vor in scattered grains, small isolated masses, or in veins of varying but small dimen- sions, at a depth of about 180 fathoms from surface.f In this mine the tin ores were all obtained from the lode in killas, which in some places, in 1867, was worth £1 ,000 per cubic fathomt ; in granite, the lode was a mere string and was almost barren of tin.§ As seen by the naked eye, the tin ore commonly occurs filling or encrusting the walls of minute cracks in the granite or killas, or it may form small strings in quartz tourmaline rock, or in quartz with chlorite, and not infrequently in masses consisting almost entirely of tinstone and chlorite with a little quartz and tourmaline. Occasionally, it is abundant in china clay or occurs in decomposed granite in the neighbourhood of the lode. The tin ore frequently occurs in the same crack with arsenical and copper pyrites, but in these cases crystals of tin are idiomorphic and were the first of the minerals to crystallise. In brecciated masses of lodestuff the tin ore is clearly seen to be associated with the earlier fragments of the brecciated material, and is itself frequently broken and crushed. Wolfram, with occasionally arsenical and copper * See "Elements of Chemical and Physical Geology," by G. Bischoff. Translated by B. H. Paul, 1859, vol. iii., p. 536. t W. Argall, "On the Occurrence of Wood-tin at Wheal Vor.'' Joum. Boy, Inst. Corn., vol. iv., 1873, p. 265. If Charles Thomas, " Mining Fields of the West," 1867, p. 24. I Carne, p. 93. MINEIULS OF THE OEE& 195 pyrites, with quartz, tourmaline, chlorite, and sometimes fluorspar, appear to be the principal minerals associated with the tinstone. Cassiterite crystals taken from the 314-fathom level at Dolcoath in 1878 are very fine and of a jet black colour " shading into brown with adamantine lustre." Some associated with limpid fluorspar and chlorite from the Wheal Harriet part of Dolcoath were deeply striated on the prism faces. In Great Wheal Vor jet black crystals of cassiterite show polysynthetic twining, while others are brown and often highly modified, and occur with chlorite and sometimes limpid crystals of apatite. Blende, copper pyrites, mispickel, iron pyrites, and pearl spar (Dolomite) also occur with tinstone in this mine.* An extensive series of tinstones are exhibited in the Museum at Jermyn Street. The following table enumerates the other metallic products, together with their mineral associates : — — Mine. Accom- panied by. Eemarks. Authority.+ Stannite Cam Brea - South Crofty- East Pool - Sparingly In some quantity Garby, p. 85. Scorrier Mine ... In small quantity De la Beche, p. 584. Barrier Mine ... ... Hall, Min. (Gwennap) Directory, 1868, p. 38. Copper Tolgus,Wheal .. . One of the pyrites Jewell, Dol- coath, Cook's Kitchen, North Eos- kear, East Wheal Crofty, East Pool, &c., &c. principal ores of the mines Consolidated Iron pyrites ... Catalogue of Mines Mineral Col- lection at Jermyn St., 1864. Tresavean - Fluorspar - ... Cam Brea - Specular iron ore and carbonate ... North Eos- Fluorspar - ... kear Buller - j» ... * K. H. Solly. Min. Mag., vol. ix., 1891, p. 207. See also William Phillips "On the Oxide of Tin." Tr. Qeo. Boc, 1814, vol. ii., p. 336. Also "Speci- mens of British Minerals from the Cabinet of Philip Rashleigh," 1797. t The references to Garby and Kashleigh relate to the following- J. Garby, Tr. R.G.8. Corn., vol. vii.,.1848, p. 71, et seq. P. Rashleigh, " Specimens of British Minerals selected from the Cabinet of Philip Kaah leigh," 1797. o2 196 NATUEAL HISTORY OF THE OEES. — Mine. Accom- panied by. Bemarks. Authority. Vitreous Carn Brea, Abundant in See " Observa- copper ore Bast Basset, lodes rich in tions relative South Basset, copper to Mineralo- Trethellan, gical History Tresavean, of the Fossils Dolcoath, of Cornwall," Wheal Jewell Klaproth. Tr. Abraham by Groschke, 1787, p. 26. Eedruthite - Carn Brea - Copper py- In upper parts R. H. Solly, rites, wol- of lode Mill. Mag., fram, tin. 1891, vol. ix., chlorite. p. 199. quartz, &c. Camborne Vean, Cook's Kitchen, Wheal Buller Grey copper Great Work - Copper py- In South B. Kitto, Rep. ore rites, tin Wheal Breage Corn. Poly. ore lode Sac, 1869, p. 48. Tresavean ... Garby, p. 88. Mine Cook's Kit- .. • ... chen, Tin- croft, Con- durrow,Tres- avean, Car- harrack. South Basset Bornite, Carn Brea, With copper Common in Brubescite Dolcoath, &c. Wheal Buller, North Wheal, Fortune Wheal Fal- mouth Camborne Vean, &c. South Tolgus pyrites ... Carn Brea J. Mitchell, Tr. B.G.S. Oorn., vol. iii., 1828, p. 338. Henwood, Table Ixvii. Indigo copper Carn Brea Garby, p. 88. Arsenate of Wheal BuUer Henwood, copper and Beau- champ Ting Tang - Carharraok ... Table Iviii. Gorland (See Tile ore and red oxide of copper) Garby, p. 90. Pedn an Drea ... ... A. W. Tooke, Mill. Bev., 1836, p. 236. MINERALS OF THE ORES, 197 — Mine. . Accom- panied by. Remarks. Authority. Arsenate of Her] and- Symons, "A copper — Sketch of the cont. Geology of Cornwall," 1884. Wood copper Wheal Unity- ... ... Came, p. 93. Llbethinite South Wheal ... . . . (phosphate Frances of copper) Condurriteor Condurrow, ... Analysis by Garby, Tr. pitch cop- Wheal Druid Dr. Faraday R.G.8. Corn., per in 1827. Cu. 60-5 per cent., As. 1-51, AS2O8 25-94, S. 3-06, Water 8-99. 1846, vol. vi. Tile ore Wheal Gor- Chlorite, ... W. Phillips, land blue and green cop- per car- bonate, arseniate of copper and iron, and native cop- Tr. Geo}. Soc, vol. i., 1811, p. 30. per y Wheal Jewell Fluorspar ... Op. cit. Tolcarne ... 1 Tincroft Copper Decomposing Rashleigh, p. ochre, red 17. crystal- lised cop- per ore,and malachite Wheal Unity ... ... Cuprite- Carn Brea - Gorland South Prances ChrysocoUa In a small vein W. Semmons, Min. Mag., vol. ii., 1878. Eed oxide of Ting Tang - Vitreous Henwood, copper copper ore and earthy brown iron ores Table Ix. Wheal BuUer, With native Catalogue Treskerby copper Min. Collec- tion, 1864. Wheal Damsel .. a Carne, p. 121. Tincroft Native cop- W. Phillips, per Tr. Geol. Soc, vol. i., 1811, p. 31. Dolcoath With black oxide West Wheal Vitreous In a cross Henwood,p.92. Virgin and native course • copper (" Tiddy's ") 198 NATTJRAX HISTOEY OF THE ORES. — Mine. Accom- panied by. Remarks^ Authority. Eed oxide of Wheal Gor- Fluorspar, IntheMuttral W. Phillips, copper — land vitreous and Great Tr.Geol.Soc, cont. copper, black oxide of copper, arseniate of copper, mispickel, quartz, and native cop- Gossan lode about 66 and 86-fm. level in Gossan 1811, p. 23. Capillary red United Mines per Native cop- In a cross- Henwood, oxide of per course p. 270. copper (" Tiddy's ") Green car- Ting Tang - Blue car- >i • Henwood, bonate of bonate. Table Ix. copper copper py- rites, and vitreous Dolcoath copper Red oxide of copper Catalogue Min. Collec- tion, 1864. Buller - ... Henwood, p. 214. Wheal Virgin With grey copper ore ... Klaproth (op. cit.), p. 28. Carharrack - ... Binner Downs Blue carb. copper ... Henwood, Table sxxix. Wheal Gor- (See Tile land ore) Trefusis ... Blue carbon- Basset, Buller Garby, p. 89. ate of cop- per Ting Tang Virgin - Carharrack - East Pool - Gorland ... Klaproth (op. cit.), p. 28. Klaproth (op. cit.), p. 28. W. Borlase, Nat. Hist, of Corn., 1757, p. 198. Cook's Ochre Rashleigh, Kitchen p. 22. Nanterrow ... In the gossan Mine (Gwi- thian) Dolcoath Ripple markec encrustation on the walls of old levels in the Entral lode Wheal Tre- .,. ... fusis Tennantite - Tresavean With Born- ite ... MINERALS OF THE ORES, 199 Tennantite- cont. Chpysocolla ■ Native copper "Wheal Jewell, West Jewell, Dolooath, North Bos- kear, Cook's Kitohen,Tm- croft. Cam Brea, Wheal Unity, Tre- vaskus, &c. Ting Tang - Gorland Cook's Kit- chen Wheal Virgin Cam Brea - Wheal land Gor- Aeeom- panied by. Copper py- rites,vitre- ous copper Carharrack - Poldory United Mines Tincroft, Dol- coath Wheal Music Consolidated, United, West Wheal Virgin Treskerby South Frances Condurrow Mine any load Tresavean Mine With red vitreous copper ore Vitreous copper Oxide of copper (See Red oxide of copper) Clayey, pri- Remarks. Authority. J. H. Collins, Min. Oorn. & Devon, 1871. Several tons obtained (See Cuprite) Henwood, Table Ix. Hall, Min. Directory, 1868, p. 39. Pryoe, Min. Comuh., 1778. M.H.Klaproth, "Observations on Minera- logy of Corn- wall," 1787, p. 25. Tr. by Groschke. '. Garby, p. 88. In large quantity (See Red oxide of copper and tile ore) In small quan- tity in strings In a cross- course (" Tid- dy's") In a pi pels ft. long, 8 ft. high, 3 in. to 5 in. wide Pseudomorph after cuprite Klaproth (op. cit.), p. 26. Rashleigh, p. 31. Henwood,p.65. Henwood,p.92. Came, Tr. B.G.S. Corn., vol. vi., 1846, p,26. B. W. W. Pen- darves, Tr. B.O.S. Corn., voLiii., 1828. (See also De la Beche, p. 591.) H. A. Miers, Min. Mag., vol. xi , 1897. 200 NATTJEAL HISTORY OF THE ORES. Mispickel Leucopyrite- Oxide of ar- senic Native arsenic Wolfram Scheelite Pliosphate of lead Arsenate load of In[manymines in the dis- trict Dolooath Great Wheal Vor Pedn an Drea, &c. Wheal Spar- non Dolcoath Pedn an Drea, &c. East Fool Mine Carbonate of lead Galena Accom- panied by. Wheal Falmouth Wheal Rose - Wheal Bose - North Downs Wheal Unity Gorland Wheal Kose (Helston) Cobalt and nickel ore Blende,cop- per pyrites, iron py- rites, tin- stone Cobalt ores Bemarks. Common in lodes. Its presence ne- cessitates the roasting of ores Carb. and phosph. of iron (See Phos- phate of lead) (See Distri- bution of Silver-Lead ores p. 181) In a cross- course (See under " Distribu- tion of Ores," p. 178) As partial re- placement of wolfram. At Wheal Maud- lin, near St. Aubtell,Miers records wol- fram after scheelite Authority, (See Phosphate of lead) Some crystal- lised on hsB- matite Catal. Min. Coll., Jermyn Street, 1864. B. H. Solly, Min. Mag., vol. ix.,1891, p. 208. C. Le Neve Poster, Min. Mag., , 1877, No. iii. Garby, Tr. B.G.S. Corn., vol. vi., 1846, p. 86. Garby, p. 86. J. H. Collins, " On Cornish Mineral Lo- calities,"Mm. Mag., 1878, p. 92. {Min. Mag., 1897) Henwood, Ta- ble Ixvii. Hfenwood, p.87. A. W. Tooke, Mining Bev., 1836, No. viii., p. 253. MINERALS OF THE ORES. 201 Native silver Wheal Basset Herland Vitreous sil- ver (glance) Red silver ore Chloride of silver Dolcoath South Tresa- vean Dolcoath, Her- land, Basset, South Basset Dolcoath North Dol- coath Blackjack Bismuthinite Bast Pool Herland Dolcoath Sparnon Accom- panied by. Galena Arseniate of silver, vi- treous and capillary silver ore, mispiokel, and iron pyrites Vitreous and red silver ores. Some associated with ohe- nocoprolite Argenti- ferous ga- lena, kup- fernickel, and pitch- blende (See under Native sil- Bemarks. ver) (See under Native sil- ver) Horn silver, crystallised and mas- sive Copper and lead ores, &c. (See Distri- bution of ores, p. 178) Cobalt ores and native bismuth Native bis- muth. Some native bis- muth asso- ciated with fluorspar Native bis- muth and cobalt ores In cross-course near its in- tersection with a lode In a cross- course strik- ing N. 30 deg. W. Only rich near a copper lode. £8,000 worth of silver ore South Entral lode Found in 1863 Some crystal- lised on ar- senical py- "rites 8 tons 6 cwts. in 1858, Acicular coat- ing. Needles lying on face of joint Authority. Carne, Tr. B.G.S. Corn., vol. i., 1818. p. 123. Carne, Tr., li.G.S. Corn., vol. i., 1818, p. 123, Henwood,p.65. R. Pearoe, " Note on Pitchblende," Tr. R.G.S., Corn., vol. ix., 1864-78, p. 102. Mineral statistics Garby, p. 86. Garby, p. 86. Garby, Tr. It.G.S. Corn., 1846, p. 86. .202 NATTJBAL HISTOEY OF THE OKES. — Mine. Accom- panied by. Remarks. Authority. Bismuthinite Beauchamp - Cobalt ore W. Borlase, — cont. Nat. Hist, of Cornwall, 1758, p. 129. Native bis- ... (See under ... muth Bismuth- inite) Stibnite Dolcoath (See under Bed silver ore) ... Falmouth Cobalt ore In a cross- Henwood, and iron course Table Ixvii. pyrites Herland Cobalt ore, In a cross- Henwood, p. iron py- course 271. rites, and quartz Wheal Vor - Cobalt ore, In a cross- Henwood, p. iron py- course 271. rites, and quartz Cobalt bloom Wheal Unity- Sparnon ... ... Garby, p. 87. Smaltite (tin, Dolcoath Native ar- ... Garby, p. 87. white co- senic (See also balt) Pryoe, p. 50.) Sparnon In veins and small bunches (one mass weighed 1,333 lbs.) Garby, p. 87. Carne, p. 113. Elizabeth - ... ... Hall, Min. Directory, 1868, p. 50. Cobalt ore - Wheal Beau- champ Bast Pool - South Crofty . (Dudnance) (See under Bismuth- inite) ... Symons, " A Sketch ot the Geology of Cornwall," 1884, p. 128. Pryee, p. 50. Wheal Gal With"cal" ... Pryce, p. 50. (Ponsanooth) (Gossan) and tin ore 5 Falmouth and (See under .. . Vor Stibnite) Kupfernickel • •• (See Distri- bution otores p. 179) ... ■ Sulphuret of Wheal Spar- (See under ■ i. Garby, Tr. nickel non Distribution R.G.S. Corn., (Millerite) of ores, p. 179) vol. vi., 1846, p. 87. Molybdenite Wheal Crofty, ■ ■■ ... Gilbert, Hist. (" Molyb- Wheal Unity, of Corn., vol. |,denum ") Gorland i., 1817, p. 268. MINERALS OF THE OBES. 203 Accom- panied by. Remarks. Authority. Wad Wheal Buckets (near Sparnon) Wheal Tolgus Pedn an Drea Sparnick Pitchblende - Uranite Johannite - Barytes Specular iron ore Magnetic iron ore Limonite Arsenate of iron Carbonate of iron South Basset Consolidated Mines and Wheal Friendship Wheal Bean- champ Tincroft, Carn Brea, Tresavean Wheal Har- mony ■worked at Treluswell and found in other places Wheal Druid, Gorland Wheal Beau- champ With small veins of galena (See under Distribution of ores p. 179) (See under Distribution of ores p. 179) Other uran- ium ores In a vein 3 in. wide in elvan Common in many mines (See under Phosphate of lead) Tincroft Dolcoath Wheal Towan Carn Brea - Wheal Basset Lemon and sulphur yellow Common as a late incrusta- tion in old levels and working places, e.g., Cook's Kit- chen Garby, p. 85. A. E. Barnett, " On Elvan Courses," Boy. Corn. Poly. Soc, 1873, p, 17. Garby, p. 86. Symons, Gazet- teer ^ef Corn., p. 212. Garby, p. 83. J. H. Collins, Min. Loc, 1871. Garby, p. 82. De la Beche, p. 618. Garby, p. 84. Tin and copper Hall, Min, Directory, 1868, p. "32. H. A. Miers, Min. Mag., vol. xi., 1897, p. 266. 204 NATURAL HISTORY OF THE ORES. — Mine. Accom- panied by. Remarks. Authority. Phosphate of iron ... (See under Phosphate of lead) In Wheal Jane crystallised on iron py- rites Sulphuret of Snolybdena In Gwennap, Wheal Friendship, Wheal Gor- land, and Gartay, p. 85. Native sul- Wheal Unity Nangiles Garby, p. 92. phur Cornish Pseddomoephs.* Chaloopyrite after bismuthine, bournonite, caleite, Redruthite, tetra- hedrite. Redruthite after g«ilena, iron pyrites, erubesoite. Erubescite after chaloopyrite and Redruthite. Iron pyrites after caleite, barytes, fluor, pyrrhotite, quart!!. Chalybite after fluor, caleite, barytes, dolomite, pyrites, bismuthine, Limonite after fluorspar (Cook's Kitchen). Professor Miers describes a hollow drusy pseudomorph of the form of mispickel in a matrix of chlorite and accompanied by a later deposit of chalybite and tarnished erubescite (Cam Brea Mine). * H. A. Miers, " On some British Psoudomorphs." Min. Mag., vol. xi., 1897- 205 CHAPTER XVII. THE MINES. . I. Linear Distribution of the Principal Mines. The principal mines are situated side by side along important mineralised belts or zones, so that in a diagrammatic manner the mines on any particularzone can be represented on a map by a single line. (Fig. 21.) Thus in the Camborne district a line on the northern margin of the Carn Brea granite represents the important lode belt upon which are situated — Camborne Vean Mine, Dolcoath, Cook's Kitchen, Tincroft, and Carn Brea Mines, A line parallel with it but further north may represent the important lodes of South Roskear, South Crofty, and East Pool Mines. The Great Flat lode OQ the southern margin of the Carn Brea granite, and the vertical series which intersect it, can in like manner bediagram- matically represented as an important mineral belt by two lines upon which are situated South Condurrow Mine (and Wheal G-renville),West Frances, West Basset, South Carn Brea (and Wheal Basset), and Wheal Uny. Similarly, in the Grwennap district, the important mines are situated along a line extending from the United Mines through Wheal Clifford, Wheal Andrew, Nangiles, Wheal Widden, and West Wheal Jane to Wheal Jane. A branch* of this series of mines runs from the Consolidated Mines to Wheal Andrew, and another branch* runs through Ting Tang to the United Mines. Wheal Damsel, Wheal Maid, and Todpool are again in linear arrangement. North of this are several series of lodes upon which important mines are situated, as follows : — Wheal Jewell and Poldice ; Wheal Gorland, Unity, and Creegbraws ; West Poldice; Unity Wood;* Killifreth.* These lines are short. Near Scorrier Grate there is a mineralised zone along which Treskerby, Scorrier Old Mine, Great Wheal Busy, and Wheal Daniell are situated. North of this there are two more series of important mines ' — New Treleigh Consols, Wheal Peevor, Great North Downs, Wheal Rose and East Downs ; and Wheal Mary, North Downs, Wheal Briggan, and Boscawen, Each of these zones is made up of several important lodes which have a bearing similar to that of the zones themselves. Hence these lines represent the linear arrangement of the principal mines, the position of the principal mineralised belts or zones, and the bearing of the principal lodes of which the belts are composed. In this manner the confusion which is sure to arise from any attempt to work out the lode systems by consideration of the par- ticulars of individual lodes is largely eliminatedi It should be * See Note at the end oi this Secbion. 206 THE MIWES. «N ^ observed that the country separating these great lode series is also iissured and mineralised, but the importance of the lodes in it is less. Reference to the diagram or geological map shows that these lode zones can be divided into two main systems, according to their PARTICULARS RELATING TO THE MINES. 207 directional characters, which may have been determined by the nature of the folding in the sedimentary roclss, produced by the pre-Devonian and post-Carboniferous movements. In the par- ticulars given above, those series marked with an asterisk (*) have a bearing of a few degrees north of east, and in some cases they appear to fault the other series, wuich has a bearing of about E. 30 deg. N. The latter make up the more important system. II. Particulars Kelating to the Mines. Miscellaneous information relating to individual mines may be obtained in the following publications, much of which it is un- necessary to reproduce ; so that the descriptions which follow are largely confined to unpublished information, together with scattered facts not already referred to in the previous pages : — The West Briton (since 1805). The Bngineering and Mining Journal (since 1830). The Mining Beview. " Survey of Cfirnmenellis District," vol. iii., 1835. (" Descriptive notice of the Consolidated and United Mines," vol. iii,, 1835). " The Mining District of Redruth." vol. ii., 1832. 1819. Thomas, Richard, " Report on a Survey of the Mining District from Chacewater to Camborne." 1843. Henwood, W. J., " On the Metalliferous Deposits of Cornwall and Devon." Tr. ie.G.S. Corn., vol. v. 1843. Watson, J. Y., "A Compendium of British Mining, with Statistical Notices of the Principal Mines in Cornwall." 1860. Pike, J. R., " Britain's Metal Mines." 1862. Salmon, H. C, " The Seton Mining District." Mining and Smelting Magazine, vol. ii., pp. 277 and 332. Also descriptions of prominent mines, pp. 74, 84, 86, 140 and in vol. i., pp. 314, 384. 1863. " The Condurrow District." Mining and Smelting Magazine, vol. iii., p. 82. 1865. Spargo, T., " The Mines of Cornwall and Devon." 1867. Thomas, C, " Mining Fields of the West." 1873. J. H. Collins, Inst. Mech. Eng. " On the Mining Districts of Cornwall and West Devon." 1874. Maynard, J., " Mines of the Illogan District." 42nd Ann, Bep, Eoij. Corn. Poly. Soc, p. 84. ■ 1876. " Note on a Cross Section from Cook's Kitchen to Wheal Emily Henrietta." Bep, Miners' Assoc. Corn, and Devon, p. 65. 1884. Symons, Brenton, " Gazetteer of Cornwall." 1890. Collins, J. H., " Origin and Development of Ore Deposits in the West of England." Journ. Boy, Inst. Corn., p. 109. 1892. Do. do. p. 111. 1893. Do, do. p. 327. 1897. Do. do. p. 195. In the following particulars relating to the mines precedence has been given to those which are now working. The abandoned undertakings, however, do not imply the exhaustion of the local mine-fields, and it may be regarded as certain that many will be again opened up in the future. The Active Mines. . Wheal. Basset.- -There are a number of lodes in this sett, but in recent yearu the ore has been obtained principally from the Great Flat lode, which 208 THE MINES. has been explored to a depth of 260 fathoms from adit measured vertically, J. he lode in some places is of enormous width. The Plat lode was first discoverea in 1876 mthis mine, and during the following years it was exten- sively explored. From September, 1883, to October, 1884, over 17,000 tons of ore were taken from the stopes, averaging 34 lbs. of black tin per ton. From October, 1884 to May, 1885, 10,809 tons were raised, averaging 46 lbs. per ton ; and in 188 , , 400 to 450 tons were raised weekly, yielding 7 tons of black tin a ween, ilie lode is traversed by numerous quartz strings. ' It consists mainly ot blue peach, which in some places is brown or dull red owing to presence of ferruginous material. In many cases the peach shows the original structure of the granite from which it was formed. The other loaes have yielded copper ores to a depth of about 150 fathoms from sur- face. Between the years 1815 and 1833, 17,416 tons of copper ore yielding ia77 tons of metallic copper, were raised.* The Great Lode underlies north and varies in width from 2 to 7 feet. At the 120 and 130-fathom levels the lode consists of quartz, flucan, tin and copper ores, and a good deal ot ferruginous matter. Griesler's Lode is situated on the north of the Great lode and under- lies north. Near the Old Sump shaft it is 1 to 2 feet in width at the 120- fathom level and contains both tin and copper ore. A /'"i?''^ on ^°'^«-— Situated north of Giesler's lode and underlies north. At the 120-fathom level near the Old Sump shaft the lode contains copper ore and is U feet in width. Paddon's North Branch.— Vavies in width from IJ to 1 foot and yielded good copper ore. Theaker's Lode branches off from the Great lode on the south side below adit level. It has a southerly underlie. William's South or Gaunter Lode.— Nearly vertical. It crosses William's lode. At the 110-fathom level it is 1 foot wide and yielded copper ore. William's Lode. — It has a good gossan and underlies S. 10 deg. It is about 4 feet in width, and consists largely of quartz, clay, and ochreous materials. VinUm's Lode is north of the New lode, which is situated below Vivian and Paddon's lodes. It underlies south and yielded copper ores. North Basset Lode.— Situated on the north of Vivian's lode and explored for copper ore to considerable depth. At the 185-fathom level it is 18 feet wide and yielded tin ore to the value of £10 per cubic fathom. North Lode. — Situated north of the North Basset lode. It underlies 23 deg. N. and varies from 1 to 12 feet in width. The lode has yielded good copper ores and consists of quartz, peach, and killas, with some mundic. Caraef described the mode of occurrence of silver in Wheal Basset. A grey silver ore accompanied by galena which did not itself contain much silver, yielded as much as 600 ozs. of metallic silver per ton of stuff. The ore was found in a cross-course about 4 inches in width, near the place where it intersects a copper lode. At 6 feeii on either side from the line of intersection of the cross-course and the lode the cross-course ceased to con- tain silver ore. Caen Bbea and Tinckoft United MiNES.^The sett includes Tincroft Mine (formerly Wheal Fanny), Cam Brea Mine, and Wheal Druid. The lodes wrought by these mines belong to the same series as those worked in Cook's Kitchen, Dolcoath, and Camborne Vean. It is almost impossible to give a complete account of the relations of the various lodes and theit branches ; and the available data are not easily reconcilable with one another. The principal lodes can be identified in the mines situated along this series of lodes. The Barncoose lode in Oarn Brea Mine is known in Tin- croft Mine and Cook's Kitchen as the North Tincroft or East Pool lode, * Phillips and Darlington. " Keoords of Mining and Metallurgy," 1867. + "On the Discovery of Silver in the Mines of Cornwall." Tr. E.Q.S. Corn,, vol. i., 1818, p. 123. THE ACTIVE MINES. 209 and ifi Dolooath as the North Entral lode. The Highburrow lode in Cam Brea and Cook's Kitchsn is known as the main lode in Dolooath. Chappie's lode of Tincrof t and Cook's Kitchen is recognised in Dolooath as Harriett's lode. Teague's lode in Carn Brea is the same as Dunkin's lode in Tinoroft and Cook's Kitchen and Richards' lode in Dalcoath. The South lode of Cook's Kitchen is known as the South lode in Dolooath. The Druid South lode in Carn Brea Mine is the same as the Providence lode in Tinoroft and Cook's Kitchen and the Brea lode of Dolooath. Druid Lode. — The underlie is from 15 deg. to 40 deg. north. The lode varies in width from 1 to 2 feet. In depth it is 4 feet wide. The eastern part of the lode is in killas and is split into two parts. Westwards, the lode is in granite and is split into three north-underlying branches. In the eastern part the lode was not of much value in the upper levels. In the granite the lode has a good gossan with clay and " prian." Black, grey, and yellow copper ores occurred in horizontal bunches from adit to the 36- fathom level. At the 112-fathom level there was both copper and tin ore, and from the 145 to the 204-fathom level the lode varied in width from 4 to 6 feet, and contained tin ore. On the whole there was not much copper below the 70-fathom level. The back (outcrop) of the lode was worked away in olden times. DnUd Gaunter Lode. — Bearing E. 20 deg. S. Nearly vertical and varies in width from 1 to 3 feet. It runs into the Druid lode on the north side at about 30 fathoms east of Druid New shaft, and is 24 fathoms north of Vigur's lode. The copper ore in this lode extended for 80 fathoms in the direction of strike between adit and the 50-fathom level, but below the 60- fathom level it was poor and very quartzose. Jenkins' Lode. — Underlie 10 deg. N. About 2 feet wide. It is situated 40 fathoms south of the Druid lode and is one of the most southerly lodes in the sett. In granite it is ferruginous and clayey. Vigur's Lode. — ^A Caunter lode running into the Druid lode on the north side about 15 fathoms east of Druid New shaft. It is nearly vertical, and roughly parallel with the Druid Caunter. In width it is about 3 feet. Vigur's lode has a good gossan and was rich in copper ore in the upper levels. At the 105-fathom level it yielded a fair amount of tin ore. Druid North Lode.— Much the same bearing as the Druid lode. Under- lie is slightly north and it drops into Teague's lode below the 200-fathom level. Yielded tin ore. Teague's Lode.— Underlie at Old Engine shaft is 13 deg. south. At Barker's shaft the underlie to the 50-fathom level is 15 deg. south. From the 50 to the 80-fathom level the underlie is 10 deg. north. Prom the 80 to the 150-fathom level the underlie is 10 deg. south. The changes in underlie did not affect its productiveness. It is from 2 to 7 feet in width, and converges with the Highburrow lode in depth. At the 141-fathom level it is 20 feet in width.* The veinstone is " priany," quartzose and ferruginous. Prom the 34 to the 105-fathom level for 100 fathoms in direc- tion of strike the lode yielded good copper ore ; and from the 80 to the 135-fathom level some tin ore. Known as Dunkin's lode in Tinoroft Mine. Dobree's Lode. — It is a branch of Teague's lode on the south side. It underlies north from 18 deg. to 30 deg. The lode contained copper ores from the 20 to the 70-fathom level for 80 fathoms in direction of strike. North or Daive's Lodes.— Branches of Teague's lode on the north side. Underlie from 27 deg. to 40 deg. They yielded copper ore from the 34 to 105-fathom level for about 50 fathoms in direction of strike, but they became unproductive at a distance from Teague's lode. From 2 to 6 feet in width. Hichen's Lode.— Underlie north 20 deg. to 40 deg. Width from a few inches to 1^ feet. Yielded copper ore from 34 to 70-fathom level but was poor below. Highburrow Lode.— Bearing E. 30 deg. N. In the upper levels it is nearly vertical but gradually underlies south. The width varies from 2 to 12 feet. The main part of the lodo is in the western part of the sett. * Hen wood. 210 THE MINES. From the 60 to Jhe 105-fathom level large quantities of tin ore were extrac- ted for a distance of 150 fathoms in direction of strike. At the 200-fathom level there was both copper and tin ore. At the 250-fathom level it was very rich in tin ore, but at the 310-fathom level the lode was wrung up in an elvan and became valueless. Phillips states that about the 100-fathom level the lode yielded both tin and copper " either mixed or running down the lode side by side."* Barneoose Lode. — This lode runs into the Barncoose Mine. The lode is about 3 feet wide. It is very quartzose and yielded tin ore at adit level. At the 100-fathom level the lode is 4 to 10 feet in width. At the 136- fathom level the lode yielded rich tin ore. Further west in Tincrof fc Mine the lode is known as the North Tincroft lode. In this part of the mine wolfram and tin ore occur. It is possibly this lode to which Carne refers when he states that wolfram and uranium oxide were found in an "east and west copper lode."f . There are a number of other lodes which have received notice from Thomas and Henwood ; but some of them cannot now be identified. All the lodes in the upper parts contained copper pyrites and vitreous copper ore. Native copperj as well as purple and indigo§ copper ores occurred. A mineral called condurrite (pitch copper) was found in the east part of Cam Brea Mine (Wheal Druid), within 10 fathoms of a cross-course. The lode yielded condurrite for a width of 3 to 4 feet, with a vein in the -middle of native copper from J inch to 2 inches wide. The lode was soft and reddish, and the condurrite was taken from it in small nodules. The rest of the lode is iron oxide, quartz, chlorite ; with a little tin ore and mispickel.|| In Wheal Druid the lodes contained specular iron, arseniate of iron, wolfram, and tin pyrites, in addition to tin ore.1[ OhrysocoUa occurred in Cam Brea, and small veins of cuprite 2 mm. in width. The felspar crystals of the granite in which they occur are partly converted to ohrysocoUa.** The mine was first worked on a large scale in 1830.+t Between the years 1830 and 1856 the mine sold by public ticketing 161,593 tons of copper ore yielding 12,039 tons of copper.ff In Carn Brea Mine the average yield of" black tin" from 1872 to 1881 was 35 lbs. per ton. In Tincroft daring the same period the yield was 53 lbs.perton.§§ The mining cost per ton during the same period was 14s.3d. The cost of dressing was 3s. 9d. Mr. Collins states that there was a poor zone in the main lode near the 238-fathom level. ||1| Henwood states that in sinking on Dunkin's lode, in the Tincroft part of the Cam Brea Mines, the first 26 fathoms was in granite. Below this to 84 fathoms below surface the lode is enclosed by killas ; and below this again is the main mass of granite. Near Martin's lode there are several irregular patches of granite, all heaved by the eastern cross-course. There is a third mass of granite extending from the main mass to within 25 fathoms of the surface. No granite veins have been encountered north of these places.lTf • ■' On the Veins of Cornwall." Tr. Geol. Soc, 1814, vol. ii., p. 154. t J. Carne, "On the Veins of Cornwall." Tr. B.0.8. Corn., 1822, vol. u., p. 61. t Henwood, p. 65. ,. § J. Garby. Tr. R. G.S., Com. vol. vu., 1847, p. 85. II J. Garby. Op. cit., vol, vi., 1846, p. 194. IT Op. cit., p. 83. ** W. Semmons. Mi/n. Mag., vol. li., 1878, p. 200. /, ■ d ; tt J. Maynard, '■ Remarks on Two Cross Sections." &c. Rep. Bm,. Corn. Poly. ^'li; t T6^.t''6'4r.ntAo,^.nt of Ore Deposits, &c.» Journ. Etyy. Intt. Corn., 1892, p. 75. Uir Henwood pp. 60, 198. THK ACTIVE MINES. 211 Cook's Kiiohen Mine. — Maynard in 1874 states that the mine had worked continuously for 130 years,* and that the lodes yielded copper ore to the Ill-fathom level, below which they have yielded mainly tin ore. In 1814 this mine was one of the most productive tin mines in Corn- wall.! The average yield of black tin per ton of ore from 1872 to 188 1 was 43 lbs. The cost of mining for the same period was about 16s. .4Jd. per ton, while the cost of dressing was 4s. 5|^d. Between 1815 and 1856, 43,606 tons of ore were sold by public ticketing, yielding 1,484 tons of copper.^ The mine has been worked to a depth of at least 430 fathoms below adit. Chappie's Lode.— The underlie is south 15 deg. to 20 deg. Eastwards it drops into the Highburrow lode, which is the main lode of Carn Brea and Tincroft. The lode has yielded immense quantities of copper pyrites and rich grey copper ore and tin, and especially at the junctigns with its numerous branches. The ore shoots follow the lines of intersection of lodes and pitch eastwards.§ In width it varies from 6 to 20 feet. At the 332 and 345-fathom levels, just below the point where Dunkin's lode drops into Chappie's, the lode varies in width from 15 to 20 feet.|| At the 400-fathom level it is 30 feet wide. The lode yielded a great deal of copper ore from the 16-fathom level to "below the 100-fathom level ; grey copper and copper pyrites mixed with " peach," " prian," and capel occurred down to the 160-fathom level. The greatest wealth began below the 200-fathom level, the lode varying in width from 5 to 8 feet, and contained good tin ore down to the 400-fathom level (below the junction of Dunkin's and South lode). Here the lode is 30 feet wide and consists of peach and capel with 4 feet of chlorite and flucan, which contained about 40 lbs. of black tin per ton of stuff for a distance of over 60 fathoms in the direction of strike. At the 320-fathom level the lode was divided into two parts (by a smooth wall) the total width of which is 12 feet. The south part (or hanging wall) consisted of peach and tin ore ; while the north part (or the foot wall) yielded copper ore. Chalybite is common in the lode. Dunkin's Lode. — This lode had a fair gossan and yielded copper ore from the 30 to the 100-fathom level, in killas and granite alike. The veinstone was mainly a ferruginous ohloritic mass of crushed quartz. From the 1 70- fathom level where a little copper was found down to the 222-fathom level the lode yielded tin ore. It varied in width from 2J to 8 feet. The lode contained quartz, fluorspar, carbonate and oxides of iron, cupreous and arsenical pyrites, and tin ore. In the upper levels it varies from 1 to 12 feet in width. At the 48-fathom level in Dunkin's lode the north wall is granite, and the south wall is slate traversed by several granite veins. At the 52, 55, and68-fathom levels the north (or foot) wall is slate and the south wall granite. At the 73-fathom level the south wall is slate and the opposite wall granite. Eddy's or Eudey's Lode. — This lode yielded copper pyrites down to the 100- fathom level, while below that, at the 121-fathom level, good tin ore was found. Richard Thomas (1819) gives a brief account of the lodes being worked in his time, but some of the names he gives to the lodes have long since been foi^otten, or the lodes have been renamed. The lodes yielded copper ore down to the 150-fathom level. Pryce states that several tons of native copper were sold from Cook's Kitchen Mine.^ Vitreous and other copper ores occurred in abundance. The occurrence of * J. Maynard, " Mines of the Illogan District." Hep. Corn. Poly. Soo., 1874, p. 86. + Daniel and Samuel Lysona. Mag. Britt. Corn., vol. iii., 1814, p. 206. % Phillips and Darlington, "Records of Mining and Metallurgy." § R. J. Frecheville, "Notes on the Great Main Lode of Dolcoath,'' Tr. R.G S Corn,., 1879 to 1887, vol. x., p. 149. II Op. cit. f Mm. Cornuh., 1778, p. 61. p2 219 THE MliraiS. mineral pitch has already beea referred to elsewhere. The average yield of black tin from 1872 to 1881 was 43 lbs. to the ton. It is in this mine that alternations of granite and killas were encountered in sinking on the lodes. Henwood* gives the following particulars i — At the SWathom level in the South lode, granite occurs in the south wall, and slate in the north. In Toys lode at the 54-fathom level the foot wall is granite while the horse of ground between two branches is partly granite and partly killas. Middle Engine Lode. — At the 33-fathoin level the north wall is slate and the foot wall granite, but at the 73-fathom level both sides are granite. At the 54-fathom level the north wall of the Hard shaft is slate and the south wall granite. The Ckobty Mines. — The largest mine in the Orofty group is South Wheal Crofty, which formerly was divided into several properties ot which North OroEty (or Bast Seton), South Crofty, East Crofty, and the Old Pool Mine were the principal. The area was divided into three sections. The western section was known as Longclose ; the middle section as Duduance ; and the eastern section as Penhellick. Fane's Lode (in Longclose section of the mine), bearing B. 8 deg. N.j The underlie is north from 14 deg. to 20 deg. Varies in width from 2 to 3 feet. The lode joins Beeves' lode as it runs westwards, and although exten- sively explored, is comparatively poor. It has yielded a little copper pyrites, and at the 71-fathom level it is in greenstone and is of a quartzose nature. Another lode 25 fathoms north of Pane's, contained copper but was value- less in depth. In width this lode was about a foot. The underlie is 10 deg. N. Another lode called the Bed Lode is situated (at the 80-fathom level) 40 fathoms north of Pane's lode. It is 1 foot wide, has a southerly underlie and consists of quartz and peach. Beeves' Lode.— Bearing B. 3 deg. S.J Underlie 15 deg. N. It is a large well-deaned lode which yielded copper ores from 20 to the 100-fathom levels. The lode has a splendid gossan, and copper ore occurred to the 90- fathom level for a distance of 350 fathoms in the direction of strike. It joins the Trevensonlode in depth. Henwood states that the lode varies in width from 1 to 6 feet and contained in addition to copper ore— iron pyrites, blende, mineral pitch, earthy brown iron ores, chlorite, and fluorspar to a depth of 125 fathoms below adit. It also yielded tin ore, and at the 205- fathom level the lode intersected an elvan and was richer in tin ore helow the elvan than above it. It was very rich in copper in the Old Pool Mine, and was productive also in Wheal Crofty (now part of North Eoskear sett)^ where it is known as the Great Gaunter, and it passes into Wheal Seton where it is the main lode. ■, i. x j.. i. Trevenson Lode.— Situated south of Beeves' lode. Henwood states that the bearing is E. 2 deg. S. Underlie is from 14 deg. to 40 deg. north. In width it varies from 1 to 3 feet. The lode yielded some copper ore but was poor below" the 110-fathom level. ^^ , ,. . Oherrij Garden Lode.— Situated south ot Trevenson lode. Underlie is 10 deg. to 15 deg. north, to a southerly direction. The lode varied m width from I to 4 feet. Henwood states that the lode contained copper and iron pvrites and blende to the 88-fathom level. May nard states that the lode yielded good copper ore at shallow levels ; below the 110-tathom level there was no copper in the lode, but there was a little tin ore. II . Longclose Lode.-Situated south of Cherry Garden lode. The lode is nearly perpendicular from surface to the 35-fathom level, but ^ not so steep in depth; the underlie varies from 8 deg. to 20 deg north The lode has a fine gossan and it yielded copper ore from adit to the 35-fathom level for 100 fathoms in direction of strike. Below this down to the lli)- fathom level the lode was not of great value. The lode also contained t &. C. Salmon. Min. mi Smelt. Mag., vol. ii., 1862, p. 17. il* "Mines' of' th^ Illogan District" Hep. Com. Poly. Soc„ 1874, p. 86, THE ACTIVE MINES. 213 blende and fluorspar. At the 126-fathom levelit is 1 foot wide and still in killas. South iode.— South of Longclose lode. Underlie south 10 deg. and varies in width from 1 to 6 feet. Yielded copper ores to the Td-fathom level. Bearing approximately E. and"W. Longclose Gaunter Lode. — Situated on the south of Longclose lode. Bearing B. 30 deg. S. (Henwood). Nearly vertical to the 35-fathom level after which it underlies N. 13 deg. It varies in width from 1 to 3 feet. The lode branched off from the Cherry Garden lode near the Engine shaft, and yielded copper ores down to the 125-fathom level. Blende, iron pyrites, fluorspar, and quartz were also present in the lode. Penhellick Lode, — Situated in the south-east part of the sett. Bearing approximately east and west. It underlies south at a varying angle. In width it is from 1 to 6 feet. There is a good gossan ; and from the adit level to the 50-fathom level copper ore occurred for 100 fathoms in direction of strike. At the 100-fathom level it still yielded copper ore ; at the 110-fathom level it was very watery. Copper Tankard Lode. — This is a Gaunter lode situated in the south-west corner of the sett. The bearing is about B. 20 deg. or 30 deg. S. At adit level the lode is 6 feet wide, and contains quartz, iron pyrites, zinc- blende, and copper ore, near an elvan. At the 24-fathom level the lode is 1 foot wide in places, and the bunches of ore of no great extent. At the 70-fathom level the lode is 3 feet 6 inches wide but valueless. The country rock at this level is diabase. Dudnance. — A lode explored at the 16-fathom level is 1 foot wide. Wheal Knight Lode. — In the western end of the sett. Bearing B. 33 deg. N. Underlie north 16 deg. to south 10 deg. In the Wheal Crofty part of the sett there are several lodes the particulars of which have been given by Henwood. MOst of the lodes contained iron and copper pyrites and other copper ores. Blende and galena were also found in some quantity. At the present time only the central and eastern part of the South Grofty sett is being worked. The lower part of the mine is well within the granite and extends below the 260-fathom level. The mine yields tin ore and a little wolfram. The North Lode underlies south at about 30 deg. at the 225-fathom level, and forms a junction with the middle lode below the 260-fathom level. The lode varies in width up to about 7 feet and yields good tin ore. Pryce's Lode. — The bearing is about B. 15 deg. N. In the upper levels the lode is nearly vertical, but its average underlie in the lower levels is about 20 deg. south. At the 205-fathom level it joins the South lode. (It forms a junction also with Palmer's lode at about 80 fathoms west of the Engine shaft. This lode underlies south about 10 deg.) At the 112-fathom level the lode is from 8 inches to 8 feet in width near Palmer's shaft. At the 260-fathom level the lode is from 3 to 5 feet in width. Pryce's lode has yielded mainly copper ores down to the 100-fathom level. Below this in the granite the lode yields mainly tin ore. At the 112-fathom level the lode divided into two parts. The north part at the 260-fathom level is 3 to 5 feet in width. The lode consists of blue capel and peach, quartz, chlorite, and fluorspar. Some of the cross-courses intersecting the lode contain quartz made up of zoned crystals. The Middle Lode is situated between Pryce's lode and the North lode. It branches off from the north side of Pryce's lode below the 100-fathom level, and joins the North lode below the 260-fathom level. It varies in underlie but is nearly vertical. Not a very rich lode. The South Lode is situated south of Pryce's lode and underlies north, joining the latter at the 205-fathom level. Bast Wheal Crofty sold by public ticketing, between the years 1832 and 1854, 100,952 tons of copper ore containing 7,280 tons of metallic copper. South Wheal Crofty between 1854 and 1856 yielded 2,209 tons of ore con- taining 104 tons of copper. North Wheal Grofty in the same time yielded 3,713 tons of ore containing 233 tons of copper.* * Phillips and Darlington. " Records of Mining and Metallurgy," 1857. 214 THE MINES. DoLOOATH Mine. — Much of the following information has been extracted from the unpublished annual reports of the mine, while the rest of the detail was obtained by personal inspection rendered possible by the courtesy of the mine manager, Mr. Arthur Thomas, and the generous assistance of the staff. The workings of the Dolcoath main lode extend to a greater depth than those of any other tin mine in the world. The deepest workings are in the eastern part of the mine, and reach 3,120 feet from surface, or about 2,940 feet below adit, the distance being measured along the underlie of the lode. The mine has held a pro- minent positiou in the mining world ever since the introduction of the pumping engine in the eighteenth century, and is mentioned by Pryce and other early writers. In the old days the Dolcoath Mine formed only part of the present property, which comprises the old mines of Wheal Harriet, Dunkin's Garden, Stray Park, Wheal Gons, Dolcoath, &c. The details of the mineral output of the mine prior to 1815 are practically unprocurable, as the information is either altogether lacking or is scattered through the pages of weekly papers published about the beginning of the nineteenth century. The total yield of metallic copper from this mine between the years 1815 and 1836, in 1838, and between 1845 and J903, was 16,100 tons. Phillips and Darlington state that for all the years between 1815 and 1856, 241,522 tons of ore were sold by public ticketing containing 17,478 tons of metallic copper. In 1841, copper ore, sold at £5 a ton, realised £18,529. The total output of black tin is 77,500 tons between the years 1853 and 1905. The Main Lode has been worked westwards in Camborne Vean Mine, and eastwards in Cook's Kitchen, where it is called Chappie's lode, and in Tincroft and Carn Brea, where it is known as the Highburrow lode.* There are at least three elvans in the settj which underlie north, but the most southerly of them probably underlies south in depth. There are over a dozen ore-bearing fissures, each of which has received a distinctive name by the miners. The main lode in the eastern part of the mine is in killas to the 80- fathom level (adit about 30 fathoms below surface). In the western part of the mine it does not reach the granite until a depth of 230 fathoms is reached. Prom surface to about the 80-fathom level the lode is vertical ; thence to the 125-fathom level it is 6 or 7 deg. south underlie. From the 125 to the 216 it is about 15 deg. south ; and at the bottom of the mine, near the 485-fathom level, it underlies south at 44 deg. In the eastern part of the mine, near its junction with the South Entral lode, it is 60 feet wide, but in descending it thins off to about 3 feet at the 145-fathom level. Near the surface the lode is 3 to 6 feet wide. Prom the 150-fathom level to the 200-fathom level near the Engine shaft the width is from 7 to 12 feet. Prom the 200 to the 338-fathom level it varies in width from 1 to 9 feet. The lode had a very fine gossan containing a little tin ore, and was exceedingly rich in copper ore down to the 150-fathom level and a little below. Prom this to the 190-fathom level there was both copper and tin ore, and Mr. Collins states that between the 170 and the 190-fathom levels tliere was a poor zone in the lode which at the time it was encountered discouraged the adventurers.^ Below the 190-fathom level no copper has been found in any quantity. In the eastern part of the mine where it encountered the South Entral lode (and was so wide) there was a good deal of quartz and fluorspar. The north or main part of the main lode, at the 180-fathom level, also con- tained fluorspar, while the remainder of the lode was chlorite and peach. At the 338-fathom level rich ground worth over £105 per cubic fathom for * E. J. Frecheville, " Notes on the Great Main Lode of Dolcoath." Tr M.e.S. Corn., 1879-87, vol. x., p. 146. t DelaBeche, p. 176. t J. H. Collins, " Origin and Development of Ore Deposits." Journ.R. Inst, Corn., 1892, p. 75. DOLCOATH MINE. 215 tin ore was encountered. At the 364:-fathom level, near the Engine shaft, the lodestufE yielded 10 per cent, of tin ore in some parts of the lode which is here 20 feet wide.* South Branch. — This lode breaks off from the main lode towards the south at about the 60-fathom level, but curving round it drops into the main lode again at the 125-fathom level. It was never an important lode, but contained copper ore from the 70-fathom level to the 120-fathom level for a distance of 60 fathoms in direction of strilce. Harriett's Lode. — In the upper levels it has a bearing of about E. 20 deg. N., but from the 70-fathom level to the 180-fathom level it gradually changes its strike until its bearing is E. 40 deg. N., and in the eastern part of the mine joins the main lode at a place where large quantities of copper ore were obtained. Where it changed its strike from E. 20 deg. N. to E. 40 deg. N., it was poor. At a point a little below where Harriett's lode joins the main lode there is a branch from the north side of the main lode which is considered to be a continuation of Harriett's lode, and to be the same as is known in Cook's iKitchen Mine as Eddey's lode. Harriett's lode had a poor gossan, and yielded no copper ore until opened up at the 110-fathom level, after which it produced copper ore down to the 180-fathom level, especially eastwards, and a few bunches of tin ore near the main lode. SoJitTi Lode. — This is an important branch of the main lode and has a general strike of about B. 30 deg. N. It is very nearly vertical to the 190- fathom level, after which it underlies S. 15 deg. \o about the 290-fathom level, and, after underlying a little more, it drops into the main lode at the 375-fathom level. It varies in width from 6 inches to 2 feet in the upper levels, but is much wider and more productive in depth, and was extremely rich in tin ore near the junction with the main lode. In the upper levels it has a peach and quartz veinstone. Richard's Lode. — This is situated between the South and Harriett's lodes. Its strike is about the same as that of the main lode. Starting from surface it underlies northwards at 13 deg., but in depth it reverses its underlie and drops into the South lode near the 242-fathom level. Westwards it forms a junction with Harriett's and the main lode. It has an average width of 2 feet, and contained a little copper ore from the 100 to the 140-fathom levels. North (or Valley) Gaunter. — The main lode branches at the Gossan shaft, near the eastern boundary of the sett. One part runs northwards and is known as the Valley Gaunter. At the point where it branches from the main lode it has a bearing E. 60 deg. N., but meeting with the South Entral lode and Silver lode (situated on the north of the main lode) its bearing became E. 30 deg. N. The underlie is 5 deg. S. Before it encounters the South Entral lode it varies in width from 6 to 10 feet, but at its junction with this lode it is from 20 to 60 feet in width. It contained immense quantities of copper ore from the 20 to the 130-fathom level, but was very poor below. It was very hard near the Great cross- course. The Valley Lode. — Situated to the south of the main lode east of the Gossan shaft. The bearing is similar to that of the main lode, but as it approaches the eastern boundary of the sett it turns more northwards. In depth it is this part of the mine which is now principally worked. It has always been a good lode. South Entral Lode. — Situated on the north of the main lode, and has a bearing of about the same amount, but it varies slightly iu the eastern and western parts of the mine. The underlie is about 13 deg. S. It varies in width from 1 to 3 feet. The walls in some places are sharply defined, and occasionally in the killas the capel is still to be seen. There was a fair gossan, and the lode was productive in copper ore from adit to the 50- fathom level for a distance along the strike of 160 fathoms. • B. J. Frecheville, "Notes on the Great Main Lode of Doleoath." Tr, B.G.S. Com., 1879-87, vol. x.,p. 149. 216 THE MINES. Silver Lode.— Situated on the north of the South Entral lode. Bearing E. 30 deg. N. Its underlie is 13 deg. N. In width about 2 feet. About £3,000 worth of silver ore was obtained from this lode between deep adit level and 15 fathoms from surface. Eastwards and in depth it was unpro- ductive.* The silver was vitreous and ruby ore. The lode contained a good deal of fiucan (clay). North Entral Lode. — Situated to the north of the Silver lode. Bearing E. 30 deg. N. Underlie 27 deg. to 3D deg. N., and is about 4 feet wide.. Another lode on the north of this is 1 to 3 feet in width, underlies south at 30 deg., and intersects it. It had only a moderate gossan, and yielded copper ore aljout adit level. At the 42-fathom level there was mundic. The Gaunter Lode.— This lode breaks off from the Dolcoath main lode on the south side at "Wheal Bryant shaft. Bearing E. 4 deg. S. Underlie is 15 deg. S., but it is steeper in depth. In width it varies from 6 inches to 1 foot. The lode encounters the South lode at about 50 fathoms west of Bryant shaft. 'It had fine bunches of gossan to within 20 fathoms from surface, and was very rich in copper from adit level to the 80-fathom level for 150 fathoms east of its junction with the main lode. The veinstone is quartzose and chloritic. It was recently intersected by the 220-fathom level cross-cut, which was driven south from the main lode, and at that depth it contained a little cassiterite. At the 70-fathom level there are a few branches from the Gaunter lode. The main lode has several small branches which are of insignificant importance. One is named Rule's Lode, which branches oS at the 70-fathom level. It contained copper ore from the 70 to the 100-fathom level for a distance of 60 fathoms along^its strike. The other is called the Culvert course, which branches off from the n-.ain lode at the 50-fathom level, and contained copper from the 50 to the 80-fathom level. Another lode of small importance, known as Martin's Lode, starts from surface between the main and South Entral lodes. It underlies north and intersects the South Entral at the 40-fathom level. This lode had very little gossan but con- tained copper near the Great cross-course. The Brea or Plantation Lode. — This is the most southerly lode in the sett. It is nearly vertical, andiwas recently intersected by the William's New shaft, which was sunk vertically to meet the 220 cross-cut. The lode contains cassiterite, mispickel, and chloritic materials. The strike is E. 30 deg. N., and in width it is about 1^ feet. General Remarks on Dolcoath Mine. — In addition to the ores of tin, copper, and silver, there occurred bismuth, arsenic, cobalt, and pitch- blende. Thus, arseniate of cobalt was found in one of the lodes containing copper,t and in some places in the main lode it was intimately mixed with tin ore to the extent of about ^ per cent.| Native bismuth and bismuth sulphide with pitchblende, arsenical cobalt, quartz, and fluorspar also occurred.§ (See also Index of Minerals, p. 195.) Tlie character of the veinstones has been described by several writers. Henwood states that in granite the lode is brecciated.il Mr. Collins exam- ined some of the ores with the microscope. A specimen of veinstone from the 314-fathom level shows veins of quartz cutting through an " acicular mass of blue tourmaline, and are themselves traversed by veins of cassi- terite." Another stone "is evidently a breccia; it consists of angular patches of fine-grained green or bluish green material, which is apparently composed in the main of a network of fine needles, embedded in a crystalline * Information obtained from unpublished MineKecords. De la Heche states that £2,000 worth of silver ore was obtained, p. 288. t J. Carne, "On the Veins of Cornwall." Tr. B.G.S. Com., 1822, vol. ii., p. 105. t R. Pearce, " Note on the Occurrence of Cobalt in connection with the Tin Ores of Cornwall " Jowm. Hoy. Inst. Corn,., vol. i v., 1872, p. 81. See also Josiah Thomas, op. eit., vol. iii., 1868, p. 142. § K. Pearce, " Note on Pitchblende in Cornwall." Tr. M.O.S. Corn., 1864 to 1878, vol. ix., p. 103. II p. 212. DOLCOATH MINE. 217 mass of cassiterite, which exhibits distinct crystals in a few places. A little quartz occupies the interspaces which are few — and this encloses many fine needles of tourmaline." Another stope from the 260-fathom level contains 60 per cent, of tin. It " is a mass of rather large grey crystals." "With the cassiterite is a little quartz and some fringed crystals of tourmaline. Some of the crystals contain embedded needles which are probably schorl."* Dr. Flett has also described some of the Dolcoath veinstones. (See p. 138.) Killas obtained from the 215-fathom level has been microscopically described by Phillips. It is " exceedingly hard with an imperfect cleavage, and is of a dark grey colour. Under the low power (400 diam.) small grains of magnetite are distinguished from which as a centre indistinct fan-like aggregations of perhaps some variety of chlorite diverge in all directions." "It also contains broken and rounded plates of mica and a few fragments of brown semi-transparent mineral, mechanically embedded in slate."]" A large mass of slaty rock was encoun- tered in the main lode on the east of the Eastern shaft at the 352-fathom level. At this place the main lode is well within the granite and about 240 fathoms below the junction of the granite and killas.|. A piece of striped hornfels was recently discovered in the lode at the 375-fathom level, near Stray Park shaft, at which point the lode is in granite. Blvans are seen at the 375-fathom level in Stray Park ; in the 220 cross- cut between Sump shaft and William's New shaft underlying north a few degrees ; ac the 220-fathom level at Sump shaft between Richard's and the main lode ; also at 375, 388, 400, and 412-fathom levels near the Old Sump shaft in the vicinity of the main lode. At the 400- fathom level near Old Sump shaft an elvan underlies in a north-easterly direction 55 deg. ; at 26&-fathom level there is an elvan below Harriett's lode. At 352-fathom level on south of South lode, at 100 and 160 fathoms east of the Engine shaft, an elvan is seen underlying south in the same direction as the lode which is situated on its foot wall. An elvan is seen at the 254-fathom plat at Valley (or Eastern) shaft and is again seen in a cross- cut on the west of the shaft. Another in the same cross-cut is again seen at the 302-fathom level between the main and South lode. An elvan crops out at the margin of the granite and underlies N. 45 deg., but becomes perpendicular and then south underlying in the granite. An elvan on the north of the Engine shaft underlies N. 40 deg. ; another cropping out about 170 fathoms north of the engine shaft underlies N. 40 deg. Dolcoath Mine has been worked for well over a century and a half. Josiab Thomas states that the depth of the mine in 1758 was 88 fathoms. In 1788 it was 183 fathoms. In 1824, 240 fathoms, and in 1868, 340 fatboms.§ At the present time the deepest workings are 490 fathoms below adit level. The cost of driving an end 8 feet high and 6 feet wide was, in 1868, about £20 a fathom in hard ground. The cost of breaking the ore and sending it to surface is about 5s. 6d. per ton.|| The average yield of black tin per ton from 1872 to 1881 was 59 lbs., while during the same period the cost of mining was 16s. lid. per ton, and of dressing 3s. lO^d. per ton.^ The following notes are extracted from the Report of the Directors issued in June, 1906, to the shareholders in the mine : — ■ The profits earned in the half-year (January to June, 1906) amount to £40,165. J ^ J The following table shows the progress of the present company's opera- tions since its commencement : — * J. H.Collins, "Cornish Tinstones and Tin Capela." Min. Mag., 1882, vol. iv., p. ,11. t J. A. Phillips. Q.J.&.S., 1875, vol. xxxi., p. 323. J J. A. Phillips, " Ore Deposits," 2nd edition, p. 213. § Josiah Thomas, Jaum, uoy, Inst. Cormvall, vol. iii., 1868, p. 192. Op. eit. f R. J. Frecheville, " Notes on the Great Main Lode of Dolcoath." Tr, B, 0.S. Com., vol. X., p. 147. 218 THE MINES. Six Months II Black Tin Average §.S Amount ending. C3 § sold price per ton of Ore. Avei price p of Blao realised. Tons. Tons. c. q. lbs. lbs. £ s. d. £ s. d. £ a. d. Dec. 31st, 1895 28,717 1,015 5 1 16 79-19 1 7 8-36 39 3 5 36.769 2 5 June 30th, 1896 30,015 1,029 19 1 10 76-86 1 5 6-33 37 4 038,311 6 5 Dec. 31st, 1896 33,712 1,009 7 25 67-06 1 110-2 36 9 236,83018 2 June 30th, 1897 35,879 1,021 17 22 63-79 1 1 7-27 37 18 7 38,760 7 2 Deo. 31st, 1897 37,686 1,073 2 1 9 63-78 1 1 6-78 37 17 440,63619 8 June 30th, 1898 3P,089 1,140 7 2 22 67-07 1 3 8-94 3916 445,22115 1 Dec. 31st, 1898 40,608 1,162 64-10 1 6 10-09 46 18 54,497 6 3 June 30th, 1899 41,101 1,037 19 1 23 56-57 113 8-21 6612 7 69,22212 8 Dec. 31st, 1899 41,639 1,040 18 1 19 56-00 1 19 8-39 79 7 11 82,65116 June 30th, 1900 45,102 1,043 9 51-80 118 3-57 8215 483,3641810 Dec. 31st, 1900 43,254 960 19 1 2149-76 1 15 11-4 8018 2 77,75014 4 June 30th, 1901 47,603 1,001 18 1 547-14 110 8-69 72 19 10 73,132 Oil Dec. 31st, 1901 48,975 1,033 13 1 1847-28 1 8 10-35 68 7 6 70,676 2 6 June 30th, 1902 48,155 934 15 2 21 43-48 1 7 10-76 7117 1 67.168 6 6 Dec. 31st, 1902 52,295 893 13 2 1938-28;i 4 9 72 8 464:716 7 4 June 30th, 1903 47,899 863 14 3 13'40-39 1 8 11 80 3 6 69,251 5 Deo. 31st, 1903 51,011 876 2 2 12,38-47 1 5 2-08 73 5 8 64,20615 6 June 30th, 1904 50,196 810 15 23 36-18 1 4 1-28 74 12 6 60,50410 2 Dec. 31st, 1904 50,353 894 8 3 39-79 1 7 5-42 77 5 5,'69,11416 4 June 30th, 1905 49,974 829 18 2 2337-20 1 6 11-26 81 2 1 67,311 16 11 Dec, 31st, 1905 48,472 866 18 3 21 40-06 112 0-46 91 17 11 79,66913 1 June 30th, 1906 49,934 920 4 3 20 41-28 1 18 11-5 10513 497,268 9 The Receipts, Expenditure, and Profits for 17 half-years on Profit and Loss Account were as follows : — First Half of 1898 Latter „ of 1898 First „ of 1899 Latter „ of 1899 First „ of 1900 Latter „ of 1900 First „ of 1901 Latter „ of 1901 First „ of 1902 Latter , First , of 1902 of 1903 Latter,, of 1903 First „ oiE1904 Latter , First , Latter , First , of 1904 of 1905 of 1905 of 1906 Eeceipts. £ 46,007 55,284 69,983 83,492 87,038 78,626 73,727 71,723 67,926 65,281 69,762 64,812 61,143 69,699 67,934 79,733 97,910 s. d. 17 8 13 1310 1511 12 2 3 5 1 10 2 5 8 10 17 11 238, 18 3 4 8 5 4 18 Working Cost. £ s. 37,019 18 1,862 7 42,910 16 46,915 3 48,866 8 50,898 11 51,949 3 50,737 8 49,054 17 48,928 12 49,031 8 49,528 10 50,182 14 53,674 13 53,350 54,691 17 54,502 18 Gross Profits. £ s. 8,987 19 16,422 6 27,072 17 36,577 12 38,172 3 27,727 11 21,777 18 20,985 13 18,871 11 16,353 5 20,731 3 15,284 8 10,960 9 16,024 10 14,584 25,041 7 43,407 19 Lord's Royalties. £ s. 1,721 18 2,27a 14 24,614 16 10,5,511 7 7,5,757 16 75,183 7 04,875 9 04,711 14 1 4,477 17 04,314 8 04,616 15 3,3,280 9 12,951 7,2,303 16 42,243 14 9 2,655 13 33,242 5 ■Net Company's Profits. £ 7,266 14,151 22,458 31,066 032,414 22,544 16,902 16,273 14,393 12,038 16,114 12,003 8,009 13,720 12,340 22,385 40,165 s. d. Oil 11 8 8 8 18 8 8 19 3 8 8 14 1 510 14 8 1311 THE ACTIVE MINES. Cost of Raising and Treating the Ore Per Ton. — 219 Charg '69, Six Months ending — Receipts. Working Lords' Costs. Royalties. £ 3. d. £ s. d. £ s. d. 31st December, 1895 17 6 1 4 4 11 30th June 1896 1 5 10 1 3 1 10 31st December, 1896 - 1 2 6 1 10 9 30th June, 1897 - 12 2 1 2i 8-i 3l9t December, 1897 12 19 6 6 9 30th June, 1898 - 14 2 19 5 11 31st December, 1898 17 3 19 1 1 H 30th June, 1899 - 1 14 1 1 11 2 3 31st December, 1899 - 2 1 1 2 7 2 7 30th June, 1900 - 1 18 7 118 2 6i 31st Docember, 1900 1 16 4 13 6 2 5 30th June, 1901 - 1 10 llf 1 1 9| 2 Oi 31st December, 1901 1 9 3i 1 8| 1 11 30th June, 1902 - 1 8 2| 1 H 1 lOi: 31st December, 1902 - 1 4 IH 18 8i 1 71 30th June, 1903 - 1 9 H 1 5i 1 11 31st December, 1903 - 1 5 4f 19 5 1 3i 30th June, 1904 - 1 4 4i 19 111 1 2 31st December, 1904 - 1 7 8 1 1 3| 10| 30th June, 1905 - 1 7 2J 114 10; 31st December, 1905 - 1 12 lOi 1 2 ef 1 1; 30th June, 1906 - 1 19 2^ 1 1 10 1 3| East Pool and Wheal Agar United. — This sett is situated on the eastern extension of the same series of lodes which are worljed in the adja- cent mine of South Crofty. Borlase mentions the Old Pool Mine, and describes the mode of working the mine in his time. Tlie " backs " (outcrops) of the lodes in Wheal Agar were worked for tin by the "old men."t The upper part of the mine is in killas to about the 135-fathom level ; below this the lodes are in granite, and are being worked at the present time. The mine has yielded enormous quantities of both copper and tin ores, and in addition has proved to be an important repository of wolfram. Between 1847 and 1856, Wheal Agar sold by public ticketing 3,022 tons of ore yielding 390 tons of metallic copper ; East Pool between 1835 and 1856 yielded 38,780 tons of ore containing 2,911 tons of metallic copper.^ Main or Engine Lode. — The underlie to the 36-fathom level is 13 deg. S. At this level the lode is in contact with an elvan which underlies north, and below it to the 60-fathom level the lode is perpendicular. From the 60-fathom level downwards the underlie is about 15 deg. south. The lode had a good gossan and yielded copper ore in abundance. At the 150-fathom level the lode is 10 feet wide, and yielded both tin and copper ores. It was wrought for wolfram below the 135-lathom level. * Borlase. Wat. Hist. Corn., V5i, p. 167. T J. Maynard, "Remarks on Two Cross Sections," &o. Bep. Roy. Corn. Poly. Soc'mi, p. 195. J Phillips and Darlington. " Records of Mining and Metallurgy," 1857. 220 THE MINES. The Great Lode. — It is from this lode that most of the wolfram of the mine has been obtained. This lode was first encountered at about the 140-fathom level. It has been worked upon to below the 300-fathom level, and has yielded good tin and wolfram ore with mispickel, &c. Pryce's Lode.— Situated on the north of the main lode and underlies north. It is the same lode that is being worked in South Crofty at the present time. Middle Lode. — Situated north of the Great lode, and has a slie^ht southerly underlie. Palmer's tode.— Vertical to the 50-fathom level, and then underlies south 13 deg. Varies from 1 to 3 feet in width. Near the western end of the sett, close to South Crofty, it forms a junction with the main lode at 50 fathoms west of Engine shaft. The veinstone consists of quartz and killas in the upper level, and the lode contained copper from the 26 to the 48-fathom level for 30 fathoms in direction of strike. North (or Beeve's) Lode. — Underlies north 20 deg. Varies in width up to 2 feet, and contains quartz and copper pyrites. South Lode.— Parallel with the main lode. Underlie N, 20 deg. At adit level the width is about 1 foot, but below the 70-fathom level it is li to 4 feet wide, and at the 130-fathom level it is 7 feet wide in places. Near the western boundary, at the 100-fathom level, the lode is 30 feet wide. At adit level the lode consisted mainly of fiucan (clay) and quartz. It yielded copper from the 40 to the 70-fathom level. From the 70 to the 100-fathom level there was both copper and tin. Copper ore was again abundant at the 130-fathom level, at which place the lode also contained tin, wolfram, and arsenic. North Tincroft Lode.— Underlie N. 27 deg. At the 70-fathom level the lode is 1 foot wide and was poor. West Basset. — The lodes of this mine have good gossans. When the mine was first opened up the copper lode was found to be very rich to P'iG. 22. — West Basset NmHh Lode. Longitudinal Section. SCALE -Feoihoms o lop zoo below the lOO-fattora level. The lodes on the south were not so rich, but yielded both tin and copper ores. The Flat Lode is heaved by the " Old THE ABANDONED MINES. 221 Lode " from the 134 to the H4-fathoin level. Both the Gaunter lode and the New Lode have yielded copper and tin.* The Main or North Lode was not rich in copper ore eastwards (Fig. 22.) Gaunter Lode. — The ore bunches dip eastwards. The width of the Icde at the 60-fathom level is 1^ feet, and it was a fairly good lode. Below the 114Tfathom level it was 3 feet in width. Middle Lode. — A good deal of tin ore was extracted from this lode near the place at which it cut the junction of the killas and granite. The Great Flat Lode was intersected in depth while working on a north underlying copper lode. At the 140-fathom level the width of the capel and lode is 40 or 50 feet, and the whole is more or less tin bearing. The leader is frequently a mere ferruginous joint. f Between the years 1852 and 1856 the mine yielded 22,135 tons of ore containing 1,541 tons of copper.^: The Abandoned Mines. Wheal Ann. — The Wheal Ann lode is the easterly prolongation of Wheal Trumpet Lode, — From the 122 to the 142-fathom level the lode has smooth walls and is enclosed in schorlaceous or decomposed granite. The lode yielded black tin ore associated with " brown iron ore."§ Balmynheek Mine. — In 1876, 2,200 tons of tin ore were stamped yielding over 1 per cent, of black tin per ton.|| Babncoose Mine. — A quantity of rich copper and tin ore was raised from this mine, but it was suspended in 1872 owing to poverty. At the 50-fathom level the lode is 3 feet wide, and consists largely of mundio and quartz. The Movihay Lode underlies north, and is thought to be a continuation of Dnnkin's Lode (in Cook's Kitchen). The Barncoose Lode underlies north about 15 deg.^ Wheal Basset ajjd Gktixs. — Tyack's Lode.— The lode varies in width from 2 to 3 feet, and has yielded tin ore from surface to the 64rfathom level. Wheal Fat Lode. — ^Varies in width from 3 to 10 feet. Has yielded tin ore. Brenton's Lode. — From the 22 to the 52-fathom level the lode varies in width from 2 to 6 feet, and has yielded tin ore. Furgenson's Lode. — 4 feet in width. From the 23 to the 50-fathom level the lode yielded good tin ore. South Tymorgie Lode. — 3 feet in width at the 30-fathom level. Tymorgie Branch. —From the 34 to the 44-fathom level the lode varies in width from 1 inch to 2 feet. Gaunter Lode. — At the 30-fathom level the lode is 5 feet in width and yielded tin ore. A horse of ground occurred in this lode. Wilkin's Lode. — Prom the 20 to the 60-fathom level the lode is 2 feet wide. Gope's Lode.— From 1 to 2 feet in width at the 35-fathom level and yielded fair tin ore. The lode at the 65-fathom level is 3 feet in width. North branch is 1 foot wide, but yielded no tin ore. Garlidna Lode, — At the 11-fathom level the granite was encountered in the south wall. J. Maynard, "Remarks on Two Cross Sections." JRev. Corft. Polv. Soc . jp.202. " + Foster, t Phillips and Darlington. "■ Records of Mining and Metallurgy," 1857. Henwood. || Foster, p. 648. f Thomas. 1871jP. 202. Foi 222 THE MINES. Harvey's Lode.— At the 20-fathom level the lode Is 2 feet in width and yielded poor ore. ■ Wheal Foster Lode. — Prom the 15 to the 35-fathom level the lode is 1 or 2 feet in width, with a little tin ore. Wheai Beauchamp.— There were five lodes worked about the year 1819i The most northerly underlies north and yielded copper. The next was wrought for both tin and copper. Underlies N. 15 deg. The two next yielded copper ore. They underlie north. The southernmost was wrought for tin ore and underlies N. 13 deg.* Bell Mine. — A copper lode underlies N. 23 deg. (Thomas.y At the 20-fathom level the leader is 18 inches wide. Wheal Bots. — A copper lode underlies S, 15 deg, (Thomas.) Wheal Bullkr. — Charles Thomas states that the dividends from the sales of copper ore since its discovery in quantity at the 20-fathom level up to the year 1867, were £270,000.t In 1820 and 1821, 972 tons of copper ore were raised yielding 97 tons of copper.:|: Wheai BOT/Lek and Beatjchamp. — Henwood gives the following particulars of the lodes of this mine : — South Lode. — Bearing E. 25 deg. N. Underlie 15 deg. to 30 deg. N., varies in width from 1 to 2 feet. Black copper ore with quartz, felspar, and earthy brown iron ore. North Lode. — Bearing E. 25 deg. N. Underlie N. 10 deg. to 30 deg. Yielded black and vitreous copper ores to the 50-fathom level. Davey's Lode. — E. 27 deg. N. Underlie vertical to 45 deg. N. Varies in width from 1 to 20 feet. The lode contained quartz, slate, black and vitreous copper ores, copper pyrites, oxide, carbonate and arseniate of copper, fluorspar, and chlorite. At the 99-fathom level there were veins of quartz and copper pyrites. Cabdrew Downs Mine. — Henwood makes the following statement in regard to the lodes : — South Lode.— Bearing B. 17 deg. N. From the 50 to the 120-fathom level the underlie is N. 10 deg. to N. 30 deg., and the width is from 6 inches to 6 feet. The lode consists of quartz, earthy brown iron ore, black copper, and iron and copper pyrites, chlorite, and fluorspar. North Lode.— B. 17 deg. N. The underlie is from 8 deg. S. to 22 deg. S, The lode varies in width from 8 inches to 2J feet, and consists of quartz, chlorite, slate, and iron and copper pyrites. Phillips and Darlington state that the Cardrew Mine yielded between 1826 and 1838, 17,143 tons of ore containing 1,141 tons of copper.:!: Cabhabeack.— The Wheal Virgin Lode underlies K. 16 deg. Another lode situated further south is said to be a continuation of Wheal Maid lode. (Thomas.) Between 1820 and 1852, Wheal Maiden and Carharrack yielded 23,552 tons of ore containing 1,542 tons of copper.:f Caeleen Mine. — The lode is wide and productive in killas, but imme- diately it enters the granite it is< reduced to a mere string.g The lode is a continuation of one of those in Wheal Vor. Caequeen Mine. — There is a great cross-course 60 fathoms east of the Engine shaft. * Thomas. + " Mining Districts of the West," 1867, p. 53. J Phillips and Darlington. " Kecords of^Mining and Metallurgy," 1857. § J. Came, "On the Veins of Cornwall." Tr. M.G.S, Corn., 1822, vol. ii.. p. 93. THE ABANDONED MINES, 223 The Ohaobwateb, Mine (or Wheal Busy). — William's Lode. — Underlie S. 15 deg. This lode is linown eastwards in "Wheal Daniell and westwards in Wheal Chance. It is the South lode of Wheal Chance, Treskerby, Wheal Boys, and Wheal Prussia. Ghacewater Lode. — A tin and copper lode having a northerly underlie of 47 deg. The lode is known in- Wheal Daniell, Treskerby, and Cardrew. Winter s Lode. — A tin and copper lode underlying N. 47 deg. The " black elvan " is situated between this and the Chacewater lode. Wheal Vor Lode. — Underlies N. 22 deg. A tin and copper lode.* Between 1815 stnd 1822, 30,140 tons of ore containing 1,882 tons of copper were sold by public ticketing ; in 1823, 198 tons containing 16 tons of copper, and between 1823 and 1856, 33,486 tons of ore containing 1,669 tons of metallic copper.f Tin, copper, wolfram, and arsenic occur. Wheai Chables. — The North Lode has a bearing E. 25 deg. N., and has an irregular northerly underlie from the 30 to 70-fathom level. In width the lode is 2 to 10 feet. It consists of quartz, slate, copper and iron pyrites, and earthy brown iron ore. At Bateman's shaft the lode is 3 feet wide but barren. Stacey's Lode. — Bearing B. 25 deg. N. The underlie is north. The lode consists of copper and iron pyrites, quartz, and slaty clay.:]: Between 1821 and 1834, 4,360 tons of copper ore were sold by public ticketing, con- taining 283 tons of copper.§ WHEAi Clinton. — Situated near Trefusis Point, Falmouth. Mr. P. J. Stephens states that the mine was started in 1854 and wound up in 1858, but that prior to this a little work was done on the same lode towards the east. The adit level driven in a long way on the South lode showed traces of lead in many places. In the No. 1 cross-cut " a fine course of ore com- posed of spar, flucan, and frequent bunches of galena " occurred, but the lode was disordered near greenstone. || The same writer states that some ore containing blende and galena was assayed and found to contain silver and " generally a little gold."l[ Sir Warington Smyth in 1857 remarked that Wheal Clinton has been worked beneath the sea between the 20 and 30-fathom level, and that lead ore was raised from the mine at this place. A cross-course at the 20-fathom level made the workings dangerous.** Consolidated Mines. (See Figs. 23, 24, 25, and 26.) — The following notes are from Henwood : — Paul's iode.— Bearing N.B. and S.W. Underlie 14 deg. to 40 deg. N.W. Prom the 70 to the 123-fathom level the lode is 2 to 4 feet wide, and contained black and vitreous copper ore, copper and iron pyrites, slate, and quartz. Glover's Lode or Kitta's Bmncfe.— Bearing E. 25 deg. N. From the 70 to the 215-fathom level the lode has an irregular southerly underlie, vary- ing from 10 deg. to 45 deg. Black, vitreous, and yellow sulphide of copper in slate. MichelVs Lode.— E. 25 deg. N. Underlies 80 deg. S., and is about 2 feet in width. It consists of quartz, slate, and iron and copper pyrites. Taylor's Lode.' — The bearing from the 150 to the 290-fathom level is E. 27 deg. N. In the upper levels, down to the 240-fathom level, it has an underlie of N. 76 deg. At the 240-fathom level it is vertical. Below this it varies from !6 deg. N. to 20 deg. N. Varies in width from 1 to 16 feet. * Thomas. t Phillips and Darlington. " Eecords of Mining and Metallurgy," 1857. Henwood. § Phillips and Darlington. "Eecords of Mining and Metallurgy," 1857. II "The Mineral Resources of Falmouth." Jlep. Corn. Poly. Soc, 1886, p. 189. IT Ir. S.0.S. Corn., 1899. ** Information obtained from an unpublished report' through the courtesy of Mr. Crawfurth Smith, of j;hg "Office of Wopds," \ylji^eliall. 224 THE MUTES. At the 150-fathom level there was a vug 25 fathoms in length. The lode contains quartz, slate, iron and copper pyrites in detached masses, and in the deeper levels copper pyrites, fluorspar, and quartz. Elvan's South Lode.— B. 18 deg. S. at the 190-fathom level. It varies in underlie from S. 26 deg. to S. 40 deg. It is 4 to 6 feet in width, land contained quartz, slate, and some oopper stilphlde. Fig. 23, — Clifford Amalgamated Mines. Whtal ^ Moor 1Z7t F^ from. Ada. Great Consolidated Mines, United Mines. Tregonning's Lode. — Bearing N.E. and S.W. From the 165 to the 228- fathom level the lode underlies S.B. 20 deg. to N.W. 12 deg. Varies in width from 3 to 6 feet, and contains quartz, copper sulphide, and slate. Fig. 24:.—Poldice. Fig. 25. — United Mines. ;i < & •a ic S F'T'ltyel Deeble's North Lode.— Bearing N. 35 deg. B. From the 250 to the 260- fatbom level the lode varies in underlie from 10 deg. to 22 desg. N., and in width from 1 to 4 feet, consisting of copper sulphide, chlorite, and quartz. It unites with Deeble's lode westwards. Deeble's Lode.— Viom the 40 to the 285-fathom level the lode varies in underlie from N. 20 deg. to S. 10 d^. From 2 to 6 feet is- width. At THE ABANDONKD MINES. 225 the 40-fathom level the lode contains earthy brown ores, quartz, copper pyrites, and black copper ore. In depth it is mainly copper pyrites with quartz. The lode joins the Wheal Fortune lode eastwards. Wheal Fortune Lode.— B. 36 deg. N. From the 160 to the 285-fathom level the underlie is N. 30 deg. to vertical, and the lode contains iron and copper sulphide and some earthy brown iron ore at the 250-fathom level. The shoots of copper dip east. In the eastern part of the mine the lode has. the same bearing, and from the 145 to the 215-tathom level the under- lie is N. 4 deg. to N. 30 deg., varying in width from a few inches to 14 feet. At the 160-fathom level the lode contains earthy brown iron ores and some Copper pyrites, and quartz in some places mixed with schorl. There is also chlorite in vuggy quartz. Ousvey Lode. — Bearing E. 32 deg. N. The underlie is 10 deg. to 32 deg. N. from the 33 to the 173-fathom level. The lode varies in width from 6 or 7 inches to 3 feet, and contains copper and iron pyrites, quartz, chlorite, and schorl. The ore shoots dip east. Between 1815 and 1856, the ore sold by public ticketing from this mine amounted to 441,286 tons containing 37,402 tons of metallic copper.* Fig. 26, — Consolidated Mines. Ckane and Bejawsa Mine. — The Wheal Seton main lode as well as that of South Boskear Mine traverses this sett. T%e Bejawsa Lode underlies north from surface to the 20-fathom level, but below that it underlies south. It varies in width from 2 to 4 feet, and has a fair gossan with quartz and mundic. The Crane Lode varies in thiclmess from 18 inches to 3 feet. The lode, generally is poor, but yielded blende, copper ores, and some lead with iron pyrites in the higher levels. It was explored to the 60-fathom level. The Briggan Lode contains copper ore with quartz and chlorite. Charles Thomas states that the West Seton main lode was worked to the 100-fathom level in this mine but only yielded a little copper ore. The elvan which traverses the West Seton Mine passes through this sett and is in contact with the lode.t Between 1851 and 1853, 671 tons of copper ore containing 61 tons of copper were sold by public ticketing.^ Ceenvee and Wheal Abraham and Sarah.— The lode is 2|to 3 feet in width and has an east and west bearing. It underlies south 15 deg. Ifc becomes poor and hard and often divided into branches in the elvan, and * Phillips and Darlington. " Records of Mining and Metallurjtv " 1857 t " Mining Districts of Cornwall , " 1867 , p . 47. t Phillips and Darlington. " Records of Mining and Metallurgy," 1857. 226 THE MINT5S. in fact " an elvan appears to be one of the components of the lode."* In .some parts of Crenver and Wheal Abraham the ore shoots have a westerly pitch.")' The mine has been worked to a depth of 220 fathoms at the Old Sump (or Middle Engine) shaft. Between 1815 and 1827, 85,851 tons of copper ore containing 6,061 tons of copper were sold by public ticketing from Wheal Abraham, Oatfleld, and Crenver. Wheal Abraham in 1854 yielded 324 tons of ore containing 5 tons of copper,:): Wheal Cupid. — The Wheal Cupid lode is copper bearing and underlies S. 13 deg. Another copper lode situated on the south underlies N. 13 deg. On the north of the Wheal Cupid lode there is a lode underlying north. (Thomas.) Wheal Damsel. — The Main Lode has been traced for over 2 miles, and is the same as the Wheal Maid lode.§ All the lodes have yielded copper ore. The Pressure Engine Lode underlies N. 13 deg. The Old North Lode underlies N. 27 deg. The Old South Lode underlies N. 23 deg. Gilbert's Lode underlies N. 13 deg. Turtle's Lode underlies N. 12 deg. Wheal Hope Lode underlies N. 15 deg.|| Between 1815 and 1842, 25,111 tons of ore containing 3,176 tons of copper were sold by public ticketing.^ Wheal Daniell. — The upper part of the lode was worked for tin for at least 10 fathoms. The lode did not yield copper near the surface.** It has been worked to the 48-fathom level. Thomas has recorded the fol- lowing particulars regarding the lodes : — Ohaceivater Lode underlies N. 40 deg. Wrought for tin ore. printer's Lode situated north of Chacewater lode underlies N. 40 deg. Wrought for tin and copper. TFilliom's Lode underlies S. 32 deg. Wrought for copper. South Lode underlies N. 17 deg. Wrought for tin and copper. Thirty fathoms south of the South lode is the Fat Sow Lode which under- lies north ; tin bearing. Thirty fathoms south of the Fat Sow lode is the Wheal Doit Lode which underlies north ; tin and copper bearing. Wheal Derrick. — The North Oarquean Lode underlies N. 27 deg. The lode yielded both tin and copper. There are three other lodes which have been wrought for copper ore. They underlie north or are perpendicular. (Thomas.) Bast Ale and Cakes Mine. — The United Mines Great lode passes into this sett. Itunderlies N. 15 deg. The South Lode underlies N. 37 deg. (Thomas.) East Wheal Chance. — A copper lode underlies south 13 deg. A Gaunter Lode bearing copper ore underlies N. 4 deg. and heaves the main jode 2 fathoms to the left. (Thomas.) East Downs. — Treivan North Lode {Briggan Lode) underlies S. 15 deg. The Soiith Lode underlies south at the same angle. (Thomas.) Mast Wheal Damsel. — The North Lode strikes E. 17 deg. N. Prom the 80 to the 150-fathom level it varies in width from 1^ to 12 feet, and underlies N. 6 deg. to 22 deg. The veinstone is composed of quartz, felspar, clay, iron pyrites, and vitreous and black copper ores. * J. Came, "On Elvan Courses." Tr. R.0.S. Com., 1818, vol. i., p. 101. t Henwood, p. 41. t Phillips ana Darlington. " Keoords of Mining and Metallurgy," 1857. § J. Came, "On the Veins of Cornwall." Tr. B.G.S. Corn., 1822, vol. ii., p. 121. II Thomas. II Phillips and Darlington. " Eeeords of Mining and Metallurgy," 1857. ** W. H. Argall. Miners' Association (Breage Meeting), 1872. THE ABANDONED MINES. 221 Middle Lode.— E. 17 deg. N. From 100 to 180-fathom level the lode varies from 2 to 7 feet and underlies 10 deg. to 30 deg. N. It consists of decomposed granite, vitreous and black copper ore, copper sulphide, iron pyrites, and earthy red iron ore. (Henwood.) East Wheal Lovell. (Fig. 27.) — Mr. Collins has described some of the lode material from this mine. He remarks that it was originally granite, but the felspar is changed to a dusty-looking material, which under high powers of the microscope seem to be imperfectly formed crystals of gil- bertite and perhaps a little tourmaline. In places, in the neighbourhood Fig. 27. — East Wheal Lovell. N. Vor^LcveL of these greyish spots, there are very distinct needles of tourmaline and radiating flakes of gilbertite. There is quartz, with fluid cavities, which includes a little black opaque mica with irregular crystals and granules of cassiterite.* Two lodes appear to form a junction westwards. The upper part of the lodes for 17 fathoms were worked by the old men, but it was since worked to the 127-fathom level. East Wheaii Seton and Wheal Emily Henrietta. — Before 1860, Wheal Emily Henrietta Was known as Tolvaddon Old Mine. Copper ore was raised from the 40 to the 70-fathom levels.f Cock's Lode. — At adit level, this lode is 1 to 2 feet in width, and con- sists of quartz and muudic. At the 40-f athom level, it is 5 feet wide and was fairly rich in copper ore. The Main Lode of Wheal Emily Henrietta underlies N. 15 deg., from surface to the 30-fathom level, but is not so steep in the western part of the mine. It varies in width from 1 to 4 feet. At adit level the lode is 2 to 4 feet wide and contained blende and copper ore with quartz. Prom the 44 to the 70-fathoni level the veinstones were chloritio and quartzose, with fair to poor copper ore. East Wheal Spaenon. — Wheal Sparnon Lode underlies south 15 deg. and intersects an elvan. It is a copper- bearing lode 4 or 5 feet wide; The Cal Lode carries tin and underlies south at 23 deg. (Thomas.) East Teesavean, — A copper lode underlies north. (Thomas.) • J. H. Collins, " Cornish TinstoneH and Capels." Min. Mag., 1882, vol iv„ p. 10. + J. Maynard, "Mines in the Illogan District." Hep. Boy. Com. Poly. Soc. 1874, p. 84. q2 228 THE MINES. Wheal Falmouth.— The lode strikes B. 40 deg, N. and underlies S.E. 20 deg. to 46 deg. From the 30 to the 70-fathom level the lode consists of chlorite, decomposed slate, and earthy brown iron ores, copper and iron pyrites, and at the 50-fathom level phosphate of iron. Also blende, purple copper ore, galena, &c. (Henwood.) Between 1829 and 1833, 1,808 tons of ore containing 87 tons of copper were produced.* Wheal Fancy. — Abandoned in 1850. In adit the lode is 4 feet wide and contains copper and iron pyrites and quartz. In shallower parts of the lode ore was obtained. Wheal Forest. — The lode has an underlie 13 deg. S. to the 45-fathom level and varies in width from 6 inches to a foot, but is 2 feet wide in some places. The lode is an altered elvan on the west of the Engine shaft and is richer here than in other places. The ore extracted was largely mundic, associated with quartz and fiacan, which was very ferruginous. Wheal Fortune (Breage). (Pig. 28.) — Tin ore occurred in killas. Collins states that the dark greyish brown killas is spotted and banded with white quartz, with light yellowish grey macled crystals of cassiterite in the joints, varying from ^ to y, of an inch across, and mingled with gil- bertite.t Fig. 28. — Great Wheal Fortwne. pie Oarnmeal Lode underlies south. The best piece of ore ground on this lode is between Hoskin's and Painter's shafts about the 68-fathom level. The lode is 4 feet wide consisting of peach and quartz. The Wheal Vor lode also traverses the sett but underlies north.J Wheal J'ribndship (Wh. Andrew).— The Great Lode underlies north 13 deg. It is a continuation of the lode which traverses the United Mines. The North Lode underlies N. 5 deg. It is a branch of the Great lode. There are two other copper lodes further north. Wheal Fortune Lode traverses this sett. In Wheal Fortune it was worked for zincblende. South Lode underlies N. 13 deg. and contains tin ore. It is a south branch of the Baldhu lode. (Thomas.) Gaelidna Mine.— Worked to the 70-fathom level. * PhUlips and Darlington." " Records of Mining and Metallurgy," 1857. t J. H. Collins, " Cornish Tinstones and Capels." Mm. Mag., vol iv., 1882' p. 15. ' J H. C. Salmon. Mm. and Smelt. Mmj., 1862, vol. ii., p. 17. THE ABANDONED MINES. 229 Wheal Gobland. (Pig. 29.)— Gfossan Lode (copper) underlies N.27 deg. It was Ijnown as Cain's lode in Wheal Unity. Unity Lode (copper) underlies N. 27 deg'. Green's Lode (copper) underlies N. 27 deg. Dennis Lode (copper). Vertical. It crosses Green's lode. The Muttral Lode is a tin lode situated 10 fathoms north of Unity lode. It underlies N. 23 deg. North Lode (copper) underlies N. 13 deg. Fig. 29.— Wheal Qorland. N S. Paul's Lode (copper) underlies N. 5 deg. Situated N.W. of the North lode. (Thomas.) The principal lode of Wheal Gorland has been traced for 2 miles and passes through Wheal Unity and Creegbraws.* Fluorspar has been raised in great quantity. In 1884 it realised £1 a ton when sold to Swansea smelters.f Captain Hambley assayed some of the gossan of Wheal Gorland and found that it contained 6 dwts. of gold and 2 dwts. of silver per ton, also 15'5 per cent, of wolfram.^ Between 1815 and 1851, 40,751 tons of ore containing 3,234 tons of copper were sold by public ticketing.§ Wheal Gbambler. — The mine contains the easterly extension of the lodes found in Pedn an Drea Mine. Some of the lodes have been worked along their outcrops for tin ore. The Grambler Lode has a rich gossan, below which good copper and tin ores were wrought. I'he water level in the mine is about 13 fathoms from surface. Between 1843 and 1856, 7,261 tons of ore containing 569 tons of copper were sold from Grambler and St. Aubyn by public ticketing. || Great North Seton. — The lode underlies N. 13 deg. It is 2 to 3 feet in width and has a fine gossan. Copper and tin ore with mundic were wrought. In depth the veinstone is a dark, hard, heavy capel with quartz. Great South Tolgds.— The Main Lode at 100-fathom level was from IJ to 2 feet wide and contained copper and mundic in a quartz veinstone. At the 125-fathom level'the copper lode is supposed to have been thrown 90 fathoms to the right. In 1855 and 1856, 1,770 tons of ore were sold containing 110 tons of copper.^ • J. Came, " On the Veins of Cornwall." Tr. R. O.8. Corn,, 1882. t Brenton Symons. "A Sketch of Geol. of Cornwall," 1884. t F.J. Stephens, "Recent Discoveries of Gold in West Cornwall." B.G.S. Com., 1899. § Phillips and Darlington. " Records of Mining and Metallurgy," 1857. II Ibid. % Ibid. Tr. 230 THE MINES. Gdarnbck Mine (Garras). — The mine was worked in 1720 and some of the lead ore yielded 100 ozs. of silver per ton.* It was again worked in 1814 and in two years produced 800 tons of silver-lead ore containing 13 parts of lead in 20 of ore. The lead contained 70 ozs. of silver per ton. The lode runs N.N.E. and S.S.W. and is about 2^ feet wide. It is heaved twice by two slides each of which throws the lode 6 fathoms. The ore richest in silver was found near these slides at the 70-fathom level.t GusTAvus Mine. — The south underlying lode was intersected in the shaft about the 35-fathom level. The lode varies in width from 2 to 4 feet and is quartzose. At the 76-fathom level it was so poor that it was abandoned. In 1853, 89 tons of ore containing 6 tons of metallic copper were sold by public ticketing.:]: Haiabezack Farm. — The 'produce of black tin varied from 10 to 56 lbs. per ton.§ Hallenbeagle Mine. — Hallenbeagle Lode (copper) underlies S. 15 deg. It is recognised in Wheal Eose, Hawke, and Messar. South Lode (copper) underlies S. 13 deg. Between these are two other lodes :— Baby's Lode (copper) underlies N. 13 deg. William's Lode (copper) underlies S. 23 deg. (Thomas.) Between 1835 and 1846, 30,576 tons of ore containing 1,803 tons of copper were sold by public ticketing. || The mine is worked to the 70-fathom level. Wheai, Habmony (or Tbeleighwood) Mine. — Wolfram occurred in thismine.^ Great Lode (tin) underlies N. 41 deg. Another tin lode on the south of the Great lode underlies N. 54 deg. Wheal Bray Lode (copper) underlies N. 13 deg. Butler's Lode underlies S. 15 deg. Biitler's North Lode contains tin and copper. PolMrihorne's Lode (tin) underlies S. 10 deg. (Thomas.) WHEAi Habriet. — The mine was abandoned in 1866. Main Lode. — The Engine shaft is vertical to the 77-fathom level (adit 40 fathoms from surface), but after this it follows the underlie of the lode; which is about 15 deg. N. The lode was not very rich and was poor from 74 to 90-fathom level. At the 115-fathom level it was about 1^ feet wide, and contained tin ore, but at the 130-fathom level it was poor. Cross-cuts were driven from the main lode, both north and south, at the 90-fathom level. North Lode. — This is 7 fathoms north of the main lode at the 90-fathom level. It was thin and poor but yielded copper ore at adit level. At the 130-fathom level it is 1 to 1^ feet wide and contains tin ore. Between 1835and 1848, 9,030 tons of ore were yielded containing 496 tons of copper.** Wheax, Hatchet. — This mine is situated in the south-west part of South Eoskear Mine. The lode runs under the main road leading from Tucking- mill to Hayle, and has an irregular but nearly perpendicular underlie. The Engine shaft, which is just north of the road, is perpendicular to the 170-fathom level, and at this place is 2| feet wide, and contains copper pyrites and fluorspar. The lod3 varies in width from 1^ to 3 feet. Wheal Hawke.— TTheat Hawke Lode (copper) underlies south 23 deg. The lode is recognised in Wheal Eose, Hallenbeagle. Tenpenny Lode (copper) underlies south 13 deg. Pendarves Lode (copper) underlies north 23 deg. * Borlase. Nat, Hist. Corn. t J. Came, " On the Discovery of Silver in the Mines of Cornwall.^' Tr. R.G.S. Corn., vol. i., 1818, p. 120. X Phillips and Darlington. " Eecordsof Mining and Metallurgy," 1857. § C. Fox, "A Deposit of Tin in Wendron." Miners' Assoc. Corn, and Devon, 1868, p. 47. II Phillips and Darlington. " Records of Mining and Metallurgy," 1857. H J. Garby, p. 84. ** Phillips and Darlington. " Records of Mining and Metallurgy," 1857. THE ABANDONED MINES. 231 Tin Lode underlies north 13 deg. and is crossed by the Wheal Hawke Lode at the 60-fathom level. (Thomas.) Wheal Jewell.— Between 1815 and 1853, 58,160 tons of ore containing 5,222 tons of copper were sold. Main Lode.— Bearing B. 20 deg. N. Underlie N. 10 deg. to 23 deg. The lode varies in width from 1 to 4 feet from the 20 to the 90-fathom level. It consists of decomposed granite, quartz, felspar, clay, black sulphide of copper, and copper pyrites. Row's Lode. — Underlies N. 16 degl to 20 deg. and varies in width from 10 inches to 1^ feet. It consists of quartz, sulphides of iron and copper, and fluorspar. (Henwood.) Thomas records the following notes in regard to " Wheal Jewell and Wheal Quick":— Wheal Quick Lode or Wheal Jewell North Lode is the same as the Poldice Great ore lode. In this mine it is split up into Wheal Quick North and South Branches. The Middle Lode (copper) underlies N. 23 deg. It is situated south of Wheal Quick lode. Sottfh Lode (copper) underlies N. 23 deg. Figs. 30 and 31. — The Lovdl Mine. N el , S- KILLAS " 'G R AN I T e' Longitudinal Section of South Lode- Fig. 32. — Wheal Luahington. •Sv?, LovELL Mine. — There are two lodes. The North Lode strikes E. 37 deg. to 45 deg. N. and underlies N.W. 20 deg. The South Lode strikes E, 48 deg. N. and underlies N.W. 30 deg. The lodes unite as they go east, as also in depth.''' (Figs. 30 and 31.) • Foster, 232 THE MINES. Wheal Ltjshington (New Dolooath). (Figs. 32 and 33.) — Wheal Fox Lode. — An adit has been driven on the lode from Forth Towan Valley. The lode is poor, although extensively explored along the outcrop. It varies in width from 1 to 2 feet. Fig. 33. — Wheal Vincent {pa/rt of Wheal Luahington). N 5. Wheal Maid. — The Wheal Maid Lode (copper) underlies south to the 30-fathom level, after which it underlies N. 13 deg. (Thomas.) Wheal Mabia.— The Good Success- Lode for John's Gossan) is a lode containing copper ore and underlying N. 23 deg. Situated to the north, there is a copper branch underlying south 10 deg. (Thomas.) Wheal Mart.— Tfce North Lode (copper) underlies S. 13 deg. The Middle Lode (copper) underlies S. 10 deg. The South Lode (copper) underlies P. 13 deg. (Thomas.) Medlyn Mock Mine.— Worked to a depth of 33 fathoms. Nangiles. (Pig. 34.)— The Baldhu Lode (tin) underlies N. 45 deg. The lode splits as it goes west. The north part westwards is the main lode in South Ale and Cakes Mine. The south part is the South lode in Wheal Friendship. Fig. 34. — Nangiles. 100 pathjOJns Nangiles Copper Lode is situated north of the Baldhu lode. The lode splits as It goes eastwards. The north part underlies north 13 deg. and was rich where it traversed a soft el van but poor in killas. The south branch underlies N. 27 deg. (Thomas.) The gossan of one of these lodes is said to be auriferous.* • D. Forbes, "Eesearches in British Mineralogy." Phil. Mag., 1869, vol. xxxvu., p. 322. J. Garby, JV. Jt. G.S. Corn., vol. vii., 1848, p. 90. THE ABANDONED MINES. 233 Between 1845 and 1848, 1,449 tons of ore oontaining 110 tona of copper were sold by public ticketing from Andrew and Nangilea.* New Whkai Lovixl.— Worked to the 70-fathom level at Hill's Engine shaft. New Wheal Seton. — The Main or West Seton Lode has a good gossan and near the surface it is 6 feet wide. At the 62-fathom level the lode is 2^ to 3 feet in width. The veinstone consists of chlorite, quartz, copper ore, and mundic. The lode lies next to an elvan which underlies north- wards, with the lode on the toot wall side. New Wheai Viegin. — New Wheal Virgin Lode (copper) underlies N. 10 deg. North Lode (copper) underlies N. 13 deg. One hundred and fifty fathoms further north there is the Olyjah Lode (tin) which underlies N. 13 deg., while 20 fathoms further north there is a copper lode which is said to be a continuation of Wheal Virgin and Wheal Hope lode. (Thomas.) Fig. 35. — North Dovms. NoETH Downs. (Pig. 35.)— The mine was worked to the 143-fathom level or 110 below adit at the Water Engine shaft. John's Gossan Lode.— E. 21 deg. N. Underlies N. 18 deg, to 30 deg. The lode is 1^ feet wide at the 30-fathom level, and consists of quartz, earthy brown iron ore, and iron pyrites. Wheal Peevor Lode.— E. 12 deg. N. Underlies S. 12 deg. to 20 deg., and consists of quartz, clay, and slate. Main Lode.—E. 14 deg. N. Underlies S. 8 deg. to 20 deg. Consists of copper pyrites, limonite, iron pyrites, blende, slate, and granular quartz. Tenpenny Lode.—K 30 deg. N. At the 30-fathom level the lode is verti- cal and IJ to 2 feet in width. Copper and iron pyrites, quartz, and earthy iron .ores. Gaunter Lode.—E. 28 deg. N. At the 30-fathom level the lode underlies N. 7 deg. to 10 deg. It varies in width from 1 to 2 feet, and consists of earthy iron ore, iron and copper pyrites, and slaty clay. Phillips and Darlington. " Kecords of Mining and Metallurgy," 1857. 234 THE MINES. Pendarves Lode. — E. 22 deg. N. At the 30-fathom level the lode is vertical and is about 1 to IJ feet in -width. Ooutains tin ore with iron pyrites and earthy brown iron ore and slate. (Henwood.) Between 1815 and 1855, 19,348 tons of ore containing 1,600 tons of copper were sold by public ticlseting.* North WHEAii Jane.— Worked to the 40-fathom level on the tin lode, and to the 10-fathom level on the lead lode. NoBTH Pool. — Yielded copper ore, but was never worked for tin. North Roskeab.— Between 1816 and 1856, 151,797 tons of copper ore containing 11,846 tons of copper were sold by public ticketing. In 1841, copper ore, sold at £7 5s. a ton, realised £28,850. At the 205-fathom level, west of Doctor's shaft, the lode is 2J feet wide, and consists of quartz with copper pyrites and tin ore. At the 216-fathom level the lode was from 1 to 8 feet wide and contained quartz, fluorspar, Fig. 36. — Ped/n, cm Drea Mine. so lOO chlorite, tin, and copper. At the 203-fathoiu level there was tinstone and mispickel, but little or no copper. In the eastern part of the mine, on the east of the Engine shaft at the 160-fathom level, the lode is 4 feet wide and contains copper and tin ore. A hot spring of temperature 102 deg. P. made the " end " at this level too hot to work in, the temperature of the air being about 100 deg. P. The Engine shaft is sunk below the 110- fathom level. Charles Thomas states that good tin and copper ore occurred in the mine in scattered bunches.:]: Henwood remarks that the North Boskear Lode bears E. 32 deg. N. and underlies N. 8 deg. to 22 deg. It varies in width from a few inches to 5 feet. The lode contained copper sulphide, fluorspar, quartz, chlorite, and iron pyrites. The South Lode has a bearing E. 32 deg. N. At the Phillips and Darlington. " Records of Mining and Metallurgy," 1857. "Mining Districts of Cornwall," 1867, p. 49. THE ABANDONED MINES. 235 37-fathom level the underlie is N. 45 deg. to 50 deg. At the 57-fathom level it is 6 deg. to 36 deg. south. It contains quartz, blende, copper, and iron pyrites. The Main Lode, in the Park an Bowan part of the mine, underlies N. 35 deg. to 40 deg., and is about 1 foot wide. The veinstone is a soft killas -with mundic. The Gaunter Lode was fair in copper and blende, at 70 fathoms west of its junction with the main lode, and varies in width from 1 to 3 feet. Pbdn an Drba. (Fig. 36.) — Thomas makes the following observations :-- North Tin Lode. — Underlies N. 30 deg. The next lode on the south yielded copper. It underlies N. 15 deg. Pedn an Drea Lode (tin). — Underlies N. 30 deg. Michell's Gossan (copper). — Underlies S. 23 deg. In 1821, 14 tons of copper ore containing 1 ton of copper were sold by public ticketing. Yielded mainly tin ore. (See p. 1 65.) Pendarves United (or Carnemough).— The sett includes the old Tryphena Mine, Tolcarne (or West Wheal GrenviUe), and Condurrow Mine. Condurrow Mine Main Lode.— From the 140 to the 155-fathom level the lode is 6 feet wide, 3 feet of which consists of flucan. At the 266- fathom level it is 2 to 3 feet wide. The leader of the lode varies from 10 inches to 2 feet in width and contains fluorspar, copper, and tin ore. At the 165-fathom level at Pryce's shaft the lode is 5 feet wide and consists of fluorspar, quartz, peach, and some iron and tin ore in capel of north wall.* Pryce's shaft was sunk on a lode 2^ to 3 feet in width. At the 140-fathom level it is 3 feet wide, and consists of capel, peach, and flucan, with yellow copper ore and tin. At this level a great deal of water was met with possessing an acrid taste, owing to the presence of copper salts, which, reacting upon metal work in the shaft, caused the precipitation of copper upon it. At the 20-fathom level a " pipe " of malleable copper was found which was 18 feet in height, 8 feet in length, and 3 to 15 inches in width.t At Woolf's shaft at the 200-fathom level there were branches of copper pyrites and grey copper ore in the tin lode. Salmon states that at the l40-fathom level the leader is 10 inches in width. The remainder of the lode is made up of ferruginous capels, plentifully speckled with quartz. These capels have no regular walls, but pass insensibly into the granite of the " country," and as they are stanniferous they are considered to be I' lode " by the miners.^ At the 155-fathom level a large vug occurred in the lode ; its dimensions were 36 feet in length, 12 feet high, and 2 to 3 feet wide. Llandower Lode. — The lode yielded both copper and tin ore at the 30-fathom level. Copper ore was plentiful at the 50-fathom level. It varies in width from 1 to 4 feet. RobeH's Lode.— Hope's shaft from 100-fathom level to the 177-fathom level is sunk on Robert's lode, which varies from 2 to 4 feet in width, and yields tin ore. A Gaunter lode branches ofi at the 90-fathom level in a north-westerly direction. Gaunter Lode. — At deep adit it is 15 inches in width. The lode has a good gossan extending below the 10-fathom level and yielded grey copper ore. It is 2^ to 4 feet wide. Scmth Lode.— Yielded copper ore at the 60-fathom level. Field's Lode (in Tolcarne). — Has a good gossan.§ Between 1818 and 1856, 20,095 tons of ore containing 1,498 tons of copper were sold by public ticketing. || • H. C. Salmon. Min. and Smelt. Mag., 1863, vol. iii., p. 82. + E. W. W. Pendarves, "Notice of the Native Copper at Condurrow Mine." Tr. M.G.S. Corn., vol iii., 1828, p. 333. J Min. (md Smelt. Mag., 1863, vol. iii., p. 82. § H. C. Salmon. Min. and Smelt. Mag., 1863, vol. iii., p. 82. II Phillips and Darlington. " Records of Mining and Metallurgy," 1857. 236 THE MINIES. Pbnnanoe Mine. — Situated about IJ miles west ot Swanpool. Tin, copper, and lead were found, but although several lodes were cut there was nothing of value discovered. In one trial the lode was 6 inches wide, iri^egular and very gossany, with quartz and traces of lead ore.* Wheal Peevoe. — John's Gossan Lode (copper), underlies N. 30 deg. This lode is recognised in Good Success Mine and Whea,l Maria. Wheal Peevor Lode (tin), 8 to 10 feet in width.t Underlies S. 23 deg. This lode is faulted by John's Gossan lode to the extent of 8 fathoms.;|: Diamond Lode (tin), underlies south 5 deg. (Thomas.) Wheal Peevor lode is also traversed by two slides both underlying north. It is faulted by them 14 feet and 9 feet respectively.§ It is also heaved by two cross-courses. Wheal Pink. — Wheal Pink Lode (copper), underlies N. 13 deg. (Thomas.) Between 1821 and 1850, 1,881 tons of copper ore containing 158 tons ot copper were sold by public ticketing. 1| PoLDioB. — Great Ore Lode (copper), underlies N. 15 deg. In Wheal Jewell and Quick it is the North lode. Poldice Tin Lode. — Underlies S. 15 deg. It is intersected and heaved two fathoms by the Great pre lode in the western part of the iume. Bissoe Tin Lode.— Underlies S. 23 deg. At the SO-tathom levet'it^is intersected by the Great ore lode. ...v. Quick's Lode (tin and copper).— It has an irregular but nearly vertical underlie. Kitty Billing's Lode (copper). — Nearly vertical. .,, ., Garby's Lpde.{ooppei). — Underlie N.. 10 deg., , .^., -s," Hainan's Lode (copper).— Underlie N. 10 deg.. (Thomas,),' The^lodess have been traced for two miles. (Came.) ; , Between 1815 and 1852, 2,992 tons of copper ore containing .208 tons pf copper were sold by public ticketing. If (See p. 234.) , PoLLADRAS DowNS MiNE. — Boj' or Engine Lode.— IE. 35 deg. N. under- lies N. 12 deg> to 34 deg. The lode varies from a few inches to 3 feet in width, and consists of slaty quartz, veinstone, with clay and strings of cassiterlte, down to the 113-fathom level, \vhere some iron pyrites also occurred. '■■'■■< Bisaa or Penhale Lode. — B. 30 deg. N. Underlies N. 8 deg. to 40 deg. and varies in width from 2 to 5 feet. In the Tipper levels it consists of earthy brown iron ore, tin ore, quartz, and quartzose slate. At the 83- fathom level there were veins of quartz and strings of cassiterite in the slate. PressMre North Lode. — E. 30 deg. N. Underlies N. 16 deg. to 34 deg. and consists of quartz, slate, and cassiterite at the 83-fathom level. Pressure South Lode. — E. 30 deg. N. The lode consists of quartz and slate and felspar clay. Cassiterite at the 83-fathom level occurs in irregular spots. Btc?uird's Lode.— E. 30 deg. N. Underlies N. 14 deg. to N. 18 deg. About 4 inches wide, and consists of slaty clay with quartzose, slate, and cassiterite. (Henwood.) PoBKELLiB United Mines. (Pig. 37.) — The lodes have a general under- lie north. Orowan Lode and Harris Lode underlie north, but are nearly vertical. They are 2 to 3 feet in width, and yielded tin ore in fair quantity. Horseflesh Lode.— South of Orowan loda and said to be a branch of the Tymorgie lode which lies further south. Towards the east this lode and * P. J. Stephens, "Mineral Besources of Falmouth." Rep. Com. Poly. Soo., 18S6. t J. Hawkins, "On the Intersection of Lodes," Tr. M.0,S. Corn,, vol ii., 1822, p. 240. ,..'.: t J. Carne. § Op. eit. Phillips and Darlington. " Records of Mining and Metallurgy," 1857. IT Ibid. THE ABANDONED MINES. 237 the-Tymorgie lode unite. It underlies north, and is a fair tin lode about H feet in width. « Great Tymorgie Lode. — Tin was found in the outcrop, but the lode is only fair. It -varies in width up to about 3 feet and underlies north North Tymorgie Lode. — At the 24-fathoin level it is as wide as 5 feet in some places, and the lode yielded tin ore to the 50-tathom level. ^ Wheal Ash Lode. — The most southerly lode is 1 to 2 feet in width, and has a northerly underlie. .. -Dates iiode;^-A good. % bunch of tin ore was found near Wheal Ash shaft. North Lode.— South of North Tymorgie lode. Worked to the 80-fathom level. The lode varies in width up to 7 feet and was richer in tin ore in the upper levels than in depth. Fig. 37. — Porkellis United Mines. s ^ ■ V ^5'B"yLcvdj South Tymorgie Lode. — 2 to 4 feet in width. An elvan which traverses the sett is supposed to be a continuation of one in Wheal Vor.* Pbovidence Mine. — The mine has been worked for tin and copper but is poor. It was abandoned in 1867.f Thomas states that it is the same lode as that worked in Wheal Druid. Whkai, Pbussia. — Wheal Prussia Lode (tin). — Underlies S. 27 deg. It is the same lode as the Wheal Vor lode in Treskerby. Wheal Boys Lode. — ^Yielded copper. (Thomas.) Wheal Rose (near Wheal Hawke). — Wheal Rose Lode (copper). — Underlies S. 27 deg. -Sixty fathoms further south is BuUfleld Lode (copper), which underlies S. 27 deg. and Wheal Moyle Lode (copper), which underlies N. 13 deg. (Thomas.) * W. H. Argall, "On Elvan Courses." Miners' AisociatUm, IS75. t J. Maynard, "Remarks on a Cross Section." Sep. Com. Poly. 8oc., 1871, p. 200. 238 THE MINES. EoSKBOW United. — The lode is met with 50 fathoms east of the turnpike leadcDg to Ponsanooth village. It is 4 to 6 feet in width, but varies down to about 2| feet. It underlies north 13 deg. and is explored to the 40- fathom level, where the granite is considered to be only 30 fathoms below. The lode has yielded mundic, with some silver, copper and uranium ores, and also some nickel. An elvan traverses the sett. Seton, WheaI/. (Pigs. 38, 39.) — This mine has yielded mainly copper ores but has produced " a small proportion of tin from its lowest quality or halvan ores."* The workings extend to below the 300-fathom level. Figs. 38 and 39.— Wheal Seton. The lode near Tilly's Engine shaft yielded copper ore to the 160- fathom level. From this level to below the 200-fathom level it is mainly a tin lode. "Warm water issued from the lode at the 170-fathom level east of Bull's shaft. South Gaunter Lode.— At the 140-fathom level west of Tilly's shaft the lode is 4 feet in width and tin bearing. North Gaunter Lode.— The lode is tin bearing from the 170 to the 200- fathom level, and consists of quartz, capel, and mundic. The North (or Great) Gaunter is the same lode as Beeves' lode eastwards, but it is heaved by a cross-course in Wheal Seton sett 20 to 25 fathoms. Westwards this lode assumes a bearing approximating to that of the ordinary lodes of the distriot.t , ,, , ,. Middle Lode.— At the 110-fathom level the lode yielded tin ore and varied in width from 2| to 4 feet. Phillips has described the killas at the 160-fathom level. It is a very hard grey clay slate in which the cleavage has been obliterated to some extent, in the majority of cases by metamorphism. No crystalline structure can be detected by the eye, and the rock in addition is traversed by quartz strings enclosing minute spots and crystals of iron pyrites. The microscopic section shows bands of transparent granular quartz alternating with layers of similar quartz through which minute hornblende crystals are dissemi- At the same level Harry Tilly describes a thermal spring, and states that the killas in its neighbourhood is traversed by joints and is not far from the Great cross-course. Thirty gallons of water per minute, at a temperature of 94 deg. ¥., issues from the lode. The lode is small and contains copper, quartzj and mundic. The water has specific gravity 1-105, and contains " C Thomas. " Mining Districts of the West," 1867, p. 48. + H C Salmon. Min. tmd Smelt. Mag., 1862, vol. ii., p. 277. J J.' A. Phillips. Q.J.Q.S., vol. xxxi., 1875, p. 324. THE ABANDONED MINES. 239 1,072 grains of dissolved material per gallon, principally salt and calcium . carbonate.* Phillips attributes the magnesia in the rock to the action of sea water which traverses the great cross-course. Wheax, Seymotje. — In the shallow parts of the lode there occurred copper and zinc.f Silver Hill (Perranarworthal).— There is a copper lode near the road leading to Perranarworthal. Another lode further north has yielded mundic. South Wheal Basset. — Teague's Lode has been profitably worked for copper ores. The lode underlies north. At the 120-fathom level it varies in width from 2 to 4 feet and consists largely of quartz. The North Lode underlies north and is 2 to 3 feet in width. This lode has a good gossan and consists of quartz and peach, with copper and tin ore. Engine Lode. — Underlies N. 13 deg. It is a large and poor lode from the 60 to the 90^fathom level. Between 1825 and 1856 the mine yielded 94,649 tons of ore containing 7,200 tons of copper.:j: South Cabn Brea Mine. — The work done in this mine is mainly upon the Great Flat lode. In this mine the Great Flat Lode was worked to a considerable extent about adit level, where it is in killas. The lode underlies from 35 deg. to 45 deg. S. At the 28-fathom level it underlies south 35 deg. The lode has a good gossan with vitreous and yellow copper ores and some tin. At the 128-fathom level the lode is 3 to 12 and even 18 feet in width. At the 164r-fathom level (95 fathoms west of the Engine shaft) the granite was penetrated, and at this level the veinstone consisted of peach, quartz, and fluorspar. Poster states that there is a copper leader in the lode, 2 to 4 feet in width, and that the lode makes a sudden bend in one place, changing its bearing from E. 33 deg. N. to E. 15 deg. N.§ Tin and copper ores occurred in bunches in the lode. The footwall in the upper levels is very near the granite, which plunges southwards at nearly the same angle as the lode.|| South Condubrow Mine. — This mine is situated on the Great Flat Lode, which is entirely in granite in this mine. Poster states that the tin-bearing part of the lode is 5 or 6 feet in width, while the lode and capel together are 12 or even 20 feet in width. It has a general bearing of E. 34 deg. N., and underlies south at 60 deg. at the 80 or 90-fathom level. The lode is a schorl rock traversed by innumerable quartz veins, a great many of which dip north at a high angle. In many places it contains chlorite and iron pyrites with kaolin, which occasionally fills up vughs in quartz veins.fl" The Middle Lode varies in width from 2 to 3 feet, producing both copper and tin. The lode underlies north but is nearly vertical. South of the middle lode is the West Basset Copper Lode, which varies in width from 3 to 4 feet. It splits up into branches at the 61-fathom level. At the 20-fathom level the lode yielded sulphides of copper in a veinstone of quartz, peach, and killas. At 120 fathoms west of Grenville shaft the copper lode heaves the Flat lode 10 fathoms, and Captain Hooper states that it is at this place that the Great Plat lode was first discovered. South Ceenver.— Worked to the 94rfathom level (115 fathoms below surface). * " Particularsof a Thermal Spring at Wheal Seton." Miners' Assoc, 1873 p. 53. t Thomas. J Phillips and Darlington. " Records of Mining and Metallurgy," 1857 § C. Le Neve Foster, " On the Great Flat Lode." Q.J.Q.S vol xxxiv 1878. ■ ■' II J. Maynard, "Report on Two Cross Sections." Sep. Corn. Poly.Soc. 1873 p. 191. ' IT " On the Great Flat Lode." Q.J, 6f,S. ,_ 1^78, vol. xxxiv. 240 THE MINES. SotjTH DoLOOATH.— The mine was worked by the ancients. The lodes have fine gossans below which was rich copper ore.* From 1829 to 1831, 286 tons of ore containing 25 tons of copper were sold by public " ticketing.f South Wheal Peancses. — The sett is traversed by five lodes which have a bearing of about E. 35 deg. N. North or Main Lode. — Underlies N. 12 deg. from surface to adit level (32 fathoms from surface). From adit level to the 50-fathom level the underlie is N. 10 deg., and from the 50-fathom level downwards it is about 5 deg. N. There was a good gossan and a bunch of copper ore to the 40- fathom level. Tin ore and quartz was also present, mixed with ferruginous materials, and fluorspar, peach, chlorite, prian, &o. Below the 40-fathom level the lode is mainly tin bearing, and varies in width from 2 to 12 feet. At the 114-fathom level it is 1 to 3 feet wide, with ore bunches. Crrillis (or St. Aubyn) Lode. — The lode near Harvey's shaft is 6 feet wide and consists largely of quartz and iron with some ore. At 45 fathoms west ol the shaft it is 2 feet wide and in an elvan. ■ •. South Lode. — This lode is 36 fathoms south of the main lode. It underlies south, and is about 2 feet in width. Little's Lode. — About 2 feet in width, and consists largely of ferruginous materials. The Gtreat Flat Lode dips into this mine from West Wheal Basset.- It was first intersected at the 185-fathom level, and has been worked upon. to a considerable depth. The bearing is E. 41 deg. N., and the underlie is 58 deg. south. The ore contains about 2^ per cent, of black tin. The Great Flat lode is intersected by three north underlying lodes.t Between 1844 and 1856, 33,522 tons of ore containing 3,252 tons of copper were sold by public ticketing;§ SoxjTH WHEAii Hawkb. — The South Wheal Hawke Lode yielded copper. It underlies N. 13 deg. and is intersected by a Oaunter Lode underlying N. 5 deg. and containing copper. (Thomas.) South Bobkeiar Mink. — There are seven parallel lodes, but only two have been seriously worked. The South Boskear Lode and a lode to the north are those upon which most work has been done. Between these lodes is another called the Boundary Lode. The Dolcoath North Entral Lode enters the sett on the south. This lode yielded copper and tin ore in Dol- coath, Tincrott, South Crofty, and Bast Pool. Both copper and tin ore were taken from the South Boskear lode at the 170-fathom level near Gregory's Engine shaft. The lode varied from 2 to 3 feet in width. At Vivian's shaft tin, copper, and arsenical ores were extracted between the 80 and the 112-fathom levels. Near the South Boskear (or Pendarves) shaft, copper and tin occurred at the 132-fathom level, while the Oaunter lode yielded copper ore. Granite was not met with in the workings, although they extend below the 180-fathom level, nor was that rock encountered in the 143 cross-cut south. Argall states that the lode was very productive near an elvan. I| The Oopper Tankard Lode passes into this sett. Between 1821 and 1850, 37,807 tons of ore containing 2,904 tons of oopper, were sold by public ticketing. In 1841, copper ore at £5 4s. a ton realised £9,932. South Wheal Seton. (Fig. 40.)— The Main Lode is 4 to 8 feet in width and contains copper, blende, and mundic, with peach, quartz, and killas veinstone. * J. Maynard, ''Remarks on Two Cross Sections." Bep, Com. Poly. Soc, 1871, p. 201. t Phillips and Darlington. " Records tit Mining and Metallurgy," 1857- J Foster. § Phillips and Darlington. " Records of Mining and Metallurgy," 1867. II W. H. Argall, *' On Elvan Courses." Miners' Assoc, 1875. THE ABANDONKD MINES, 241 The North Lode underlies N. 35 deg. and varies in width from 3 to 4 feet Ttie lode forms a junction with the main (or Marriott's) lode at the 60-fathom level. Blende, copper ore, and galena oocurted at the 50-f athom level, with quartz and killas veinstone. Fig. 40,— South Wheal Sdon. "} .4 •3 i I ~T — ^Cll ^ P X.lt N. "1 LEVtU •J 1 \ "^^^^^^^fi^ F'Mevci Si TT^tc^^a South Wheal Towan. (Pig. 41.) —Slide Lode. — Bearing N.B. and S.W. It underlies N. 22 deg. to 35 deg., and varies in width from 7 or 8 inches to 3| feet. It consists of earthy brown ore, quartz, and slaty clay. At the 36-fathom level there is quartzose slate and brown iron ore and copper pyrites. Fig. 4:1.— South Wheal Towan. South Lode. — B. 24 deg. N., underlies S. 16 deg. to 30 deg. Varies in width from 2 to 4i feet. It consists of earthy brown iron ore, some chlorite, and ^pots of copper pyrites to the 36-fathom level. Mineral pitch occuried in both mines. (Henwood.) The minn is worked to the 114-fathom level. The shoot of ore pitched from Wooleock's shaft to 242 'J'lIE MINT.S. Engine shaft. 24,161 toas o£ copper ore contaiaiag 1,610 tons of copper were sold by South Wheal Towan and Wheal Lydia between 1817 and 1847.* South Tbesavean Mine. — The Engine Lode was worked for a consider- able distance along the outcropr and at adit level it varies in width up to about 3 feet, and yielded low-grade tin ore. Pitchblende with kupfernickel, native silver, and rich argentiferous galena also occurred.| Wheal Spaenon. — Wheal Sparnon Lode. — Copper and tin. Underlies S. 15 deg. North of Wheal Sparnon lode is the North Lode. Copper and tin. Underlies N. 13 deg. Belfry Lode (is S. of Sparnon lode). Tin. Underlies S. 45 deg. Another lode further south contains copper and underlies N. 27 deg. (Thomas.) Gold was found in a burrow and in a cross-course.:]: 1,547 tons of ore containing 128 tons of copper were sold by public ticketing between the years 1815 and 1827.§ Wheal Spinster. — The lode has been worked for tin at surface for at least 10 fathoms. No copper ore was found in the upper part of the lode.|| 4,520 tons of ore containing 400 tons of copper were sold by public ticketing between the years 1820 and 1829.^ Wheal Squire. — Vnited Mines Great Lode. — Copper. Underlies N. 15 deg. A lode north of this yielded tin. It underlies N. 15 deg. Further north is Oocks' Oossan Lode. Copper. Underlies 10 deg. N. Oatex' Lode. — Copper. Underlies N. 5 deg. North of Gates' lode is Pos's Lode, which contains copper and tin ore, and underlies N. 23 deg. Old North Lode. — Copper. Underlies N. 23 deg. Old South (or Andrew's) Lode.^ Copper. Underlies N. 15 deg. Wheal Lovely (or Flat) Lode. — Lode contains copper and tin, and under- lies N. 45 deg. South Flat Lode. — Copper. Underlies N. 45 deg. Pearce's Lode. — Copper. Underlies N. 15 deg. Another copper lode underlies N. 15 deg. (Thomas.) Came states that a lode in Wheal Squire underlies N. 54 deg. 20,082 tons of ore containing 1,724 tons of copper were sold by public ticketing between the years 1816 and 1853.** Stray Park Mine. — The Main Lode underlies S. 14 deg., and varies in width from 2 to 10 feet. There is a good gossan in the upper part of the lode, and below this to the 124-fathom level it was very rich in copper ores. At the 15-fathom level the lode was 9 feet wide, and contained tin ore. At the 180-fathom level, where it traverses an elvan, the tin ore was rich, while the lode varies in width from 3 to 4 feet. At the 204-fathom level it is 14 feet wide, and contains good tin ore down to the 250-fathom level. The Engine shaft struck the granite at the 115-fathom level. Towards the east, at the 180-fathom level, the lode divided. The south part contained copper ore. South Lode. — Underlie 13 deg. N. Varies in width from 1-| feet in the upper levels to 5 feet at the 250-fathom level. At the 180-fathom level it is 2 fathoms south of the main lode. The lode was rich in copper ore from the 80 to the 160-fathom level, below which it yielded mainly tin ores. * Phillips and Darlington. " Records of Mining and Metallurgy," 1857. t R. Pearce, " Note on Pitchblende in Cornwall,'' Tr. M.G.S. Corn., vol ix., 1864 to 1878, p. 102. t J. Garby, " Notice of the Occurrence of Gold in a Cross-Course.'' Tr. B.G.S. Corn., 1846, vol. vi., p. 265. § Phillips and Darlington. " Records of Mining and Metallurgy," 1857. II W. H. Argall. Miners' Assoc. (Breage Meeting), 1872. . ,11 Phillips and Darlington. " Records of Mining and Metallurgy," 1857. ** Op. oit. THE ABANDONED MINES. 243 There are three lodes north of the main lode, which were intersected by a cross-cut at the 100-fathom level. The first is 28 fathoms north of the main lode. It is 1| feet in width and underlies N. 20 deg. This lode yielded copper and tin ore. The second is 45 fathoms north of the main lode. It is a poor lode, with a northerly underlie, and aliout 1 foot in width. The third lode is 67 fathoms north of the main lode. It underlies N. 10 deg., and contains copper ore with quartz. Between the years 1829 and 1856, 38,610 tons of ore containing 2,748 tons of copper were sold by public ticketing. In 1841, copper ore sold at £6 3s. a ton realised £5,972. SwANPOOi, Mine. — Thiamine was worked at about the same time as Wheal Clinton. In 1855 it was down to 80-fathom level, four shafts having been sunk on the lode. At the 20-fathom level the lode is in one place 9 feet wide, and consisted of flucan with gossan, and rich bunches of galena yielding 1 J to 2 tons of lead ore per fathom. At the 40-fathom level the lode is 2 feet wide and consists of gossan, flucan, mundic, and large stones of mixed blende and lead ore. At the 80-fathom level it is 2 feet wide, and consists of quartz, mundic, and flucan, with good branches of galena. The lode underlies south.* Silver and a little gold also is said to have occurred in the lode."!" On the eastern side of Swanpool Lake are three levels driven on three lodes. Several shoots of lead were passed through, especially in the Middle Lode, which is 20 inches in width and composed of flucan, quartz, and galena.:|: Wheal Tehidy. — There are some ancient workings on the upper parts of the lodes, but the mine was first seriously worked in 1835. North or Tin Lode. — Underlie 35 deg. N. The lode varies in width from 1 to 3 feet. It is a continuation of the East Pool or Tincroft North lode. It contained copper and blende as well as qnartz and flucan. Gaunter Lode. — This lode has an irregular underlie northwards. It varies in width from 1 to 2 feet from adit to the 70-fathom level and yielded copper ore and mundic in a quartzose veinstone. 2,121 tons of ore containing 179 tons of copper were sold by public ticket- ing between the years 1835 and 1856.§ Ting Tang Mine.— AfatJi Lode.—E. 12 deg. N. Underlies N. 8 deg. to 30 deg. The lode contained copper pyrites, earthy brown iron ore, black and vitreous copper ore. At the 80-fathom level there was some chrysocolla with black copper and copper pyrites. At the 90-fathom level there was oxide of copper. At the 140-fathom level there was blue and green copper carbonate with chlorite, and quartz. Middle Lode.—'E. 21 deg. N. Underlies N. 4 deg. to 22 deg. and varies from 1 to 4 feet in width. It contained earthy brown iron ore, vitreous and black copper ore, and red crystallised oxide of copper at the 90-fathom level. At the 140-fathom level there was granular quartz, chlorite, and vitreous copper. Boche's Lode.—'Ei. 8 deg. S. Underlies N. 10 deg. to 22 deg. Varies in width from 1-| to 3 feet and contains quartz, chlorite, iron and copper pyrites, earthy red iron, and vitreous and black copper ore from 90 to the 120-fathom level. (Henwood.) Thomas states that there is a Flat Lode in this mine which yielded both copper and tin. It is the continuation of Wheal Lovely and Wheal Squire lode, and underlies N. 45 deg. Seven fathoms south of the Plat lode is a Mwridic Xode (which is the South Flat lode of Wheal Squire) underlying N. 45 deg. Between 1816 and 1835, 38,124 tons of ore containing 3,235 * F. J. Stephens, " Mineral Resources of Falmouth." Rep, Corn, Pohi 8oc 1886, p. 189. ^' " t F. J. Stephens, " Recent Discoveries of Gold in West Cornwall." Tr R G S Com., 1899. J F. J. Stephens, "Mineral Resources of Falmouth." Rep. Corn Pohi Soo 1886, p. 189. § Phillips and Darlington. " Records of Mining and Metallurgy," 1857. h2 2 44 Tim MINES. tons of copper were sold by public ticketing, and 841 tons containing 50 tons o£ copper between 1845 and 1847.* ToLOARN.— JVortfc Zode. —Copper. Underlies N. 15 deg. (South lode in Wheal Jewell). South Lode. — Copper. Underlies N. 15 deg. Tbepdla Mine. — TrefulaLode. — Copper. Vertical. (Thomas.) Trelbigh Consols (Good Suoobss) Mine. — Good Success or John's Gossan iode.— (Copper). Underlies N. 23 deg. North Good Success Lode is situated 60 fathoms further north. It is a copper lode underlying N. 23 deg. Between 1833 and 1855, 21,904 tons of ore containing 1,420 tons of copper were sold by public ticketing.| Tbemenheeibe Mine. — Worked to the 204-fathom level. Tbesavean Mine. (Pig. 42.)— The Main Lode bears B. 30 deg. N., and underlies S. 6 deg. to 30 deg. down to the 276-fathoin level. It varies in ■width from 1 to 10 feet, being widest at the 206-fathom level. It con- sists of quartz, earthy brown ore, black copper, and copper and iron FiQ. 42 Tresavean K TRESAVEAN MINE -- SCALE -FaXhoTTLS (o loo zoo pyrites. There was quartz and schorl at the 264-fathom level. At the 228-fathom level the lode was very rich in copper sulphide. Mr. Collins has described blue peach from this mine, and remarks that i€ is a slightly stanniferous capel showing a " shadowy granitic structure."! * Phillips and Darlington, "Records of Mining and MfetallurgSr," 1857. t Mm. Mag., vol. iv., 1882, p. 13. " Cornish Tinstones and Capels."' " THE ABANDONED MINES. 245 Thomas states that there are four lodes all of which have yielded copper. They underlie south. Between 1815 and 1856, 163,259 tons of ore containing 15,702 tons of copper were sold by public ticketing.* Wheai, Towan.- Gfi-eat Zode.— E. 20 deg. N. Underlies S. 8 deg. to 28 deg. Prom the 36 to the 142-fathom level the lode varies in width from 3 inches to 12 feet. In the upper levels the lode consists of earthy brown iron ore, Iron pyrites, quartz, chlorite, tin ore, and copper pyrites and some blende. In the deeper levels the lode contains copper and iron pyrites and quartz coated with carbonate of iron. (Henwood.) Between 1815 and 1835, 26,0.'J8 tons of ore containing 1,465 tons of copper were sold by public tioketing.f Tkeskrebt Mine. (Fig. 43.)— 0/d South Lode. — Copper. Underlies S* 15 deg. (continuation of William's lode in Chacewater Mine). Fig. 43. — Treekerby Mine. North Lode.— Copper. Underlie N. 10 deg. (a branch of the old South lode). Middle iode.— Branch of the old South lode. It underlies north and falls into the North lode. Wheal For Lode.- Tin. Underlies S, 27 deg. It is called Prussia lode in Wheal Boys and Butter's lode in Wheal Harmony. Chacewater or William's Lode. — Copper. Underlies N. 40 deg. for 50 fathoms in depth and then underlies N. 27 deg. William's South Lode.— Copper. Underlies N. 28 deg. Teague's Lode.— Copper. Underlies S. 23 deg. Flat Lode. — Copper. Underlies N. 40 deg., crosses the Chacewater lode at the 70-fathom level. Carquean North Lode. — Copper. Underlies N. 1 5 deg. Oarquean South Lode.— Copper. Underlies N. 5 deg. (Thomas.) Phillips and Darlington state that between the years 1815 and 1832 only 6 tons of copper ore were sold at public ticketing. Tbevenen Mine, — Carue states that the lodes were richest at a depth of 150 fathoms from surface.]; Tee WAN Mine. —Trewan North Lode. — Copper, Underlies S. 15 deg. (It is the Briggan lode.) Phillips and Darlington, Op. eit. t p. 90. " Records of Mining and Metallurgy," 1857. 246 THE MINES. Treumn South Lode. — Underlies S. 23 deg. Between these lodes is a tin lode underlying N. 27 deg. Trewirgie Dovrsa.— North Lode. — Contains copper. It underlies N. 7 deg. The South Lode contains copper and underlies N. 7 deg. (Thomas.) Wheal Trumpet. — Wheal Trumpet Lode. — (Westerly continuation of Wheal Ann lode.) Bearing B. 22 deg. N. Varies in width from 4 inches to 1 foot. Underlies N. 6 deg. to 24 deg. Prom 73 to 117-fathom level it con- tains earthy brown iron ore and cassiterite. At 157-fathom level the granite is friable and the lode contains quartz. (Henwood.) Union, Wseal.— Wheal Union Lode. — Tin and copper. Underlies N. 32 deg. Orove Lode is situated north of Wheal Union lode. It contains tin, and underlies N. 32 deg. (Thomas.) In 1838, 101 tons of copper ore containing 6 tons of copper were sold by public ticketing.* United Hilis. (Pig. 44.)— Lode strikes B. 26 deg. N. Underlies N. 42 deg. to 60 deg. It varies in width from 4 inches to 7 feet to the 52-tathom Fig. 44. — United Hills. SCAue -TaiJxorrts so i6o 70 F"^ Level level, and consists of quartz, quartzose slate, copper and iron pyrites en- closing irregular masses of slate. (Henwood.) Between 1826 and 1847, 54,473 tons of ore containing 3,582 tons of copper were sold by public ticketing.j Within the Tywarnhaile sett the lode has been worked upon for a distance of 400 fathoms. The width of the lode is very irregular, and the ore occurred in hard quartz, slate, or capel. At the 50-fathom level east of Bennett's shaft a cross-cat was driven south to intersect a Gaunter and the Wheal Charles lode. The Gaunter lode at the 80-fathom level was 2 feet wide and contained zincblende and iron pyrites. United Mines.— Old Lode.— B. 27 deg. N. 2 to 8 feet in width. Un- derlies N. 6 deg. to 30 deg. It consists of quartz, slate, clay, earthy brown iron ore, black copper ore, and copper pyrites. At the 128-fathom level there was granular quartz, slate, zincblende, copper pyrites. * Phillips and Darlington. t Op. Bit. " Records of Mining and Metallurgy," 1857. THE ABANDONED MINES. 247 At the 92-fathoni level there was a branch bearing E. 20 deg. N. about 2 feet wide and underlying S. 10 deg. to 20 deg. It contained quartz, slate, and copper pyrites. Another at the same level is 4 inches wide, and underlies S. 50 deg. to 60 deg., and consists of quartz, slate, and some copper and iron pyrites. Middle Lode.— B. 30 deg. N. Lode vertical, and quartzose. Varies in width from 2 to 3 feet. Michell's Lode.— E. 25 deg. N. Underlies S. 8 deg. to 20 deg., is 4 or 6 inches in width, and consists of quartz and slate. A branch of Michell's lode bears B. 20 deg. N., and underlies S. 6 deg. to 20 deg. It is 3 inches in width and consists of quartz, slate, and copper pyrites. Mundic or Buzsas Lode, — E. 25 deg. N. Varies in width from a few inches to 4 feet. Underlies N. 12 deg. to 30 deg. Contains copper pyrites, quartz, and slate to 148-fathom level. Bawden's South Lode. — E. and "W. Underlies S. 10 deg. to 24 deg. It is 3 inches to 3 feet in width. At the 148-fathom level it is composed of quartz, copper, and iron pyrites. Ba^cde«'s^'orfh Lode.— E.22deg. N. Underlies S. 17 deg. to 30 deg. It is 1-J to 3 feet in width. It contains copper pyrites and quartz. Nicholls' Branch.— K and W. Underlies S. 12 deg. to 30 deg., and varies from 1 to 3 feet in width. Contains copper pyrites and quartz at 98- fathom level. Polkinhorne's Lode. — E. 15 deg. S. Underlies N 14 deg. to 25 deg. It is 2 feet in width and consists of quartz, slate, and schorl at 92-fathom level. A Branch of Polkinhorne's Lode bears E. 20 deg. N. and underlies S. 16 deg. to 30 deg. It consists of quartz, slate, and schorl rock. Gellard's North Lode.— B. 28 deg. N. Varies from 1 to 4 feet in width and underlies S. 16 deg. to 22 deg. from the 46 to the 54-fathora level. It contains quartz, felspar, black copper, and copper pyrites. Gellard's South Lode.— IS. 20 deg. N. at the 46-fathom level. The lode underlies S. 16 deg. to 28 deg. and varies in width from 1-| to 2 feet. It contains copper pyrites, black copper, quartz, and slate. Mellet's Lode.— E. 30 deg. N. Underlies N. 10 deg. to S. 20 deg., and varies in width from 1 to 3 feet. Consists of quartz, slate, and copper pyrites. Great South Lode.— E. 30 deg. N. (in the Ale and Cakes part). From the 163 to the 213-fathom level the underlie is N. 16 deg. to N. 40 deg. It varies in width from a few inches to 8 feet, and consists of quartz, copper pyrites, barytes, &e. The ore shoots pitch eastwards, (Henwood.) Thomas has recorded a few particulars regarding the numerous lodes of the United Mines, but has called the lodes by different names from those which Henwood gives them. Between 1815 and 1856, 304,528 tons of ore containing 22,681 tons of copper were sold by public auction,* (See Consolidated Mines.) Wheal Unity. (Figs, 45 and 46.)— Wheal Vnity Lode.- Copper. Underlie N. 25 deg. The lode was worked in Wheal Gorland. North Lode. — Copper. Underlies N. 27 deg. Branches ofE from Unity lode and then rejoins it. South Lode.— Copper. Underlies N. 10 deg,' Francis Lode. — Copper. Underlies S, 15 deg. Wheal Solid Lode.— Tin. Underlies S, 10 deg. Frances and Wheal Solid lode unite in depth, Barrett's Lode.— Copper. Underlies S. 10 deg. Cain's North Lode.— Copper and tin. Underlies N. 30 deg. Cain's South Lode. — Copper. Underlies N. 10 deg. Trefusis Lode.— Tin and copper. Underlies N, 13, This lode is the most southerly in the sett. North of it is Blarney's Lode, which consists largely of elvan in which tin ore occurs. It underlies N, 10 deg, Peter's Lode.— Copper. Underlies N. 23 deg, (Thomas.) Phillips and Darlington, " Records of Mining and Metallurgy," 1857. 248 'I HE MINES. 108,698 tons of ore containing 8,836 tons of copper were sold by- public auction from Wheal Unity and Poldice between 1815 and 1849.* Wheax Unity Wood.— Pits an Vollar Lode.— E. 30 deg. N. From 30 to 80-fatliom level, the lode underlies N. 16 deg. to N. 30 deg., and varies in width from -I to 3 feet. It consists of quartz, chlorite, fluorspar, iron and copper pyrites. Little Ore Lode. -E. 30 deg.; N. Underlies N. 30 deg. to 38 deg., and is about 6 inches wide. It consists of quartz and slaty clay. Fig. 45. — KiUifreth. Unity Vood. SCALE -JatfLOms lOO ZOO Fig. 46.— Ffsi Polddce. Unity Wood. W. 10 '■.■» ^^ Longitudinal Section. Trefusis Lode.— E 25 deg. N. Underlies N. 8 deg. to 24 deg. From the 26 to 62-fathom level It varies in width from 1| to 8 feet, and con- sists of quartz, copper pyrites, chlorite, and slaty clay with fluorspar and iron pyrites. Great Elvan Lode.—'E. 30 deg. N. Underlies N. 45 deg. to 50 deg. It is 4 fathoms in width, and contains large quantities of tin sprinkled through it. Trestrail's Elvan.— ^. 30 deg. N. Underlies N. 10 deg. and varies in width from 1 foot to 2 fathoms. It is a fine-grained schorl rock with felspar. There were large quantities of tin above a slide. (Henwood.) * Phillips and Darlington, " Records of Mining and Metallurgy," 1857. THE ABANDONED MINES. 249 Between 1827 and 1842, 32,756 tons of ore containing 2,465 tons of copper were sold by public auction.* Wheal Uny.— The Great Plat Lode strikes E. 22 deg. N., but west- wards tho strike is E. 37 deg. N. The general underlie is 44 deg. The lode is wrought for a distance of 300 fathoms in the direction of strike. It lies very near the junction of the granite and klllas but is mainly en- closed in granite.! The lode from the 190 to the 200-fathom level is practically vertical at Hind's shaft. The average width of the lode is 10 feet, but it is as narrow as 4 feet in some places, as at the 180-fathom level on the east of the Engine shaft. It contains 56 to 70 lbs. of black tin per ton of ore, the percentage of black tin diminishing where the lode is wide. The shoots of tin pitch eastwards. Hind's shaft is sunk to the 214-fathom level. King's shaft is sunk to the 160-fathom level. At the 190-fathom level several tons of rich copper pyrites were broken in the lode in 1884.^ Between 1826 and 1856, 755 tons of ore containing 39 tons of copper were sold by auction. § Wheai, Vibgin.— f^ieol Virgin Lode — Copper. Underlies N. 16 deg. TerrUl'B Lode.— Copper, Underlies S. 13 deg. Cross Cut Lode,— Copper. Underlies S. 13 deg. Tregonning's Lode. — Copper. Underlies S. 13 deg. South Lode.— Copper. Underlies N. 15 deg. Between Tregonning's and South lode there is a tin lode underlying N. 50 deg. There is elvan on the south wall and killas on the north wall. North of the South lode is a copper lode underlying N. 10 deg. (Thomas.) Between 1841 and 1847, 22,974 tons of ore containing 1,656 tons of copper were sold by !Hiction.{| Fig, 47, - Cfi£AT WHEAL VOR ^a tenons smowino ^»oxim i ty op sHAFta to i.ooca) Wheal Voh. (Figs. 47 to 51.)— The Metal Lode bears E. 10 deg. to 15 deg. N., and underlies 10 deg. to 25 deg. N. Wood-tin was found in the lode about the year 1867 at 180 fathoms from surface, on the west of the Metal shaft. About 1873, similar ore was found 80 fathoms • Phillips and Darlington, " Records of Mining and Metallurev." 1857 + Fosterjp. 640. ^' X K. H. 'Thomas, " Some Observations on the Great Flat Lode in W^heal Uny " Sep. Corn. Poly. Soo., 1886, p. 184. § Phillips and Darlington, " Records of Mining and Metallurgy," 1857. II Op. cit. 2.50 THE MINES. further east in the same lode, which is about 2 feet in width.. At this level the lode widened out rather suddenly, while the veinstone became more chloritic, less quartzose, and contained a large amount of tin, either in separate segregations or mixed with the veinstone. "Wood-tin occurs either in scattered grains, in small isolated masses, or in veins of varying and inconsiderable width, sometimes as thin Fig. 48. , GREAT WHEAL VOH ( S£CTtOftS SHOWING PROXIMITY Of SMARTS TO i.ODgS.) as paper, but it is always in a fibrous condition. Some of the masses exhibit concentric structure, of clove brown and brownish yellow laminae, but the structure is radiately crystalline. These aggregations of divergent crystals sometimes enclose kernels of ordinary tin ore that radiate from minute cavities.* At the 162-fathom level, wood-tin occurred in large kidney-shaped masses associated with crystalline cassiterite and quartz in part of the Wheal Fig. Ad.—Sithney Wheal Metal. Metal lode. The lode was 6 feet in width, and worth £600 per cubic fathom. The wood-tin occurred intermixed with ordinary crystalline tin- * W. H. Argall, " On the Occurrence of Wood-tin in the Wheal Metal Xode at Wheal Vor." Joitm. Boy. Inst. Corrmall, vol. iv., 1873, p. 255. THE ABANDONED MINES. 251 stone, together with much chlorite, chalcedony, dolomite, felspar, and pyrites.* Charles Thomas, writing in 1867, remarks that for some time the returns of tin ore were 200 tons a month, yielding 150 tons of fine tin. In many Fig. 50. GB EAT /lo N CI ruOl N A L. I j^or MAIN WHEAL von sketch) 235 f^LaiA places the lode was worth £1,000 a cubic fathom. It was rich to the 300- fathom level, and then became poor.! Before 1870, it is stated to hare yielded over £3,000,000 worth of tin and copper.:(: Fig. 51.— PewAaJe Wheal 7or. Henwood records the following particulars of the lodes of Great Wheal Vor: — * J. H. Collins, " Cornish Tin Stones and Capels," Min. Mag., vol. iv., 1882, •f Mining Fields of the West, 1867, p. 24. X K. Hancock, "On the Mineral Deposits of the Old Wheal Vor." Bov Com Poly. Soc., 1870, p. 101. * ' 252 'IHE MINES. The Main Lode, in the Oarleen or eastern part of the mine, bears R. 28 deg. N., and underlies N. 10 deg. to 25 deg. It varies in width from a few inches to IJ feet, and consists of chlorite, quartz, slate, cassiterite, and iron pyrites at the 55-fathom level. At the 125-fathotn level there was some arsenical pyrites with chlorite and cassiterite. The main lode in the Wheal Vor and Wheal Vrea (or eastern) part varies in width from 3^ feet to 20 feet, being widest at the 140-(athoni level. At the 85-fathom level there was copper pyrites and black copper ore. At the 121-fathom level the quartzose slate was traversed by strings of cassiterite. At the 131- fathom level there is a bed of quartzose slate extending 10 feet from the lode on the north side. At the_ 140-fathom level a similar bed extends to 20 feet from the lode. The lode consists of quartzose slate, cassiterite, quartz strings, and drusy quartz cavities lined with crystals. At the 240- f athom level there was cassiterite, iron pyrites, and felspar. It was worked to the 285-fathom level at Bounder's shaft. Wheal Sosen Lode. — Bears E. 24. deg. N., and underlies N. 20 deg. to 36 deg. At the 40-tathom level there was earthy brown ore and quantities of cas- siterite. The lode at the 100-fathom level consists of quartz, chlorite, and slate. At the 70-fathoni level there is a bed of quartzose slate traversed by quartz veins. Carne* states that there are two elvans in the eastern part of the mine. The largest is on the north, and is 24 feet wide, bears N.E. and S.W., and underlies N. .56 deg. The lode was about 2 feet wide inkillas, but in elvan was 5 feet, and in some places was so broken up into branches as to make the whole elvan for 20 feet worth working. Henwoodf states that there are two elvans. The northern one is 2 feet wide, and underlies 20 deg. to 30 deg. N. The southern is 8 fathoms in width, and underlies 40 deg. to 50 deg. N. The lode was productive in both elvans. In the southern one the tin ore occurred in a somewhat sprinkled manne* In elvan the tin ore occurred either in unconnected masses and irregular bodies or as short veins. " Floors " containing tin ore strike off in a nearly horizontal direc- tion into the killas, and are similar in composition to the lode. The fact that the lodes only yielded tin ore while in killas and became poor on entering the granite is a well-known peculiarity of the district. Between 1821 and 1842, 4,296 tons of ore containing 330 tons of copper were sold by public auction.if A company has recently been promoted to re- work the mine in view of the demand for tin. Wendeon United Minbs.— The Engine Lode.— At Engine shaft it is in granite at the 35-fathom level. It varies in width, down to that level, from 2i feet to 4 feet. At the 60-fathom level the lode is 4 feet to 6 feet wide. The lode was a fair one, and good bunches of tin ore were found at the 35-fathom level. , ^, Flanders Lode.- Width of lode is 1 foot to 3 feet. The granite was encountered below the 86-fathom level. A poor to fair tin lode. Liddecoat's Lode.— This crosses the Flanders lode at 10 fathoms west of Hill's shaft. Varies in width from 3 feet to 4 feet. The veinstone is chloritie. The junction of Flanders and Liddecoat's lode was productive of tin ore. LMd<-coat's North Part.-At the 70-fathom level it varies in width from U feet to 2 feet and contains fair tin ore. ,j. „, .. ■^i.v. Rtehard-s Lode.- At the 20-fathom level it is 2 feet to 3feet in width. Whml Fat Lode.-At the 35-fathom level the lode is 4 feet to 5 feet in width, with low-grade tin ore- Wkst Conduerow. (Fig. 52.)-There are six lodes in this sett.^ Sh'ose sTaft °s on k lo^de which at adit level yielded tin and copper ores In width the lode is from 1 foot to 5 feet. li 22 faThoms south of Kellivose lode there is another, varying in width from 6 inches to 18 inches, which yields tin ore. At 60 fathoms further south there is a lode yielding tin ore. it 45 fathoms south of the last there is another known as the Bounty North Lode. * " On Elvan Courses." " Tr. B. G.S. Corn.. 1818, vol. i., p. 103. I Sps and Darlington. " Records of Mining and Metalluvgy," 1857. THE ABANDONED MINKS. 253 At 14 fathoms farther south Is the Bounty Lode, varying in width from 1 foot to 2 feet. This lode has a good gossan, and yielded tin ore. The KelUuose Lode.— Bearing B. 35 deg. N., and underlies N. 27 deg. The lode has a good gossan and consists of quartz and killas with tin and copper ore. At the adit level alternations of slate,, clay, and granite were met with near the shaft (Park shaft). At Purser's shaft the lode yielded tin Fig. 5'2.-^West Condurrow. and copper and there was much flucan. At the 12-fathom level in the same shaft it is 3 feet to 3| feet wide, and consists of quartz, prian, and killas, with bunches of copper and tin ore. At the 24-fathom level the lodestuff is quartz and peach in granite. North Lode. — Greenstone was met with when sinking operations were commenced on this lode.* West Wheai, Damsel. — Tremayne's Lode has been worked upon down to the ISMath^m level. Thirty fathoms north of Tremayne's lode is the Wheal Damsel North Lode, which is about 1^ feet wide and yielded copper ores. The New North Lode is opened up as far as the 90-fathom level. Darlington's Lode intersects Tremayne's lode in depth, producing tin ore in the deep levels. 6,392 tons of ore containing 378 tons of copper were sold by public auction between 1852 and 1856.t West Dolcoath. —The Main Lode is situated below an elvan. At adit level the width of the lode is about 2 feet. The veinstone consists of quartz, chlorite, flucan with mundic, and black and yellow copper ores. It is supposed to be a continuation of the Dolcoath main lode. West Feanoes.— Smith's, or the New, shaft is sunk on the Great Flat Lode to the 174-fathom level. The lode consists of peach, quartz, and tin ore. Near a cross-course the lode is large, and contains a little tin ore throughout. Poster states that it has similar characteristics to those of the same lode in West Basset Mine, except that the leader, instead of being a mere joint, is a quartz vein 2 or more feet in width. The stan- niferous part of the lode is under the leader, and the underlie of the lode in this mine is from 40 deg. to 53 deg. south, varying within these limits in the short distance of 80 fathoms.:]: West Wheal Jane.— Worked to the 70-fathom level at Clemow's shaft. West Wheal Sbton.— There are several lodes, but they are mainlv branches of the main lode. The lodes contained blende and copper to below the lOO-fathom level, and yielded tin ore below that horizon Old North or Main Lode.- Underlie N. 30 deg. The lode is associated with an elvan, and appears to have been richest in its immediate vicinity It varies in width from 1^ feet to 3 feet in the upper levels, where it was ntrf; particularly rich in copper ore. Below the 120-fathom level the lode is 3 feet to 5 feet or even 10 feet in width, and yielded both tin and copper * Information Obtained from the Pendarves Estate Office through the cour fcesy of Mr. Vercoe. t Phillips and Darlington. '' Records of Mining and Metallurgy " 1867 J Foster. 254 THE MINES. ore. It was rich at the 226-fathom level, at which place it is only 5 feet distant from elvan. The ore ground as a whole pitches west with the junction of the lode and elvan, but there was another good ore bunch near Mitchell's shaft, where the veinstone was a dark chlorite with'quartz and fluorspar. At the 275-fathom level the lode was productive in tin ore. la some levels, particularly in the higher horizons, it yielded blende and mundic. North Part. — The old North lode branched at the western Engine shaft, where the north part was 4 feet wide, and at the 20-fathom level con- sisted of a soft killas veinstone with blende and mundic. At the 110- fathom level the lode is 2 feet to 3 feet wide. South Part. — At the 112-fathom level the lode is 6 feet wide in some places. North Lode. — This lode is a branch of the old North lode at the 70-fathom level, near Harvey's shaft, on the underlie side of the lode, 2 feet wide with copper ore. South Lode. — This is a branch of the old North lode. Prom the 100- fathom to the 130-fathom level the lode is 4 feet to 7 feet in width, and contains tin and copper with flucan, quartz, and mundic. New South Lode.— Nearly vertical, but has a slight northerly underlie. Between 1848 and 1856, 14,766 tons of ore containing 989 tons of copper were sold by public auction.* West Wheai. Towan. — The lead lode as seen in the cliff at adit level is 2 feet wide. It yielded lead and tin ore with mundic. Hampton's Lode.—F.rom the 25-fathom to the 43-fathom level the lode is 1 foot 3 inches wide, and contains a little tin ore. Middleworks' Lode.— Underlies south 20 deg., and is about 2^ feet wide. Goad's iode.— This lode branches offl downwards from the Middleworks' lode at an angle of about 10 d^. S. West Wheal Vibgin.— Wfceal Tirgin Lode.— Copper. Underlies N. 15 deg. It is intersected by Wheal Maid Lode. (Thomas.) Carnej states that the Great Caple Lode is called a tin lode, and is traversed by Tregonnitig's Copper Lode, but that in depth the lode was poor in tin ore and became copper bearing. The Main Lode is 9 feet wide in some places, but it is on an average about 3 feet. In Tiddy's cross-course (Consolidated Mines) vitreous copper ore and red oxide of copper with native copper were found in a few rich bunches.^ Miscellaneous Diagrammatic Sections of Mines. Fig. 53. — Wkeal Christopher. * " PhUlips and Darlington. " Records of Mining and Metallurgy," 1857. ■ .96. [en wood, p. 92. + p. 96. THE ABANDONED MINES. 2.'55 Fig. 64. — Cli^ Down Mine. SCALE -FathjOTTVS o loo zoo Fig. 55. — Gli§ Down Mine. Section in Valley. N. ll Fig. 56. — Clyjahand Wentiuorth. ,•0 256 THE MINES. Fig. 57.— Wheal Wcntwortk. Fig. 58.— -Medlyn Moor Mine. IT -S ■ »\ / S -1 / ^^ <» / D ^ aST^Lexell 5 "^ ^ i Fig. 59. — Nancekuke Mines ( Wheal Clarence). i i SCALE — Faihorrvs So lOO ISO Longitudinal Section of Lead Lode, showing Cross Sections of Lodes Intersected by it. P'iG. 60.— North Pool Mine. Fig. G}.—NoHh Wheal Vor. BOr^Lmd, THE ABANDONED MINES. 257 Fig. 62. — Polrose Mine. Fig. 63. — South Lmell Mine. N. ^, 01 SCAUE SO FaihxirTLS PLAN OF BESTRONCUET CREEK MINE ' ■-'^ ' ' Fig. 64. Wcsternj JSanJc of Taylors Short Strippvng IiB-vels 1 "0 u <0 '— Deep Levels ShxdLaw Levels Deepjiev^ SECTION OF RESTRONCUET CREEK MINE ^ Taylors Charles W. Shaft, Shaft aJboutf 6' OvUJo ^□C Rot^ 258 CHAPTER XVI [I. MINING ECONOMICS. Inteoductory Eemaeks. This area embraces the most important mining district in Corn- wall, and although in late years mining has declined in the region owing to foreign competition and the consequent deprecia- tion in value of the ores for which the area is so celebrated, it is stili justly famous for its ancient historical connections, its mineral wealth, and the geological problems which it presents.. The abundance of the metalliferous minerals encountered in mining operations early attracted the attention of man, and in more recent times the variety of its mineral products has afforded a fascinating field for study to observers in the various branches of the science. As a field for economic enterprise it once held a premier position, and could the history of the financial side of this mining area be adequately written, it would form a voluminous record of facts and figures connected- with the dealings of specu- lators of slight scientific interest. Some of the rich repositories of tin and copper ore have yielded immense fortunes to their lessees and to the lords of the soil. This is now changed, and there remains awildernessof mine burrows, enginehouses.and smoke stacks, spoiling the appearance of the country, but bearing mute witness to the prosperous mining days of the past. Since 1865 the decline was fluctuating but gradual, as first copper and then tin suffered from outside competition. It should, however, be remembered that with mining at greater and greater depths the expenses of working (pumping, hauliiig, &c.) increased to an extent suflSciently great to seriously affect the industry, and with many of the richest ore bodies already worked out, the condition of the mines contributed in no small degree to the final collapse. The disastrous drop in the price of tin about the middle of the seventies saw the closing down of many mines which had the price been maintained might yet be working. The value of tin ore at the present time is so high that as time goes on it may be confidently expected to once more raise the status of Cornish mining. The only barrier to immediate progress in this direction appears to be the difficulties which will have to be encountered in opening up the old sites already so extensively explored, since the ramifications of levels and working places are such as to present a diflBcult problem in the unwatering of the submerged mines, many of which are connected underground by a vast system of drivages. There is brightness, however, in the reflection that a few of the mines have survived the period of depression, and one at least has worked without cessation for over 150 years, and still holds a high place in the tin-mining world, being the largest, deepest,and mostproductive tin mine in existence. HISTORY OF THE MINING INDUSTRY. 259 In the preceding pages it has been found necessary to make constant use of published works on the district, since so few of the mines are now accessible. Among the more important publica- tions those of De la Beohe and Henwood have been of great service. In later times the names of Collins and Le Neve Foster are intimately connected with Cornish mining. The ancient History of Cornwall has been written again and again, but the leading works are those of Carew, Camden, Borlase, Hawkins, De la Beche, and Hunt. In this memoir an attempt has been made to deal with the various points of interest to miners in the region. In the methodical treatment which is adopted there is no claim to originality, but some of the old problems have been revived and viewed in a new aspect. The alluvial, or stream tin-deposits, which have been so well described by Henwood, and others, are now exhausted, but their origin and mode of occurrence have beec discussed by Mr. HiU in Part I, of this memoir. The tables, which give the detailed output for individual mines from 1815 onwards, should be regarded as a general measure of the relative importance of the mines, and not as being strictly accu- rate, since in former days the records were not preserved so carefully as they have been latterly. In conclusion, it should be mentioned that assistance has been freely given by Mine Captains and others, who have afforded every facility for observations underground. In Cornwall the survey is indebted for much information to the Dnchy OflBce, the Estate Offices of Tehidy and Pendarves, and to Messrs. Henderson & Son, of Truro, and others, where mine plans and records have been placed at our disposal. In London similar facilities have been afforded at the Home Office and the Office of Woods and Forests. The scales to which the mine plans are drawn vary from 4, 6, 8, 10, 12 to 20 fathoms to the inch, of which 8 fathoms to the inch is the commonest. < History of the Mining Industry. There are good reasons for the belief that the Phcenicians exported tin from Cornwall several centuries before the Christian era. Borlase states that the Eomans and Greeks also " studiously insinuated themselves into the same traffic." Until the middle of the 13th century Cornwall was the most important source of tin, but the ore was obtained from alluvial deposits and the backs of the lodes, the latter of which were worked away, leaviug open cuts called " coffins " or " goffins." The works of Pryce and Borlase give excellent accounts of the early history of mining, and are of particular interest as dealing with the time about which the steam engine was introduced, and it may be said that it is from this period that the working of tin and copper ores became an important national industry. The main obstacle in early times to the progress of deep mining in Cornwall was the inability of the miners to cope with the subter- ranean watet which flooded the excavations. Before the intro- s2 260 MINING ECONOMICS, duction of the steam engine the water was raised in kibbles by means of a whim worked by horses. The Eag and Chain pump* was another device for lifting water. The old " Fire Engine " is the first steam pump, and, as modified by Trevithick, was a great advance on earlier appliances. The most important invention was made by Newcomen, whose Cornish pumping engine, with Watt's modification, was destined to assist mining operations enormously. Prior to this the mines could not be worked to great depth, and the old Pool Mine, for instance, was only 55 fathoms in depth at the time Borlase wrote, while the deep workings of Bullen Garden Mine were in 1778 only about 90 fathoms from surface. As Borlase quaintly remarks, it was necessary "that to obviate the inconvenience (of water) the captain should be a kind of engineer." The introduction of gunpowder in the Cornish mines about the beginning of the 18th century was another important advance in mining work. Pryce gives an interesting account of the state of copper mining at the period of its inception, and says that the people were ignorant alike of its value and the modes of dressing it. Thus, he states in ] 778 that " though the richness of our copper works is not a late discovery, yet it is not a hundred years that the knowledge of working them to good effect hath been under- stood." About the year 1 700, some Bristol merchants, by their interest in the copper mines, stimulated the industry, while about 1730 large quantities of copper ore were raised from Eoskear, Pool, and other mines, in spite of the prevailing local ignorance of the value of the ores. From 1726 onwards the yearly output is tabulated in the statistical table, and a perusal of those tables will show that the output increased fairly steadily year by year until past the middle of the 19th century, when the decline commenced. The richest and most accessible ores were rapidly being exhausted, and the prices for copper ore had fallen off owing to outside competition. With increasing depth, many of the mines yielded tin ore in such quantity as to warrant their exploitation for tin instead of copper, so that many mines once yielding copper ore exclusively now yielded tin ore in abundance, and transferred the attention of investors to tin mining. (Fig. 64.) From 1750 to 1800 the tin mines were yielding a tolerably uniform annual amount of black tin, but early in the last century they commenced to increase their output, and there was a steady rise in the annual returns of black tin up to the sixties. From the seventies to the present time, although the output has been fairly well maintained, it gradually decreased, while in the last ten years it has fallen off considerably. Foreign competition so lowered the price of tin ore that many mines failed in the seventies, For several years past the price of black tin has been increasing, and there is every reason, should the record high figure now * Invented by Captain Safory, of Exeter. Borlase, Nat. Hist, Com., 1768, p. 170. HISTORY OF THE MINING INDUSTRY. 261 reached be maintained, for looking forward to the opening up of many of the old mines. The statistics published by the Home Office sines 1881, and those contained in the Memoirs of the Geological Survey, show that the number of working mines has suffered a great decrease in the last fifty years. The following tabular statement gives the number of mines in this district which at the various dates were yielding tin or copper ores. Many of the mines were, of course, yielding both ores: — Mines yielding Tin ore Copper. 1858 - - - - 50 70 1863 - .... 56 90 1868 - - .... 48 52 1873 - - - - 74 40 1878 - .... 36 30 1883 ... - 42 20 1888 .... - 32 10 1893 - - - - 25 6 1868 16 3 1903 - - 15 5 The amount of copper ore produced from the mines in the Camborne area in late years is only a few tons per annum, and is scarcely worth consideration, some of the ore being obtained while prospecting old sites. The following tabular statement of the outputs of three promi- nent mines which are still working is of peculiar interest, as it traces the evolution of mining from the upper levels to the deeper- seated zones, accompanied by the substitution of tin for copper : — DOLOOATH. Wheal Basset. Bast Pool. .Is. I;2g5 M • • ■S^ M . s .2 f,- ■— 1 CD ^ . Year Copp Ore Metal Coppi 3^ as 8"^ 3a is as 1° 3l M^ T. Cvrts.lT. Cwts. T. Cwts. r. Cwts. T. Cwts. r. Cwta- r. Cwta. T. CwtS' T. Cwts. 1845 3,504 0,233 14 • ■• <•• 929 73 5 1846 2,156 138 12 ... • •■ • •■ 633 43 15 1847 2,057 135 8 • *• 608 34 2 1848 1,254 95 2 ■ •• 1,088^ 64 16 1849 1,028 77 10 ■ ■■ • •■ 1,136 66 17 1850 1,115 72 11 • >* ... 1,422 70 2 1851 801 55 8 3,442 0487 17 , , 2,050 0106 16 1852 832 42 14 5,966 0503 13 21 1,740 86 10 20 16 1853 1,040 51 17 360 7,207 0'608 2 31 2,157 98 11 22 1854 992 45 10 363 10 8,378 0646 9 46 2,034 99 4 49 11 1855 711 28 6 352 7 7,713 0680 12 25 11 2,287 0134 13 38 8 1856 617 24 8 416 13 7,600 0594 18 20 2,821 0178 14 49 13 1857 566 25 18 544 S,183 ... 32 3 2,535 0138 19 51 9 1858 593 34 8 635 10 4,754 414 4 45 4 1,300 66 15 36 7 1859 757 38 15 723 18 4,258 365 13 42 9 1,280 54 15 44 2 1860 712 28 14 805 1 3,894 0300 14 60 1 1,896 93 9 58 5 1861 417 18 18 864 7 2,931 0231 19 51 15 2,435 0120 6 49 15 1862 508 29 16 985 19 2,599 0211 17 48 18 2,944 0149 8 97 8 1863 636 39 16 1,026 9 1,998 0154 77 16 3,264 0155 16 134 17 1864 621 39 3 1,029 18 1,726 0138 5 117 7 2,805 0126 3 136 18 1865 607 44 13 94' I 9| 2,036 183 111 158 10 2,083 93 91 25' r 1 2C2 MINING ECONOMICS. DOLCOATH. Wheal Basset. East Pool. ^ 8 . •2 s M . «.- •SS M • s . ■Mi J4 . ^ 1^ a &<5 3a ai o §0 go go r. owts.l r. owts. r. Owts. r. Owts.l r. Owts.l r. Owts. T. Owts.l T. OwtB. T. Owts.- 1866 688 52 1 919 7 2,108 174 9167 3 1,808 97 9 379 13 1867 267 15 18 847 18 1,700 132 7292 13 1,582 76 14 321 8 1868 153 12 11 984 4 1,539 115 12264 17 1,753 79 15 364 14 1869 153 10 11 813 8 1,572 130 8313 4 1,641 85 325 8 1870 57 3 17 1,034 15 1,341 106 12353 9 1,854 90 14 S51 17 1871 86 5 11 1,169 18 442 35 2335 2 2,430 125 12 109 19 1872 46 3 3 1,284 16 528 38 8 255 7 2,520 138 8 90 14 1873 16 1 1 1,045 6 488 67 1 286 6 1,933 95 17 384 1 1874 75 5 16 1,120 19 396 41 8 310 18 1,920 95 9 419 18 1875 4 > t ... 1,241 10 714 62 17 248 1,823 85 12 571 5 1876 41 2 8 1,263 5 759 67 13 147 6 1,806 90 18 364 1 1877 30 6 2 1 1,404 13 448 9 40 10 164 8 1,527 90 12 392 1878 13 11 12 1,539 2 227 18 23 8 208 6 2,564 11 151 .4 489 15 1879 4 4 3 1,780 8 99 2 8 23 2,362 7 112 10 864 9 1880 *.. ... 1,737 14 29 12 2 7 15 1,350 3 75 13 1,268 4 1881 ... ... 1,816 5 ... «• • 8 4 903 18 45 15 1,317 14 1882 ... 1,976 3 60 9 380 16 19 1 1,536 2 1883 1,875 12 ■ •> 173 10 48 2 10 1,402 1884 ... 2,423 3 ... ... 267 3 376 *. . 1,573 1885 ... ... ::,555 3 . t . 395 229 .*. 1,512 1886 .. . ... 2,383 • *. i79 4 ..♦ 1,440 1887 ... ... 2,366 1 1. 370 ... 1,233 1888 ... ... 2,239 ... t •* 416 9 15 1,179 1889 "3 2,125 ... 386 10 26 396 312 ... 1,105 1890 2,023 10 "3 * • • 995 1891 ... ... 2,131 12 ... ..■ 402 451 1,070 17 1892 ... ' 2,535 • .* 458 15 • .. 1,004 1893 2,421 9 432 10 729 938 7 1894 2,126 ... 470 4 730 ... 940 1895 1,766 ... *• • 536 4 373 877 189€ ... 2,039 7 ... ,,, 554 C ... ... 529 6 1897 2,095 C ... • *■ 539 C 64 ... 309 189e ... ... 2,302 1 .• . 356 C 16 770 189£ 1 4 c ... 2,078 If ! '.'.'. ... 268 C 22 ... 816 190( ) ... ... 2,004 J t ... • •> 523 C ... 739 1901 ... ... 2,035 11 ... ... 575 C 10 ... 699 190S J 1,828 i ) ... 794 C 31 663 190r i '.'.'. 1,739 r r 11 ( ) ... 728 C 27 ... 706 Q 1904 \ ... 1,705 4 t ... 613 C 863 ... 661 190E > 1,696 1( •) ... ... 768 I 70 ... 585 10 Notes on Tin-Ore Dressing in the Camboene Area. Older Methods.— Writing over a century and a half before Borlase, Carew,*inhis quaintly-worded description of Cornwall, gives a very good insight into the state of mining at that time. ^ Among other subjects the. dressing of ore is dealt with, and from 0»rew s account the methods in use in his time were very simple. The ore was first broken with hammers " and then carried to a stamping mill, where three, and in some places sfes, great logs of timber bound at the ends with * Survey of CornivaU, 1602.- TIN-ORE DRESSING. 263 iron, and lifted up and down by a wheel driven with water, do break it smaller. If the stones be over moist they are dried by the fire in an iron cradle or grate. From the stamping mill it passeth to the crazing mill, ■which between two grinding stones, turned also by a water wheel, bruiseth the same to a fine sand ; howbeit of late times they mostly use wet stampers and so have no need of crazing mills for their best stuff but only for the crust of their tails."* After the stuff was stamped it was spread on a sloping green turf and " softly tossed " while a current of water flowed through it and washed away the waste. The processes of tin ore dressing about the middle of the 18th century have been well described by Borlase,| and later by Pryce,|: who utilised the same diagram as Borlase to illustrate his description. Borlase re- marks that the ore was passed under stamps weighing 140 lbs. apiece. The grating was a plate of metal 1 foot square and ^ in. in thickness, and was " full of small holes punched in it about the bigness ol a moderate pin." The pulp from the stamps passed through three pits in succession, making a settlement in each according to density. The material from the first or fore-pit was the richest. The stuff from the other two pits was known as the " slimes." The overflow from the pits went to waste. The Jontents of the fore-pit were dug out and treated in a huddle 7 feet long, 3 feet wide, and 2 feet deep. The tin-dresser stood in this pit and spread the material on a plane sloping surface at the head of the buddle ; the stuff being spread in the form of a series of small ridges parallel with the direction of a current of water which passed over the plane from a launder, or trough. In this way the slime was washed out of the stuff, and the whole of the material fell over into the pit in which the tin-dresser stood, and there settled in three grades, according to quality ; that nearest the head being the purest. The head was put into a kieve (or tub) and washed by stirring (tozing or tossing) for a quarter of an hour, so that the light waste rose to the top, which after settling was skimmed off. The rich part at the bottom of the kieve had to be rebuddled, and again put in kieves. Finally, it was " packed " by smartly tapping the kieve with a hammer, so as to shake the heaviest minerals to the bottom. The skim- mings were saved and treated with other products. The two othet classes of stuff from the first buddling operation underwent a similar treatment. The slimes which were deposited in the second and third pits just below the stamps were treated In a different way from that in which the coarse material from the first or fore-pit was treated. The slimes were con- ducted to a pednan (or circular pit) where they were stirred, and made gradually to overflow into a long pit divided into two parts. The part near the pednan was smaller than that further away, which was 10 feet long, 3 feet wide, and 8 inches deep, and separated from the smaller by a wooden partition. The material from the pednan passed successively over into the two parts of the long pit. In the larger part of th ' •fine tin." TIN-ORE DRESSING. 2?3 It "all passes through a sieve of 120-mesh. The tailings from the Prue vanners are a reddish brown powder, consisting of grains of quartz with many dusty ferruginous inclusions ; and very fine particles of tourmaline, quartz, chlorite, and ferruginous minerals. Cassiterite is present only in small quantity ('SS per cent.), but after a series of operations it is separated and ultimately sold as " slime " tin. The material is very fine, nearly all passing sieve of 120-mesh. The use of the upwa;rd current separator for treating the calcined concentrates from the vanners appears to be most important and could not be dispensed with. From a general standpoint, the most striking feature in the micro- scopical diagrams of the various products is the want of uniformity in the sizes of the grains, which, except in a few cases, points to a defect in the usual methods employed. If the_ tin grains were themselves of uniform size this objection would not be of much importance, but a large pro- portion of the tin occurs in very minute particles, aiid it is a rule in all dressing appliances to separate this " slime " from the coarser-gr^-ined " crop " tin as soon as possible, and subject each to a separate series of operations. No convenient method has yet been discovered for accu- rately sizing the grains, so that a certain amount of loss is inevitable, but a saving on the present system might be made by the judicious employ- ment of upward current separators in which the minerals could be classi- fied according to the relative speeds with which they fall through water. Each product might then be treated by itself ; the " crop " on Frue vanners or Buss tables, and the slimes on Luhrig vanners or on revolving tables. A fine degree of stamping is essential, but the production of an excessive amount of slime might be obviated by the use of wire screens, so that the pulp could pass away from the stamps as soon as possible after crushing. - A few samples were obtained from the large tin stream works near Reskudinnick, called Kieve Mill. The waste material from the dressing floors of the mines is discharged into the Eed River, and successively treated by a, number of stream work companies situated at various points along the stream. The material under examination has therefore already been treated by stream works before it arrived at Kieve Mill. The river as it approaches the works is divided into two parts by a wooden partition, and arranged in such a way that the water can be made to flow through one part or the other by means of sluices. This is done- so that the amount of water passing at difEerent times of the year may be regulated to a steady flow. By means of stops, or transverse partitions in the river, the coarse particles of sand being carried along in the current are arrested and sink in the bottom of the river just above the works. The water carrying slime flows on into long pits, any one or more of which can be used or not as desired (Plate XXI.). Here the slime is allowed to settle. Fig. 6, Plate XXIII., is a sample of the sands which have settled in the river just above the works. In appearance it is a clean speckled sand containing from -f to 1-J per cent, cassiterite. Under the microscope the grains are seen to be both large and small. In testing the sizes of the grains by sieves 3 per cent, remains on SO-meah sieve, 53 per cent, on 60-mesh, 22 per cent, on 90-mesh, 7 per cent, on 120-mesh, while 15 per cent, passes a sieve of 120-mesb. The larger grains are subangular oi; rounded. Quartz occurs in large grains with many fluid cavities, and con- tain» other inclusions, such as tourmaline ; fluorspar, chlorite, and a little tourmaline and oxide of iron are also present. The large opaque minerals seen in the plate are principally quartz crowded with tourmaline needles (peach). Some of it is bright green chlorite and mica. There is_also some brown staining which appears as half-tones in the largest fragment. The dusty-looking inclusions are mainly fluid cavities in quartz. Fig. 7, Plate XXIIL, is a sample of the slime from the settling pits. Seen in bulk, the slime is a brown or reddish brown impalpable powder, and contains •5 per cent, cassiterite. Under the microscope most of the particles are extremely small. Tourmaline is plentiful, chlorite and fluorspar are also present. - Limonite and hfematite occur in particles and as staining. Most of the grains are too fine to be readily identified in the slide, and all pass through a sieve of 120-mesh. The slime is stirred up in a current of water and passed on to ragging frames, of" which there are a great number. 274 MINING ECONOMICS. (Plate XXIV.). The concentrate is settled in pits, and passed over another series of frames into settling pits, after which it is treated on revolving tables of the Bartle type. Then it proceeds to buddies. The slime tin so 'collected is similar in appearance to Pig. 5, Plate XXIII., but is even finer, and consists of an impalpable dark purplish brown powder. The grains are clean and sharply angled, of uniform size, and all pass through a sieve of 120-mesh. Cassiterite (40 per cent.) with tourmaline, much haematite, and a little fluorspar appear to be the most abundant minerals. The coarse sands which settled in the stream above the works (Fig. 6, Plate XXIII.) are washed down periodically by a strong current of water into " strips " or troughs, in which transverse wooden partitions or " stops " are fixed at intervals. The lighter sands flow out of the strips, but the heavier sink and are dug out periodically. Fig. 8, Plate XXIII., is a sample of the material which was deposited in the " strips." It is a clean dark speckled sand, consisting of quartz, chlorite, oxides of iron (limonite and heematite), tourmaline, fluorspar, and some ohalybite. There are a few grains of cassiterite (about 1 per cent.). This material is pulverised in a rotary mill and worked over on revolving frames and buddies. In this way particles of cassiterite which were locked up in grains of quartz., &c., are liberated and extracted. Tested by means of sieves it is found that 3 per cent, remains on a 30-mesh, 60 per cent, on a 60-mesh, 20 per cent, on a 90-mesh, 7 per cent, on a 120-me3h, while 10 per cent, pass through 120-mesh. A sample of the sands from the river, about | of a mile below the works at Kieve Mill, is a clean dark speckled sand, consisting of quartz with fluid cavities, and tourmaline inclusions, fluorspar, tourmaline, chlorite, a little chalybite, and some iron oxide. Cassiterite is seen in several cases iactually adhering to larger fragments of other minerals. The sample con- tains about li per cent, of tin. Tested by sieves 3 per cent, remains on 30-mesh, 70 per cent, on 60-mesh, 19 per cent, on 90-mesh, 4 per cent, on 120-mesh, while 4J per cent, pass through a sieve of 120-mesh. Mineral Statistics.* * Compiled from statistics contained in: — Tr. S.G.S. Corn., vol. i., ISIS, &c., for years 1815 to 1832 (copper only). Ch-ylls's Annual Miming Sheets (Redruth) for years 1833 to 1836 (copper only). Tr. B.G.S. Com., vol. v. (Kenwood), p. 466, for year 1838 (copper only). Geol. Sep. Corn., Devon, and Wtst Somerset (De la Beche), 1839, for year 1837 (tin only). Mining JReviem, '1839 and 1840, for tin ore in 1838 and 1839. Mem. Geol. Swrvey, vol. ii., 1848, for years 1845 to 18+7 (copper only). Records Royal Sehool of Mimes, vol. i., part iv., 1853, for years 1848 to 1852 (copper and lead from 1848 to 1852 ; tin in 1852). Mem. Oeol. Survey (Minersil Statistics), 1853 to 1881 (for all minerals, the output of zinc, mundio, arsenic, nickel and cobalt, umTjer and ochre, iron, &c., commencing in 1854 ; public ticketings, stannary returns, and inspectors' r^orts). General Report and Statistics, part iii., OBip«t, issued by the Home Office, all minerals for years from 1882 to 1904. Under the heading of Remarks the output of copper ore and copper for a stated interval prior to 1857 is obtained from the Records of Mining aAd Metallwrgy, by John Arthur Phillips and John Darlington. These figures fill in to a certain extent the lucuna in the official statistics, i.e., the years 1837 to 1844, and represent the sales at public ticketings in Cornwall. The returns prior to 1882 are approximate only, so that figures representing the total outputs of minerals for the years mentioned must be regarded as general relative measures of the actual output and not as being strictly accurate. Not only do the annual returns in the early statistical tables difier according as the returns were made by the stannaries, public ticketings, or inspectors' reports,, &c.,- but much of the ore was sold by private contract and the sales never recorded. In early years it was customary for the smelters to demand 21 cwts. to the ton, while in a number of other ways the tables are rendered inaccurate. Statistics are not obtainable for the years 1837 to 1844 (with the exception of copper in 1838 and black tin in 1837). Another point to which attention should be called is error arising from the ambiguity caused by different mines bearing the same name, and in such cases it is frequently almost impossible to determine from which mines certain annual outputs refer. Such names for instance as "Prosper," "Providence," "Virgin," " Fortune," are common names for mines. Under the heading of Remarks the figures for the period up to 1856 are those given by Phillips and Darlington. The output since 1857 is also given so as to complete the statistics furnished by them. MINERAL STATISTICS. 275 Output of Copper Ore ami Copper from 181B to 1836, cmd 1845 to 1905; and of Black Tin from 1862 to 1905. Total yield and largest Name of Mine. amount raised in one year. Bemarks. Black tin. Copper ore. Copper. Tons. Tons. Tons. Balmynlieer 350 ... • •■ Yielded between 1868 and Mine 84 ... • ■■ 1880. Baldhu - 2 ... ■ •• In 1880. Barncoose ... 206 26 In 1819, 1820, and 1821 (Phillips and Darlington). Basset, Wheal - 14,178 94,200 8,100 Prom 1815 to 1827 ; 1832 to 794 7,713 680 1836, and from 1851 to 1905. Basset, Consols «>• 330 18 Prom 1859 to 1861.'' Bassett and 2,900 ... • •■ Prom 1861 to 1875. Grylls 314 ... • ■■ Bell Tin Mine 10 ... • •• In 1874. Bellvean Mine 4 ... ... In 1879 and 1880. Bissoe Bridge - 44 ... ... In 1833 and 1839. Bissoe Pool - A ... • .• In 1896. Bolenowe 138 5 In 1842 (according to Phillips and Darlington). Boscawen and 1 69 3 In 1832, 1833, and 1834, and Wheal Andrew in 1894. 5,091 tons of copper ore containing 273 tons of copper were sold be- tween 1831 and 1845. Boys, Wheal - Brewer, Wheal 5 22 ^ Between 1873 and 1878. 1,420 130 Between 1845 and 1852. • ■■ 1,142 78 5,373 tons of copper ore containing 328 tons of copper were sold be- tween 1842 and 1853. Buckets, Wheal ... ' 2,700 1,281 170 85 Between 1846 and 1849. BuUer, Wheal - 1,410 98,700 14,340 Between 1845 and 1875. 167 13,560 850 Buller and 41,700 2,600 Between 1823 and 1828. Beanehamp Bnrra Burra Mine Calvadnack ... 6,539 260 443 12 1832 to 1836 and in 1838. In 1862 and 1863, and in 1875 and 1876. 1,150 138 170 ... ... Between 1854 and 1875. Camborne 1,180 80 Between 1853 and 1891. Consols Camborne Vean 350 77 189 37,500 3,297 15 2,770 229 Between 1816 and 1832, and 1845 and 1855. Between 1815 and 1856, 29,932 tons of ore con- taining 2,259 tons of copper were sold. Cam Brea 29,600 1,195 158,200 10,430 11,300 1,050 From 1833 to 1836, in 1838, and between 1845 and 1895 ; tin in 1837, 1838, and 1839, and since 1852, T 2 276 MTNTNG ECONOMICS. Name of Mine. Total yield and largest amount raised in one year. Black tin. Copper ore. Copper. Kemarks. Cam Brea — cont. Cam Brea and Tincroft United Cam Camborne Cardrew Consols Carharrack Carvannel Cathedral Mine (Consols) Cliance, Wheal (Gwennap) Chance Consols ClarencejWheal Clifford Amal- gamated Tons. Clifford United Clowanoe, Wheal Clyjah and Wentworth Combellack and Mengearn Comford, Wheal (and North Tresavean) Oondurrow 6,587 696 115 42 H H 365 136 39 125 26 2,030 Tons. 8,454 1,533 6,310 1,247 15,900 1,594 2,500 474 585 312 14,800 1,323 3,998 67 144,300 15,180 7,580 1,461 2,500 874 1,570 128 30,200 Tons. 363 75 305 62 850 107 180 37 40 21 1,530 156 337 2 9,140 965 612 118 155 50 85 19 2,020 161,593 tons of ore contain- ing 12,039 tons of copper were produced between 1833 and 1856, From 1857 to 1895, 75,900 tons of ore containing 5,858 tons of copper. Between 1896 and 1905. Between 1862 and 1879, Between 1827 and 1836. 17,143 tons of ore contain- ing 1,141 tons of copper were sold between 1826 and 1838. In 1885. Between 1851 and 1856, 1,782 tons of ore contain- ing 139 tons of copper were sold. From 1857 to 1859, 700 tons of ore con- taining 40 tons of copper. From 1874 to 1881. Between 1815 and 1828. Between 1826 and 1827 (Phillips and Darlington). In 1835, 1865, and 1866. Between 1833 to 1836 and between 1845 and 1876. Between 1835 and 1856 "Wheal Clifford" sold 9,495 tons of ore contain- ing 725 tons of copper. Between 1857 and 1872, 135,400 tons of ore con- taining 8,480 tons of copper. Between 1893 and 1895. Between 1815 and 1824. Between 1854 and 1862. Between 1878 and 1883. Between 1845 and 1885. From 1845 to 1876. MINERAL STATISTICS, 277 Kame of Mine. Total yield and largest amount raised in one year. Black Tin. Copper ore. Copper. Bemarka. Condnrrow- cont. Consolidated Mines Tons. 404 Cook's Kitchen 32 8,510 349 Copper Bottom Crane Mine (and Bejawsa) Creegbraws and Penkevil Crenrer, Abra- ham and Oat- fleld Cnpid, Wheal - Courtis, Wheal Damsel, Wheal 1,320 134 960 804 77 20 Tons. 1,941 331,300 15,523 38,800 2,120 265 1,770 326 14,530 2,062 112,050 11,073 44 2,290 354 37,600 2,919 Tons. 128 27,000 1,530 2,100 161 '25 160 28 875 119 7,740 797 2 120 20 3,300 304 20,095 tons of ore contain- ing 1 ,500 tons of copper were sold between 1818 and 1856. Prom 1857 to 1865, 10,400 tons of ore containing 543 tons of copper. From 1815 to 1836, in 1838, and from 1845 to 1857; some black tin in 1837 and since 1852. 441,286 tons of ore contain- ing 37,402 tons of copper sold between 1815 and 1856. In 1857, 1,105 tons of ore containing 59 tons of copper. From 1815 to 1836, in 1838, and from 1845 to 1897; some tin in 1837, 1838, and 1839, and since 1852. 43,606 tons of ore contain- ing 2,4S4 tons of copper sold between 1815 and 1856. In 1835, 1836, and in 1860. 1,436 tons of ore contain- ing 121 tons of copper were produced between 1836 and 1851. In 1851, 1852. and 1853 and since 1862. Between 1815 and 1832, and 1845 and 1902. 15,496 tons of copper ore containing 1,022 tons of copper sold between 1815 and 1856. Between 1815 and 1832, and 1845 to 1870. From 1855 to 1862. In 1838 and from 1864 to 1869. 2,341 tons of ore containing 142 tons of copper were sold between 1838 and 1844. From 1815 to 1836, in 1838, and 1845 to 1872. 278 MINING ECONOMICS. Total yield and largest | - amount raised in one year. Name of Mine. Bemarks. Black Tin. Copper ore. Coppe*. Tons. Tons. Tons. Dolcoath (Wh. 77,300 230,300 16,100 Prom 1815 to 1836, in 1838, Harriet, &c.) 2,555 9,807 794 and from 1845 to 1905. From 1815 to 1856, 241,522 tons of ore con- taining 17,478 tons of copper. Prom 1857 to 1874,6,300 tons contain- ing 375 tons of copper. Druid, Wheal - ... 214 176 28 22 In 1815 and 1816. East Wheal 87 15,050 1,520 From 1826 to 1832, )845 to Basset • t* 2,039 308 1878. East Basset and 5| • ■• ... In 1864 and 1865. Grylls East Carn Brea 6 22,080 4,021 1,365 230 Since 1859. East Wheal i'i 54,000 3,500 From 1832 to 1836, in 1838, Crofty 37 6,173 483 and between 1845 and 1855. 100,952 tons of ore contain- ing 7,280 tons of copper sold between 1832 and 1854. East Wheal i ... In 1891. Damsel East Downs (and At 85 4 From 1863 to 1899. Silverwell) East Wheal • t • 231 11 Between 1859 and 1861. Ellen , , 198 10 East Grenville 23 327 16 In 1875, East Wheal 2,405 ... Between 1859 and 1891. Lovell 232 ... East Pool and 38,490 88,300 5,010 In 1836, 1837, and 1838, and Wheal Agar from 1845 to 1905. 38,780 tons of ore contain- ing 2,918 tons of copper were sold from East Pool between 1835 and 1856. From 1857 to 1903, 54,310 tons containing 2,769 tons of copper. East Wheal 1* 1,720 122 Between 1847 and 1875. Seton East Wheal 57 17,140 1,260 Between 1847 and 1863. Tolgns • •• 713 36 East Treskerby ■ •■ 36 3 Between 1863 and 1865. East Trumpet - 20 ... ... Between 1868 and 1871. East Wheal Vor 32 ... ... In 1856 and 1857. East Wheal Uny 32 352 32 Between 1881 and 1884. ,,, 156 14 Ellen United, • •• 12,600 750 Prom 1834 to 1836, in 1838, Wheal ... 1,541 77 and between 1845 and 1865. MINERAL STATISTICS. 279 Name of Mine. Total yield and largest amount raised in one year. Black Tin. Copper ore. Bemarks. Tons. Ellen United, Wheal— cont. Emily Henri- etta, Wheal Emma, Wheal - Enys, Wheal (Enys Mines) Falmouth and Sperries, Wheal (and Falmouth Consols) Fanny, Wheal Fursden, Wheal Garlidna United (and Polen- grean) Gerry, Wheal - Gorland, Wheal Girambler, Wheal Grambler and St. Aubyn Great Wheal Baddern Great Briggan Great Wheal Busy (Chace- water Mine) 259 78 2 174 15 50 4 30 13 1,860 284 Tons. 1,820 627 530 323 1,150 207 8,450 1,740 187 38,500 2,959 11 8,440 1,490 1,390 506 92,100 4,108 Tons. 136 45 27 14 40 10 780 166 8 2,850 243 1 740 112 96 31 4,600 314 20,025 tons of ore contaiii- ing 1,365 tons of copper were sold between 1826 and 1854. From 1855 to 1865, 3,290 tons of orO containing 1.59 tons of copper. Between 1862 and 1871. In 1875 and 1876. Between 1853 and 1859. In 1832, 1833, 1834, and between 1860 and 1872. Between 1819 and 1833, 1,808 tons of ore were sold containing 87 tons of copper. From 1815 to 1822. In 1860. Between 1861 and 1880. In 1824 and 1825 (Phillips and Darlington). Between 1815 and 1836 ; in 1838 and 1845, and 1878. ' In 1835 and in 1872. From 1845 to 1868. 7,280 tons of ore contain- ing 569 tons of copper were sold between 1843 and 1856. From 1857 to 1868, 2,690 tons contain- ing 297 tons of copper. Between 1848 and 1858. Between 1861 and 1866. Between 1815 and 1836, 1845 and 1897,and in 1904. 33,486 tons of ore contain- ing 1,669 tons of copper were sold between 1823 and 1856. From 1857 to 1866, 35,660 tons contain- ing 1,432 tons of copper. 280 MINING ECONOMICS. Name of Mine. Total yield and largest amount raised in one year. Black Tin. Copper ore. Copper. Remarks." Gustavus Mine Great Wheal Lovell Great North Downs Great ' North Tolgus (Wheal Elizabeth) Great South Tolgus Great Wheal Vor Grenville, " Wheal Hallenbeagle (Boscawen) and Croft Gothal Harmony and Montague - Henry, Wheal Hope, Wheal Jane, Wheal - Jewell, Wheal - Killifretb King Edward (part of South Condurrow)' Tons. 64 Tons. 89 Tons. 6 i4 9,110 2,513 4,120 640 182 215 101 66 9,620 847 16,500 3,297 2,270 743 1,100 256 205 75 4,635 1,006 i 2,330 738 10,020 2,879 190 67 510 152 3 22,450 2,309 2,400 350 "i 1,860 503 4,910 J.Oll 150 39 491 118 3,830 344 9 740 286 38,100 4,061 30 14 3,015 526 4,060 259 3 681 128 56 11 Between 1852 and 1864. Between 1871 and 1876. iSetween 1862 and 1897. From 1832 to 1834 and be- tween 1845 and 1862. Between 1854 and 1869. Between 1853 and 1877. Copper from 1822 to 1826, 1832 and 1836,and in 1838. 4,300 tons of ore contain- ing 330 tons of copper were sold between 1821 and 1842. Between 1860 and 1905. Prom 1834 to 1836, in 1838, and between 1845 and 1859. 30,580 tons of pre contain- ing 1,803 tons of copper were produced between 1835 and 1846. Between 1820 and 1834, and • from 1845 to 1880. Between 1819 and 1844, 29,407 tons of ore con- taining 2,950 tons of cop- per were sold. In 1835, and between 1815 and 1847. Between 1826 and 1832, and 1845 and 1866. 5,584 tons of ore containing 534 tons of copper were sold between 1824 and 1837. Between 1847 to 1895. Prom 1815 to 1836, and in 1838. 58,160 tons of ore contain- ing 5,222 tons of copper were sold between 1815 and 1853. Between 1859 and 1904. In 1904 M1N£BAL STATISTICS. 281 Name of Mine. Total yield and largest amount raised in one year. Black Tin. Copper Ore. ■ Copper. Remarks. Lovelli Wheal - Lovell, The, Mine Loyell Consols Lydia, Wheal - Maid, Wheal (and Carhar- rack) Maria, Wheal - Mary, Wheal - Mary Consols, Wheal ; Medlyn Moor Mine . -s Metal and Flow, Wheal Moont Carbis- TMoyle, Wheal - Music, Wheal Nancegollan - Nanceknke Nangiles and Wheal An^ drew New Cook's Kit- chen New Dolcoath New Wheal Frances New Wheal Render New Wheal Lovell New Wheal Seton NeW^outh;Ellen New Treleigh ' CoBaola (and New Tre- leigh) New Trevennen New Trumpet Consols (Lov- ell United) Tons. 750 132 577 64 184 80 29 540 54 77 44 6 40 106 470 179 45 12 6 375 95 3 22 Tons. 3,900 2,267 27,800 4,281 41,150 ,15,684 7,670 1,596 2,"370 721 285 4,600 1,046 3,020 459 2,820 522 220 112 155 128 59 25 2,820 485 3 560 Ton& 234 136 2,015 362 4,540 1,578 460 119- 200 66 6 750 176 206 34 390 40 18 10 12 11 3 2 140 22 Between 1852 and 1863. Between 1874 and 1876. In 1871. Between 1845 and 1847. Between 1821 and 1836, 1838, and from 1845 to 1852. 23,552 tons of ore contain- ing 1,542 tons of copper were sold between 1820 and 1852. Between 1845 and 1847. Between 1827 and 1836, 1845 and 1872. Between 1830 and 1832, 1845 and 1849. Between 1874 and 1880. Between 1885 and 1901. Between 1882 and 1885. Between 1861 and 1863. Between 1815 to 1825, and in 1832, 1833. In 1854. Since 1851. Between 1845 and 1876, and in 1905. Between 1877 and 1891. Between 1872 and 1^75. In 1861 and 1862. Between 1861 and 1863. Between 1865 and 1874. In 1863. In 1862. Between 1859 and 1869. i In 1861. 89 Between 1875 and 1&S8. 282 MINING ECONOMICS. Name of Mine. Total yield and largest amount raised in one year. Black Tin. Copper ore. Copper. Kemaiks. New Wheal Vor and East Wheal Metal Nelson, Wheal North Basset - North Wheal BuUer North Wheal Busy North Busy United North Wheal Crofty North Wheal Damsel North Dolcoath North Downs - North ^ Wheal Frances North Wheal G rambler North Hallen- beagle North Wheal Jane North Lovell - North Metal - North Penstru- thal North Pool - North Boskear (and Wheal Crotty) North Tres- kerby Tons. 125 165 38 5 220 1,610 "k 12 70 19 9 8 60 1,440 190 150 12 Tons. 6 27,800 5,104 280 1,020 264 750 253 9,170 1,582 580 322 43 22,800 1,492 440 2,670 511 61 47,670 6,447 132,070 7,419 19,270 2,323 Tons. i 2,200 552 22 60 18 45 14 535 100 45 24 3 1,890 132 30 210 45 2,860 433 9,710 265 1,290 146 Between 1859 and 1861. In 1863. Between 1846 and 1866. Between 1822 and 1852 (Phillips and Darlington). Between 1854 and 1861. Between 1875 and 1887. Between 1854 and 1899. Between 1852 and 1854. Since 1862. From 1815 to 1836, and from 1845 to 1871. Tin in 1837 and since 1852. 19,348 tons of ore contain- ing 1,600 tons of copper were "sold between 1815 and 1855. From 1856 to 1871, 10,500 tons of ore containing 855 tons of copper. Between 1857 and 1862 . Between 1859 and 1867. In 1862 and 1863. Between 1861 and 1875. Between 1871 and 1874. In 1883 and 1884. Between 1880 and 1886. Between 1845 and 1867. Between 1819 and 1836, 1845 and 1874. 151,800 tons of ore contain- ing 11,850 tons of copper were sold from North Eoskear between 1816 and 1856. From 1857 to 1874, 15,600 tons contain- ing 1,155 tons of copper. Between 1859 and 1882. MINERAL STATISTICS. 283 Name of Mine. Total yield and largest amount raised in one year. Black Tin. Copper ore. Copper, Kemarks. Old Wheal Bas- ' set Old Wheal Tol- gus Old Tolgus United Fedfi an Dcea (and Sparnon Consols) Pendarves United Pendarves and St. Aobyn Penhale Wheal Vop Pennance Penstruthal (andPenstm- ttial Consols) Perseverance Mine (and Wentworth and Copper Hill) Peevor, Wheal Pink, Wheal - Plenty, Wheal- Polorebo- Pdldice - Poldice and East Wheal Maid Tons. Tons. 570 160 28 Tons. 36 10 8 145 ... 7,700 367 1,090 240 57 18 2,660 476 575 125 34 10 85 36 370 590 105 59,500 8,385 35 10 2,740 672 19 10,870 1,285 732 86 3,280 649 5 1,830 408 i 120 30 155 11 102 30 1,525 307 15,300 2,485 965 153 . i ... ... Between 1854 and 1860. In 1859. In 1859. Between 1854 and 1891. Between 1866 and 1881. In 1854. Between 1866 and 1869. Between 1866 and 1872. Between 1825 and 1836, 1845 and 1879. Between 1819 and 1846, 51,830 tons of ore con- taining 3,073 tons of copper were sold. Between 1856 and 1877. Between 1872 and 1889. Between 1815 and 1833, 1845 and 1855. 1,881 tons of ore contain- ing 158 tons of copper were sold between 1821 and 1850. In 1838 (Phillips and Dar- lington). Between 1884 and 1890. In 1838 and between 1845 and 1873. Tin in 1837, 1838 and 1839, and since 1852. 2,992 tons of ore contain- ing 208 tons of copper were sold between 1815 and 1852. From 1868 to 1873, 3,635 tons of ore containing 231 tons of copper. In 1891. 28i MINING ECONOMICS. ! ! Total yield and largest amount raised in one year. Name of Mine. Black Tin. Copper ore. Copper. Bemarks. Polgine, Wheal Polhigey Moor and Polhigey New Mine Prosper, Wheal Prosper United Prussia, Wheal (andCardrew United) Baven, Wheal - Bedruth Consols Bose, Wheal Boskear - St. Andrew St. Aubyn United St. Day United (St. Day Manor — Pol- dice, Unity Wood, Wheal Maid, and Wheal Gor- land) Soorrier Consols Seton, Wheal Seymonr,Wheal South Basset South BuUer - South Buller and Beau- champ Tons. . Tons. Tons. ••• 495 41 28 ... — 86 311 7 39 194 3 830 22,490 1.020 191 4,523 234 206 13 3 4 1,447 117 >•• 565 45 ... 740 50 18 12,820 834 ... 3,717 223 ... 23 1 370 15 43 1,380 91 3,280 22,900 -1,360 480 3,175 230 15 990 113,050 7,080 ... - 5,402 451 ... 675 43 37,100 3,020 ... 3,390 267 • *• 2,220 211 127,796 8,554 In 1836 and 1837 (Phillips and Darlington). Between 1864 and 1874. Between 1862 and 1870. Between 1863 and 1872; Between 1874 and 1883. Between 1825 and 1828. Between 1836 and 1843 (Phillips and Dairlington). Between 1S62 and 1872. In 1864 and 1865. In 1845. Between 1871 and 1892. Between 1852 and 1893. 9,728 tons of ore -contain- ing 658 tons of copper were sold between 1852 and 1856. Prom 1857 to 1867, 11,170 tons con- taining 602 tons of cop- per. In 1874 and 1875. In 1838 and from 1845 to 1877. Largest output in 1847. In 1815 and 1816 (Wheal Aiin), and in 1877 and 1878 (Wheal Seymour). Prom 1833 to 1836, in 1838i and between 1845 and 1861. 94,649 tons of ore contain- ing 7,200 tons of copper were sold between 1825 and 1856. In 1822 and from 1863 to 1865. Between 1821 and 1856, accoiding to Phillips and Darlington. MINERAL STATISTICS. 285 Name of Mine. Total yield and largest amouut raised in one year. Black Tin. Copper ore. Copper. Remarks. South Carn Brea South Condup- row South Wheal Orofty South Dolcoath South Wheal Ellen South Wheal Frances South Wheal Lovell South Penstru- thal South Boskear Tons. Tons. 845 3,550 129 628 11,430 1,060 861 247 5,080 33,700 • •• 3,208 • •• 1,800 .>■ 273 • •■ 2,600 *.. 747 9,710 66,590 728 6,463 81 4 ... 175 21,600 ... 1,464 South Tolcarne and West Condnrrow South Tolgus 640 25 1862. Treworlis 412 690 36 Between 1860 and 1873 and 52 407 22 in 1882. Trumpet 4,510 4 1 Between 1854 and 1880. Consols .- 298 • •• Trumpet 12 *(• ■ •■ Betww 1863 and 1865 United 288 MINING ECONOMICS. Name of Mine. Total yield and largest amoaut raised in one year. Black Tin. Copper ore. Copper. Bemarka. Tryphena United Hills United Mines (Gweiin^ United) Unity and Unity Consols Unity and Pol- dice Unity Wood, Wheal, and Wheal Union Uny, Wheal Vii^in, Wheal (part of Clif- ford Amalga- mated) Vyvian, Wheal Tons. 31 26 250 77 40 22 570 128 7,660 423 92 26 Tons. 74 26^10 3,390 284,400 14,374 83,100 6,897 21,620 858 2,860 353 7,420 946 4,140 378 Tons. 16 1,490 209 19,800 1,012 6,890 554 1,290 56 155 27 415 72 235 22 In 1847 and 1848 andin 1862. From 1822 to 1836, 1845 to 1847. 54,473 tons of ore contain- ing 3,582 tons of copper were sold between 1826 and 1847. Some tin in 1837 and since 1852; between 1815 and 1836, 1845 and 1861 ; in 1880 and 1881, and from 1893 to 1901. 304,530 tons of ore contain- ing 22,680 tons of copper were sold between 1815 and 1856. Between 1857 and 1861, 43,110 tons of ore containing 2,063 tons of copper. Between 1852 and 1855. Between 1815 and 1832. Between 1815 and 1836, in 1838, and since 1853 ; tin in 1837 and since 1B52. 32,760 tons of Ore contain- ing 2,465 tons of copper were sold between 1823 and 1842. Between 1853 and 1893. Between 1826 and 1856, 755 tons of pre yielding 39 tons of copper were sold. Between 1857 and 1866, 2,070 tons of ore containing 112 tons of copper. In 1815 and from 18.34 to 1836, and from 1845 to 1847. 22,974 tons of ore contain- ing 1,656 tons of copper were sold between 1821 and 1847. From 1832 to 1836, in 1838, and between 1845 and 1864, 8,277 tons of ore contain- ing 500 tons of copper were sold between 1827 and 1856. Between 1857 and 1864, 200 tons of ore containing 10 tons of copper. MINERAL STATISTICS. 289 Total yield and largest amount raised in,( sne year. Name of Mine. Bemarks. Black Tin. Copper ore. Copper. Tons. Tons. Tons. Wellington, >■• [2,830 213 Between 1822 and 1827 Wheal (Phillips and Darlington). Wendron Con- 2,390 48 8 Between 1854 and 1869. sols 269 >•> .f . Wendron United 27 • >> ... In 1853>nd in 1875, 1876. Mines West Basset - 10,150 101,500 7,155 Between 1852 and 1890. 1,000 7,673 532 West BuUer - ^ 1,170 125 In 1849. WestCarvannel 110 ... In 1859. West Clifford - <•* 73' 3 In 1865. West Wheal 18 29,150J 1,560 Between 1852 and 1874. Damsel • •> 2,166 117 West Wheal 8,940 28' 11 Between 1854 and 1896. Frances m West Wheal 68 70.' 4 Between 1871 and 1876. Gorland West Wheal ■ ■• 11 ... In 1859. Grenville West Wheal 410 50 • •■ Between 1854 and 1889. Jane 58 ... ... West Wheal 8 6.620 410 In 1832 and 1833 and be- Jewell 1,883 113 tween 1845 and 1852; tin 1837 and in 18.52. Between 1831 and 1852, 12,578 tons of ore con- taining 858 tons of copper were sold. West Wheal 1,200 ,,, ... Between 1879 and 1887. Peevor ^ West Pink 130 280 15 In 1832, 1833, 1834. and 1835. West Poldice 650 1,152 90 From 1832 to 1836; be- (and West Pol- 158 336 28 tween 1874 and 1884 ; tin dice United) in 1837 and since 1852. West Wheal 3,720 114,450 9,300 Between 1848 and 1890. Seton 299 7,155 520 West Wheal • >> 3,390 383 Between 1818 and 1822. Squire ■ ■■ 1,148 139 West Stray- 2 3,635 275 Between 1854 and 1868. Park • *■ 485 37 WestTolgus - A 47,700 4,020 Prom 1832 to 1836 and be- tween 1861 and 1883. West Tresavean 5 ■ .. In 1837. West Wheal 520 .•< • .* Between 1853 and 1882. To wan 114 ... West Trethellan ... 1,390 435 63 20 Between 1845 and 1850. West Wheal • r« 90 H In 1818. Virgin West Wheal i .■• ... In 1878. Vor 290 MINIXG ECONOMICS Oitiput of Minerals, other than Tin and Copper, from IS4.8 to 1905, Name of Mine. Basset Consols Basset Valley Bissoe Pool - Boscawen - Buller.Wheal Burra Burra Mine Camborne Consols Camborne Vean Cam Brea - Tons. 14 Total yield and largest amount raised in one year. Hi Tons. 01 Hi 2i Cam Brea and Tin- ... croft United Cam Cam- borne Carvannel - Clifford Amal- ... gamated - ... Comtord, .1 • Wheal (and North Tre- fiavean) Concord, 60 Wheal Condurrow - Consolidated ... Mines Cook's Kitchen Ozs. 144 Tons. 120 55 36 en h O o a 33 320 •a g ? n Ftf CI U ^ Tons. Tons. 43 1,011 974 60 4| 5,550 550 a •§ a-" CO o o o 200 30 4,140 302 3,142 421 72 .a a p n -§ O Other products. I- Tons. 1,050 13 34 120 ons. In 1879. ... 139 tons arsenical pyrites since 1864. ... In 1857. ... 16 tons arsenical pyrites. • •. 390 tons of wolfram (239 high- est yield in one year). ... 40 tons of arsenical ... pyrites. Between 1845 and 1847. 222 tons arsenical pyrites. MIIXEEAL STATISTICS. 291 Total yield and largest amount raised in one year. ri ri Name of ^i .2 n ° O.'S Other Mine. i 13 1 1 i o 5 1 o §1 a a a s 1 products. )H ^ o Tons. Tons. Ozs. Tons. Tons. Tons. Tons. Tons. Orane Mine - 2 H 13 ... ... ... ... Creegbraws ... ... 3i 160 50 ... 106 4 tons and Pen- arsenical kevil - pyrites. Crenver, ^ 31- 15 ... 744 i ... Abraham, ... ... ... 296 ... ... andOatfield Cupid, Wheal ... ... • !• 22 tons fluorspar. Couptis,Whea1 Damsel, ... 3 ... ... 114 tons of Wheal fluorspar. Daniell, ... ... ... 15 In 1872. Wheal Dolcoath (?) 12 1,550 102 634 tons arsenical pyrites (276 high- est out- put in one year). 2 cwts. bis- muth ore. East Downs (and Silver^ ... ... ,— ... ... ■ •• 107 tons of arsenical pyrites. well) Bast Wheal 413 320 17,100 487 ... ... ... ... Between 1856 and Falmouth 1861. East Pool and ... ... 15 21290 ... ... 1,860 tons of wol- Wheal Agar fram, 100 tons of sodium^ tungstate, ■J ton uranium ore, 4i tons co- balt ore, 4tonsbis- muth ore, 1 ton of ore con- taining nickeljco- balt, and bismuth.' East Wheal ... ... 125 ... ... ... Seton V 3 292 MINING ECONOMICS. 1 Total yield and largest amount raised in one year. r} ' b Name of 1 o c3 ,1 .a Other Mine. i 'i £ 1 §-g i products. C8 1 a 11 (b;s is 1 „ Ozs. "" H o Tons. Tons. Tons. Tons. 1 Tons. Tons. Tons. Bast Wheal ,, , * i* ... 11 47 •*■ ... ... . Tolgus j Emily Henri- • •■ • i. ... 12 12 1 ... etta, "Wheal 1 Falmouth and 60 41 353 180 47,800 ...10474 Sperries, ... 9,045 ...'3,005 ... Wheal Fortune, ... ... • •. ■ *. ... ... >.• 3J tons Wheal >. silver ore in 1880. Gorland, . i • ... ■ ■* ... ... 18 .• . ... aojtonsof Wheal "wolfram. Great Wheal 3,160 2,230 37,611 202 362 • •• ... 60 14 tons ar- Baddern 628 447 9,400 ... ... ... ... senical pyrites. Great Wheal 3i 2* 44 148 155 38 ... 20,720tons Busy of arseni- cal py- rites (5,778 largest output in oneyear). Great Korth ... ... ... ... 373 tons Downs - arsenical pyrites (248 tons largest output in oneyear). Great South ... .. • 2 ... 15 ... ... Tolgus Great Wheal ... ... ... 41 ... ... Vor - Hope, Wheal 141 100 1,968 H ... ■ ■■ ... Jane, Wheal 203 138 2,921 586 33,340 243 3,666 '100 88 tons ... ... 102 5,118 ... 1,149 ... . arsenical pyrites. Jewell,Wheal 20 14 ... • a* ... • >• ... ..> Killifreth - ■" ... 17 360 ... 6 12 tons arsenical pyrites. Nancekuke - 747 505 13,709 >.. ... ■ *> ... ... Nangiles and ... ... 146 2,770 163 16 62 Wheal An- ... ... ... *.• 1,481 ... ... ... drew NewTreleigh ... ... ... n ■ ■• ... ... ... Consols (anc New Tre- leigh) J MINERAL STATISTICS. 293 Name oi Mine. Tons. North Wheal Busy North Busy- United North Wheal Crofty North Dol- coath North Wheal Jane North Pool - North Ros- kear North Tres- kerby Old Wheal Basset Old Tolgus United Pedn an Drea (and Spar- nonConsols) Pendarves United PerseTerance Mine (and Wentworth and Copper Hill) Peevor, Wheal Poldice Prosper, Wheal Prosper United Total yield and largest amount raised in one year. O C3 a 1-4 Tons. oa Oza. Tons. 415 382 584 310 u o o a 1 ! ° Tons, 92 172 5i Tons. o: 1,470 380 i to "S a i! •n i 1 O Tons. Tons. 23 6 370 166 10 14 * i sp 12 200 51 200 17 1,340 16 974 75 56 873 216 209 1,160 340 249 Other products. 24 tons of arsenical pyrites. 992 tons arsenical pyrites (545 tons highest output in one year). 228 tons of silver ore. In 1858, 2i tons of silver chloride. 96 tons arsenical pyrites. 119 tons fluorspar. 321 12 tons arsenical pyrites. 1,822 tons arsenical pyrites. 294 MINING ECONOMICS. IS^ Total yield and largest amount raised in I one year. ri h Name of Mine. i t^ 2 H 0* O .2 a a Other products. o "S C c -M eg p.. ca CM C3 > o a 11 £5 n go C 33 1" a a J3 a 1 . _._ H ?_ Tons. Tons. Ozs. Tons. Tons. Tons. Tons. Tons. St. Aubyn ■ • • ■ •■ ... *.. .. . *• • *.. ... 172 tons United fluorspar. StDayUnited ■ •• .•• ... ... .. • 38 ... 124 tons (St. Day arsenical Manor — pyrites ; Poldiee, 49 tons UnityWood, fluorspar. Wheal Maid, Wheal Oor- land) Seton, Wheal ... 19 25 1,900 155 10' tons of fluorspar. Seymour, >• > ... ... 25 ... ... ... ... Wheal South Cam • ■■ / ... 4 . Brea South Con- ... 4 diirrow South Wheal • *■ ... ... 1,110 3,251 19 tons of Crofty wolfram. South Wheal 4 3 ... 137 42 Ellen South Garras 1,930 506 1,025 243 71,930 23,455 ... 11 ... ... ... Between 1855 and 1860. South Eos- 35 655 kear ... 257 South Wheal ... 92 In 1872. Seton » South Tolgus i i ... 8 77 ... ... (South Wheal Tol- gus) Stray Park - ... 42 ... Swanpool 895 706 179 141 3,579 ... ... In 1859 and 1860. Tincroft 22 15 ... 3,286 553 Tolgullow • •• ... 222 184 152 tons United (and - arsenical West Pol- pyrites. dice) Trannack, • •■ • •■ ... 3i ... ... Wheal Tresavean - H 3 312 ... United ... 271 1,290 158 Mines ... •'.. ... ... 996 .,. ... Unity and i * .. • ... 243 ... Unity Con- sols - MliSEEAL STATISTICS. 295 Total yield and largest amount raised in one year. Name of Mine. 2 o ' 1 i a) a J a"< Rl CM 1 p Other products. Unity Wood and Wheal Union Uny, Wheal - West Wheal Damsel West Wheal Damsel and Cupid West Wheal Jane West Wheal Peevor West Poldice (and West Poldice United) West Wheal Seton West Tolgus West Wheal Towan Tons H 26 Tons. 19 Ozs. 158 Tons. 390 76 97 Tons. 21 6 27,170 4,300 6 24 200 Tons. 129 382 20 4,026 Tons. 207 Tons. 50 638 tons fluorspar (332 tons highest yield in one yeaT.) 256 tons fluorspar. Stream Worbs, <&c. — Tin Ore obtained from Mine Refuse, Foreshores, &c, Red "River and River from Cam Brea and Tincroft. Metallic tin Year. Dressed tin oie. obtainable by smeltfng. Value. Tons cwts. Tons cwts. £ 1882 1,252 726 53,306 1883 1,103 16 541 42,350 1884 - 1,154 2 635 35,016 1885 . 1,142 18 • 628 10 37,218 1886 - 1,104 3 • ■• 48,177 1887 - 1,010 10 • •• 46,486 1888 - 1,446 6 867 63,182 1889 - 911 >•> 43,392 1890 - 1,302 ..* 52,080 1891 - 880 33,704 1892 - 905 4 34,780 296 iHNING. ^COiSrOMICS. River from Wheal Basset, West Basset, Wheal Vny, &c., to Portreath. Metallic tin Tear. Dressed tin ore. obtainable by smelting. Value. Tons cwts. Tons cwts. £ 1882 - 265 148 8 11,309 1883 - 255 10 125 . 9,200 1884 - 171 17 93 6,039 1885 - - 184 9 103 6,887 1886 - 170 10 ... 7,679 1887 - 207 1 ... 9,690 1888 - - 206 3 123 9,852 1889 - 278 ■ • ■ 7,619 1890 - 428 ... 17,126 1891 - 330 ... 10,469 1892 - 261 2 ... 10,016 Total Annual Production of Tin Ore of Oornivall from Abandoned Mine- heaps, Waste from Mine Dressing Floors, Stream Works, &c.* Year. Black tin. Metallic tin. Value. Tons cwts. Tons. £ 1882 - 1,654 950 • ■■ 1883 - 1,439 709 t • • 1884 - 1,415 778 • •> 1885 - 1,395 a 770 • •• 1886 - 1,337 802 ..• 1887 - 1,278 767 ..■ 1888 - 1,742 1,045 >•• 1889 - 1,272 763 • •• 1890 - 1,796 1,078 • >* 1891 - 1,301 780 ■ •• 1892 - 1,282 769 1893 - 1,228 737 45i601 1894 - .1,300 780 29,075 1895 1,000 400 25,000 1896 - 716 322 15,603 1897 877 14 395 22,057 1898 - 746 335 20,020 1899 - 709 319 32,088 1900 - 761 342 39,030 1901 - 687 309 30,805 1902 - 825 350 40,049 1903 - 839 356 42,136 1904 - 721 334 37,387 1905 - 818 18 377 46,824 Refuse Heaps of Abandoned Mines, "Old Men's" J Surrows, &e. Year. Dressed tin. Metallic tin. Value. Tons cwts. Tons cwts. £ 1882 - 17 17 10 6 870 1883- 8 14 4 18 483 1892 - - - 86 19 56 10 4,364 1893 - 64 16 42 2 2,952 1894 - 72 5 46 19 2,544 Mainly from the mine tailings flowing down the rivers above mentioned. INDEX TABLES OF THE MINES. 297 Index Tables of the Minbs. The following table contains an alphabetical list of the mines included in this sheet, together with tlie parishes in which they occur. The mines now working are the Basset Mines, Carn Brea and Tincroft United, Cook's Kitchen, South Crofty, Dolcoath, East Pool and Wheal Agar :— Mink. Parish. Mine. Pabish. Abraham Consols - Agar, Wheal Crowan Illogan Chance, Wheal f Gwennap { Eedruth Ale and Cakes Gwennap Charles, Wheal - St. Agnes Andrew, Wheal - Gwennap and Christopher, Wheal St. Agnes Kea Clarence, Wheal - Illogan Ann. Wheal - f Kenwyn \ Wendron Clifford, Wheal Gwennap ^^.mXf TT iLVaL ~ Clifford Amalga- Annie, Wheal Gwinear mated Gwennap Clinton, Wheal Gwennap Baddern (Baddon), Clinton, Wheal My] or Wheal Kea Clowance, Wheal - Crowan Baldhu - - . Kea Clowance Wood Bal Ding Wendron Mine - Crowan Balmynheer Mine - Wendron Clyjah and Went- Banns, Wheal - - St. Agnes worth - - . Eedruth Barberry, Wheal - Eedruth Combellack Mine Wendron Barncoose Mine - Illogan Comford, Wheal - Gwennap Basset, Wheal Illogan Concord, Wheal St. Agnes Basset and Grylls - Wendron Cook's Kitchen Illogan Beauchamp, Wheal Gwennap Copper Hill - / Eedruth \ Camborne Bell and Lannarth Gwennap Bell vean Mine Gwennap Copper Bottom Crowan Bissoe Pool - Gwennap Copper Tankard - Camborne Bodilly Consols - Wendron Cornwall Mine St. Agnes Bolenowe Camborne Courtis, Wheal Crowan Boscawen Mine - Kenwyn Crack Crowder Boys, Wheal - Eedruth Mine - Gwinear Bramble, Wheal - Sithney Crane and Bejawsa Camborne Brewer, Wheal Gwennap Creegbraws - Kenwyn Briggan, Wheal - Eedruth Crenver and Wheal Britannia, Wheal - Gwennap Abraham - Crowan Brook, Wheal Gwinear Crofty, Wheal Camborne Buckets, Wheal Eedruth Crowan and Wen- Buller and Basset dron Mines Wendron United Wendron Cudy, Wheal - Wendron Buller, Wheal Eedruth Cupboard Hill Burra Burra Mine- Kenwyn Mines Gwennap Busy, Wheal Kenwyn Cupid, Wheal Gwennap ,Cusvey - - - Gwennap Calvadnack Mine - Wendron Camborne Consols - Camborne Vean Captain, Wheal Carbona Mine Cardrew Consols Carharrack - Camborne Camborne Eedruth Crowan Eedruth Gwennap Damsel, Wheal Daniell, Wheal Derrick, Wheal Dolcoath Mine Dopps Mine - Dream, Wheal Gwennap Kenwyn Eedruth Camborne Eedruth Wendron Oarleen Mine Carnarthen - Carn Brea Breage Illogan Illogan Druid, Wheal Drym Mine - Illogan Crowan / Illogan \ Wendron Illogan Carn Camborne Camborne Duchy, Wheal Carnemow Carnmeal Mine Camborne Breage Dudnance Carnkie Illogan Carqueen ■> Gwennap East Wheal Abra- Car Venn al Gwennap Gwennap Kenwyu ham - - - Crowan Cathedral Mine Bast Ale and Chacewater Mine - Cakes Gwennap 298 MINING ECONOMICS. Mine. Parish, Mine. Pabish. C Gwennap Grambler, Wheal - Gwennap ' East Wheal Basset < Illogan Great Condurrow - Camborne (.Redruth Great Consolidated Gwennap East Wheal BuUer Gwennap Great Wheal Bad- East Cam Brea Redruth dern (Baddon) - Kea East Wheal Chance Kenwyn Great Wheal Busy Kenwyn East Wheal Crofty Illogan Great East Lovell Wendron East Wheal Damsel Gwennap Great Wheal For- Bast Downs Mine - St. Agnes tune - Breage East Wheal Ellen - St. Agnes Great Drym Con- East Wheal Pal- Kea Kenwyn sols - - - Crowan mouth Great Wheal East Wheal For- Lovell Wendron tune - Sithney Great Wheal Metal Breage East Grenville Camborne Great North East Wheal Lovell Wendron Downs Redruth East Wheal Music - St. Agnes Great North East Pool Mine niogan Tolgus Illogan East Bosewarne - Gwinear Great St. Vincent - Illogan East Wheal Seton - f Camborne \ Illogan Great South Tolgus Redruth Bast Wheal Spar- Great Wheal Vor - Bieage non - - - Gwennap Grenville, Wheal - Camborne Bast Wheal Tolgus Redruth Grillis, Wheal Illogan East Towan - St. Agnes Gustavus Mine Camborne East Tresavean Camborne Gwinear Consols - Gwinear East Treskerby St. Agnes East Trumpet Mine Wendron Hallenbeagle Mine Kenwyn East Wheal Virgin Gwennap Hangman's Barrow Crowan East Wheal Vor Sithney Harmony, Wheal Redruth Bdgecumbe, Wheal Elizabeth, Wheal - Gwennap Illogan Harriet, Wheal - " Sithney Camborne BUen, Wheal - / Illogan \ St. Agnes Hatchet, Wheal - Camborne Hawk, Wheal Redruth Emily Henrietta, Hender, Wheal Crowan Wheal Emma, Wheal Illogan Breage Henry, Wheal / Kenwyn 1 Gwennap Buys, Wheal - Wendron Hope, Wheal /Kea \. Gwennap Falmouth and Sperries Kea Illogan Mine Illogan Fancy, Wheal St. Agnes Fanny, Wheal Illogan Jane, Wheal - Kea Fire, Wheal - Illogan Jewell, Wheal Gwennap Forest, Wheal Illogan r Gwennap Kellivose Mine Camborne Fortune, Wheal i Breage KiUifreth Mine Kenwyn (.Illogan King Edward Mine Camborne Poster, Wheal Pox Hole Sett Wendron Illogan Knight, Wheal f Illogan \ Camborne Prances, Wheal - Camborne Friendship, Wheal Gwennap Lily, Wheal - Redruth Pursden, Wheal Sithney Little North Downs Redruth Garlidna Wendron Longclose Mine - Illogan Gernick Crowan Louisa, Wheal Redruth Gerry, Wheal Cambdrnfe Lovell, Wheal Wendron Gilbert, Wheal - Redruth Lower Bolenowe GillyMine - Camborne Mine - - - Camborne Gine, Wheal - Camborne Lushington, Wheal Illogan Girl, Wheal - Gwennap Lydia, Wheal Illogan Gons, Wheal - Camborne Good Success Mine Redruth Maid, Wheal Gwennap Gorland, Wlieal Gwennap Margaret, Wheal - Gwinear INDEX TABLES OF THE MINES. 299 Mine. Maria, Wheal Mary, Wheal Medlyn Moor Mine Mengearn Messar, Wheal Metal, Wheal Millet, Wheal Montague, Wheal - Mount, Wheal Mount Carbis Music, Wheal NancegoUan Nanoekuke, see South Wheal Ellen - Nangiles Nelson, Wheal New Burra Burra - New Clifford - New Cook's Kit- chen New Dolcoath New Wheal Frances New Hallenbeagle New Hendra Mine New Wheal Lovell New North Pool New Rosewarne Mine - New Wheal Seton - New Treleigh New Trevenen New Trumpet Con- sols - New Vor and Metal United New Wendron Mine - - - North Wheal Basset North Briggan North BuUer North Wheal Busy North Crofty North Wheal Dam- sel North Dolcoath North Downs North^Wheal Fran- ces North Gram bier - North Hallen- beagle North Wheal Jane North Lovell Mine North Metal Mine North Wheal Metal North Penstruthal North Pool Mine - North Prospidnick Parish. Sedrath Redruth Wendron Wendron Redruth Breage Crowan Redruth Sithney Redruth St. Agnes Crowan lUogan Kea {Camborne Crowan Kenwyn Gwennap niogan Camborne Crowan Kenwyn Breage Wendron lUogan Gwinear Camborne Redruth Wendron Wendron Sithney Wendron / St. Agnes \ Illogan Redruth Redruth Kenwyn Illogan Gwennap Camborne Redruth Illogan Redruth St. Agnes Kenwyn Wendron Sithney Breage Gwennap Illogan Sithney MiNB. North Roskear North Treskerby - North Trewan Mine - - - North Wheal Vor - Old Wheal Basset - Old Wheal Jewell - Old Wheal Lovell - Old Pool Mine Old Trevenen Miile Park an chy Mine - Pedn an Drea Peevor, Wheal Pellor, Wheal Metal Pendarves Consols ,Penhaldarva Penhale Mine Penhale Wheal Vor Penkevil Pennance Mine Penrose, Wheal Penstruthal Mine- Perseverance M ine Pink, Wheal Plenty, Wheal Polcrebo Poldice Mine Poldory Poldown Polhigey Mine Polgine Mine PoUadras Mine Prosper, Wheal Providence, Wheal Prussia, Wheal Quick, Wheal Raven, Wheal Releath Mine Retanna Hill Rose, Wheal Rose Ann Mine Roselidden Mine - Roskrow United St. Aubyn United - St. Day United - Sarah, Wheal Scorrier Consols Scorrier Old Mine Seton, Wheal Seymour, Wheal - Silver Hill - Sithney, Wheal - Sithney Carnmeal Mine - - . Parish. / Camborne \ Illogan Sti Agnes Redruth Illogan Gwennap Wendron Illogan Wendron Gwennap Redruth Redruth Breage Camborne Kenwyn Breage Breage Kenwyn Gwennap Budock Gwennap Redruth / Gwennap \ Redruth Redruth Crowan Gwennap Gwennap Breage Wendron Camborne Breage Kenwyn Illogan Redruth Gwennap Redruth Wendron Wendron St. Agnes St. Agnes Wendron St. Gluvias / Gwejinap \ Redruth Gwennap Crowan St. Agnes Kenwyn Camborne Kenwyn Perranar- worthal Sithney Si thney 300 MINING ECONOMICS. Mine. Sithney Wheal Metal Sithney Wheal Vor South Wheal Basset South Cam Brea - South Wheal Clinton South Condurrow - South Crenver South Orofty South Dolcoath - South Wheal Ellen South Wheal Pran- ces South Garras South Gorland South Great Tol- gus South Wheal Gren- ville - - - South Wheal Hawk South Lovell South Penstruthal South Roskeaf South Wheal Seton South Tinoroft South Tolcarne South Wheal Tol- gus South Wheal Towan South Tresavean - South Wendron Mine - . - Sparnon, Wheal; Sparrow, Wheal Sperries, Wheal - Spinster, Wheal - Squire, Wheal Susan, Wheal Swanpool Tallack, Wheal - Tehidy, Wheal Tincroft Ting Tang Mine - Todpool Mine Tolans Mine - i Tolcarn Mine Tolgullow Tolglus, Wheal Tolgus United Mine - - - Towan, Wheal Towan Consols Trannaok, Wheal - Trefula Mine Trefusis, Wheal - Tregajorran Tregonebris - Parish. Sithney Sithney lUogan Illogan Gwennap Camborne- Crowan Illogan Illogan St. Agnes Illogan Kenwyn Gwennap Eedruth Camborne Redruth Wendron Gwennap Camborne Camborne Illogan Camborne Redruth St. Agnes Perranar- woi'thal / Constantino \ Wendron Redruth Illogan Kea Gwennap Gwennap Camborne Falmouth St. Agnes Illogan Illogan Gwennap f Gwennap \ Kenwyn Eedruth Gwennap Kenwyn Eedruth Redruth f Illogan \ St. Agnes St. Agnes Sithney Redruth Gwennap Illogan Wendron MiNB. Trelawney, Wheal - Treleigh Consols - Treleighwood Mine Trelusback Mine - Tremenheere Trenear Mine Trenithick Mine - Trenithick Wood Mine - - - Tresavean Mine - Treskerby Mine - Tretharrup - Trethellan - Trevarno Mine Trevensou Trevenen Bal Treviskey Trevoole Treworlis Mine Trewirgie Downs - Trumpet Consols Tryphena, Wheal - Tywarnhayle Mines Union, Wheal Union Mines United Hills - United Mines Unity, Wheal Unity Wood, Wheal Uny, Wheal - Virgin, Wheal Vor, Wheal - Vraws, Wheal Vrea, Wheal - Vyvian, Wheal Wallis, Wheal Well close Mine Wellington, Wheal Wendron Consols - Wendron United Mines Wentworth, Wheal West Basset - West Bosprowal West Wheal BuUer West Carvannel - West Clifeord West Condurrow - West Wheal Dam- sel- West Dolcoath West Frances West Wheal Gren- ville - - - West Wheal Jane - West Wheal Jewell Pabish. Redruth Redruth Redruth Stith'ians Wendron Wendron St. Agnes Wendron {Gwennap Redruth Gwennap Gwennap Gwennap Sithney Illogan Wendron Gwennap Crowan Wendron Redruth Wendron Camborne St. Agnes / Redruth \ Wendron Gwennap St. Agnes Gwennap Gwennap Kenwyn Redruth Gwennap Breage Sithney Breage Constantine Breage Wendron Camborne Wendron Wendron Redruth Illogan G win ear / Camborne \ Illogan Gwennap Gwennap Camborne Gwennap Camborne Illogan Crowan Kea Gwennap INDEX TABLES OF THE MINES. SOI Mine. Pabish. Mine. Par)SH. West Lovell - Wendron West Wheal Tol- f Illogan \ Bedruth WestWheal Lush- gus - ington Illogan West Trefula Eedruth West Wheal Seton Camborne West Tresavean Gwennap West Wheal Towan Illogan West Trethellan Gwennap West Stray Park Camborne West Wheal Virgin Gwennap West Peevor - Redruth West Wheal Vor Breage West Poldice / Kenwyn \ Gwennap Widden, Wheal fKea \ Wendron The following index gives the positions of the mines on this sheet. The Roman numerals indicate the numbers of the 6-inch and 25-inch maps issued by the Ordnance Survey. The letters indicate the quarter sheets of the 6-Lnch maps, while the figures represent the numbers by which the 25-inch maps are designated. Thus Dolcoath Mine LXIII., S.W. 9 means that Dolcoath is situated on the 6-inch Ordnance map LXIII. in the S.W. quarter sheet ; while on the 25-inch map it is situated on sheet LXIII. in map No. 9. BREAGE, Parhh of. Carleen Mine, LXXV., N.B. 4. (or Carleen Wheal Vor.) Cammeal Mine, LXXV., N.E. 8. (and Wheal Fortune.) Emma, Wheal, LXXV., N.B. 8. Fortune, Wheal, LXXV., N.B. 8. Great Wheal Fortune, see Wheal Fortune. Great Wheal Vor and PoUadras, LXXV., N.B. 4. Great WTieal Metal, see Wheal Metal. Metal, Wheal, LXXV., N.B. 4. North Wheal Vor, see Penhale Wheal Vor. New Hendra Mine. North Wheal Metal, part of Wheal Wallis. Penhale Wheal Vor, LXXV., N.E. 4. Penhale Mine, see Penhale Wheal Vor. Pellor Wheal Metal. Poldown, see Great Wheal Vor. PoUadras Mine, see Great Wheal Vor. Vrea, Wheal, part of Great Wheal Vor. Vor, Wheal, LXXV., N.E. 4. West Wheal Vor, see Wheal Emma. Wallis, Wheal, see Penhale Wheal Vor. BUDOGK, Parish of. Wheal Penrose, LXXVIL, N.E. 3. CAMBORNE, Parish of. Bolenowe, LXIIL, S.W. 14. Camborne Consols, LXIII., S.W. 9. Camborne Vean, LXIII., S.W. 9. Cam Camborne, LXIIL, S.W. 9. Camemow, see Pendarves United. Copper Tankard, LXIIL, N.W. 5. Copper Hill, LXX., N.W. 2. (see also in Redruth Parish.) Crane and Bejawsa, LXIIL, S.W. 9. Crofty, Wheal, part of North Ros- kear. Dolcoath Mine, LXIIL, S.W. 9. Bast Grenville, LXIIL, S.W. 14. East Wheal Seton, LXIIL, N.W. 5. (part of Bast Crofty, see in Illogan Parish.) East Tresavean, LXIIL, S.W. 14. Frances, Wheal, see Camborne Vean. Gerry, Wheal, LXIIL, S.W. 9. Gilly Mine, LXIIL, S.W. 9. Gine, Wheal, see Polgine. Gons, Wheal, part of Dolcoath. Great Condurrow, LXIIL, S.W. 10. (part of Pendarves United.) Grenville, Wheal, LXIIL, S.W. 14. Gustavus Mine, LXIIL, S.W. 9. Harriet, Wheal, LXIIL, S.W. 9. Hatchet, Wheal, LXIIL, N.W. 5. Kellivose Mine, LXIIL, S.W. 13. King Edward Mine, part of South Condurrow. Knight, Wheal, LXIIL, N.W. 5. Lower Bolenowe Mine, LXIIL, S.W, 14. Nelson, Wheal, LXIIL, S.W. 1.3. New Dolcoath, see Polgine. 302 MINING ECONOMICS. New Seton, LXIIL, N.W. 5. North Dolooath, see Dolcoath. North Eoskeair, LXIII., N.W. 5. Pendarves United (Consols), LXIIL, N.W. 5. Polgine Mine, LXIIL, S.W. 14. Roskearnoweth, part o£ North Ros- Seton, Wheal, LXIIL, N.W. 5. South Condurrow, LXIII, S.W. 14. • South Wheal Grenville, LXIIL, S.W. 14. South Roskear, LXIlL, N.W. 14. South Wheal Seton, see Gilly Mine. South Tolcarne, LXIIL, S.W. 13. Susan, Wheal, LXIIL, N.W. 5. Tryphena, Wheal, LXIIL, S.W. 13. Wellington, Wheal, see Roskear- noweth. West Wheal BuUer, LXIIL, S.W. 14. West Condurrow, see Kellivose and South Tolcarne. West Dolooath, LXIIL, S.W. 13. West Wheal Seton, LXIIL, N.W. 5. West Stray Park, LXIIL, S.W. 9. G0N8TANTINE, Pariah of. South Wendron Mine, LXXVL, N.B. 4. Vyvian, Whoal, LXXVIL, N.W. 1. CROW AN, Pariehof. Abraham Consols, see Crenver and Wheal Abraham. Carbona Mine, LXX., S.W. 9. Clowance, Wheal, LXIX., N.E. 8. Clowanoe Wood Mine, LXIX., S.E. 12. Copper Bottom, LXIX., N.E. 8. Courtis, Wheal, LXIX., S.E. 12. Crenver and Wheal Abraham, LXIX., S.E. 12, Crowan and Wendron Mine, see Parish of Wendron. Drym Mine, see Crenver and Wheal Abraham. East Wheal Abraham. Gernick, LXX., N.W. Great Drym Consols, LXIX., S.B. 12. Hangman's Barrow, LXX., N.W. Hender, see Copper Bottom. Millet, Wheal, LXIX., S.E. 16. NancegoUan, LXX., S.W. 13. New Wheal Prances. Nelson, Wheal, LXIIL, S.W. 13. Polcrebo Downs, LXX., S.W. 9. Rosewarne United, LXIX., N.E. 4. Sarah, Wheal, LXIX., S E. 12. South Crenver. Trevoole, LXX., N.W. 1. West Wheal Grenville, LXX., N.W. 1. FALMOUTH, Parish of. Swanpool Mine, LXXL, S.E. 15. GWENNAP, Parish of, Ale and Cakes Mine, see United Mines. Andrew, Wheal, LXIV., N.W. 2. Beauohamp, Wheal, LXIIL, S.E. 12. Bell and Lannarth, LXIIL, S.E. 11. Bellvean Mine, LXIIL, S.E. 12. Bissoe Pool, LXIV.. N.W. 6. Brewer, Wheal, LXIIL, S.E. 12. Britannia, Wheal, LXIV., N.W. 5. Carharrack, LXIIL, N.E. 8. Carqueen Mine, LXIIL, N.E. 4. Cathedral Mine, LXIIL, N.E. 8. Carvannel Mine, LXIIL, S.E. 12. Chance, Wheal, LVI., S.E. 16. Clifford, Wheal, LXIV., N.W. 5. Clifford Amalgamated, see United Mines and Great Consolidated Mines. Clinton, Wheal, LXIIL, N.E. 4. Comford, Wheal. LXIIL, S.E. 12. Cupboard Hill Mines, see United Mines. Cusvey, part of Great Consolidated Mines. Damsel, Wheal, LXIIL, N.E. 8. East Ale and Cakes, see United Mines. East Wheal Basset, LXIIL, S.E. 11. East Wheal Buller, see Wheal Beauchamp. East Wheal Damsel, LXIIL, N.E. 8. East Wheal Sparnon, see Wheal Grambler. Bast Wheal Virgin, part of Great Consolidated Mines. Bdgcumbe, Wheal, LXIIL, S.E. 12. Fortune, Wheal, see Great Con- solidated Mines. Friendship, see Wheal Andrew. Girl, Wheal, part of Great Con- solidated Mine. Gorland, Wheal, LXIIL, N.E. 4. (part of St. Day United.) Grambler, Wheal, LXIH, N.E. 8. (and St. Aubyn.) Great Consolidated Mines, LXIV., N.W. 1. Henry, Wheal, LXIV., N.W. 1. Hope, Wheal, see West Wheal Damsel. Jewell, Wheal, LXIV., N.W. 1. INDEX TABLKS OF THE MINES. 303 Maid, Wheal, LXIV., N.W. 1. (part of St. Day United.) Moyle, Wheal, see Ting Tang. New ClifEord. North. Damsel, see West Wheal Jewell. North Penstruthal, LXIII., N.E. 4. Old Wheal Jewell, part of St. Day United. Park an Chy Mine, LXIII., N.B. 4. Pennance Mine, LXIII., N.E. 8. Penstruthal Mine, LXIII., S.E. 12. Rnk, Wheal, LXIII., N.E. 4. Poldice Mine, LXH^, N.W. 1. (part of St. Day United.) iPoldory Mine, part of United Mines. Quick, Wheal, see Old Wheal Jewell. River Colnv Mine, LVI., S.E. 12. St. Aubyn United, LXIII., N.E. 4. St. Day United, LXIV., N.W. 1. South Wheal Clinton, LXIII., S.E. 12. South Gorland, see West Wheal Jewell. South Penstruthal, LXIII., S.E. 12. Spinster, Wheal, see Wheal Damsel. Squire, Wheal, LXIII., N.E. 8. Ting Tang Mine, LXIII., N.E. 8. Todpool Mine, LXIV., N.W. 1. Tolearn Mine, LXIII., N.E. 4. Trefusis, Wheal, LXIIL, N E. 7. Tresavean Mine, LXIII., N.E. 12. (and Tretharrup.) Treskerby Mine, LVI., S.E. 16. Tretharrup, see Tresavean, Trethellan Miae, LXIII., S.E. 12. Treviskey Mine, LXHI., S.E. 12. Union Mine, see Wheal Andrew. United Mines, LXIV., N.W. 5. Unity, Wheal, LXIV., N.E., 1. (part of St. Day United.) Virgin, Wheal, part of Great Con- solidated Mines. West Carvannel. West Clifford, see Ting Tang Mines. West Wheal Damsel, LXIII., N.E. 8. West Wheal Jewell, LXIII., N.E. 4. West Poldiee, LXIIL, N.E. 4. West Tresavean, LXIIL, S.E. 12. West Trethellan. West Wheal Virgin, part of Great Consolidated Mines (in Tolcarne.) West Poldiee, LXIIL, N.E. 4. OWINEAR, Parish of. Annie, Wheal, LXIL, S.E. 16. Brook, Wheal, LXIL, S.E. 16. Crack Crowder Mine, LXlI., S.E. 16. East Eosewarne, LXIL, S.E. 16. Gwinear Consols, see Eosewarne United. Margaret, Wheal, LXIL, S.E. 16. New Eosewarne Mine, LXIX., N.E. 4. (part of Eosewarne United.) Eosewarne Consols, LXIX., N.E. 4. Eosewarne United, LXIX., N.E. 4. WestBosprowal, LXIL, S.E. 16. ILLOGAN, Parish of. Agar, Wheal, LXIIL, N.W. 6. Barncoose Mine, LXIIL, N.W. 6. Basset, Wheal, LXIIL, S.E. 11. Carnarthen, see South Dolcoath. Cam Brea, LXIIL, N.W. 6. Carnkie Mine, see Wheal Basset. Clarence, Wheal, LVI., N.E. 7. Cook's Kitchen, LXIII., S.W. 10. Druid, Wheal, part of Carn Brea. Duchy, Wheal, LVI., S.W. 10. Dudnance, part of South Crofty. East Wheal Basset, LXIIL, S.E. 11. Bast Wheal Crofty, LXIII., N.W. 6. East Pool Mine, LXIIL, N.W. 6. East Wheal Seton, see Emily Henrietta. Elizabeth, Wheal, see Great North Tolgus. Ellen Wheal, LVI., S.E. 11. Emily Henrietta, LXIIL, N.W. 6. Fanny, Wheal, LXIIL, N.W. 6. Fire, Wheal, LVI., S.W. 10. Forest Mine, LXIIL, S.W. 14. Fortune, Wheal, see Wheal Agar. Pox Hole, LXIIL, S.W. 10. Great North Tolgus. LVL, S.W. 14. Great St. Vincent, LVL, S.W. 10. Grillis, LXIIL, S.W. 14. Illogan (part of Tincroft), see Wheal Providence. Knight, Wheal, LXIIL, N.W. 5. Lushington, Wheal, LVL, N.W. 6. Lydia, Wheal, LVL, N.E. 7. Longclose, part of South Crofty. Nancekuke, see Wheal Clarence. New Cook's Kitchen, LXIIL, N.W. 6. New North Pool, LXIIL, N.W. 6. North Wheal Basset, LXIIL, North" Wheal Crofty, LXIIL, N.W. 6. (partof East Crofty.) North Wheal Frances, LXIIL, S.W. 10. North Pool Mine, LXIIL, N.W. 6. North Eoskear, LXIIL, N.W. 5. Old Wheal Basset, see South Wheal Ellen. Old Pool Mine, part of North Crofty. 304 MINING KCONOMICS. Providence, Wheal, LXIII., S.W. 10. Bobarts, "Wheal, LVI., S.W. 14. South Wheal Basset, LXIII., S.B.ll. South Garn Brea, LXIII., N.B. 7. South Crofty, LXIII., N.W. 6. (part of East Crofty.) South Dolooath, LXIII., S.W. 10. South Wheal Ellen, see St. Agnes Parish. South Wheal Prances, LXIII., S.W. 10. South Tincroft, LXIII., S.W. 10. Sparrow, Wheal, LVI., S.E. 11. Tehidy, Wheal, LXIIL, N.W. 6. Tincroft, LXIIL, N.W. 6. Towan, Wheal, LVI., N.E. 7. Tregajorran, LXIIL, N.W. 6. Trevenson, part of South Crofty. West Basset Mine, LXIIL, S.W. 10. West BuUer, LXIIL, S.W. 14. West Wheal Frances, LXIIL, S.W. 10. West Wheal Lushington, LVI., S.W. 10. West Wheal Tolgus, LXIII. N.W. 2. West Wheal Towan, see Wheal Lushington. KEA, Parish of. Andrew, Wheal, LXIV., N.W. 2. Baddern, (Baddon), Wheal, LXIV., N.W. 2. Baldhu, LXIV., N.W. 2. Falmouth, Wheal, LVII., S.W. 14. Falmouth and Sperries, Wheal, LVIL, S.W. 14. East Wheal Falmouth, LVII, S.W. 14. Great Wheal Baddern, see Wheal Baddern (Baddon). ■Hope, Wheal, LXIV., N.W. 2. Jane, Wheal, LXIV., N.W. 2. Nangiles Mine, LXIV., N.W. 2. Sperries, Wheal, LXIV., N.W. 2. West Wheal Jane, LXIV., N.W. 2 Widden, Wheal, LXIV., N.W. 2. KENWYN, Parish of. Ann, see Wheal Seymour. Boscawen Mine, LVI., S.E. 16. (part of Great Wheal Busy.) Burra Burra Mine, LVIL, S.W. 9. Busy, Wheal, see Great Wheal Busy. Chaoewater Mines, see Great Wheal Busy. Creegbraws Mine, LXIV., N.W. 1. (and Penkevil.) Daniel], Wheal, LVIL, S.W. 13. Bast Wheal Chance, LVI., S.E. 16. Bast Wheal Falmouth, LVIL, S.W. 14. Great Wheal Busy, LVIL, S.W. 13. Hallenbeagle Mine, see Boscawen, part of Great Wheal Busy. Henry, Wheal, LXIV., N.W. 1. Killifreth Mine, LVI., S.E. 16. New Burra Burra. New Hallenbeagle, see Boscawen. North Wheal Busy, LVI., S.E. 12. North Wheal Jane, LVIL, S.E. 15. Penhaldarva. Penkevil, see Creegbraws. Prosper, Wheal, LXIV., N.W. 1. Scorrier Old Mine, LVL, S.E. 16. Seymour, Wheal, LVIL, S.W. 13. South Garras. Todpool Mine, LXIV., N.W. 1. ToIguUow, see Unity Wood and West Poldice. Union, see Wheal Unity Wood. Unity Wood, Wheal, LVIL, S.W. 13. West Poldice, LXIIL, N.E. 4. MYLOR, Parish of. Clinton, Wheal, LXXL, S.E. PERRANARWORTHA L, Parish of. Silver Hill South Tresavean, LXIV. REDRUTH, Parish of. Barberry, Wheal, see Wheal Plenty. Boys, Wheal, LVL, S.E. 16. Briggan, Wheal, LVL, S.E. 16. Buckets, Wheal, LXIIL, N.E. 7. Buller, Wheal, LXIIL, S.E. 11. Burncoose, Wheal, LXIIL, N.B. 7. Captain, Wheal, LXIIL, N.E. 7. Cardrew Consols, see Wheal Prussia. Chance, Wheal, LVI., S.E. 16. Clyjah and Wentworth, see Perse- verance Mine. Copper Hill, part of Wheal Buller. Cupid, Wheal, LXIIL, N.E. 4. Derrick, Wheal, LXIIL, N.B. 3. Dopps Mine, see Pedn an Drea. Bast Wheal Basset, LXIIL, S.W. 11. East Carn Brea, LXIIL, N.E. 7. East Wheal Tolgus, LXIIL, N.E. 3. Gilbert, Wheal, LXIII., N.B. 3. Good Success Mine, see Treleigh Consols. MINING ECONOMICS. 305 Great North Downs, LVII. S.E. 16 Great South Tolgus, LXIII., N.E.7. (North BuUer.) Harmony, Wheal, LXIII., N.E. 3. Hawk, Wheal, LVI., S.E. 16. Lily, Wheal, LXIII., N.B. 4. Little North Downs. Louisa, Wheal. Mary, Wheal, LVI., S.E. 15. Maria, Wheal, see Treleigh Consols. Messar, Wheal, see Great North Downs. Montague, Wheal, LXIII., N.B. 3. Mount Carbis, LXIII., N.B. 7. New Treleigh, see Treleigh Consols. North Briggan, LVI., S.E. 16. North Buller, see Great South Tolgus. North Wheal Buller, LXIII., N.E. 7. North Downs, LVI., S.E. 15. North Grambler. North Trewan Mine, LVI., S.E. 16. Pedn an Drea, LXIII., N.B. 7. Peevor, Wheal, LVI,, S.E. 15. Perseverance Mine, LXIII., N.E. 7, Pink, Wheal, LXIIL, N.B. 4. Plenty, Wheal, LVI., S.E. 15. Prussia, Wheal, LVI., S.E. 15. Raven, Wheal, LXIIL, N.W. 2. St. Aubyn United, LXIIL, N.E. 4. South Great Tolgus, LXIIL, N.B. 7. South Wheal Hawk, LVL, S.E. 16. South Wheal Tolgus, LXIIL, N.E. 3. Sparnon, Wheal, LXIIL, N.E. 7. Tehidy, Wheal, LXIII., N.W. 6. Tolans Mine, see Bast Wheal Tolgus. Tolgus, Wheal, LXIII., N.E. 3. Tolgus United Mine, LXIIL, N.E 3. Trefula Mine, see Wheal Lily. Trelawney, Wheal, LXIIL, N.E. 8. Treleigh Consols, LVI., S.E. 15. Treleighwood Mine, LXIII., N.E. 3. Tresavean Mine, LXIIL, S.E. 11. Trewirgie Downs, see Wheal Buller. Union, Wheal, LXIII., N.E. 3. Uny, Wheal, LXIIL, N.E. 7. Wentworth, see Perseverance. West Peevor, LVI., S.E. 15. West Wheal Tolgus, LXIIL, N.W. 6, West Trefula, LXIIL, N.B. 3. ST. AGNES, Pa/rish of. Banns, Wheal, LVT., N.B. 7. Charles, Wheal, LVI., N.E. 7. Cornwall, LVII., N.W. 5. Concord, see North Treskerby. East Wheal Ellen. (?) East Downs Mine, LVI., S.B. 16. East Wheal Music, LVL, N.E. 8. East Treskerby. (?) Bast Wheal Towan, LVL, N.E. 7. Ellen, Wheal, LVL, S.E. 11. Fancy, Wheal, LVL, N.B. 7. Music, Wheal, now Wheal Bllen. North Wheal Basset, LVI., S.E. 11. North Hallenheagle, LVL, N.B. 8. North Treskerby, LVL, S.B. 16. Rose, Wheal, LVI., S.E. 16. Rose Ann Mine, LVI., N.E. 7. Scorrier Consols, LVL, S.B. 12. South Wheal Ellen, LVL, S.B. 11. South Wheal Towan, LVL, N.E. 7. Tallack, Wheal, LVL, N.B. 7. Towan Consols, LVI., N.B. 7. Towan, Wheal, LVL, N.B. 7. Trenithick Mine, LVL, N.E. 8. Tywainhayle Mine, LVL, N.B. 7. United Hills, LVL, N.B. 7. ST. GLUVIAS, Parish of. Roskrow United, LXIV., S.W. E. SITHNEY, Parish of Bramble, Wheal, LXX., S.W. 13, Christopher, LXX., S.W. 13. Bast Wheal Vor. (?) East Wheal Fortune, see Sithney Wheal Vor. Fursden, Wheal, LXX., S.W. 14. Harriet, Wheal, LXXVL, N.W. 2. Mount, Wheal, LXXVL, N.W. 2. New Vor and Metal United. North Metal Mine, LXXV., N.E. 4. North Prospidnick, LXX., S.W. 13. Peverill, Wheal, see Wheal Furs- den. Polcrebo Downs, LXX., S.W. 9. Prospidnick Mine, LXX., S.W. 13. Sithney, Wheal, LXXVL, N.W. 5. Sithney Carnmeal Mine, LXXVL, N.W. 1. Sithney, Wheal Metal, LXXV., N.E. 4. Sithney Wheal Vor. (?) Trannack, Wheal, LXXVL, N.W. 2. Trevarno Mine, LXXVI., N.W. 1. Vraws, Wheal, see North Prospid- nick Mine. STITHIAN8, Parish of Trelusback Mine, LXIIL, S.E. 16. X 306 MINING ECONOMlCa. WENDRON, Parish of. Ann, Wheal, LXXVI., N.W. 2, (or Trumpet United.) Bal Ding, LXX., S.B. 12. Basset and Grylls, Wheal LXX.. S.B. 11. Buller and Basset United Mine LXIII., S.B. 15. ' Balmynheer Mine, LXX., N.B. 7. Bodilly Consols, LXX., S.W. 14. Calvadnack Mine, LXX., N B 7 Cudy, Wheal, LXX., S.B. 15. ' Crowan and Wendron Mine, for- merly Eeleath Mine. Combellack Mine, LXXVI., N.B. 3 Dream, Wheal, LXX\X, N.W. 2 Duchy, Wheal, see Old Wheal Lovell. East Trumpet Mine, LXXVL, N.W. 2. East Wheal Lovell, LXX., S.B. 15. Buys, Wheal, LXX., S.B. 11. Foster, Wheal, LXX., S.B. 11. Garlidna, LXX., S.B. 11. Great Wheal Lovell,LXXVL,N.E.3. Great Bast Lovell. Lovell, Wheal, LXXVI., N.B. 3. Medlyn Moor Mine, LXX., S.B. 11. Mengearn, LXXVI., N.B. 3. New Wheal Lovell, LXXVI., N.B. 3. New Trevenen. New Trumpet Consols, LXXVI., N.B. 3. New Wendron. North Lovell Mine, LXX., S.B 11 Old Wheal Lovell. 01^^Tr|venen Mine, LXXVL Polengrean, see Garlidna. Polhigey Mine, L^X., N.B 7 Porkellis United, see Ba.sset and Grylls, Porkellis Moor, LXX., S.E. 15. Keleath Mine or Crowan and Wen- dron Mine, LXX., S.W. 10. Eetanna Hill Mine, LXX., S.B 12 Koselidden Mine, LXXVI., N.W 2 bouth Lovell. South Wendron Mine, LXXVL N.B. 4. Tregonebris see Bast Wheal Lovell. Tremenheere Mine, LXXVI N.W. 6. ■' Trenithick Wood Mine, LXXVI N.W. 6. ' Trevenen Bal, LXXVL, N.W. 2 Trevenen Mine, LXXVL, N.B. 3 Trenear Mine, LXX., S.B. 15 Treworlis Mine, LXXVI., N.W. 6 Trumpet Consols Mine, LXXVI N.W. 2. ^AVi., Wellclose Mine, LXXVI,, N.W 2 Wendron Consols, LXX., S.B. 15 ' Wendron United Mines, LXX. Widden, Wheal, LXXVL, N.W. 2 West Lovell. Total Yield of Tin and Coppek in Cornwall (Fig. 65.) The following statistical table has been compiled from numer- OHS publications containing details of the annual output of ore, yield of metal, amount realised by sales, produce, standard price,' and price of metal on market, but it should be remarked that the figures given by some of the authorities who have made indepen- dent estimates for certain years do not agree. This is probably owing to the same general difiBculties as were experienced in estimating the total yield of the individual mines, namely, that the private sales were not formerly divulged in the way that the amounts sold by public ticketing were. The table, which up to 1882 is largely from Hunt's "British Mining," may be regarded as fairly reliable, and since 1882 as quite trustworthy. In. its preparation the following are the principal works that have been consulted : — Pryce. — "Mineralogia Oorniibiensis,'' 1778. Annual output of copper ore from 1726 to 1775, Prior to 1760 the amounts are only given in round figures (p. 14). TOTAL YIELB OF TIN AND COPrER. 307 o o o <0 o o o o o o o o o o o o o o o o o o o o o o o * to Q) n o o o o o o n o o o o o o O o o o o o o t- CO lO * to eu "~ a < TC 2 308 MINING ECONOMICS. Gilbert, O. S. -" History of Cornwall," vol. ii., 1817, p. 707. Annual output of tin (in blocks* and tons) from 1750 to 1816. Trans. Boy. Geol. Soc. Corn., vol. ii., 1822, vol. iii., 1828, vol. iv., 1832. Yield of copper ore and copper, &c., from 1771 to 1832. Grylls, H.— " A Synopsis of Mining from 1729 to 1833." Copper ore, copper, &c., from 1729 to 1832. Blocks of tin from 1750 to 1832. Lemon, Sir Charles. — Journ. Stat. Soc, vol. i., 1838, p. 70. Courtney, J. S. — "A Treatise on the Statistics of Cornwall," Rep. Boy. Corn. Poly. Soc, 1838, p. 81. Tonnage of tin from 1750. Came, J . — " Statistics of the Tin Mines of Cornwall and of the Con- sumption of Tin," Journ. Stat. Soc, vol. ii., 1839. Tonnage from 1750 to 1837. De la Beche, H. T.— " Geological Report of Cornwall, Devon, and West Somerset," 1839, p. 606. Copper ore and copper, &c., from 1771 to 1838. " Mineral Statistics," Mem. Geol. Surv., 1848 to 1881. Copper ore, copper, black tin, metallic tin, standard and market prices, &c. Grylls, H.— " Annual Mining Sheet," No. 21, 1852. Copper ore, &o., from 1833 to 1852. Hunt, E. — " British Mining," 1884. Copper ore, copper, black tin, metallic tin, standard and market prices, &c., from 1726 to 1882. " Mines and Quarries, General Report and Statistics " (Home Office), part iii., Output. All products and prices from 1882 to 1905. In the statistical table the price of copper has been given in two ways : (1) the price which the miner received for each ton of copper in the ore sold, and (2) the price of copper on the London market. In a third column the standard for copper is also given, and this is the sum which governed the money transactions between the smelter and the miner, and was not a sum actually paid. The term has been explained by Percy, Lemon, Bickard, Phillips and Darlington, Salmon, Hunt, and others. In the early days of copper mining the smelters generally made contracts with the miners for definite periods and undertook to buy the ore at a certain rate, which was determined by a standard price pre- viously agreed on by the miner and smelter, and this was usually the selling price of tough cake copper. The standard having been settled, the sum whicfi the miner received for the copper in the ore was at this rate ; but he paid back to the smelter a certain sum known as the " returning charges," generally £2 15s. per ton of ore. These " return- ing charges" were generally in excess of the actual cost of smelting, so that this was one source of profit to the smelter. The miner further gave him an extra cwt. in the ton to cover losses in «arriage, and he also made allowance for moisture. Another source of profit to the smelter arose from the fact that the percentage of copper shown by the assayer's results was generally lower than the percentage procurable in smelting.! As there was a certain '" returning charge " due to the smelter on every ton of ore, it paid him better to buy low-grade ores than rich ones, as the proportional cost of extraction per ton of metallic copper to the total amount of the returning charges was less. It was to the smelter's advantage to keep the standard as low as possible and to the miner's interest to raise it. * A block weighs from 360 to 380 lbs. There are, roughly, about 64 blocks in a ton. The weight of a block has, however, varied from time to time. In 1305 it was 126 lbs. ; in 1577, 308 lbs. ; in 1587, 324 lbs. ; in 1597, 335 lbs. ; in 1607 it was 346 lbs. Sir John MacLean, Journ. Boy. Inst. Corn., 1874, p. 187. t " The amount of copper obtainable by smelting British ores is about ^ or 4 per cent, more than the amount calculated from flie dry assay. Thus, in the case of an ore containing 5 per cent, of metal by dry assay, the actual yield has Iieen taken as 5J per cenc."— "General Statistics," pare iii.. Output, p. 200. TOTAL YIELD OF TIN AND COPPER. 309 As competition increased and the market price of copper became fixed by auction at public ticketings, the importance of the " standard " was dimin- ished, but for the sake of comparison it was calculated, after the sales, from the market price of copper and the produce of the ore. In early days, therefore, the standard was an amount agreed upon by the miner and smelter, and determined the amount the miner was to receive for the ore. In later times it ceased to have any value beyond affording a means of making comparison, and instead of being a sum agreed on, it was an amount calculated from the selling price of the copper. Method of calculating the price of Copper in early days. Tough cake copper sold at £120 per ton. (Has nothing to do with the estimation.) The standard agreed on = 118. Suppose 140 tons of ore containing 8 per cent, of copper on sale. Returning charge = 140 x ^62 15 = £385. Amount of copper in ore, viz., 8 per cent. = ]1'2 tons. Value of copper in ore, according to standard = 11-2 x £118 = £1,321-6 .". Amount received by miner = £l,321-6-£385 = £936'6 = £67 per ton. Method of calculating the standard in later times,* 140 tons of ore containing 8 per cent, copper, sold at public ticketing, for £936-6 The standard is calculated as follows : — The returning charge =140 x £2 15s. = £385. .-. £936-6 + £385 = £1,321-6 .-. £1,321-6. 11-2 = £118 per ton (standard). The smelter, in estimating the value of the ore before making his offer to the miner, generally consults a table prepared from actual practice, showing the cost of working the ore, which guides him in his calculation. The following is an abbreviated example of a page in the smelters note book : — £ s. d. Cost of working 5 per cent copper ore is 16 19 10 per ton of copper , 10 »» )) 11 3 6 )» )i , 15 »j »j 9 4 10 "/ )) , 20 if calcined, is 8 9 2 »» »» . 20 if not calcined, is 6 19 2 »» »» , 30 if calcined, is 6 9 2 »» )» " , 30 if not calcined. is 5 9 2 »» )j ' , 50 if calcined, is 4 15 8 i» t» " , 50 if not calcined, is 4 3 8 »» »t n , 70 D (precipitate) 3 15 5 )) ), With regard to tin, the "standard is the amount paid by the smelter per cwt. of metal contained in the ore, as calculated from the results of an assay by the dry method, after deduction of IJ from the produce per 20 (b, per cent.) for returning charges. By an old trade custom there is alSQ a de- duction on the weight of the parcel of tin ore of 3 lbs. per cwt. It is customary to reckon the price to the nearest eighth of a pound steTling above or below the calculated price."t * The standard price should nofc be confused with the term standard copper which, according to Brown and TurnbuU, " ^ Century of Copper, ISOO- «»" tains 96 per cent, of copper. Tough copper containing 991 per cent, bee also Part III., "General Statistics." t "General Statistics," part iii., Output. OaU MI NING HDONOMICS. Date. Blaclj Tin. Metal- lic Tin Price per Ton Metal lie Tin. Copper Ore. Metallic Copper. Standard Value of Copper at Mine, per Ton. Tons. Tons £ s. d. Tons. Cornwall Tons. £ s. d. £ a. d. 1726 ... 5,000 1727 ... • • • 6,700' 1728 ... ... • . . 6,800 1729 ... ... ... 6,870 1730 ... ... 6,900 1731 ... ... ,,i 7,000 1732 ... ... 7,290 1733 ... ... • < ■ 7,000 1734 ;.. ■ •• 6,000 ... 1735 1.. 5,240 1736 ... ... • •■ 8,000 ... 1737 ... ... 9,000 ... 1738 ... • •• 10,000 ... ... ... 1739 ... ... 11,000 ... 1740 ... ... 5,000 . .. ... ... 1741 ... ... . •• 5,500 1742 ... ..; 6,050 . .. ... ... 1743 ... ... 7,040 .. . . .. 1744 • t. 7,230 ... 1745 ... ... ... 6,700 . i . 1746 ... ... 7,000 ... . • . 1747 ... ... ... 4,900 .1. 1748 ... ... 6,000 1749 ... ... 7,200 .. . ... 1750 ... 2,876 64 17 6 9,400 ... ... 1751 2,273 65 2 6 11,000 1752 ... 2,550 67 2 6 12,050 1753 ... 2,516 68 13,000 ... ... 1754 ... 2,724 67 17 6 14,000 ... ... 1755 . .. 2,757 67 14,240 ... ... 1756 2,774 62 12 6 16,000 ... 1757 ... 2,752 59 5 17,000 ... 1758 .. . 2,720 56 5 15,000 ... ... 1759 2,637 56 16,700 1760 .. • 2,717 56 15,780 ... ... 1761 . . . 2,395 59 17 6 17,004 1762 2,584 64 15 16,054 ... ... 1763 ... 2,736 68 17 6 17,898 ... ... 1764 ... 2,618 69 21,489 ... ... 1765 ... 2,757 69 16,774 ... 1766 .. . 3,055 69 21,251 ... ... ... 1767 .. . 2,850 69 18,502 ... ... 1768 2,667 69 ,23,671 ... ... ... 1769 ■ a. 2,898 69 26,655 ... ... ... 1770 ... 2,977 66 10 30,776 ... ... ... 1771 2,823 65 27,896 3,347 81 {Estimated) 1772 3,159 63 5 27,965 3,556 81 53 1773 2,852 54 27,663 3,320 70 45 0- 1774 2,458 52 10 30,254 3,630 68 44 1775 2,619 60 29,966 3,596 78 53 1776 2,652 59 15 29,433 3,532 79 54 1777 2,770 59 10 28,216 ' 3,386 77 52 1778 2,515 60 10 24,706 2,965 72 49 1779 2,678 60 31,115 3,734 73 48 1780 2-,926 61 5 24,433 2,932 83 58 1781 2,610 64 5 28,749 3,450 77 52 1782 ."..' 1 2,546 70 28,122 3,375 70 45 Q TOTAL YIELD OF TIN AND COPPER. 311 Date. Black 1 Tin. 1 kletal- r ic Tin. - Price per Don Metal- lic Tin. Copper Ore. Metallic Copper. Standard. Value of Copper at Mine, per Ton. Tons. Tons. £ s. i . Tons. Cornwall. Tons. £. s. d. £ s. d. 1783 2,570 70 35,799 4,296 76 51 1784 2,685 70 10 36,601 4,392 72 47 1785 2,885 72 36,959 4,434 71 46 1786 3,399 72 39,895 4,787 T 75 50 1787 3 204 72 38,047 4,500 67 J) 43 1788 3,352 66 10 31,541 3,800 57 40 1789 3,405 62 10 33,281 ^ 3,900 63 47 1790 3,193 72 10 34,700 4,100 1791 ..! 3,470 79 36,500 \ 4,250 K 'if 4 Til fi ted 1792 ... 3,809 92 10 38,300 4,450 Xi/0(i llUlXllf^U'r 1793 3,202 98 40,000 } 4,650 1794 3,351 95 10 42,816 4,920 88 67 1795 3,440 93 43,589 5,070 87 64 1796 3,061 96 10 43,313 5,120 J 93 70 1797 3,240 97 47,909 5,201 96 72 1798 2,820 94 51,358 5,600 ... ... 1799 2,862 97 51,273 4,923 121 95 1800 2,522 101 55 981 5,187 133 3 106 1801 2,328 105 56,611 5,267 117 5 90 1802 2,627 108 10 53,937 5,228 110 18 84 1803 2,914 109 60,566 5,615 122 95 1804 2,993 109 64,637 5,375 136 5 106 1805 2,742 il2 10 78,452 6,234 169 16 138 1806 2,855 120 10 79,269 6,863 138 5 106 1807 2,426 117 10 71694 6,716 120 91 1808 2,330 114 67,867 6,795 100 17 74 1809 2,508 122 76,245 6,821 143 12 113 1810 2,006 157 66,048 5,682 132 5 100 1811 2,384 141 10 66,786 6,141 120 10 90 1812 2,373 128 71,547 6,720 111 1 82 1813 2,324 134 74,047 6,918 115 7 86 1814 2,611 156 10 74,322 6,369 130 12 99 1815 2,941 140 10 78,483 6,525 117 16 85 1816 3,348 114 10 77,334 6,697 98 13 68 1817 4,120 93 10 76,701 6,498 108 10 76 Corn wall and 1818 D 4,066 3,315 2,990 evon. 84 15 86,174 6,849 134 15 104 1819 1820 ... 75 5 73 5 88,736 91,473 6,804 7,508 127 10 113 15 92 80 71 74 78 99 97 72 75 72 73 69 68 72 74 79 73 82 1821 1822 ... 3,373 3,278 75 13 95 10 4 98,426 104,523 8,515 9,140 103 104 1823 4 213 94 15 95,750 7,928 109 18 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 .•• 5,005 4,358 4,603 5,555 4,931 4,434 4,444 4,300 4,323 4,065 3989 4 228 4054 88 91 6 77 76 73 5 74 73 15 73 10 72 15 72 15 78 91 109 10 8 99,700 107,454 117,308 126,710 130,366 124,502 133,904 144,402 137,357 138,300 1432Si6 150,617 140,981 7,824 8,226 9,026 10,311 9,921 9,656 10,748 12,044 11,947 11,191 11,225 1^270 ir647 no 114 123 3 106 1 112 7 109 14 106 5 100 100 111 114 106 11 115 12 C 312 MINING ECONOMICS. 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Medlyn Moor, granite of, 58. Mine, note on, 232. Menagissey, 73. Menerdue, 11. Messack, 76, 78. Point, 30, 94. Metamorphio aureole, 4, 7. zone, microscopic characters, 82-86. Metamorphism on granite margin, 81—86. Meteoric waters, action on lodes, 187—194. Mica traps, 14, 74—80 ; age of, 75, 80 ; analysis, 77 ; distribution, 76 ; joints, 76, 78 ; lithological character, 74—76 ; microscopic characters, 77, 78; weathering, 75. Micro-granite, 65. Microscopic characters, of chert, 28, 37 ; elvan, 66-73 ; granite, 56— 63 ; greenstone, 42—52 ; killas, 26, 36, 39, 40, 82—85 ; mica trap, 77, 78. examination of products from ore dressing, 269 — 274 ; struc- tures of veinstones, 155. Middle Point, 18. Mine plans, 9, 259. Mineral area, 6—9 ; geology of, 113 ; scenery of, 10, 11. localities, 195—204. pitch in killas, 185. statistics, 275-289 ; 306— 314. veins, 7. See Lodes. Minerals, table of, 195—204; secondary deposition of, 187— 194 ; order of arrival in lodes, 182, 183, 184 ; conditions affecting deposition, 184 ; characterising tin lodes, 168, 169 ; in cross- courses, 160 ; order of arrival, 131, 182, 183, 184 ; Collins, J. H., and Flett, J. S., on order of arrival, 183. INDEX. 331 Mines, alphabetical list of, 297 — 301 ; in each parish, 301—306 ; abandoned, 221—256 ; active, 207 — 220 ; number working in last 50 years, 261 ; output of tin and copper, 275—289; output of minerals other than tin and copper, 290—295; linear distri- bution of, 205—207 ; bibliography relating to individual mines, 207 ; elvans in, 119 — 123 ; granite, 114 — 118 ; greenstone, 124 ; cross- courses, 158, 159, 160; killas, 185, 186; minerals, 195—204; lead and silver in, 181, 182 ; pitch of ore bunches, 161 ; chutes and courses of ore, 161, 163 ; vertical distribution of the ores in, 175 — 178 ; subordinate ores, 178-180. Minettes, 46. Mining industry, 10 ; decadence of, 9, 11 ; history, 259 -261 ; econo- mics, 258 — ^314. — ■ — maps, 10, 259. Mongleath, 46. Mount Hawke, 112. Murchison, Sir R. I., 3, 19, 93. Music, Wheal, stock-work in, 165. Mylor, 92 ; mines in parish of, 304. — Creek, 94. series, 14, 16, 25—29. NancegoUan, 107. Naneekuke Common, 12. Nangiles Mine, notes on, 232, 233. Nansavallan, 109. — W»od, 66. Nare Point, 18. Native metals and oxides in upper parts of lodes, 188. Newbridge, strike of lodes at, 149. New Cook's Kitchen, granite ridge in, 117. Wheal Virgin, lodes of, 233. Lovell, note on, 233. Seton, lode of, 233. Newham, 74, 109. See Lower Newham. Newton, B. T., 28. Nickel, occurrence of, 179 ; output from East Pool, 291. Nine Maidens, 106, 109. North Wheal Frances, granite in, 114. Jane, note on, 234. Roskear, description of, 234, 235. Downs, lodes of, 233, 284. Pool, note on, 234. Ochre, output from mines, 290 — 295. works, 112. Ordovician. See Lower Palseozoic. Ore bunches, 161 ; form of, 161 ; origin, 161 ; width, 163 ; Mois- senet, M. L., on origin of, 187 ; relation to granite and killas junction, 161 ; relation to joint- ing, 161 ; to breceiated masses, 161 ; connection with granite, 171—173 ; chute, 161 ; pipe, 161, 164, 165. dressing, 262—274 ; products from, 269—274. Ores, natural history of, 161 ; genesis, 167 — 171 ; concentration of, 9 ; local conditions affecting deposition, 184 ; association with elvans, 182, 184, 185 ; relation to greenstone, 186 ; connection with granite, 167, 175—178; distribu- tion, 171 ; occurrence at granite margin, 171—173 ; distribution of subordinate, 178 ; table of minerals, 195 — 204 ; solution and redistribution, 187 ; secondary deposition, 187 ; order of arrival in lodes, 131, 182—184; vertical distribution of tin and copper, 175—178; lead and silver, wolfram, zinc, bismuth, antimony, nickel, cobalt, manganese, uranium and gold, 178—180. Organic remains, 4, 36, 37. Outcrops of lodeSj tin in, 190. Output, tin and copper from individual mines, 274—289 ; minSrals other than tin and copper from individual mines, 290 — 295 ; of tin and copper from mines of Cornwall collectively, 310—314 ; tin-ore from mine heaps, 296 ; tin-ore from stream- works, 295, 296 ; Dolcoath since 1845, 261—262; Wheal Basset since 1851, 261—262 ; East Pool since 1845, 261—262 ; fluctuating, 260. Oxidation ot ores, 187 ; depth of, 194. Oxide of iron, output from mines, 290—295^ zone, 188. Palaeozoic divisions. See Lower Palseozoic. Parish, mines in each, 301 — 306. Peach, C. W., 37. , 137 ; Pryce, W., Carne, J., Phillips, J. A., Poster, C. Le Neve, Flett, J. S., on, 138. Peduan, 263. Pedn an Drea, granite in, 115 ; oar- bona, 165 ; lodes, 235. Peevor, Wheal, description of lodes, 236. Pegmatite, 53. Penooose, 67, 107, 109, 332 INDEX. Pendavves United, notes on, 235. Estate Office, 259. Pendennis, 29. Point, 14, 33, 76, 78, 79. Pendower, 14, 15, 37, 90, 91, 93, 100, 103. Pengegon Coombe, 71. Pengreep, 13, 42, 44. Peniiale, 50. Moor, 69, 85. Pennance, 14, 64, 94. • Mine, note on, 236. Point, 34, 92. Penpoll, 76, 101. Creek, 31. Penryn.'lO, 11, 12, 52, 76, 78, 80, 82, 86, 106, 107, 108, 111. Creek, 13, 18, 44, 46, 83. Pentuau, 98. Penwarne, 83, 107. Penwerris, 45. Perranarworthal, mines in parish of, 304. Perranwell, 10, 67. Petroleum in killas, 185. Pink, Wheal, note on, 236. Pipe, definition of, 161. Pitch of ore bunches, 161 ; relation to granite and killas junction, 161. • mineral, 185. Philleigh, 14, 30, 34. Phillips, J. A., 50, 51, 63, 65, 74, 76, 77,85, 86. Pill, 94. Plain of marine denudation, 2, 3, 5. Pleistocene deposits, 88—89, 90—98. sea, 5. Pliocene sea, 5. Pneumatolysis, 168 ; in acid plutonic rocks, 169 ; in basic plutonic rocks, 169 ; Teall, J. J. H., on, 169. Point, 112. Polcrebo, 14, 73, 106. gravels, 3, 88, 89. Potdice, lodes of, 236. Polladras Downs Mine, notes on, 236. Pollard, Dr. W., 111. Polmarth, 72. Polwheveral, 83. PoDsanooth, 13, 42, 53, 60, 84, 107, 110. Porkellis, 102, 109. Moor, 11, 59, 111. United Mines, lodes of, 236, 237 Porthcurnick, 15, 93, 100, 103. Porthoustock, 110. Porth Tow in, 14, 32, 33, 35, 40, 85, 103; mining district, 175; strike of lodes of, 149. Portreath, 36, 92, 100. Portscatho, 91, 93. Portscatho series, 14, 17, 33—37. Praze, 13, 53, 61, 73, 107, 110. Prian, 138 ; Hunt, E., on, 138. Probus, 14, 39. Products from ore dressing, 269. Produce of mines, fluctuating, 260 ; tinand copper, 275—289; minerals other than tin and copper, 290 — 295 ; of Cornwall, 310—314. Productiveness of lodes at intersec- tions. 186 ; near elvans, 184, 185 ; in greenstone, 186. Prospidnick, 107. Providence Mine, note on, 237. Prussia, Wheal, lodes of. 237. Pseudo-conglomerates, 21—22. See Crush conglomerate. Pseudomorphs, 191, 204 ; Miers, H. A., on, 191, 204. Pulla Cross, 66. Pulp, 270, 272. Pumping engine, 260. Purple and green slate, 29—32. Pyrites, output from mines, 290— 295. Pyroxene hornfels, 84. Quarries, elvan, 109, 110. , granite, 107. , greenstone, 110. Quartzite, 19, 26—28. Quartz pjrphyrv, 57. veins, 27, 29, 33, 45. Radiolaria, 4, 32, 37. Radiolarian chert, 18, 29. Ragging frames, 267. Raised beaches, 5, 15, 91, 92 ; gold in, 180. Rame Common, 59. Recent deposits, 99-^103. Red River, 2 ; output of tin ore from stream works, 295. Redruth, 11, 12, 13, 14, 28, 63, 64, 84, 111 ; mines in parish of, .304 ; mining region, 174 ; strike of lodes near, 149 ; bearing and width of cross-courses, 158. References, abbreviation of, 113. Eeid, Clement, 89, 100. Reskajeage Downs, 12, 14, 32, 33. Reskudinnick Mill stream works, 273. Restronguet, 100, 101. Creek, 13, 14, 27, 28, 31, 47, 87, 94, 95, 97, 98, 11^. Returning charges, 308. Revolving frames, 266. River terraces, 102. Road metal, 110. Roberts, S., 99. Rogers, Rev. J., 37, 99. Rose, Wheal, lodes of, 237. Rosewarne, 70. INDEX. 333 Boskear Mines, distFibution of ore in, 176, 177. Roskrow Uuited, note on, 238. Ruan Lanihorne, 6, 14, 30, 34, 103, 111. Saint Agnes, mines in parish of, 305. Anthony, 33, 103. Day, 7, 11, 13, 28, 32, 63, 67, 97, 111. • United Mines, course of ore in, 172. Gluvias, mines in parish of, 305. Just, 14, 92. Creek, 30. Mawes, 14, 30, 92, 94. Sand dunes, 103. Sands from tin-ore dressing, 269 — 274. Sarah, Abraham and Crenver Mines, notes on, 225, 226. Saveock Water, 68, 109. Scenery, 2, 10—12. Schistose structures, 23. Scorrier, 11, 28, 97, 105 ; underlie of lodes, 150. Scovan, Pryce, W., "Phillips, W., Thomas, R., Hunt, R., on, 138. Screens, 264, 265. Secondary deposition of ores, 187 ; chemistry of, 191 — 194 ; Emmons, S. P., on, 188 ; Van Hise, O. B., 189 ; De Launey, L., and E. Puohs, 189 ; Vogt, J. H. L., 189 ; Penrose, R. A. P., 189; Finch, J. W., 189; Hill, J. B., on, 190. Sedgwick, Rev. Prof. A., 3. Semmons, W., on veinstone in Carn Brea, 210. Separators, upward current, 271 ; mai^netic, 267 ; products from, 271, 272. Seton, Wheal, 86 ; notes on, 238, 239, Seymour, Wheal, note on, 239. Shear structures, 21. Shortlane End, 14, 76, 79. Silver, 9 ; output from mines, 290- 295 Hill, lode of, 239. and lead, distribution of, 181 ; genesis of lodes, 170. Sills of greenstone, 124. Silting of estuaries, 6, 100, 101. Silurian. See Lower Pateozoic. Sithney, 29 ; mines in parish of, 305. Sketch map showing geology, 8. Skinner's Bottom, 35. Slate, 20. See Killas. Slickensides in lodes, 147. Slides, 36, 157. See Cross-courses. Slime tin, 271, 273 ; note on, 272 ; examination of, 273. Smelting, cost of, 309. works, 112. Smith, Edward, 98. Soils and vegetation, 104—106 ; on granite margin, 106 ; of granite area, 105, 106 ; depth of solid granite, 106 ; Pal basin, 104 ; greenstone area, 106 ; killas area, 104 ; mica-trap areas, 106 ; mineral area, 105. Solutions, circulation of, 187 — ^194 ; effect of plutonic intrusion, 187. Somervail, A., 19, 86. South Wheal Basset, notes on, 239. Carn Brea Mine, description, 239. Condurrow, notes on, 239 ; dip of granite, 114 ; depth of granite, 117. Crenver, note on, 239. Crofty, veinstone of, 155 ; granite in, 117, 118; dressing of ores at, 270-272. Dolcoath, note on, 240 ; dip of granite, 114. Frances, notes on, 240. Wheal Hawke, note on, 240. Roskear, 47 ; notes on, 240. Wheal Seton, lodes of, 240. Tolcarne, dip of granite, 114, 117. Wheal Towan, lodes of, 241. Tresavean Mine, note on, 242. ■ Wendron Mine, ore pipe in, 164. Sparnon, lodes of, 242. Sparry Bottom, 67, 111. Spinster, Wheal, note on, 242. Springs, 111. Spurr, J. B., on lodes in joints, 132. Squire, Wheal, lodes of, 242. Stamps, Cornish, 264; Californian, 264. Standard, 308, 309, 310—314. Statistics, mineral, 274 — 314 ; of tin and copper from mines indivi- dually, 275 — 289 ; minerals other than tin and copper, 290—295 ; fluctuating output of mines, 260, 306; bibliography of, 274, 306, 308. See under Output. Steam engine, 260. Stephens, P. J., 18, 29, 45, 47 ; on gold in raised beaches, 180 ; Pen- nance Mine, 236 ; Swanpool Mine, 243 ; Wheal Clinton, 223. Stithians, 106 ; mines in parish of, 305. Stookwork in Wheal Music, 165. Stone industry, 106, 110. Stratiform granite, 54, 62. Stray Park Mine, lodes of, 242, 243. Stream-tin, 6, 95—97. deposits, 15. -. valleys, 11, 334 INDEX. Stream-tin works, output of tin from, 295, 296. Stress, direction of, 23. Strike of killas, 23 ; lodes, 148. Structure of killas, 19 — 24. Submergence, 5. Submarine forests, 5, 15, 99, 100. Submerged valley deposits, 97 — 98. Sulphide zone in lodes, 188 ; second- ary enrichment, 188, 189, 190 ; oxidation of, 188—190. Sulphur ores, output from mines, 290, 295. Sunny Cove, 90, 92, 94. Superficial deposits, 14. Surface waters, effect on lodes, 187—194. Swanpool, 12, 29, 92, 100. ,Miue, notes on, 243. Table, Wilfley and Buss, 265 ; revolv- ing, double-deck, and Acme, 266. Tailings, tin in, 272. Teall, Dr. J. J. H., 37, 75, 77 ; on pneumatolysis, 169. Tehidy, Wheal, notes on, 243; probable depth of granite in, 118. Thickness of lodes, 153. Thomas, Richard, 101, 113. Tidal estuaries, 1. Timber, 105. Tin, 9 ; smelting, 112 ; standard, 309. and copper lodes, connection with granite, 167 ; genesis, 170 See Lodes. Tin-ore dressing, 262 — 274 ; pro- ducts from, 267—274. , magmatic extraction of, 168, 169 ; secondary concentration in outcrops of lodes, 190 ; depth of, 183 ; vertical distribution in lodes, 175 — 178 ; output from mines, 275 — 289; output from Cornwall, 310—314. Tinoroft and Carn Brea United Mines, notes on, 208 — 210 ; granite in, 117. Ting Tang, granite in, 115 ; lodes of, 243. Titaniferous iron ore, magmatic ex- traction, 169. Tobban Horse, 36. Tolcarne, 107 ; lodes of, 244. Tolvern, 101. Toughway joints, 148. Towan, 100, 103. Beach, 91, 94. , Wheal, lodes of, 245. Towntanna, 66, 109. Trachyte, 42, 46. Trannack, 61, 85. ■ , Wheal, 52, 110; granite of 61. Trebowland, 71. Vean, 43. Tredeague, 71. Trefula Mine, lodes of, 244. Trefusis Point, 26, 92. Tregannock Mill, 13. Tregarne Mill, 82. Tregathennan, 61. Tregenver, 26. TregoUs, 72. Tregoney, 6, 100. Treleigh, 47. Consols, lodes of, 244. Treleighwood Mine, notes on, 230. Trelissick, 74, 76, 77. Trelonck, 111. Treluswell, 13, 42, 53, 60, 61, 84, Tremenheere, not^ on, 244. Trend of lodes, 148. Trenoweth, 73. Tresahoe, 108. Tresavean Mine, note on, 244 ; granite, 115 ; ore chute, 173. Tresevern Croft, 72, 109. Treskerby Mine, granite of, 115; lodes of, 245. Treslothan, 51. Treswithian Downs, 73. Trethannas, 57. Tretharrup. See Lower Tretharrup. Tretheague, 107. Trevales, 56, 66, 109. Trevenen Mine, note on, 245. Treviades, 83. Trevinoe, 66. Treviskey, 13, 42. Trevissome, 47, 83. Treroole, 73, 110. Trewan Mine, lodes of, 245, 246. Trewirgie Downs, lodes, 246. Trist, S. J., 37. Troon, 71. Trumpet, Wheal, lodes of, 246. Truro, 9, 14, 31, 32, 102, 111. River, 74. Truthall, 61. Tuckingmill, 48, 51, 70, 110. Tungstate of soda, output from mines, 291. Turnaware Point, 14. Tyack, W., 88, 89. Umber, output from mines, 290 — 295. Unconformity, 39. Underlie, angle of, 118 ; of lodes, 149, 150 ; Great Flat lode, 150 ; relative of lodes and elvans, 151. Union, Wheal, lodes of, 246. United Hills, notes on, 246. Mines, lodes of, 246, 247, 150 ; main lode, 153. Unity, Wheal, lodes of, 247. ■ Wood, Wheal, lodes of, 248. INDEX. 335 Uny, Wheal, notes on 249 ; granite in, lU, 117. Upheaval, 5. Upland basins, 102. Upper parts of lodes, 188. Uranium, distribution of, 179 ; out- put from East Pool, 291. Ussher, W. A. B., 19, 75, 90 ; on quartz veins, 133. Vadose circulation, 187. Valleys, 2 ; age of, 101 ; along fault lines, 36 ; systems, 102. Van Hise, C. E., on circulating waters, 187. Vanner, Frae, 265. Vegetation, 12; influenced by aspect, 105 ; and soils, 104—106. Veinstone, breccia ted, 131, 132, 133 ; comby, 131 ; banded, 132 ; origin of, 131 ; miners' terminology, 154 ; microscopic structure, 155 ; of Carn Brea, 155 ; South Crofty 155 ; Wheal Bnys, 155 ; Dolcoath, 156. Velanhausi ',88. Vercoe, H., - "iS. Vertical distribution of tin and copper ores, 175 — 178. Veryan series, 14, 17, 37—38. Victoria Point, 79. Virgin, Wheal, lodes of, 249. Vor, Wheal, 112; lodes of, 249, 250, 251, 252 ; tin stone in, 166 ; "floors," 167; minerals in crossr course, 160 ; relation of ore to granite, 172. Vugs, 138; in Dolcoath, 138; in Wheal Hose, Consols Mine, Great Condurrow, 139. Vyvian, Wheal, ore body in, 165. Walls of lodes, 139. Water, circulating, 187 — 189 ; vadose, 187 — 189; oxidation by oxygen in, 188 — 194 ; flowage in rocks, 188, 189, 190. Water level, 112. supply, HI, 112. Weathering in lodes, 188—190 ; chemistry of, 190—194. Weeth, 70. Farm, 48. Wendron, 7, 57, 107, 109; mining district, 175 ; strike of lodes, 149 ; United Mines,252; mines in parish of, 306. West Basset, lodes of, 220. Condurrow, lodes of, 252, 253. Damsel, lodes of, 253. Dolcoath, lode of, 253. — — Frances, noteon,'253. — — Wheal Jane, note on, 253. Poldice, granite in, 115. — Wheal Seton, lodes, 253, 254. Towan, lodes of, 254. Wheal Virgin, lodes of, 254. Wetherell magnetic separator, 267. Wheal. See under name of mine. White Alice, 72, 59. Whitley, H. M., 99, 100, 103. N., 93. Width of lodes, 153 ; origin of, 154 ; Moissenet, M. L., on, 187 ; Dol- coath, 163. of elvan, 118—123. Wilftey table, 265. Wolfram, distribution of, 178 ; out- put from mines, 290, 291, 292, 294 ; magnetic separator, 267. Woods and Forests, Office of, 259. Woolf's Cross-course in Wheal Vor, 160 ; Godolphin Bridge Mine, 160; Wheal Rose, 160. Yield of mines, fluctuating, 260. See Output. Zinc, 9 ; distribution of, 178 ; output from mines, 290—295. Zones of ore deposition, 170 ; secondary enrichment, 188 — 194. w FQ « is si oJ3 09 QJ &^ to g " « Id ID ?! o n ?! < *H Plate IV, Sunny Cove, Falmouth Portscatho Sl^te Series showing contor(:ion and quartz veining. ■J O o •a o a u - c J3 H S! o U< tfi « o '3 s eg u^ O BC e^ ■T3 C X tf) <; H 3 '5 > w p a, ^ u 3 J) S CJ Q ■^ ■« -4-1 O « p V J E £ JS il = d ,c 2 °' t- GJ CJ u — J- — o-.S n 5 rt ^ 3 -« OJ c « *" — ^ " s § •as; " a P = « ? Q ■3 ..- c j3 rt P t o .r y: S « 5 Ji- c-t; ™ O G I, •5 o o ® S^^ », So O S c S _.» u >, ^ p u u o I- .2 a) ^ U •O p fl c - C W L, "C 2 4) U " o g u CO H < > 'A H < E-i P4 O O iJ o ■A » B H i; o o o O ■o! H .< o o K R >• EH b O o as R •A w Ph P3 O O •A o "A K fi K H -t! O O O Plate XXll Products from Ore Dressing. X 20. (see Chapter xviii.). Plate XXIII. Products from Ore Dressing. X 20. (see Chjflster xviii,). K «»fe*&^'ib!3>SH'"