QE Z62 M5t5 R35 BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIFT OF Henrs M. Sage 1S9X i3(,onAi, ^Mfe.. 5777 Cornell University Library QE 262.N5R35 1906 The geology of the country near Newquay. 3 1924 004 530 832 Cornell University Library The original of this 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/cu31924004530832 MEMOIRS OF THE GEOLOGICAL SURVEY. ENGLAND AND WALES. (EXPLANATION OF SHEET 346) THE GEOLOGY OF THE COUNTRY NEAR NB ^WQU AX. BY CLEMENT EEID, F.RS., F.L.S., F.G.S., and J. B. SCRIVENOR, M.A, F.G.S. WITH CONTBIBUTIONS BY J. S. Flett, M.A., D.Sc., W. Pollabd, M.A., D.Sc„ and D. A. MaoAlisteb, AR.S.M. FCBLISBBD BY OBDEK or IHB LOBDB C0HHI9SI0NEBB OT HIS UAJXSIY'S IBXABCBT. LONDON ; PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, By WYMAN & SONS, Limited, Fkttee Lane, E,C, And to be purchased from E. STANFORD, 12, 13, and 14, Long Acee, London ; JOHN MENZIES & Co., Rose Street, Edinburgh ; 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. Price Three Shillings, LIST OF MAPS, SECTIONS, AND MEMOIRS OF THE GEOLOGICAL SURVEY OF ENGLAND AND WALES, AND MUSEUM OF PRACTICAL GEOLOGY. J. J. H. Tball, M.A., D.Sc, F.E.S., Director of the Geological Survey and Museum, Jermyn Street, London, S.W. The Maps and Memoirs are now issued by the Ordnance Surrey. They can be obtained from Agents or direct from the Ordnance Survey Office, Southampton. Museum Catalogues, Guides, &c., are sold at the Museum, 28, Jermyn Street, London. A Complete List of the Publications can be obtained from the Ordnance Survey Office, Southampton. Price 1«. aSNESAL UAF (one inch to i miles). ENGLAND AND WALES.— Sheet 1 (Title) ; 2 (Northumberland, &o.) ; 8 (Index of Colours) ; i (I. ot Man) ; 6 (Lake District) ; 6 (B. Yorljshire) ; 7 (North Wales) ; 8 (Central England) ; 9 (Eastern Counties) ; 10 (South Wales and N. Devon) ; 11 (W. of England and S.E. Wales) ; 12 (London Basin and Weald) ,■ 13 (Cornwall, &c.) j H (South Coast. Torquay to I. of Wight) ; 16 (S. Coast, Havant to Hastings). Sheet 1, 2«. : sheets 2 to IS, 2e. 6d. each. Prated in coUntrt. HAPS (one-inch). Old Series. Nos. 1 to 110 in whole sheets and quarter-sheets, hand-coloured, in two editions. Solid and Drift— except 92 N E., SE., 93 NW., SW., 97 SB., 98 NW., SW., SB., 101 SB., which are published Solid only. Prices, whole sheets, 49. to 8«. 6A. ; quarter- sheets, U. 6. each. VESTICAL SECTIONS, 1 to 86, price Ss. M. each. MEMOIRS OF THE GEOLOGICAL SURVEY. ENGLAND AND WALES.- (EXPLANATION OF SHEET 346) THE GEOLOGY OF THE COUNTRY NEAR NEWQUAY. BY CLEMENT EEID, F.R.S., F.L.S., F.G.S., and J. B. SCRIVENOR, M.A, F.G.S. WITH CONTRIBUTIONS BY J. S. Flett, M.A., D.Sc., W. Pollard, M.A., D.Sc, and D. A. MacAlister, A.E.S.M. I'UBLISHBr BY OKBER OF THE LORDS COMMISSIONEKS OF HIS MAJESTY'S TREASURY. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, By WYMAN & SONS, Limited, Fetter Lane, E.G. And to be purchased frum E. STANFORD, 12, 13, and 14, Long Acre, London ; JOHN MENZIES & Co., Rose Street, Edinburgh ; 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. Price Three Shillings. (iii) PREFACE This Memoir deals with the area included in the New Series One-inch Map 346 (Newquay). The original Survey was made by. De la Beche, with assistance from officers of the Ordnance Survey, and the results were published on Sheets 30 and 31 (Old Series) in 1839. Additional lodes were subsequently in- serted by Sir W. W. Smyth, and revised editions of the maps were published in 1866. On comparing the earlier maps, so far as they relate to the area in question, with the map now issued, it will be noted that the main difference lies in the fact that the Devonian rocks have been separated into three groups: the purple and green rocks of Watergate Bay, which are regarded as the equivalents of the Dartmouth Slates, the Meadfoot Beds, and the Staddon Grits or Ladock Beds. The literature relating to the area is somewhat extensive, but deals mainly with the mining area around St. Agnes, which has been carefully studied by Henwood,Warington Smyth, K. Hunt, J. A. Phillips, C. le Neve Foster, and J. H. Collins. During the progress of the Survey we have received assistance from many observers, whose names will be found in the following pages, but to Messrs. Howard Fox,W . D. Barnes, Walter Barratt, Prof A. C. Seward, Capt. Turner, Dr. G. J. Hinde, and Dr. R. H. Traquair our thanks are especially due. The re-survey has been made on the Six -inch Maps, which are available for reference in the Geological Survey Library, and of which MS. copies may be obtained. The northern half of the area was surveyed by Mr. Reid, and the southern by Mr. Scrivener, Mr. Reid superintending the whole. Mr. MacAlister has added certain lodes, not traceable in the tield, from old mine plans, and has written the Appendix giving detailed accounts of the mines. Dr. Flett and Mr. Scrivenor are responsible for the descriptions of the microscopic characters of the rocks. The plates are from photographs taken by Mr. T. C. Hall. J. J. H. TEALL, Director. Geological Survey Office, 28, Jermyn Street, London, 10th November, 1906. 8934. 500— Wt. 23989. 1/07. Wy. & S. 4369r. (iv; CONTENTS. Page Pkeface by the Dieectok- - iii Chapter 1. — Introduction - - - 1 Chapter II. — Lower Old'Eed Rocks - - 5 Chapter III. — Lower Devonian Slates and associated Greenstone 12 Chapter IV. — Lower Devonian Sandy Series ... 30 Chapter V. — Granite ... - - - 36 Chapter VI. — Elvans or Quartz-Porphyry - 51 Chapter VII. — Mica Trap or Minette - - - 58 Chapter VIII. — Pliocene ----- - -62 Chapter IX.— Drift - - - - 65 Chapter X. — Economics - 72 Appendix I.— Mines - . - - - - . 91 Appendix II. — List of Principal Works on the Geology of the District 120 Index - ----- 123 ILLUSTEATIONS. Page Fig. 1. — Sketch-Map showing distribution of the minerals - 91 Fig. 2 and 3.— Blue Hills Mine. Cross Sections - - 93 Fig. 4. — East Blue Hills. Cross section 93 Fig. 5. — Wheal Coates. Cross sections - - 96 Fig. 6. — East Wheal Rose. Cross sections 97 Figs. 7 and 8. — Great St. George. Cross sections 98 Figs. 9 and 10. — Penhalls Mine. Cross sections 99 Fig. 11. — Polberro Consols. Cross section 101 Fig. 12. — Polberro. Cross section - 102 Fig. 13. — St. Agnes Consols. Cross section- - 102 Figs. 14 and 15. — Wheal Prudence. Cross sections - - 103 I'ig. 16.— West Kitty. Cross section - 105 Fig. 17. — Friendly and Pink Mines. Cross section 105 Fig. 18. — North Wheal Chiverton. Cross section • - 106 Fig. 19. — TrewoUock Mine. Cross section - 106 Fig. 20. — Perran United. Cross section 106 Fig. 21. — Wheal Frederick. Cross section - 106 Fig. 22. — Wheal Liberty. Cross section - - 106 Fig. 23.— Cam Perran. Cross section - 106 Plate 1. — Cliff in Stem Cove, showing low dip of shear-planes, resem-\ bling beds - ' . - . .... Plate 2. — Fallen block at Stem Cove, showing contorted bedding crossed by shear-planes - . - Plate 3. — Puckered slate showing strain-slip, the true bedding not being recognisable - - Plate 4. — Bands of greisen in the Granite of Cligga Head - Plate 5. — Consolidated sand-dune with vertical cylindrical pipes at Fistral Bay . - Plate 6. — Sand-dune overwhelming meadows near EUenglaze, St. Cubert - - - - 13 a THE GEOLOGY OF THE COUNTRY AEOUND NEWQUAY. CHAPTER T. INTRODUCTION. The district described in this Memoir is comprised in Sheet 346 of the Geological Survey Map. It lies in Cornwall, and takes in an area of about 105 square miles, including the north coast from Watergate Bay to St. Agnes Head. The only town of any size is Newquay; but there are various ancient villages, including St. Agnes (locally called St. Anns), Perranporth, St. Mawgan, St. Columb Minor, Newlyn East, and Crantock. The market town of St. Columb Major lies just outside our eastern limits; Truro is a few miles to the south. Most of the district consists of an undulating table-land of no great height (commonly about 300 feet). This ends seaward in abruBt cliffs, and is cut up by numerous valleys, the majority of whicti follow approximately the dominant strike of the rocks and run from east-south-east to west-north-west. This trend of the valleys makes it difficult to carry road or railway parallel with and near to the coast, and it will be noticed that the main highways keep well inland, so as to run as much as possible across the level plateau. On looking across this smootn table-land, the only break observable in its monotony is formed by certain isolated hills, which rise to considerably greater heights. The highest of these is St. Agnes Beacon, which reaches 629 feet. Two others, Newlyn Down and Denzell Downs, reach respectively 490 feet and 605 feet, and in the distance, outside our district, similar isolated hills will be seen. In former days this region was largely devoted to fishing and mining. Now mining has almost ceased, except round St. Agnus, and the pilchards have altered their range. On the other hand, agriculture is increasing, a^jd the deeply-indented rocky coast is year by year attracting more visitors. Its mild and equable climate would make it more of a winter resort were it not so 8934. ^ 2 GEOLOGY OF NEWQUAY. wind-swept. In old times fuel was scarce, and all the trees and even brushwood seem to have been cleared off, for mine-timber and for charcoal for the tin-smelter; thus an impression has got about that trees will not grow. A glance at the plantations shows, however, that they will grow excellently if allowed the chance ; but that it is too windy for isolated trees. It is a pity that the maritime pine is not more planted, and allowed to seed on the numerous spoil-heaps of the abandoned mines. Even if it did not grow well on these unsightly, barren mounds, it would add greatly to the beauty of the country, and would give the much-needed shelter. The uncultivated lands, except the bare mine-tips, are densely covered with gorse intermingled with heather ; the wetter parts are varied with bog-myrtle and royal fern, or form brakes with small trees, principally sallow and alder. There is no natural grassland (except the tidal-marshes), the gorse here tending to overrun and overpower everything. Peat is rare. The geological formations represented in Sheet 346 are as follows : Sedimentary. Blown Sand. Recent - -! Peat. Alluvium, p f Valley Gravel and " Head." Jr-LEISTOCENE ^ ^^:^^^ -^^^^ Pliocene Sand and clay of St. Agnes. S ( Lower f Sandstones and silty slates, with bands of silicified M J Devonian I ^"^' ^'^'^ traces of carbonates. o \ ' Meadfoot Beds (calcareous slates, etc.,of Newquay). > Lower / Purple and green shales and grits with Pteraspis O [ Old Eed I of Watergate Bay. Igneous. Permian 1 Mica trap or Minette. Carboniferous? [ Elvan or Quartz-porphyry dykes. I (iranite. Devonian 1 Greenstone. No strata earlier than the Pteraspis-hearing purple and green rocks of "Watergate Bay have yet been reached in this area. The ores found are those of tin, copper, lead (with a considerable amount of silver), iron (siderite, haematite and limonite), with smaller quantities of arsenic, wolfram, manganese, zinc-blende, and uranium. Before proceeding with a detailed description of the geology it may be convenient to say a few words on the general structure The most striking features in the geology are the persistent east and west (or rather east-south-east and west-north-west) strike of the rocks, combined with a high (ftp, usually southward and averaging as much as 40°. This high dip in one direction would at first sight seem to imply that we are dealing with an enormous INTEODUCTION. 3 thickness of Palaeozoic rocks; but closer examination leaves little doubt that such is not the case. The key to the geological structure will be found in the anticlinal arch of Watergate Bay, where the lowest beds come to the surface. This anticline will be fully described in the next chapter ; it will suffice here to say that it is cut by a multitude of overthrust faults having a considerable hade to the south, so that on the south side of the arch they tend to bring up the same bed again and again, while on the north they cut out certain strata entirely. These faults probably represent sheared folds ; but south of the main anticline there is seldom any clear evidence of such folds. Besides the overthrusting there occurs a shearing or slaty cleavage ■ approximately parallel to the overthrust planes, so that on the south side of the axis overthrust, cleavage, and bedding tend nearly to coincide, and fossils, though badly flattened, sheared-out, and distorted are not usually cut across. On the north side of the arch, on the other hand, there is much contortion, and the cleavage as often as not cuts across the bedding, shown by colour-bands and fossils. In homogeneous strata this cleavage is often exceedingly difficult to distiaguish from bedding ; it gives the general effect of a steady southward dip, where in reality the strata are much contorted, but have an average northerly dip. In Plates 1 and 2 this relation of cleavage to bedding is well illustrated. The high chlf, seen in Plate 1, seems at first sight to be formed of evenly bedded rock with a gentle seaward dip. The fallen block shown in Plate 2, proves, however, that this even bedding is really cleavage, cutting though a system of sharp folds, here indicated by a faint colour-stripe. In another photograph (not reproduced) the shearing is seen to cut across a wavy band offish-bones, some of the bones being crumpled or rolled up in a very curious fashion. The contortion, however, though masking the anticlinal structure, does not obliterate it. North and south of the axis the same strata are repe0,ted, though with outcrops varying enormously in width. The axis is not far from the northern limits of our area ; but deposits of identical character occupy its northern and southern margins. Subsequent to the formation of the structures just described, or perhaps during their formation, the granite was intruded among tne sedimentary strata, apparently in the form of laccohtes or subterranean lakes of molten rock. StUl later, and probably while part of the granite was yet fluid, long fissures were formed, and filled with material differing but httle from, and apparently derived from, the stiU fluid part of the granite. Tbese are the " elvan " dykes, which cut both granite and slate, rising as wall-like masses,, traversing contortion, cleavage and overthrust, but showing some tendency to follow the obvious hue of least resistance and hold a course parallel with the general strike. 8934. -V 2 4 GEOLOGY OF NEWQUAY. A small number of dykes, apparently of later da,te, are composed of mica-trap or minette. They are characterised by extreme irregularity and a marked tendency to zig-zag along the joint planes. Their general trend is north and south. These are the leading points in the geological structure of the district; other features, and the relation of the underground structure to the surface contours will be dealt with in later chapters. Before proceeding, however, with the geological description, it may be convenient to draw particular attention to the tides on this coast. Much of the most interesting part is only accessible at low- water spring tides, and many other parts at other times can only be reached by long detours. Fortunately low- water spring tides on this coast occur near the middle of the day, the time of low- water at fiiU and new moon being about 11 o'clock and the lowest tides coming at mid- day about twenty-four hours later. Care should be taken to avoid being caught by the tide in some of the smaller coves, especially Stem Cove. Though in most places it would be practicable to climb out of reach of the waves, it might be necessary to remain till next day. The rocky foreshore is in parts diflScult in daylight, and after dark it would be quite impracticable or very dangerous. The commencement of a ground-swell, which often rolls in with- out warning in quite calm weather, should also be noted; for this swell may easily make it impossible to round points which otherwise would be passable for an hour or two longer. The swell, even in calm weather, is usually too heavy to allow of landing from boats. CHAPTER U. LOWER OLD RED ROCKS. The earliest strata which come to the surface within the area which this Memoir describes, occur in a faulted and much broken anticline which has its crest close to the Horse Rock in Watergate Bay. The deposits consist of fine-grained sandy micaceous shales or slates, with occasional bands of grit. Their colours vary between reddish-purple and pale green ; but towards the top these alternate with bands or thick beds of black or dark- grey snale, which yield numerous remains of Pteraspidian and other fish, characteristic of the Lower Old Red Sandstone. Fish remains occur also, though more scattered and more badly pre- served, from top to bottom of the purple and green strata ; but no other fossils have been found. Measurement of the thickness of this series is^ difficult, for the beds are very uniform in character, vvell-marke'd seams are rare, and everywhere the continuity is broken by overthrust faults, which sometimes repeat, sometimes cut out, parts of the series according to the relation of the dip to the thrust-planes. Repeated measurements on each side of the anticlinal axis give varying results; but the probable total thickness of the strata above the sea level is about 800 or 1,000 feet, with no sign of a base. As the series is most complete on the southern side of the axis, we will first describe the section seen in the cliffs as we travel southward. The crest of the anticline, and consequently the oldest beds exposed, will be found at the foot of the cliff between Creepinghole Pomt and the Horse Rock in Watergate Bay, the Horse Rock being an isolated hog-backed stack pointing seawards, and Creepinghole Point lying just north of it. The dips at this point are somewhat confused ; but a distinct arch is visible, the general dip being to the right and left as one faces the cliff. The lowest strata consist of alternating purple and green shales and silts, with little sign of cleavage, and within a foot of the lowest bed of all a fragment of the so-called Pteraapis conmhica was found. From the crest of the anticline to Horse Rock the strata sink about 100 feet, and a pale-green band on a ledge just south of the Horse Rock yielded a well preserved fragment of Pteraspis, as well as several badly preserved pieces. From Horse Rock to Sweden Rock (a stack 170 yards to the south), and thence on to Zacry's Islands, the southern dip becomes more pronounced (about 30°). Several thrust faults cross the beds ; but they do not seem to cause any great amount of repetition. The measurements as far south as the base of the massive purple bed, which descends to the beach-level between 6 GEOLOGY OF NEWQUAY. the two Zacry's Islands, give a thickness of about 700 feet_ of strata already traversed— so much of this chff gives a succession unbroken by faults that it is difficult to see how the total can be much less. The yertitsal chfi' is here about 240 feet and is free from talus. Contortion does not seem much to affect the massive strata of this cliff. The conspicuous purple bed which forms the landmark just mentioned is about 20 feet thick. From it to the extensive dip-slope which forms the southern face of the larger of the two islands another 150 feet of alternating purple and green beds is crossed. This dip-slope is formed by a pale-green band full of black plates or films, often several inches across. These plates usually show no organic structure ; but careful search disclosed the unmistakable striated Pteraspidian pattern on one corner of one of the specimens, and others showed indications of the same Sattern almost obliterated. There seems therefore to be httle oubt that most of these plates are organic; but it is quite possible that some of the perfectly smooth badly- preserved ones may belong to Eurypterids, though no undoubted trace of these Crustacea has yet been observed. On continuing our walk southward we cross another 50 feet of purple and green silty strata with scattered Fteraspis, before reaching the first conspicuous bed of black shale. This shale is well seen in a little unnamed cove 250 yards south of Zacry's Islands, unless there happens to be a great accumulation of sand. We can examine about 10 feet of hard, platy, black or dark grey glossy shale, full of seams of fish bones. The band is well seen in ledges on the foreshore, and is also visible at the base of the cliff; but upwards it is generally cut out by a strike fault, so that 20 feet above the shore it is entirely missing. The presence of this fault suggests that possibly still more of these black shales might be found below the sea-level, and that their total thickness may really be more comparable than at first sight appears with the better-developed fish-beds near the Watergate Hotel. Next follow 50 feet more of purple and green strata, to the top of the highest purple seam, succeeded by a mass 60 feet thick of pale green silts. Above these come fiinely laminated alternat- ing seams of green silt and black shale, 10 feet up in which was found the highest fragment of Fteraspis yet observed. Similar laminated black and green shales, often much sihcified, continue upwards for another 50 feet, to a thin seam of sandstone, which has been taken provisionally as the upward limit of this division. These transition beds gradually change upwards by the intercala- tion of brownish calcareous seams, the first marine fossUs observed (a crinoid stem and a simple turbinate coral) having been found about 100 feet above the last seam with Pt&raspis. The transition can be observed on either side of Fern Cavern ; which will be found in a small cove midway between Zacry's Islands and Flory Island. The beds about here are a good deal OLD RED EOCKS. 7 faulted and dip at about 35° ; the lithological transition seems however, to be complete. We -will now return to our starting-point near the Horse Rock and describe the strata on the north side of the axis ; but here it must be remarked that it was found impossible to obtain any satisfactory measurements on that side. Not only are beds cut out by faults, but they are repeated by S-shaped folds, and tend to dip seaward at high angles. There is also the added difficulty that the cleavage, instead of being faint and coinciding with the bedding, commonly crosses it at a considerable angle ; in places it obviously cuts through contortions that are barely recognisable. This renders the true dip so imcertain that it is often impossible to follow any particular oed. From Creepinghole Point northward to Tinners Point (halfway to the elvan) purple and green strata form a cliff of about 200 feet ; but several overthrust faults come in ; and not more than 300 feet of strata can be measured between the centre of the axis and the lowest bed of black shale seen in the cliff — how much is cut out cannot be estimated, except from a comparison with the southern limb of the fold. North-east of Tinners Point the black shales come on in the upper part of the cUff, and from a large fallen block on the talus below a spine, referred by Dr. R. H. Traquair to a new species of Parexus, was obtained. The quarry at the edge of the cliff' above shows grey platy shale and thin seams of grit, resting on softer greenish shale, the highest purple band being out of reach a few feet below the quarry. A few yards further north the black shales and the purple and green strata are cut by a north and south elvan dyke, which, however, does not appear to shift the junction. An irregular seaward dip of about 25" here causes a good deal of slipping ani makes it somewhat difficult to see exactly what has happened; at any rate the junction is seen near the middle of the cliff on the right side of the dyke and is only a little lower on the left. The dip causes the black shales to sink gradually northward till they reach the beach-level at the old mine-adit just south of the Watergate stream. The spoil-heaps of this mine show that the purple and green strata rise to the surface 200 yards inland, at a point above 170 feet above the sea. This would give a dip of about 17°. This seaward dip is also very marked near the Watergate Hotel, causing the purple and green strata to appear in the quarry near the high road, and bringing them in at the top of the cUff a quarteiwof a mile north of the hotel in a very curious way. At that point a landslip has caused the purple and green strata to slip over the platy shales, which are really higher m the sequence. .This seaward dip, which seem to be connected with a north and south fault nearly parallel with the coast, is, however, very local, for a quarter of a mile inland the strata take the usual east and west strike, 8 Geology of newquay. On returning to the beach below the Watergate Hotel \re find the black Pteraspis shales well exposed at the foot of the clitl ; but best seen on the north side of the stream for about 300 yards, in ledges dipping seaward. It was here that the rteraspis-iem&ms were first discoyered on the north coast by Mr. Eupert Vallentm and Mr. Howard Fox,* the forms determined by Dr. Smith Wood- ward from Mr. Fox's collection being Pteraspis cornuhica, Phlyctwnaspis, and Climatius. To this fauna several additions were made during the Survey, and the specimens were sub- mitted to Dr. Traquair, whose prehminary account of them will be found on p. 11. A few hundred yards_ further north the shales (apparently on a slightly different horizon) yielded a coarsely striated spine belonging apparently -to Ctenacanthus. Though the purple and green strata disappear beneath the sea- level, the black shales, full of S-shaped folds, continue to be ex- posed in the cliff and in the shore-reefs as far north as the end of Watergate Bay. The whole cliff, though reaching 250 feet in height, is composed from top to bottom of these black or grey shales and slates ; but their true thickness is probably much less than the height of the cliff would suggest. In the first place, the cliff is not vertical ; but slopes back, so that the general seaward dip may make the same stratum appear at the top of the cliff and on the foreshore just opposite. Also, contortions repeat the beds again and again, the appearance of a fairly steady dip being deceptive. Cleavage also, dipping irregularly seaward, cuts through the contortions, often in these homogenous shales nearly obliter- ating the original bedding except for a faint colour-stripe. This non-correspondence of cleavage and bedding is excellently shown in Plates 1 and 2, and in two places where seams full of fragments of Pteraspis are cut across, the fossil plates being partly cleaved and partly twisted and rolled up. TRe one locality is at the base of the cliff in a little cove 250 yards north of the stream ; the other is on the rocky ledge crossed by the footpath leading down Strase Cliff to the beach, past the conspicuous ruin known as the " Eyrie." Neither of these spots is good for collecting, though fossils are so abundant ; it is more satisfactory to search points where cleavage and bedding coincide and the fossils are not so badly distorted. The northern end of Watergate Bay shows also much crump- ling and strain- slip cleavage (see Plate 3), as well as a strong development of quartz- veins. Headlands and points on this coast are commonly due to the local Recurrence of vein quartz, or of silicified rock, rather than to the normal greater hardness of particular strata. Stem Point, which forms the northern limit of Watergate Bay, still shows at the foot of the cliff' black shales with Pteraspis, fallen blocks from the top yielding occasional marine fossil s. At '■ "Geological Notes," Trans. Hoy. Geol. Soc. Coi-nwall, vol. xii., 1899 pp. 356, 357 ; see also Geol. Mag.., 1900, pp. 148, 149. ' OLD RED ROCKS. ^ Stem Cove, immediately to the north, the transition beds, consisting of laminated black and green silicified shales exactly like those at the south end of Watergate Bay, are seen on the foreshore, and in them also occurs a thin bed of sandstone, here increased to 5 feet. Close to this sandstone, and apparently only a few feet below it, two or three fragments of Fteraspis were found. Resting on it occurs an isolated stack of rock (the second after passing the Point) the upper part of which consists of laminated very siliceous black and green shales full of badly preserved crinoids and simple turbinate corals. The last bed of Pteraspis and the first with marine fossils apparently occur within 50 feet ; but here also there seems to be a perfect litho- logical passage, except for the thin sandstone which has been taken as the iDoundary. At the deepest part of Stem Cove an overthrust fault, which is also a lode, brings the deposits of Old Red type to an abrupt termination, causing black shale with Pteraspis to abut against calcareous shales with crinoids. This fault is interesting as being the only one for which we can form any estimate of the amount of throw. It hades to the south at 50°, and has caused a vertical displacement of at least 150 feet, for the marine beds seen on the shore on its north side are not the siliceous transition beds, but belong to the calcareous shales with brown streaks, occurring somewhat higher in the Devonian series. This fault causes the fish-beds to overlie the marine strata, or rather to appear in the cliff as an oblique wedge lying between two masses of marine strata. Stem Cove is only accessible at spring tides. It now remains to trace the Old Red strata inland, till the axis of the anticline sinks, so as to make them disappear beneath the surface, just at the eastern limit of our district and close to St. Columb Major. It was thought at first that a distinction could be made between the purple and green strata and the overlying grey and green Pterasjois-heds, and an approximate boundary was traced on the Map. It was soon discovered, how- ever, that Pteraspis occurs throughout the series, and that black shales occur low down, and purple and green beds high up. Still the line is a useful one and has been engraved as far as it can be traced, for it shows the curious irregularity in the width of the outcrop, produced by overthrusting and by the abnormal seaward dip north of Watergate. To commence, as before, with the centre of the anticline and with the oldest strata,_we find abundant evidence inland of the occurrence of the purple and green rocks, for the characteristic colour and appearance is as marked in weathered fragments in the ploughed fields as in the cliff. This area shows also a con- siderable proportion of stones of hard grit. Actual exposures of these rocks are not so common; though there are sufficient to show that the axis runs in an east-north-easterly direction near Bedruggo, turns more to the east at Carnanton, and coincides with the east and west valley east of Halveor. 10 GEOLOGY OF NEWQUAY, On either side of this area comes a belt of grey shales and slates, often ending upwards in a recognisable thm band of sand- stone. This belt is of extremely irregular width, owing to dupUcation or cutting out of strata by strike faults at various pomts. The harder masses of black platy shale in it have been quarried for local use, as they come out in convenient flat masses and stand the weather fairly well. In all probability prolonged search would yield remains of Pteraspis m these rocks inland also, were it not that the fine sculpture is usually obhterated by a thin white crust, which even on the coast does not appear to be removed by weathering, but is easily scoured away by the sea- sand, or can be removed artificially by the use of a hard brush. TiU this crust is taken off, the fossils are scarcely distinguishable from inorganic films, except in the thin broken edge, easily over- looked in a mass of rock. Quarries in black shales, probably belonging to the Pteraspis- beds, will be found north-east of Hendra Veor, near the stream north of Parkyn's Shop, by the roadside a quarter of a mile east of Great Halveor, in Carnanton Woods, a quarter of a mile north ot Deer Park, and in the village of Trevarrian. These shales in isolated sections are not easy to distinguish from some of the hard non-calcareous platy grey shales which occur high up in the marine Devonian rocks in the neighbourhood. The Lower Old Red rocks as a whole are almost non-calcareous in this area ; the Lower Devonian rocks immediately above are either highlji cal- careous, or show evident trace of the former presence of cg-lcareous fossUs. No trace of contemporaneous volcanic activity has been ob- served in the Old Red rocks of this area, and only one intrusive rock, a thin dyke of mica trap which runs across the strike at Lower Tresawle. It can only be traced a few yards and has a thickness of about 15 feet. Dr. Flett states that it is so much decomposed that its original nature is open to some doubt ; but it contains the corroded xenocrysts of quartz which are so common in the lamprophyres, and is probably a weathered minette. The fossils of the Old Red rocks of Watergate Bay include nothing but fish-remains of types closely similar to those of the Lower Old Red Sandstone. The singular absence of marine fossils, such as brachiopods, crinoids, and corals, the presence of these peculiar fish, and their association with purple and green strata, such as during all geological periods tend to be associated with inland seas or lagoons, all combine to point to the strata of Watergate Bay as something quite distinct from the overlying marine Lower Devonian rocks. In this district though there may be a passage in the hthological character, we can as yet find no trace of any transition or alternation of the lacustrine and marine faunas. The passage- beds, however, are worth further examination, especially after storms have removed the loose sand. old red rocks. 11 Notes on Fish-eemains from Watergate Bay in Cornwall. By R. H. Traquair, M.D., LL.D., F.R.S. The greater number of the fish-remains collected at Watergate Bay by Mr. Clement Reid, F.R.S., and submitted to me by the Director of the Geological Suryey, consist of fragments of Fteraspis cornubicus {Steganodictywm, comubicum, McCoy). Judging from these fragments, this species must have obtained a very considerable size, as has been already noted by previous observers. There are also a few pieces of the finely tuberculated plates called by McCoy Steganodtctyum Carteri, — afterwards supposed by Lankester to be possibly referable to Gephxdaspis. Having examined the type of Steganodictyum Carteri in the Sedgwick Museum, Cambridge, it does not seem to me to belong to Gephalaspis, but rather to some Coccostean form. Among other fragments is one of the surface of a large spine with longitudinal nodulose ribs hke those of Ctenacanthus, to which genus I would refer it provisionally. There is also a portion of a comparatively small spine with straight longitudinal ribs, which much resembles one figured many years ago by the late Mr. C. W. Peach. The most perfect spine, however, is a slender one over three inches in length, which is apparently referable to a new species of the Acanuiodian genus Parexus, though the characteristic denticles of the posterior aspect are not visible. I have abstained on this occasion from bestowing specific names on the last three forms, deferring that until the names appear along with detailed descriptions and figures in a forth- coming Memoir, which will include also the fish-remains occurring in the Lower Devonian rocks of the southern shores of the county. 12 CHAPTER III. LOWER DEVONIAN SLATES AND ASSOCIATED GREENSTONE. About one half of the area described in this Memoir is occupied by more or less calcareous shales, slates, and thin lime- stones, which where unweathered, are of a uniform pure grey- without any other tints in the cliffs, except for certain narrow bands of a pale green rock, which may be a much altered volcanic ash. These calcareous rocks of • Newquay seem to rest quite conformably on, and to pass gradually down into, the Pteraspis- beds already described. Upwards they change gradually into higher series of silty shales, having a slightly different character. Their upward limit is formed by the grit beds which occur towards Perranporth on the south, and in the headland beyond Mawgan Porth on the north. It has been found quite impossible to obtain any trustworthy estimate of the thickness of this series of shales and slates, for they are greatly disturbed and are constantly repeated by over- thrust faults. The scarcity of bands of marked lithological character, the rarity of beds of recognisable fossils, and the exceedingly bad state of preservation of the fossils, combine to render the working out of the geology very difficult. In many cases we are doubtful whether a certain band is repeated again and again, or whether we are dealing with a continued sequence of similar strata, in which particular conditions, such as those leading to the formation of phosphatic nodules, tend to reappear time after time. In the Newquay cliffs, however, though the same set of beds may be repeated several times, it gradually gives place to another of slightly different type, and these again change to a third type as the strike is crossed. The simplest way to explain the structure will be to describe the cliff section, continuing southward and northward from the points, on either side of the anticline, which we left off in the last Chapter, and remembering that amid all the confusion there is a general dip to the south on the one side of the anticUnal axis and to the north on the other. It should also not be forgotten that the coast is much indented, and that the general trend near Newquay is not at right angles to the strike; the strata therefore seem to be thicker than is really the case. Making every allowance for these various elements of uncer- tainty, it is still clear that we are dealing with a mass of shales of considerable thickness, not with some thin bed constantly repeated by folding. It does not appear that the marine shales and slates of Newquay can be less than a thousand feet in thick- ness, and they may be much more. I.OWER DEVONIAN SLATES. 13 The base of the calcareous shales is well seen in the clifl close to Fern Cavern, which lies north of St. Columb Forth and due west of Trevelgue Farm. The junction with the Pteraspis-heds. has been described in the last Chapter ; it remains to continue the upward sequence from the point where it was left. _ Next above the thin sandstone, which has been taken pro- visionally as the base of the series, come black glossy shales, interlaminated with green sandy grit. These seem to have a thickness of 20 feet ; hut they are here so much broken by faults that the real thickness is very doubtful. They occur exactly at Fern Cavern. On the south side of the Cavern they are followed by dark-grey somewhat siliceous slates, with thin brown seams (apparently altered limestone), a few feet up in which the first marine fossils, a crinoid and a simple turbinate coral, were found. Probably marine fossils might be found lower; but the beds lower in the series happen unfortunately to dip into the cliffs in such a way that no dip-slopes are exposed. Badly sheared fossils are not easy to see, except on dip-slopes, and at the point the foreshore is usually hidden by sand. The rocks between Fern Cavern and Flory Island consist of grey calcareous shales, with thin seams of much sheared lime- stone, and a few phosphatic nodules. Fossils are not abundant, crinoid ossicles being the most common. In these rocks at Flory Island and on the mainland opposite an extremely irregular lode of ironstone was formerly worked. The ore consists, as is usual in the killas of Cornwall, of carbonate of iron (siderite), and good crystals of this mineral can still be found in the lower part of the lode, below high- water level. In the upper part of the lode the iron is in the state of limonite. On the south side of the small bay which is bounded on the north by Flory Island will be found the Cathedral Cavern, in the flying buttresses of which a thick vein of yellowish or whitish crystalline calcite, in places silicified, occupies a bedding plane. It can be traced also here and there nearly to the western point of Forth Island, or Trevelgue Head as it is called on the Map. This calcite vein is quite unlike the fossiliferous limestones seen in the cliff above. Close to the cave known as the Banqueting Hall, a path descends to the beach. The upper part of this path crosses bare rocky ledges, reached by the spray during violent storms. The ledges consist of alternating bands of grey or ferruginous calcareous shale and sheared bluish limestone, the thickest lime- stone being about 2 feet thick. Both shale and limestone are crowded with fossils, well shown on the washed and weathered dip-slopes ; but the fossils are so badly sheared as to be quite indeterminable. The most common forms are parts of the -very thick stem of a crinoid, simple turbinate corals (perhaps Zaphrentis), and some curious fossils with an oblong aperture straight hinge with bilateral symmetry, and a radiating or fibrous structure, These last suggest a Calceola, though clearly 14 GEOLOGY OF NEWQUAY. not the known Middle Devonian species. _ No undoubted braeliiopods were observed. A good deal of time was spent in endeavouring here to obtain better fossils ; but without success. The foreshore below exposes similar strata, with occasional casts of a doubtful Favosites in black phosphate. These_ phos- phatised corals, commonly associated m the nodules with an mdeterminable Bellerophon, now form a characteristic feature in the shales at short intervals ; it is not quite clear, however, whether the same set of thin beds is repeated again and again, or whether similar conditions tend to recur. In every case the abundant phosphatic nodules are associated with shales excep- tionally calcareous, with thin seams of hmestone, and with one or two thin bands of pale-green rock. This last is probably a fine-grained .volcanic ash, though it is never sufficiently well preserved to show satisfactorily under the microscope. These pale-green streaks are very noticeable in the unweathered dark- grey shales near the foot of the cliff ; but they are not so easily recognised in the upper bleached part, or inland. The floor and sides of the curious gash which separates Forth Island from the mainland are worth examining, for they show particularly good sections cut at right-angles across crumpled slates. The gash seems to have origmated along a joint ; but it appears to have been widened artificially to make part of the defences of the old camp, and still later its bottom has been smoothed for the more convenient passage of small boats in and out of Forth Harbour. The dip-slopes on the Harbour side of the camp yield many large fragments of a crinoid stem more than an inch m diameter, and also a few other fossils too badly sheared for determination. On the opposite (south) side of Forth Harbour these calcareous shales dip into the cliff at about 35°, again showing a seam of phosphatised corals. A siinilar set of beds reappears for the third time just round the point west of Glendorgal. The whole coast is full of overthrust faults, nearly all of the remarkable caves in this neighbourhood originating in them ; but it is not clear to what extent the repetition of beds above alluded to is due to overthrusting, or how much is due to fold- ing, Most of the few apparent folds can be interpreted in two ways, either as folds sheared through their axes by overthrust faults, or as overthrust faults which, as the almost inevitable result of the friction, have caused a reversal of the dip above and below the plane of the fault. It is impossible to determine which interpretation is correct, for we have seen no set of beds so* characteristic that it is possible to say that here they are right side up, there upside down. More often the overthrusts in Siis neighbourhood nearly coincide with bedding-planes, which then show little sign of curvature. The small coves which lie between Glendorgal and Lusty Glaze call for no remark, except that the thin bands of limestone are LOWER DEVONIAN SLATES. 15 well seen in dip-slopes just above the beach near the northern end of the sand-dune. The limestone yields the usual crinoid stems, turbinate corals, and doubtful Alveolites and Pachypora. Behind the sand-dunes there is a small mine-adit, apparently only an unsuccessful trial for ironstone. Another adit will be seen in a narrow zawn or fissure south of Lusty Glaze, and others near the Criggars ; these are connected with shafts on the plateau above and yielded a little lead ore. An exceptionally conspicuous overthrust fault is traceable on the shore near LustyGlaze,making a gash in the cliff, then running west-south-west, and forming the south boundary of the cove. Grey shale, with thin limestones, pale-green bands, and phosphatic nodules, again appear immediately this fault is passed. Then come two or three more parallel overthrust faults befor&we reach the Criggars, which are the bold rocky ledges below the two tumuU. The Criggars run about east and west, and dip south at about 45°. They form one of the geological landmarKs on this coast, as they yield a number of phosphatic casts of fossils in an unusual state of preservation. The rocks consist of much sihcified dark- grey calcareous shale, with several thin Umestone seams, also silicified, and bands of phosphatic nodules. The hard nodules have to a great extent resisted shearing, though the softer slate has streamed past them, carrying witti it part of the phosphate. In some cases the fossils are partly calcareous, partly in the state of casts in phosphate, one good Favosites, now in the Survey Collection, having one end in its original- state, the other end being a good cast in phosphate of the mtemal structure. About 10 or 15 feet below the main band of phosphatic nodules come two or three thin bands of pale-green slate, very conspicuous in the dark grey slate near the sea-level. These greenish-white bands are seen also in the cliff opposite ; where, however, the phosphate band is faulted out by another overthrust. They, or similar bands, reappear near the top of the cliff south of the Criggars and run down to the beach-level at the cave which occurs close to the point which forms the north-east end of Tolcarne Bay. This cave also has been excavated along an overthrust fault. Fallen blocks here show phosphatic nodules with Bellerophon, one oi the blocks showing within a few inches a pale-green band also. The fossils, from the Criggars, determined by Mr. E. T. Newton, are : — Favosites ? Monticuliporoid ? Heliolites 1 Bellerophon. Turbinate corals. A turreted gasteropod. There is also a curious sponge-like fossil with several rows of large Eores connected with tubes of peculiar shape. This we have een unable to determine ; but Dr. Hinde, who was kind enough also to examine it, does not think that it is a sponge. It is unfortunate that this fossil should remain undetermined, for it is 16 GEOLOGY OF NEWQUAY. one of the few that holds out any hopes for determining more exactly the age of these beds. The cUfts west of Tolcarne Point show little of interest ; they run along the strike of the rocks, which dip inland. Below Borthwicks they yielded an Actinoceras, an elongated gasteropod, a simple turbinate coral, and the usual ossicles and fragments of stem of crinoids. At Giant's Cove, which is a small cove near the Island and just east of the end of the sea-wall at the Town Beach, the soft shales contain simple corals flattened almost to _ the thinness of paper. This cove was one of the original localities from which C. W. Peach obtained fossils* ; he found fragments of a trilobite, Phacops latifrons ; but we have not succeeded in finding any determinable fragments of trilobite on this part of the coast. The next section of interest will be found in Tithy Cove, a small cove shut in by a wall and lying immediately to the north of the Harbour. The calcareous shales and their fossils here resemble so closely those above the Banqueting Hall, that it is difiicult to resist the conclusion that they are the same beds repeated. A short distance further, beyond the last of the fish cellars, occurs an irregular rocky platform, from which the raised beach has been swept away. The slates here have weathered so as to show a few small fossils, among which were found a tubercled fragment apparently belonging to a Coccostean Fish, a turbinate Coral, and a small Monticuliporoid Coral. Several thin bands of limestone crop out on this platform, alternating with hard platy shale. Hard dark-grey calcareous shale, with occasional thin lime- stones, all more or less silicified, form the whole of the Headland, the rocks on the east being the same as those on the west. A few dykes of volcanic rock have baked the shale, thus helping it to resist denudation by the sea. Fistral Bay possesses only a low cliff of much-weathered shale, the mine-tips among the dunes showing that this shale is dark-coloured, soft, and only slightly silicified. The mine was worked for silver-lead with an excep- tionally high percentage of silver ; but the lode was too thin for profitable working. In East Pentire a gradual change takes place, the rocks becoming gradually more slaty, harder, less calcareous, and having a higher dip. They stiU, however, contain occasional beds of fossils and seams of limestone, the last of which wiU be found immediately north of the more easterly of the " Barrows " marked on the Map. At this point 30 or 40 feet of softer more calcareous strata occur between masses of hard slate. In certain layers these beds are full of a spherical or hemispherical much compressed Alveolites, not seen elsewhere. They also contain doubtful Monticuliporoids, simple corals, and crinoids ; but nothing specifically determinable. Now in the Penzance Jliiseum, LOWER DEVONIAN SLATES. 17 Towards Pentire Point East the rocks become much harder, and distinct bands of hard quartzose unfossiliferous grit appear. The most eonspicious of these bands is well exposed in the quarry at the Point and forms, with an associated quartz-reef, the backbone of Pentire and of the outlying rock known as the Goose. These hard beds show as a marked feature for several miles inland, and as they separate decidedly calcareous rocks from slates without much lime, the division is a convenient one, and has been engraved on the Geological Map, though at present it is quite uncertain whether it is of any palseontological value. South of this line the only fossils yet found, except indeterminable crinoid stems, are two lamellibranchs/ the one picked up in the soil of East Pentire, the other (a Cardiola) found in a quarry of sandy shale and grit 4 miles to the east, near Kestle Mill. It is singular that no lameUibranch should yet have been found in the calcareous series near Newquay, whilst two occur among the few fossils found in the higher non-calcareous slates. West Pentire and Forth Joke show slates more sheared and glossy, harder, with more of the pale-green volcanic-ash seams, and a few of grit. The only fossils are a few crinoid ossicles, usually replaced by silica, or in the state of hollow moulds. Mr. W. D. Earnes made a careful examination of this part of the coast ; but was unable to find any other fossils, though he succeeded in tracing crinoids as fiar south as Holy Well. The fossils are so badly preserved that, they would be overlooked were it not for the occasional occurrence ot an undoubted fragment of crinoid. Kelsey Head shows rocks still more sheared and with a dip of about 60°. In these slates occur two thin bands of Greenstone which will be described later on. They look like sills ; but they are too much sheared and altered chemically for one to be sure and they may represent contemporaneous volcanic rocks. At Holy Well the slate is dark-grey, with numerous bands of less fissile, more calcareous, pale-green slate, perhaps volcanic. The dip has here risen to 70°, but the bedding, where recognisable, is stul parallel to the cleavage. On the south side of Holywell Bay the disturbance becomes more marked, the grey slates being much contorted, crumpled, and veined with quartz. The strike is still a little north of west, but the dip has become so high that the bedding is vertical, or even overturned 5° or 10°, so that it dips at 80° or 85° to the north. Overthrust faults are still common ; but amid the general confusion it is impossible to say whether they play any important part in the general structure. At Ligger Point the high cHffs are a confused irregular mass of grey shale, full of quartz-veins and knots, with much minute crumpHng and contortion, and indications of passing into a crush- conglomerate ; but the dip seemingly is not quite so high, varying from vertical to about 80° to the south. Along this part of the coast, often visible in the cliffs and crossmg each of the small 8934. B 18 GEOLOGY OF NEWQUAY. bays, runs the valuable silver-lead lode of Wheal Golden and Penhale Mine. Some of the disturbance may therefore be connected with the opening of this fissure, for there is in the slate a marked jointing parallel with the lode, another striking set of joints lying nearly horizontal. This regular jointing is the more striking as no very persistent direction is usually noticeable in the jointing of the slates in this district. The Gravelhill Iron Mine, where the cliff ends, shows slates of the same character ; though there, as might be expected, they are much stained with iron. Then comes half a mile' of cliff entirely hidden by sand-dune banked against it, and we can only judge of the geology from the loose fragments seen in the tips from the shafts, and in the basins scoured out by the wind m the middle of the sands above. The shaft at the southern engine house of Gravel Hill shows hard, dark-grey, much- sheared and broken slate, like that we have been describing; but the bare hollow close to the shaft is strewn with pieces of a coarse sandstone or grit, a thin bed of which must crop out close by, imder the sand. Another bare spot shows fragments of greenstone and of a pyroxene rock, which seems also to crop out here, though niany pieces of stone have been scattered about by human agency. The structure of the loose stones is beautifully brought out by the erosive action of the drift-sand. Half a mile to the south of Gravel Hill the chfi' is again visible for a short distance. It shows an elvan dyke cutting grey silty contorted shale full of quartz lenticles, similar material being found in the tip from the shaft above, though the upper part of this shaft is in banded grey and sooty shales, more hke those of Perranporth. One of the trial-holes a quarter of a mile to the north-east of this elvan shows perhaps a faint trace of metamorphic spotting in some of the slate thrown out, though nothing of the sort is seen in others. Where the cliff again becomes visible, near Carn Haut, the slates have taken on the Perranporth characteristics, consisting of black and grey silts in thin alternating layers, with here and there a few bands of grit, which, however, disappear further south. These banded rocks were provisionally named the Perran Shales; they have been separated from the rocks of Newquay and classed with the sandy rocks described in the next chapter. The continuation of the description of this coast will therefore be found in the next Chapter. Leaving for the present the inland exposures, it wiU be convenient next to describe the Meadfoot Beds on th.e northern side of the anticline, seen first in Stem Cove (see p. 9). It will be remembered that in Stem Cove the thin sandstone which forms the base of the series is followed by the very siliceous laminated black and green shales full of badly preserved crinoids and other marine fossils. This is followed, as on the south side of the arch, by dark-grey and black platy shales with thin pale- LOWEK DEVONIAN SLATES. 19 green bands and brown calcareous streaks, these rocks yielding crinoids_ and simple turbinate corals. Mr. Walter Barratt has found in them a single specimen apparently belonging to Pleurodictyum. Griffin's Point is quite inaccessible ; ''but similar beds are found also on its north side. Beacon Cove can only be approached by a zigzag somewhat broken path on its north side. On crossing the Cove at low- water a set of thin beds exactly like those seen in the Criggars near Newquay will be found in the ledges which bound the bay. They consist of dark-grey calcareous shales with brown streams, traces of limestone, bands of phosphatic nodules containing Pachypora, and two or three of the thin pale-green bands which suggest volcanic ash. The north side of the Cove shows dip- slopes of dark platy shale very slightly calcareous, with numerous impressionsor pyritous casts of lamellibranchs and Pleurotomaria. The fossils are badly preserved, and all that Mr. E. T. Newton was able to make of them was that they included a Favosites, a simple coral, probably numerous Cardiola, Pleurotomarial Beller- ophonl a large Gonularial and au extremely obscure Orthocents. Between the two fossiliferous beds in Beacon Cove conies a belt of sandstone and sandy shale, which suggests the grit bands which separate the calcareous from the non-calcareous slates at East Pentire, near Newquay. The difference in the width of the two outcrops of calcareous shales, would on this assumption, be enormous ; but it has already been shown that in the southern outcrop the strata are apparently repeated agam and again. Near Beacon Cove, on the other hand, each overthrust fault tends to reduce the width of the outcrop, by cutting out beds, though it is impossible to make out exactly what each fault does. Hard dark-grey platy beds have been quarried at Berryl's Point for flags and hnteis, but they make slates of poor quahty. They are followed northward, on the south side of Mawgan Perth, by hard, platy shales with pale-green bands and a few black phosphatic nodules, few fossils being found in this part of the series, which greatly resembles the rocks of Holywell Bay. On the north side of Mawgan Porth, where the path descends from Trenance, the shales are non-calcareous and blackish, weathering green near the joints. They contain a few casts of crinoids, and a gasteropod was also seen. Nearer Trenance Point there is a tendency to banding in the strata, which may represent the Perran shales. They show a few pale-green seams and grit bands ; but the only fossils noticed were rare joints of crinoids. At the furthest point accessible at low- water spring- tides these shales can be seen passing into a massive greenish grit, which forms Trenance Point and, alternating with sandy shales, occupies a considerable area inland. These strata will be descrilDed in the next Chapter. Thus, as we travel northward, the non-calcareous slates, though greatly contorted and fuU of S-shaped folds, become duller, less 8934. B 2 20 GEOLOGY OF flEWQUAY. mineralized, and have the plates of mica less oriented. They also more commonly retain impressions of fossils, which, however, seem already to have lost their calcareous substance before the shearing took place. Such impressions would he easily obliterated by subsequent movement. The dead-black or grey non-calcareous platy shales, such as are seen on the north side of Beacon Cove, if slightly more sheared and mineralized, would be (juite indistinguishable from the hard shales between Pentire West and Ligger. The inland extension of the strata just described, need not be followed in great detail, for really good sections are few and far between, and are seldom deep enough to penetrate the weathered and oxidised surface layers. Fossils are extremely rare, and are also badly preserved near the surface. The point that perhaps most strikes the observer with regard to the inland area is the persistent east and west strike and apparent high southerly dip nearly everywhere. There is a slight convergence of the strikes towards St. Columb Major, so that the marine beds enclose the Old Red anticline, and there appears also to be some uncertainty of strike near the St. Agnes and Cligga granite masses, otherwise the variation is very small. Notwithstanding this well-marked strike there is little trace of any correspondmg surface features. The true dip is most difficult to obtain. We can prove by beds of fossils that, on the coast, bedding and cleavage usually coincide ; but this is not sufficient to decide the question, for we have no means of distinguishing between a normal and an inverted sequence. Towards Mawgan Forth, however, the slates are full of S-shaped folds, and it is obvious that the apparent dip is only the dip of the limbs of the fold or of the slaty cleavage. The apparent dip there is always southerly, though the real dip is towards the north. The seams of fossils also dip towards the south, except just at the nose of the folds, where the true bedding is masked by shearing. Inland it is impossible to trace these folds, or the numerous overthrust faults which cut them ; though there is abundant evidence of shearing parallel to the strike. Still, the overthrust- ing and shearing, however much they may pile up the strata, duphcate particular beds, and cut out others, have not sufficed to obliterate the original anticlinal structure, which can yet be traced inland, like a palimpsest manuscript under late writing. The antichne, however, would never have been suspected without a close examination of the coast, and it is interesting to find that it agrees so well with what Mr. Ussher had previously made out to be the structure in other districts where the Pteraspis beds come to the surface. The inland geology being what it is, the most convenient way to describe it will be to note the important sections as they occur along the strike; commencing at the north. LOWER DEVONIAN SLATES. 21 The grit-bed which appears in the chif on the north side oi' Beacon Cove, and seems to mark the junction of the calcareous with the non-calcareous slates, can be traced inland through Trevarrian village to Tolcarne Merock, where it forms a low crag below the farm. The behaviour of this mt-bed, which sweeps round so as nearly to touch the Old Red boundary near Trevarrian, strongly suggests that the overthrust fault, the line of which now forms the iron-lode in Beacon Cove, may be of considerable importance. It seems to run along the junction of the Old Red and Meadfoot beds for some distance, apparently cutting out a considerable thickness of the strata inland. At Trevarrian, where the effect is most marked, this fault has probably been joined by the more directly east and west striking overthrust seen in Stem Cove. The grit-band, which is probably only thin and impersistent, cannot be traced east of Tolcarne Merock, none of the numerous road-sections near Mawgan Pyder showing it. All these cuttings are in platy slate with a high southerly dip. A deep well west of Higher Tolcarne (in course of sinking during the survey) showed gi'ey calcareous slate with brown films, exactly like the slate which normally comes in this position, just above the Lower Old Red strata. A quarry at Trembleath is in grey calcareous slates with thin limestones, like those of Stem Cove and St. Columb Porth, no fossils were observed. From Trembleath to the east margin of the map (which is close to St. Columb Major) little is to be seen ; out a road cutting at St. Columb Bridge shows a trace of a much-silicified rotten greenstone, interesting as possibly equivalent to the large masses at Trebudannon, on the south side of the arch. The ground south of the anticlinal axis and north of the St. Columb river is not of much interest, the sections being shallow. The next strip, that extending southward to the Gannel, is more important. Commencing as before at the coast, we find at Pentire Point East the marked ridge of grit which separates the calcareous from the non-calcareous slates. This grit forms a ridge through the Warren, strikes diagonally across the Gannel at the steep bluff below the tea-gardens, and then seems to form the crest of the hiU nearly to Trevemper. For a mile it is hidden under the alluvium ; but reappears towards Kestle Mill and Coswarth. Beyond this it cannot be followed, for the whole of the slates are becoming more sandy and more like the rocks seen at Fowey. The gradual change to rocks of the more sandy Fowey type becomes noticeable in the area between Colan and Kestle Mill, for though the thin grits on the Newquay coast have jielded no fossils, uiose inland have yielded several. The places where these fossils have been found are, an old pit a quarter of a mile west-south-west of PoUawym, where a decalcified grit contains 22 GEOLOGY OP NEWQUAY. fragments of crinoids, and a sandstone quarry in the wood a quarter of a mile south-east of Kestle Mill. At this latter place the first piece of flagstone picked up showed a well- preserved ferruginous impression of part of a Cardiola ; but no other fossils could be found. Another resemblance of the rocks near Colan to those of the Fowey type is the appearance of thin bands of purple shale, such as is not seen m the cliffs near Newquay. With these are found also traces of greenstone close to Kestle Mill. Il is not, however, till we reach the district between Trebudannon and White Cross that the greenstones become a conspicuous feature. Here massive siUs suddenly appear and the rock has been quarried for road-metal, and should be more extensively used, for it is the toughest stone in the district. The mode of occurrence of the greenstone is peculiar, and suggests a sheet or siU, folded and afterwards cut by a north-and-south fault. The two main masses form belts about half a mile long and a mile apart, striking from west to east ; then they are suddenly lost. East of the line where they disappear two narrower bands come in at Crugoes and Lower Killaworgey ; but these bands also cannot be traced far. If the bands are all part of the same faulted siU, and the structure is anticlinal, the downthrow would be to the east ; but if it is a syncline, the downthrow would be to the west. These greenstones will be more fully described later on (see p. 24), suffice it here to say that an excellent section will be found not far from the high road west of Trugo, and other smaller quarries in each of the outcrops. In Trebudannon Lane there is a trace of much-sheared greenstone, apparently imconnected with the other masses. The railway cuttings on the line between Newquay and St. Columb are not of great interest. At Quintrel Downs the long cutting shows gritty and perhaps sandy slate, weathering red and dipping in various directions, though mainly southward. The slate becomes grey or more or less silty towards Coswarth. The cutting east of the dyke of mica trap is in grey slates with traces of a purple band. Similar grey slates with a purple band appear in the cutting east of Tresithny. This cutting gives a continuous section almost up to the metamorphic aureole which surrounds the St. Austell granite, but even at its east extremity no clear indication of metamorphic spotting could be ound. Penhale Moor Mine was sunk in grey glossy or somewhat bleached slate, showing no metamorphic spotting; but other small sections nearer to Blue Anchor show spotting, and the slate at Park of Mines (just outside our area) is decidedly spotted. None of this part of our area is sufficiently near to the granite to show more decided trace of metamorphic action than these obscure rhomboidal spots ; but the outer limit of this aureole has been laid down on the map as accurately as the obscurity of the ground permitted. Even beyond the limit LOWER DEVONIAN SLATES. 23 of the spotting the fine-grained slate commonly shows a slight change of colour; though this obscure outer aureole is too indefinite to map. The inland sections around Cubert are not good. A thui greenstone, probably a continuation of one of those seen in Kelsey Head, was found by Mr. W. D. Barnes in a slate quarry on the eastern edge of Cubert Common. Another exposure occurs at Carevick, a fourth at Trewothall and a fifth at Traifal. All these are approximately in the same line and show a local strike of east-south-east. Another trace of sheared greenstone occurs out of the line, near Trenissick. The cuttings of the Perranporth branch railway from Newquay as far as Newlyn East show nothing but grey slate; but the sections are not deep, for in this old mineral line cuttings are avoided by sharp curves and steep gradients. As we travel southward the dips become higher, as they do on the coast, and the rocks become more disturbed. The area north of Cubert and Newlyn East shows an average dip (or perhaps rather pitch of the folds) of about 45" ; but the cuttings of the Cornwall Mineral Railway, near Treworthen, the Peru Mine, and Rejerrah show grey non-calcareous, much-silicified slates, much contorted and with the bedding nearly vertical. Near Newlyn East dips of 50° and 60° occur at Degembris. Microscopic Features of the Lower Devonian Rocks or THE Vicinity of Newquay. By J. S. Flett. In the sedimentary series effects of interstitial movement and crushing are usually conspicuous, though much depends on the composition and original structure. Specimens of tne sandstone, shales, and limestones along the coast from Newquay to Perran- porth show that the arenaceous rocks as a rule best retain their original characters, and that interstitial movement in them is most marked where there are argillaceous bands in a gritty matrix. The rounded form of the sand grains is still preserved, but at their edges a variable, though small amount of fine, granulitic material can usually be detected and, where the original rock has contained much argillaceous matter, felspar or calcite, the evidence of deformation is always more conspicuous. The pure argUlaceous beds (phyUites) around Tolcarne consist essentially of white mica in minute parallel scales, frequently arranged in undulating lines, with greatly flattened lenticles of quartz between. Chlorite, iron-oxides, pyrites, dark graphitic dust, rutile, and occasionally a little ealcite appear also in these rocks, and they are often stained with limonite in irregiUar patches and streaks. In many of the sections a second cleavage or iimxveichvMgsdivage is very well shown crossing the principal 24 GEOLOGY OF NEWQUAY. cleavage nearly at jight angles^ and sometimes occasioning a sligEt faulting of the more quartzose bands of the phyllite. The argillaceous seams in the limestones also show this structure in great perfection. Intercalated with the micaceous phyllites there are thin pale-green bands which contain large quantities of chlorite and of iron oxide weathering into sphene. Felspar may also have been originally present, but as the rocks are both de- composed and greatly sheared this can no longer be proved. It is probable, as Mr. Reid has suggested (see pp. 14, 19), that these beds are igneous, but whether they were tuffs or crystalline rocks before they were sheared cannot now be determined. Sections of the limestone beds of Tolcame Head almost invariably show numerous fragments of crinoids and other organisms more or less completely destroyed by recrystallisation and crushing. Most of these limestones are impure and have calcareous bands alternating with others which correspond in composition and structure to the phyUites and sandstones. These thin bands of different composition stand out clearly in the slides, and folding, reversed faulting, granuhtisation, develop- ment of cleavage and ausweichungsctivage can all be studied in the microscopic sections. The crinoidal fragments often preserve their structure even in rocks which have been considerably deformed, but where the alteration has proceeded far enough they pass into a mosaic of clear recrystaUised calcite. Before this stage is reached and while the fenestrate character of the fragments is not yet obliterated they often show the develop- ment of polysynthetic twinning in consequence of internal movement along the glide-planes of the crystals, and as is usually the case in twinning developed by strain, the twin planes are often curved or bent and may be found in one part of the fragment but die out before reaching the opposite side. That the gUde planes do not always determine the way in which a calcite crystal will yield under a stress is shown by the occur- rence in the shdes of many crinoidal plates which have been converted into an interlocking mosaic without the formation of twin-plates or the obhteration of the perforate structure by which their echinodermal nature can be recognised. Greenstones. By J. S. Flett. The rocks included under this group are aU much sheared and consist essentially of plagioclase felspar, chlorite, iron-ores and leucoxene, with sometimes a little albite, quartz, green fibrous hornblende, and secondary muscovite, calcite, and Hmonite. They are mostly in the state of felspathic chlorite schists ; hornblende occurs rarely, but is the principal ferromagnesian in the greenstone of St. Piran's Chapel. No primary augite or ORfiENSTONT?:. 25 olivine is present in any of tliein. The felspar, where it is not entirely decomposed or broken down by shearing into micaceous aggregates, usually forms lenticles round which the other ingre- dients (chlorite, muscovite, leucoxene, etc.] arrange themselves in flowing lines. It is impossible to say whether the rocks were originally lavas (though some of them contain calcareous rounded kernels which may be the traces of amygdules) or intrusive masses, but where they are least sheared and their felspars still retain their original outlines in some measure, it is clear that the original structure of most of these rocks was porphyritic with a rather coarsely crystalline ground mass. No examples of ophitic greenstones have been found within this sheet, though they are not uncommon in other parts of Cornwall. There can be little doubt that they have sunered greatly from decomposi- tion, both before the period at which they were sheared and subsequently ; hence many of them are reduced to highly schistose aggregates of chlorite, muscovite, calcite, quartz and leucoxene in which no trace of the original structures and minerals is to be found. In several places in this sheet masses or veins of pyroxene, epidote, axinite and garnet have been observed in association with greenstones. Specimens were obtained at St. Piran's Chapel, Great Retallack mine, and at Trugo and Crugoes near St. Columb Major. Mr. Scrivener paid particular attention to the outcrop at St. Piran's Chapel and gives the following description of it : " Close to the old cross which forms a land-mark on the Perran sand hills there is an outcrop of an intensely sheared greenstone, which can be traced for some way by means of mine debris from trial shafts. Ai one spot two pits have been sunk on the outcrop, apparently with the hope of striking a branch of the great Perran iron lode. One of these pits has disclosed the presence of a massive garnet rock ; the other a massive axinite rock. On the joint faces of the green- stone and in druses good crystals of dull green epidote occur. No mineral of economic value was found. " As the exposure of the garnet rock was not satisfactory a portion of the ground was cleared, with the result that the garnet was shown to have a position clearly within the greenstone and to be of the nature of^a vein with a course parallel to the con- taining rock. The thickness of the vein could not be estimated with accuracy ; but it must be at least three feet where the ground was cleared. It does not appear from the evidence in the field that the garnets are anywhere mixed with the axinite. " The killas* in the immediate neighbourhood of the green- stone shows none of those characteristics usual in Cornish rocks affected by the contact metamorphism of a granite mass. The nearest granite is at Cligga Head. This has an exceptionally *The term killas is commonly applied in Cornwall to the contorted slaty rocks. 26 GEOLOGY OP NEWQUAT^. well-defined metamorphic aureole, but the garnet rock is out^ side it." The garnet rock is a somewhat porous mass of brownish green garnets, many of which show dodecahedral faces, while the presence also of facets belonging to the icositetrahedron was con- firmed by means of the reflecting goniometer. Most of the crystals, however, are so closely in contact with one another that their crystalline form is imperfect except where they abut on the cavities which are abundant in the rock. Their lustre is dull as a rule, only the best faces having the resinous character- of garnet. Under the microscope they are traversed by numerous cracks, mostly irregular, bvit occasionally forming a nearly rectangular network. They are pale yellowish-green, or almost colourless, and enclose small grains and well-shaped prisms of pale yellow or colourless epidote, spots of quartz, gTains of brown ferriferous carbonates which dissolve readily in hot dilute acid, (but not in cold), small patches and spherulitic clusters of green chlorite, and rounded or irregular cavities which are mostly empty but sometimes contain a fluid with a minute bubble. These garnets form the great bulk of the rock, but between them there are sometimes fairly large, irregular crystals of epidote, areas of chlorite which may, perhaps, represent original pyroxenes, and a small amount of clear quartz in which many colourless needles belonging to some undetermined mineral are embedded. These garnets are all doubly refracting, so that no part of the sections remains dark when rotated between crossed nicols. Some of them also have a strongly marked zonary banding parallel to the crystalline faces. The strength of the birefrin- gence A'aries a good deal, but where greatest is only a little less than that of quartz and in polarised light the colours are grey or whitish grey, and when the shdes are thick they may be yellow or purphsh violet. The better shaped crystals mostly belong to the " dodecahedral type " of Klein and polarise in sectors which correspond to the dodecahedral faces, and in convergent light yield a biaxial figure ; but usually the structure is far less regular, and in polarised light the sections often have a fibrous or spherulitic appearance. There are also cases in which a polysyn- thetic structure with rectangular cross hatching Hke that of leucite is very evident, though the lamellae at times tend to be spindle-shaped like those of microcline. The aximte from the same locality forms greyish or brownish green masses with a dull lustre except on occasional well formed crystalline faces. Some of the crystals are slightly violet in the hand specimen, and more rarely a faint violet colour and very feeble dichroism may be observed in the microscopic slides. Good crystals are found only lining cavities ; the mass of the rock consists of irregular grains often several millimetres in diameter. They frequently break up between crossed nicols into irregular areas with interlocking borders, the result apparently of strain, but they are not crushed or granulitised. Their commonest enclosures are long, narrow prisms of colourless epidote, which often have fibrous terminations, and very minute cavities, the largest of which show mobile bubbles. Dusty grains of brown carbonates, decomposing into limonite, also pervade the mineral. At the Great Retallack mine, near the north side of Perran sands, Mr. Scrivenor obtained specimens of green pyroxene with an extraordinary resemblance to actinolite in the hand specimens. It forms dark-green, bladed prisms with a divergent or even plumose habit. Under the microscope the rock proves to be a mixture of pale-green pyroxene, yellow-green epidote, carbonates and chlorite. The epidote and pyroxene are so like one another in most respects that great care is necessary in identifying them ; neither mineral has as a rule idiomorphic transverse sections ; the augite is much the more abundant and is weathering into green chlorite and fibrous -amphibole. Granular carbonates and spherulitic chlorite occupy the interspaces. The specimens also contain a considerable amount of zinc-blende, and a little trans- parent interstitial quartz. A short distance to the east of the Great Ketallack mine is the well-known Duchy Peru mine from which Warington Smyth has reported " garnet, zinc-blende, and boldly crystallised hornblende (of the radiated strahlstein character)."* There is a possibility that the hornblende is really a pyroxene similar to that describea from Great Retallack and that, as Smyth suggests, the lodes of these two mines are the same. At Trugo and at Crugoes, near St. Columb Major, pyroxene- epidote-axinite rocks are also found in association with green- stones, and garnet has been reported by W, W. Smyth from this locality!. The mode of occurrence of this greenstone has been described on p. 22. Towards Crugoes, close to the edge of the map, and nearer to the aureole of metamorphism surrounding the St. Austell granite, the rock is much more altered and recrystallised. Unfortunately here it is only found in an old mine-level and in a small abandoned . quarry, both so overgrown that nothing can be seen of its relations to the surrounding country. The specimens from Crugoes obtained by Mr. Reid came from some large blocks which had been left unbroken, and were being removed for road-making. In the hand specimen they are finely, or rather coarsely crystalline rocks, green or yellowish-green in colour, occasionally showing divergent groups of pyroxene prisms and small vitreous crystals of brownish-violet axmite. The greenstones and grey- wackes among which they occur are platy and highly sheared, * Trans. R. Geol. Soc. Cornwall, vol x., 1882, p. 24. t Ibid., vol. ix., 1878, p. 38. 28 GEOLOGY OF NEWQUAY. and not unfrequentlj^ are tilled with very small grains of augite and epidote which give them a pale-green colour. The pyroxene is a diopside with extinction an^le r ; c = 40". Transverse sections have the prism faces very small or absent, and the predominance of the pinakoids is very marked. The prismatic cleavage is usually well developed and in addition there are two others following the vertical pinakoids, but less perfect. Some of the crystals are weathering to chlorite and secondary fibrous green hornblende ; their only common enclosures are liquid cavities with mobile bubbles. The epidote is yellowish-green, only feebly dichroic ; its crystals are often idiomorphic in transverse section with the usual faces, but like the pyroxene are irregularly terminated. In some of the slides both of these minerals occur as stellate aggregates of small prisms. Axinite and quartz fill up the spaces between the above mentioned ingredients and show no trace of crystalline form except where they line small cavities in the rock. The axinite has often a distinct violet colour in the sections. Both minerals contain fluid ca^aties, but scarcely any other enclosures. Small crystals of sphene are present in one of the slides, and patches of granular carbonates may also be found. In all respects, except in the absence of garnet, these two occurrences are parallel. Although at St. Piran's and Retallack the garnet, axinite and epidote do not occur in the same hand specimens, and only the epidote is common to the three aggre- gates, the general character of all the minerals is so strikingly similar to those described from St. Columb Major that there can be no doubt that the same origin and method of formation must be ascribed to them. This mineral paragenesis, viz., epidote, axinite, pyroxene and garnet, recurs in other parts of Cornwall and always in association with greenstone. They may be found within the aureole of spotted slates or outside it, as in the two cases above described. Sometimes they form veins, but they seem also to occur as nodules, streaks and patches. Sometimes they are metaUiferous, as at Duchy Peru and Retallack, where they carry zinc-blende, but this is far from being general. The killas of West Cornwall contains only very small amounts of hme, and lime-silicates such as the above minerals can arise only in the greenstones or possibly in the limestones which begin to come in around Newquay. It is clear that they may have been derived from veins or patches of impure carbonate of lime, such as are frequent in sheared greenstones. The action of the granite is indicated not only by the characters of the minerals but also by the axinite, which contains boric acid, a substance always traceable in Cornwall to the emanations of the intrusive granites. In the killas it combines to form tourmaline, but when the rocks are rich in lime, datolite and axinite are the boro- silicates formed. It may be noted that Professor Busz* has described contact- * Ne'nes Jahrh.fur Mineralogie, B.B. xiii., 1900, p. 125. GRBENSTONE. 29 altered limestones from the E. Avon in Devonshire, which contain garnet, (datolite), axinite, augite and quartz — exactly the same mineral paragenesis as that which we are considering. Where the garnet-axinite augite-epidote veins are found out- side the area where the slates are spotted or otherwise affected by the heat of the granite we are reduced to the hypothesis that the original calcareous substances have been much more susceptible to thermal action than the highly argillaceous killas, and such idiosyncrasies, as they may be termed, have frequently been pointed out in contact aureoles. But it is also probable that in such cases the minerals occur in fissures along which heated vapours were ascending, and this is supported by the occasional occurrence of ore deposits in such veins. The Perran lode is an excellent example. In other words, these axinite rocks are " pneumatolytic " formations. 30 CHAPTEE IV. LOWER DEVON [AN SANDY SERIES. On either side of the anticHnal axis which we have been describing, a series of silts, sandy slates, sandstones, and coarse grits comes in. These sandstones apparently have a general northward dip in the northern area and a slight general dip, to the south in the southern. They are also much and sharply folded ; so that in both cases there appears to be a high southerly dip, which in reality is in general nothing but the pitch of the limbs of the folds. Towards the northern hmit of the area, sandstones and sandy- slates, striking west-north-west, make the high land of Denzell Downs and end in vertical cliffs at Trenance Point, which forms the northern limit of Mawgan Porth. The sandstones are hard, quartzose, and gritty, cemented to a large extent by redeposited silica, and often pass into a tough quartzite. They commonly occur in thin beds with partings or alternations of softer sandy micaceous shale. Towards their top (beyond our northern limit) they tend to become finer-grained and more shaly, and in lithological character greatly resemble those near St. Agnes and Perranporth, though there appears to be no definite division between these sandv shales and the coarser grits. The colour at the base of the cliff is always grey or greenish-grey, usually of a lighter tint than that of the dark-grey slates below. In the upper part of the chff the sandstones are reddish or buff', the sandy shales often becoming pink or salmon-coloured. Only one fossil has yet been found in this area, which, however, is worth further search, for it is important to fix the exact age of this division. An excellent section of the sandy strata near Mawgan will be found in a large quarry a quarter of a mile north of Denzell. Here is seen a clear exposure of 20 feet of flaggy grit and grit shale, with an apparent southerly dip of 10°. Other small quarries within our hmits will be foimd close to the north-east corner of the map and near Daymond's Buildings, and in the cuttings for the old canal which led to the edge of the cHffs at Trenance. The best section, however, is in the cliff just outside the area, near Trenance, where the sandstones can be seen to form enormous folds, often cut by overthrust faults. This cliff is not easy of access ; but at extreme low-water spring-tides a section of the transition of the sandstone into the shales below can be examined on the north side of Mawgan Porth. Though the rocks are greatly folded, the junction seems to be a normal passage, with- out either fault or recognisable unconformity ; it is impossible, however, to speak with confidence on this point. The sandstones of DenzeU Downs strike east-south-east, and this strike if prolonged would make them meet and be continuoijs LOWER DEVONIAN SANDSTONE. 31 with the similar grits of Ladock, on the south side of the anticlinal axis, which strike a little north of east. The continuity, however, is broken by the intrusion of the St. Austell granite, and we are unable in this or in the adjoining area to con- nect the two masses of sandstone. We must therefore treat the southern area separately. In the southern part of the district the sandy strata form a much wider belt, trending approximately east and west, from St. Agnes Head and Perranporth to Ladock, where they pass out of the area described in this Memoir. These sandy deposits consist mainly of soft fine-grained sandstone and soft silty slate ; but in them occur locally and more rarely large masses of hard slate and hard coarse grit. Grit, however, except eastwards towards Ladock and Grampound, is less conspicuous than at Denzell Down. It is not easy to recognise particular bands in an unfossiliferous mass of this sort ; but one narrow belt seems to occur again and again across the strike. This belt consists of striped black and pale grey slate, very glossy where in contact with certain thin bands of hard cherty carbonate. If this is really the same narrow belt, repeated four times in about three miles, the strata, notwithstanding their width of outcrop, are probably of no great thickness. The sandy and silty beds on careful testing prove to be slightly calcareous ; the matrix of the grits and some small veins in the silts tending to effervesce with acid. Here and there in the bed- ding planes occur thin white or greenish-white streaks which, like the similar streaks in the slates of Newquay, seem once to have been calcareous, though now few of them will effervesce. A noticeable feature in this division is the occasional occur- rence of thin bands of silicified cherty grit or quartzite, which seem to correspond with the thicker silicified bands in the northern outcrop. In the northern area, however, these silicified bands are sufficiently thick for gate posts and standing-stones to be made of them ; in the southern the thickest seam appears not to exceed a foot, and most of them are much thinner. The usual colours of these rocks vary from- black to grey or greenish-grey, with certain bands almost white ; but for a con- siderable depth the strata have usually changed to buff or pink, with occasional belts pale-green or bleached nearly white. The freestone of which Perranporth and St. Agnes are built is of these colours, quarries in sandstone not going sufficiently deep to reach the unoxidized rock. A short description of the cliff section from Perran Bay to Chapel Porth will best explain the nature of these rocks ; but it must be borne in mind that two additional elements of un- certainty affect this part of the coast. In the first place there is the doubt as to the mechanical effect of the intrusion of the two granite masses of Cligga Head and St. Agnes Beacon ; in the second place there is the great difficulty in recognising the strata 32 GEOLOGY OF NEWQUAY. where they have been metamorphosed, altered by mineral im- pregnations, bleached, or oxidised. The new cuttings of the Perranporth railway give a better idea of certain parts of the series ; but the cuttings are rapidly breaking down under the influence of the weather, for these rocks where unmetamorphosed are usually much softer and more silty than the slates around Newquay. The junction of the Newquay slates with the silty " Perran Shales " is hidden under the sand dunes ; but at the point where the cliff again becomes visible, at Cam Haut, the rock is distinctly of the Perran type, consistiog of black and grey silty shales with thin bands of grit. About 400 yards further south, near the adit of Wheal Vlow, faint metamorphic spotting can be detected and we enter the aureole surrounding the Cligga Head granite. A quarter of a mile south of the Wheal Vlow adit and under Cam Clew, the colour striping becomes very distinct, the rock consisting of black and pale-grey shales, extremely glossy where in contact with certain thin seams of cherty carbonate. This belt of striped shales with thin seams of hard chert-like carbonate closely resembles a band found between Pentuan and Mevagissey.* It apparently occurs again around the Roman Camp north of Tregony, and is found also at several points in the railway cut- ting south of Perranporth. If this is m truth a single band, as appears to be the case, it forms a useful horizon in the Lower Devonian, which can be traced fi'om sea to sea. Banded silty shales continue southward as far as Cotty's Point, where a mass of sandstone appears for a short distance. Banded strata reappear, however, at Wheal Ramoth, at Chapel Rock, and on the south side of the river ; but they are gradually becoming more and more baked and metamorphosed, so that south of the river they are so hard that they were at first thought to represent the Portscatho strata. These baked and altered silty rocks with subordinate bands of coarser sand occupy the cliff for some dis- tance ; but between TreveUas Porth and Trevaunance Cove they are again little altered and form a bay. Here again they show clear indications of having once been calcareous, though it is difficult now to find a vein that wiU effervesce with cold dilute acid. Near Trevaunance Coombe, however, the curious thin bands of cherty carbonate again occur in much striped slate. The flat-lying folds on this part of the coast are venr striking, alternations of hardy and softer strata making the cliff in places greatly resemble that of Hayle. The hard bands, however, are seldom grit, but are usually fine-grained and silty, like the softer ones. . Similar silty strata with subordinate bands of sandstone form St. Agnes Head ; but here again they are much baked and * See Howard Fox and J. J. H. Teall, Trans. R. Geol. Soc. Cornwall, vol. xii., 1896, pp.. 51, 53; and "The Geology of the Country around Mevagissey. Mem. Geol. Survey. LOWER DEVONIAN SANDSTONE. 33 Spotted, the aureole extending south-westward as far as Forth To wan, which lies just outside our district. The railway from Perranporth to Chacewater lies outside the metamorphic aureole and crosses the strike of the deposits just described for several miles ; it will be advisable therefore to say a few words about the sections exposed in these cuttings, for the rocks are usually very soft and in a few years they will be almost entirely hidden. The cuttings were being made while the Survey was in progress. The cuttings immediately south of Perranporth show silty slates with a little sandstone and thin bands of cherty grit. In a strongly banded belt opposite Anchor one-inch band^ of cherty carbonate again occur. In the cuttings north-east of Carnabargus these strata give place to a fine-grained soft sandy slate or sand- stone, with a thin band of coarser grit, largely made up of shale pebbles. This belt is very like the grit of Grampound, but softer and finer-grained. Then follow silty strata for about a mile before another soft coarse sandstone is observed in the cut- ting north east of Mithian. Alternations of silts and shaly sand- stones occupy the cuttings for the next mile. Near the viaduct between Mithian and Goonbell will be found the large ci uarry from which was obtained the soft sandy freestone which has been used for all the railway bridges. This quarry is strikingly like some near Bodmin, but the stone is decidedly softer and finer-grained than the hard grit of Grampound. Only one or two thin seams of the coarse grit mth shale pebbles could here be found. Near Goonbell Halt shaly fine-grained sandstone, with slate and a little coarser sandstone again occurs in the cutting. Then silty beds continue to the edge of the map. Just south of the district, at Trenithick, hard finely-laminated puckered slate, with calcareous veins, is found, and perhaps the same thin seams of cherty carbonate again come on, thoiigh they are not exactly like those further north. The cuttings east of Perranporth need not be described; they are entirely in silty and sandy much- banded strata of the Perran type, and are rapidly being hidden by land-slips and vegetation. These strata seem to become more and more sandy eastward. This sandy i3elt, followed inland from St. Agnes and Perran- porth, is found to have an eastward strike. The included slates are well exposed in several road sections, as, for instance, at Henver, Trerice, and St. Allen; at these three localities their apparent thickness is such that one is led to believe that the slates form lenticles of at least 100 feet in thickness within the series. For the most part these slates seem to be evenly bedded and soft ; but contortions are met with here and there. The grits are frequently exposed in quarries and present the same features as on the coast for some distance along their strike. In the parish of St. Allen, however, a change becomes evident. In a 8934. C di GEOLOGY OF NEWQUAY. small exposure at Trefronick the grits are found to be coarser than usual, and also to be very rich in white naica. On following the outcrop eastward it is seen that the grits are both becoming coarser, and are developing at the expense of the shales. The first good exposure where this can be seen is between Treworgan and Lanner Farm, where a quarry has been worked for many years for road metal. The grits and slates here are very tough, owing partially to silicification. Mr. J. H Collins states that the matrix is somewhat calcareous * East of St Allen the evidence of the coarsening and thickening of the grits is abundant in the fields ; and at a point where the roads passing north of Nansough Farm crosses a little valley there is another good exposure. The best exposure of all, however, is at Bissick, in the Ladock valley, where the slates are quite subordinate. IJp to the edge of the map there is clear evidence of the grits continuing towards Grampound. As in every exposure the coarse grits are essentially alike, it will not be necessary to describe them at more than one of the localities mentioned, for which purpose we may select the quarry near Nansough Farm. The exposure here consists almost entirely of grit, the slates being poorly represented. The grains are more or less rounded; they vary considerably in size, the largest being perhaps one-eighth of an inch in diameter. The grit bands are jointed in a manner similar to that which obtains in the elvans ; and it is no doubt partly owing to this that they are locally spoken of as " elvan." Throughout the mass of the grit, fragments of sheared slate are common ; they are very thin and also angular, owing to the shearing. Of the other grains the commonest are quartz ; but grains of quartzite and green- stone are occasionally met with, and in this connection it should be remembered that J. A. Phillips described these grits both at St. Allen and at Ladock.f At the former locaHty abundant plagioclase is recorded, with a little hornblende, white mica, epidote, and rarely tourmaline. At Ladock the occurrence of greenstone or "dunstone" fragments is mentioned. On weathering these grits take on a buff colour, which gives to the ploughed land an appearance not generally seen in this part of Cornwall. Fossils are said to occur. In the south-eastern part of the map the coarse grits are not by any means confined to one narrow horizon in the series, but extendover nearly the whole of the outcrop indicated. Viewing the series as a whole on this map, it would appear that to the west it consists of a series of grits and shales, in which the shales play an important part ; but that as one proceeds eastward the shales become subordinate and the grits increase both in size of grain and thickness, just as would be expected to happen if one were approaching a shore line. There can be no doubt that * Trans. JR. Inst. Cornwall, 1881, p. 18. t Quart. Jov/rn. Geol. Soc, vol. xxxvii., 1881, pp. 10, 11. LOWER DEVONIAN SANDSTONE. 35 these coarse grits are identical with the conglomerates mentioned by De la Beche as striking westward from the south coast through Grampound and St. Allen ; and that they are a continuation of the less developed grit bands in the cliif-section at St. Agnes. A mile or two beyond the southern limit of the area described in this Memoir, the Lower Devonian sandy strata above described seem to abut against and rest on rocks of Lower Palaeozoic age. Since the above was written a fossil has been found in the Ladock quarry and placed in the Truro Museum. It is an Orthis, which Dr. Ivor Thomas, who examined it, thinks is probably new. The fossil collector of the Survey was sent to search for more, but could find none, though he learnt that others had been seen though not preserved. They probably come from one particular band. The fossil, being a new species, does not help us to fix the age of the Grampound Grit ; but it shows that further evidence may be forthcoming if the quarries are carefully searched. 8934. C 2 36 CHAPTER V. GRANITE. None of the larger granite masses of Cornwall rises to the surface within the area under consideration, though in all proba- bility granite at no great depth underlies much, if not all of it. The St. Austell granite mass approaches nearest, nearly touching our eastern border, and sending its metamorphic aureole into the map for a short distance near Enoder. There are, however, two small outcrops of granite, the one close to St. Agnes Beacon, the other at Cligga Head, which are of great interest as showing the alteration of granite into greisen, and the relation of the granite to the tin-lodes. The Cligga granite is a remnant of a larger mass, the rest of which has been lowered beneath the present sea-level by a north-and-south fault. St. Agnes. The St. Agnes granite is situated on the west of the Beacon, midway between that hill and the sea. The exposures are extremely unsatisfactory, and now that the mines on this side of the Beacon have ceased working it is difficult to obtain an accurate idea of the form of the outcrop ; but as far as can be judged from the evidence this is an oval, trending approximately north and south, the northern portion being covered by the Pliocene sands and clays. Although big detrital quartz grains are scattered here and there in profusion over the surface of the outcrop, the rock itself can only be seen exposed in two quarries, one an old fireclay quarry close to the road by Beacon Cottage, the other a smaller disused quarry sixty yards due south of the eastern extremity of the big open-work on Wheal Coates. In this open-work the granite itself is not exposed ; but a few veins can be seen traversing the metamorphosed killas. Debris derived from veins of granite was also noted on the top of the Beacon. In the two quarries mentioned above, the granite is seen to have been greatly altered, the felspar being almost obliterated and the rock passing into a greisen. In the old fireclay quarry kaolin has been developed in workable quantities. Traces of the jointing can be seen, but the exposures are not sufficiently good to enable one to determine their direction with accuracy. The best spot for the study of St. Agnes granite is the old shaft of Wheal Bungay, between Tubby's and St. Agnes Heads. Here granite debris in large quantities has been brought up from the workings, and it is possible to gather some idea of the petrological constitution of the mass and its modified forms, although it is no longer possible to study them in situ. GRANITE. 37 In the freshest hand specimen obtainable the orthoelase is distinctly porphyritic, and varies in colour from a rose pink to white. A second generation of the same mineral is now represented by light green pseudomorphs. The mica has evidently been considerably altered, its lustrous surface and rich brown colour being destroyed. The quartz grains are not so numerous, and are further remarkable for exhibiting a crystal outline. The ground mass of the rock has a pecuHar speckled appearance, owing to the presence of numerous minute grains of quartz and tourmaline in a felspathic base. In another specimen the orthoelase has been replaced by secondary minerals entirely, but the outlines of the individuals can be still easily traced. The quartz grains are distinctly idiomorphic and not so numerous as in a typical granite. Biotite is absent ; tourmaline apparently so ; and the rock also differs from the fresher specimen in the ground mass being crowded with minute flakes of muscovite. A third specimen shows the extreme state of alteration of the original rock. It differs essentially in being extremely quartzose and in the almost total disappearance of the felspar crystals, the rock having in consequence a very dark hue. A few traces of the biotite can be seen ; and numerous dark spots suggest tourmaline. The original quartz grains are distinct, and as in the first specimen, often show a crystal outhne. The ground mass of the rock is full of minute quartz grains and muscovite flakes. This rock is a good example of a greisen. Under the microscope the felspar is found never to be in perfectly fresh condition. Kaolinization is in many cases well developed, and where this is absent, the felspar has been altered to secondary quartz, muscovite, and topaz, the latter mineral occurring in small irregular grains without any trace of colour. The second type of alteration can generally also be seen developed to a varying extent in the kaohmzed crystals. One or two good examples occur in these shdes of the complete replacement of the orthoelase by muscovite, quartz, and cassiterite, topaz being in these cases apparently absent. In addition to the orthoelase a httle plagioclase is present. The biotite is either completely colourless or pale vandyke brown. The grains are ragged, show strong absorption, have pronounced pleochroic halos, and include large zircons, which on account of the bleaching that has taken place, stand out in strong rehef Quantities of magnetite are also included. Besides the biotite and muscovite, gilbertite, a sub-species of muscovite first described by Thomson, occurs in nests. In section the large original quartz grains can be easily distinguished from the smaller grains of secondary quartz derived chiefly from the orthoelase. Some of the smaller grains in the ground mass may, however, have been original. All are crowded with fluid inclusions and in some cases a zone 38 GEOLOGY OF NEWQUAY. particularly rich in these surrounds the original grains, an arrangement which is due to a deposition of secondary, and optically continuous, silica on the quartz of earlier crystallization. The inner contours of these zones show that the original grains were nevertheless idiomorphic. In one specimen small quartz grains were seen completely surrounded by a band of minute flakes of muscovite. Tourmaline, with somewhat irregular outlines, is abundant in all the specimens cut. It is of a deep brown colour, but sometimes shows blue frayed terminations and an edging of blue on the prism faces. The absorption is not so pronounced as is generally the case in tourmaline. A rough cross fracture parallel to the base is constant, and, in addition to this parting, traces of a fine cleavage can be sometimes discerned at right angles to the cross fracture. Greenish pleochroic halos surrounding included zircons and other material are very common, as also are inclusions of irregular quartz grains. A few of the more ragged tourmaline crystals have a well-defined spongy quartzose border. A few minute pale blue grains in the original quartz may possibly be referred to tourmaline. Irregular grains of cassiterite occur which may be original. The St. Agnes granite is remarkable for the disappearance of the felspar, the rarity and peculiar condition of the biotite, the occurrence of secondary silica, muscovite, topaz, and the presence of cassiterite and brown tourmaline. That most of the secondary sihca, the muscovite, topaz, and in part, at least, the cassiterite, have replaced the felspar cannot be doubted after a study of the slides. The question of the origin of the tourmahne remains. In the first place, it is a very significant fact that the biotite has a much smaller ratio to the original quartz and felspar than is usual in the Cornish granites, and that such crystals as are present have been very materially affected without the production of chlorite. Again, the included zircons with their pleochroic halos and the fine cleavage at right angles to the cross fracture point to something pecuhar in the tourmahne. Now since it is known from a large number of analyses that brown tourmaline is essentially a magnesia tourmaline, and that it is also rich in iron, and contains titanium, one is led to the conclusion, that some at any rate, of the brown tourmaline has been derived from the biotite, an alteration suggested by Professor Bonney in the case of Trowlesworthite.* In the change from biotite to brown tourmaline, secondary siUca must be set free as in the change from felspar to tourmaline, but in a smaller ratio^n fact about 17 per cent, of the silica in the biotite. This silica would almost certainly recrystallize as quartz, as it has done in the alteration of the felspar to muscovite and topaz, and, by this means the inclusion of quartz in the tourmaline and the spongy quartzose borders can be explained. * Trans. Boy. Ge.ol. Soc. Cormvall, vol. x., 1887, p. 182. GRANITE. 39 There is no a priori reason why the tourmaline should not be partially an original constituent of the granite. Thus supposing that boron was present in the molten magma, as can be shown to have been the case in the Cligga granite mass, molecules which would otherwise have crystallized as biotite might have solidified as brown tourmaline, the earlier formed zircons and magnetite occupying the same position as they do in biotite, and the zircons being accompanied by the same pleochroic halos. The halos alone are not conclusive evidence of the secondary nature of the tourmahne, as similar phenomena occur in minerals other than micas. Still the quartz inclusions and the fine cleavage crossing the basal fracture, a cleavage which cannot be referred to tourmaline, but is similar to that in biotite, if we assume that the basal plane of the latter has become a prism plane in the tourmahne, are phenomena which strongly favour the view that the greater part of the brown tourmaline has been derived by metasomatic action from biotite.* In the Cligga granite it is possible, by a study of the divisional E lanes, to picture the form of the mass as originally intruded ; ut at St. Agnes, owing to the poor exposures, no such re-con- struction is possible. However, taking into consideration the limited extent of the mass, its isolated position, distinctly porphyritic character, and the peculiar idiomorjphism of the quartz grains, it may be safely assumed that this outcrop is a section across a long but slender apophysis rising vertically from the igneous mass which connects the great granite masses of Cornwall under the killas. Before leaving this granite outcrop, a brief note is necessary on the well-known so-called pseudomorphs after orthoclase obtained formerly in large numbers from the workings of Wheal Coates. They are generally spoken of as pseudomorphs in cassiterite after orthoclase, and have been described by various authors : more- over there is no large collection of Cornish minerals that does not contain some of these interesting specimens. At St. Agnes, the fine collection of Mr. Naylor Came may be mentioned, which contains a number of examples of this replacement, fully illustrating the gradations in the percentage of cassiterite present. In order to avoid any confusion in terms, it must be stated that these are not in the strict sense of the word pseudomorphs in cassiterite, but replacements by an aggregate of minute grains of TTassiterite, quartz and muscovite. According to the greater or less percentage of cassiterite present in the aggregate the colour is dark brown or light brown ; indeed some specimens are so light both in colour and weight that they suggest that there is no cassiterite in them at all, but only iron- stained quartz and muscovite. The outlines of the felspar crystals have been most faithfully preserved, so that the complex * J. B. Scrivenor, " The Granite and Greisen of Cligga Head," Qtuirt. Joum. Geol. Soc, vol. ix., 1903, p. 150. 40 GEOLOGY OF NEWQUAY. groups, and the commonly occurring Carlsbad twins can be discerned as clearly as though the crystals were perfectly fresh, although of course the faces haye lost their lustre. No fresh specimens were obtained during the summer of 1902, except in the slides described above. Cligga Head. Owing, no doubt, to the excellence of the cliff exposure, the Cligga Head granite has been noted by several writers, but never- theless has not as yet been described microscopically. Conybeare in 1817 ; Joseph Carne in 1818 ; Sedgwick in 1820 ; Oeynhausen and Dechen in 1829 ; Boase in 1830 ; Henwood in 1838 and 1843 ; De la Beche in 1839 ; and C. le Neve Foster in 1877, have all described this isolated mass, emphasizing the peculiar stratified appearance, which C. le Neve Foster shewed to be due to bands of greisen traversing the granite. A figure in Cony- beare's paper portrays this stratification ; but unfortunately the leading features of the sketch are not true to nature. At the time when C. le Neve Foster described the Cligga Head section, it was easily accessible by a path leading from Perran- porth along the top of the cliffs, but since that time Messrs. Nobel's Explosive Factory has been established on the headland, with the result that it is now necessary to apply to the Company for permission to visit the chff. The flat ground on the headland, now occupied by the factory, was formerly the site of extensive copper mining operations under the names of the Perran United and the Perran St. George Mines. The piles of debris from the old workings are being utilized in earth-works built round the various houses of the factory ; and the accumu- lation of cold water in the levels is being pumped up through the Devonshire shaft, where the engine house is still standing, for use in those parts of the factory where it is necessary to maintain a low temperature. The form of the granite outcrop, hke that of the St. Agnes granite, is elongated, with the major axis trending north and south ; and the cliff section, which faces due west, shews innumerable divisional planes trending 20° north of east. Off the shore and west of tne cliff, are a number of rocks, chiefly of granite ; but those opposite the southern end of the granite are of altered killas. At the extreme south of the outcrop the granite is seen to be resting on a wall of killas steeply inclined to the north. It will be evident from a glance at the disposition of the killas and granite islets off .the shore that the outcrop of the granite must have trended from the south iseaward to the north-west, and moreover a study of the divisional planes near the junction with the killas will reveal the form the granite had originally at this end of the outcrop. The length of the exposure is a little less than three-eighths of a mile ; and in the northern half of this the divisional planes, GRANITE. 41 seen in section, and (in one part, where an enormous mass of the granite has fallen away) in " plan," are plane surfaces, dipping at a high angle, 60° or thereabouts, to the north-nofth-west. In the southern half of the section, however, the divisional planes as seen in section, are no longer plane surfaces, but first bend over in a sharp anticline and then form a syncline, the southern hmb of which rests on the abrupt wall of kihas. The visible junction between the hmb of the syncline and the killas is a plane surface, but if one ascends the precipitous path leading from this part of the beach to the top of the cliff, it will be evident that the junction of the granite with the killas on the east of that part of the granite where the syncline is seen, is a slightly curved surfac(3 with the shallow concavity pointing westward, and facing the killas islets. That the form of these well-marked divisional planes has been determined by the form of the surface of the killas into which the heat of the granite radiated, a loss which resulted in the contraction of the igneous mass, cannot be doubted ; for the divisional planes in the Hmb of the syncline can be seen to be parallel to the kiUas wall ; while the curved surfaces on the east at the top of the chff are also following the killas. Seeing that the granite cannot have extended farther than the killas islets, a restoration of the denuded granite would probably shew that the curved divisional planes facing westward rose sharply not many yards away from the existing cliff, the extremity of the reconstructed granite having the form of a tongue curving under a large convex and over a concave surface of killas, which surfaces would so govern the planes of contraction as to make them assume, in section, the form of a syncline of varying degrees of abruptness, according to the direction in which the section is cut. In the same way it may be argued that where, in the existing cliff section, the divisional planes constitute an antichne, the granite was in the form of a tongue curving under a concave and over a convex surface of kiUas. On the east the junction of the granite with the kiUas is obscured by piles of debris, except at the point mentioned and in the cliff facing north at the other end of the outcrop. This junction can only be seen from a boat, and proves to be a plane vertical surface, along which the sea has driven a narrow chasm for some feet. This junction is remarkable in itself, but still more so when it is remembered that the divisional planes here are striking towards it almost at right angles, without any signs of curvature. Fortunately, it was possible to obtain very valuable evidence on this point from an old Mine Report, dated 1857 and 1858, by Captains Tamblyn, Thomas, Tonkin and John R. Pill. In Captain PiU's portion of this report it is stated that at the time when De la Beche made his survey it was not known that the main mass of the granite was found in mining operations at a point about a quarter of a mile to the east of 42 GEOLOGY OF NEWQUAY. Cligga Head, at a depth not much below sea level. Captain Tamblyn also mentions " a patch some hundreds of fathoms further east, lying to the north." Again, quite independently of the above testimony, it is possible to infer the presence of a large granite mass, either hidden by the killas or denuded away by the sea, for the aureole of metamorphism affected by the igneous mass was found to be out of all proportion to the existing outcrop, and to point to a considerable mass to the north of Cligga Head. Now, although, since the shutting down of the mines, it is impossible to see more of the granite junction on the east than already described, it may be assumed that the vertical junction on the north is continued southward for some way, for De la Beche, in his Report, writes : — " The granite of Cligga Point, which has been found by mining operations to abut against the slate on the east in the manner of a dyke," etc. That the Cligga Head granite was not intruded as a dyke is sufficiently demonstrated by the behaviour of the divisional planes in the northern portion of the section. The first view of the north cliff section instantly suggests the solution of this vertical junction, which is that it is a faulted junction. This is supported by all the known facts, and assuming it to be the correct solution, the fault has a north and south course, perhaps a few degrees to the west of north, with a vertical downthrow of at least 300 feet, without any ap- preciable complication due to horizontal movement* This fault, which has the nature of a cross course, clearly does not affect the whole of the eastern limit of the granite exposure, as can be seen from the divisional planes where they are curved. Supposing then that the line of dislocation leaves the granite at the commencement of the northern hmb of the anticline, the existing granite mass can be considered as divided into two separate portions : a northern portion bounded on the east by a fault, and representing a remnant of the main mass of the granite ; and a southern portion, representing an apophysis, or tongue, thrown out with a sinuous course from the body of the granite. In addition to the east and west divisional planes, a series of ill-defined joints can be observed with a. north afid south trend. Three comby quartz veins also cut the granite, two with a north and south course, the third trending east and west. These mark fissures opened in the granite after the formation of the great divisional planes. A number of east and west normal faults, the " strike faults " of the killas, hading both north and south, can be seen in the cliff, throwing the divisional planes for short distances, an inch or so to perhaps as much as ten feet. * This is shown by the fact that the St. Agnes elvan, which, about the line of this fault, is vertical, continues on its course without interruption — . see below p. 55. GRANITE. 43 On descending the path leading down to the beach by way of the big chasm in the cUff south of Chgga Head, the nature of the rock in the remnant of the main mass of the granite can be easily studied. The divisional planes are marked by quartz veins, bounded on either side by a dark band of greisen, which gives way to the granite. The complete thickness of the greisen bands, that is the sum of the thicknesses of greisen on either side of the quartz vein, varies from an inch to 20 inches. The intervening granite, owing to the frequency of the greisen bands, rarely exceeds 20 inches in breadth. Continuing along the beach to where the tongue commences it is found that in that portion the granite and greisen alternations become much more frequent and thinner ; indeed, at the extremity, the latter dies out altogether in some cases, but still even then the divisional planes remain well marked and contain minerals which will be described later. It is very commonly found that the greisen flanking one of the divisional planes has become confluent with that flanking its neighbour, both in the tongue and in the main mass, which shows that the metasomatizing agents which affected the granite along the divisional planes over the breadth of the greisen bands were able in places completely to alter the whole thickness of the intervening granite; but apart from this the granite proves to have been altered to a certain d!egree by these agents throughout the mass — in such close proximity are the divisional planes — which makes it impossible to obtain perfectly fresh specimens of the rock. The mode of occurrence of the bands of greisen above described is illustrated in Plate 4, at the end of this Memoir. It will be seen from a hand specimen of the granite that the biotite is considerably bleached, and has a bronzed appearance. In one specimen collected, the orthoclase, which is white, and sometimes forms porphyritic crystals an inch long, does not show much evidence of decomposition ; but where the section is ex- posed to the action of the sea, the felspar has, as a rule, been completely removed. In addition to the white orthoclase, there is another, and not so abundant felspar, which, when present, forms a band on the extreme edges of the granite against the greisen, in place of the white felspar. In colour it is pink, with a tinge of orange which becomes more pronounced as decompo- sition advances. Under the microscope very minute crushed fragments show that it has the structure of a microchne-perthite. When traced into the greisen aU the felspar is found grad- ually to disappear. Close to the granite, and in the case of the porphyritic crystals, nearer the quartz veins, their form can still DC distinguished in the mass of quartz and mica ; but more generally they are completely lost. A few of the biotite crystals can be seen in the greisen, but even paler than in the granite. The original quartz grains, which both in the granite and greisen snow traces of crystalline outline — but not distinctly as is the case in the St. Agnes granite — remain apparently intact in 44 GEOLOGY OF NEWQUAY. the altered rock, and can be easily distinguished with the un- aided eye. Numerous minute dark crystals of tourmaline occur throughout the granite and greisen. Taking advantage of the opportunity of studying microscopic- ally the change from granite to greisen, a series of sections was prepared starting from the granite and continuing to the quartz vein in the centre of the greisen bands. Although the micro- scopical characters are in the main the same as those observed in the St. Agnes granite mass, there are some additional and im- portant points which call for a further description. As in the St. Agnes granite, the felspar here has been sub- jected to two distinct types of alteration, kaolinization, and the alteration to secondary quartz, muscovite, and topaz. This second alteration is not restricted to the greisen, but has affected the felspar in the granite also, although not to the same degree, for the topaz is very sparsely developed ; indeed, it was only by crushing up a considerable quantity of the rock that a few grains, similar to those in the greisen both of the Cligga Head and St. Agnes masses, were obtained. Moreover, the develop- ment of quartz and muscovite, which is more pronounced than the kaolinization in the greisen, is distinctly subsidiary in the granite. The biotite has the same characters as in the St. Agnes mass, the faint vandyke brown colour, the pronounced pleochroic halos, and the large included zircons. One crystal shows the commencement of a sagenite web, and a grain of brown tourma- line is sometimes embedded. The original quartz, both in the granite and in the greisen, forms large grains with few but large fluid cavities. On the periphery of almost every grain, however, the fluid inclusions are much more numerous and slightly smaller than in the centre. In the quartz near the central quartz vein, where it becomes hard always to distinguish between the original, secondary, and vein quartz, an occasional zircon and tourmaline crystal are included. But the most remarkable inclusions in the original quartz are numerous elongated prisms with terminal faces, sometimes lying with no particular arrangement, but often orientated to the prism and pyramid planes. The average length of these inclusions is 0"16 mm., their colour is a pale blue, and their form suggests that the mineral is tourmaline That these tourmaline inclusions are original constituents of the granite, not a secondary product derived from the felspar or biotite, is evident from an examination of the slides. Brown tourmaline identical with that in the St. Agnes granite is abundant. Nests of gilbertite and irregular grains of cassiterite occur in the greisen. The former mineral also occurs in the vein quartz, in which bunches of wolfram, sometimes of considerable extent, and of cassiterite in good crystals, are commonly met with. In the northern portion of the section especially, the quartz veins are frequently rendered quite black by a continuous mass oi GRANITE. 45 small tourmaline crystals, whicli are seen under the microscope to be of a fine blue colour. A basic sulphate of copper, which has been derived from copper pyrites, discolours the rocks in some places. It has already been stated that in the extremity of the tongue the greisen bands get very thin, and sometimes die out altogether. This is not the only change that takes place, for other modifica- tions of the granite make their appearance. These consist of veins of orthoclase, never of very great extent, and of porphyritic crystals of biotite, reaching half an inch in diameter. The biotite is perfectly fresh, and gives a characteristic axial figure. It is noticeable too that the biotite in the granite at this end of the cliff is much fresher than in the northern part, and it mav bear a greater proportion to the other " constituents, although this is hard to determine, on account of the altered state of the mineral in the rest of the exposure. In a large fallen block at the bottom of the path leading up to the top of the cUff. where the syncline is seen, the divisional planes were raund to be marked by fi.ssures containing, besides wolfram and quartz, minerals not noticed in the quartz veins to the north. They are large crystals of topaz, a lithia mica, and a pink felspar. The topaz occurs in short prisms, rarely exceeding a quarter of an inch m length, colourless or very pale-green, and in one case forming a continuous coating on the face of the fissure. The form of the crystals is simpler than that described by Greg and Letsom, and by Mr. J. H. Collins, as commonly occurring in the Cornish topaz. A typical crystal was measured and found to be made up of 120, 021, and 111. The vertical striations and the cleavage parallel to 001 are well developed. The mica is brown when viewed in its natural state, but when powdered it exhibits a trace of that peculiar colour characteristic of lepidolite. It never shows a distinct outline ; and it was found impossible to obtain a percussion figure. The spectroscope gives a strong reaction for lithium ; and the powdered mica is unaffected by prolonged treatment with hot hydrochloric acid. The axial angle is about 60° (2E). In spite of the colour of the crystals, which is more characteristic! of zinnwaldite than lepidohte, the absence of a percussion figure and the resistance to hydrochloric acid make it unsafe to refer it definitely to the former mica, and it will be best to speak of it simply as a Hthia mica. The pink felspar at first suggests orthoclase or microcline ; but on powdering a fragment very minutely and examining the structure of the cleavage fragments with crossed nicols and a high power it was found that it was identical with the microcline- perthite occurring in the granite. C. le Neve Foster records chlorite from Chgga Head ; it is very plentiful in the debris from the lodes worked in the old mines on the present factory grounds. Garnet also has been found at the Headland in past years, but it does not seem to have been recorded 46 GEOLOGY OF NEWQUAY. in any published work. A specimen was seen in St. Agnes, in the possession of Mr. Gripe ; and Capt. Harper, of AVheal Kitty, also spoke of its occurrence. The arguments for supposing that the brown tourmaline has been derived from the biotite have been fully entered into in the case of the St. Agnes granite, and need not be recapitulated here, as the evidence on which those arguments are based is precisely similar in the Cligga Head mass. A fuller discussion of the question of the brown and blue tourmaline will be found elsewhere.* It will be seen from the above description that the Cligga granite is much the same in mineral characters and arrangement as the St. Agnes mass ; but at the same time there are points of "difference that require emphasising. Thus .the St. Agnes granite is more pronouncedly porphyritic than that at Cligga Head, and differs from a normal granite in that the original quartz grains, apart from the deposition of secondary silica on them in optical continuity, are distinctly idiomorphic, like those in an elvan. This is less markedly the case in the Cligga granite, but here there is no evidence to show that before the secondary silica was deposited the quartz grains were idiomorphic, and therefore it is concluded that the crystal outline has been induced solely by that secondary quartz. Although it is possible that problematical bodies in the quartz of the St. Agnes granite may be referred to tourmahne, as yet there is no definite evidence that tourmaline as an original constituent is enclosed in the quartz grains, as is undoubtedly the case at Cligga Head. Again we have no evidence at St. Agnes of differentiation such as that exemplified by the veins of felspar and porphyritic biotite ; and at Chgga Head we do not find the replacement of orthoclase by cassitente together with muscovite and quartz. Metamoephism. The aureole of metamorphism round the Cligga Head granite is very marked, and by its means the extent of the hidden portion of the mass can be deduced in such a manner as to corroborate the evidence afforded by the old mining report quoted above (see account of the Cligga granite). The type of metamorphism is one characteristic of the west of England, resulting in the production of tourmaline schist, owing to the introduction of boracic acid. In the case of the Cligga granite we can distinguish besides the zone of tourmaline schist, which marks the 'actual contact, a zone of bleaching and spotting, and on the outside of the aureole, a zone of spotting without bleaching. The spotting on the outer limit of the Cligga aureole becomes very sporadic, a fact which makes the boundary line rather vague. West of the St. Agnes granite indeed this irregularity was found * J. B. Scrivenor, " The Granite and Grisen of Cligga Head," Quart. Journ. Geol. Soc, vol. lix., 1903, p. 150. METAMORPHISM. 47 SO disconcerting as to make it impossible to separate with con- fidence the aureole to the outcrop of granite west of the Beacon from signs of alteration brought about by granite, or some igneous rock, connecting the St. Agnes granite with the larger masses to the west, and which does not reach the surface. In the Cligga aureole the first traces of spotting were found on the long stretch of sandy beach near the adit of Wheal Vlow. Thence towards Cotty's Point it becomes more and more defined, and on crossing the Forth, the killas is found to be not only densely spotted but bleached to a pale buff colour. This spotting and bleaching can be well seen again in the much broken cliffs between the old engine house of Wheal Prudence and Hanover Cove, south of the granite outcrop, where a partial silicification, subsequent to the metamorphism, has rendered the mudstones and shales of the sandstone series more durable than they would otherwise be. In a quarry at Bolenna, in Perran Coombe, the bleaching and spotting can also be seen. Taking into consideration the extension towards the north-east that the granite originally had, and judging from the evidence in Perran Coombe and near Wheal Prudence, it would appear that the zone of spotting alone is of no great width. In the zone of bleachmg the spots are of a pale colour, so much so that they may be passed over at the first glance, owing to the similarity m shade with the light coloured kiUas. They are elongated and larger than those farther from the granite, reaching as much as one-eighth of an inch. The bleachmg has affected both the sandstone series and the Perran Shales, as can be seen in the cliffs and rocks on the west side of the Forth ; and the effect has been such as to render the two divisions of the killas of a very similar appearance, so that only a close examination of the Chapel Kock and those lying to the west of it enables one to recognise the alterations of black and grey shales characteristic of the unaltered Ferrans. Beyond bleaching and spotting a further effect has been produced here, not observable at Wheal Prudence. This is a series of close set divisional planes trending north-east and south-west, that is, parallel to the long axis of the aureole, and therefore parallel to the axis of the origmal granite mass. It is probable, seeing that the general dip of the killas here is to the south-west, and that in this district the major joints are at right angles to the strike, that they are joint planes which, on account of the baking of the fine mudstones by the granite, are better developed than elsewhere. As one walks along the top of the cliff from the Forth towards the Explosives Factory one notices that in spite of the bleaching the minor contortions in the kiUas are beautifully preserved. This is especially marked in the big quarry on Droskyn Point. Between the patch of blown sand to the south of this and the Shag Rock an exposure by the side of the path reveals a little tourmaline schist. This appears to be in connection with a lode. 48 GEOLOGY OF NEWQUAY. where tourmaline schist is not uncommon, even at some distance from any granite ; but it is worthy of note that about here is the spot where Capt. John Pill states that the main mass of the granite comes nearly up to sea-level. From the Shag Rock to the junction with the granite the killas is all bleached. The actual junction with the granite could not be examined on account of the impossibility of putting the boat far enough in. On the south the junction of the killas and the Cligga granite is beautifully exposed at the extremity of the apophysis between Cligga Head and Hanover Cove. Here, owing to the greater resistance of the metamorphosed killas to the destructive action of the sea, a steep wall of tourmaline schist extends for nearly fifty yards westward beyond the crumbling granite mass. The schist is in colour a deep rich brown, and it is traversed by numbers of thin quartzose veins with brecciated fragments of the schist and tourmaline. White mica also occurs in the schist in patches. ' On account of the difficulty of making one's way round the end of the wall of tourmaUne schist towards the Hanover Cove it is impossible to say exactly where the schist ends ; but, roughly speaking, six feet away from the junction the bleached killas predominates, although along lodes, which here all run east and west ; tourmahne schist persists for a great distance, perhaps beyond the limits of the zone of spotting without bleaching. The spotted and bleached shales and mudstones of the Sandy Series extend from Hanover Cove as far as Wheal Prudence, and can be examined closely in the chffs. It appears that the alternation of shale and mudstone tas been in great part effaced by the granite ; but in one or two places this can still be distinctly discerned owing to a process of silicification which took place after the metamorphism. This can be very well seen in the steep gully leading from the dressing floors of Wheal Prudence down the cliff". In the aureole of the St. Agnes granite the poor nature of the exposures makes it impossible to trace satisfactorily the successive stages of metamorphism as in the Chgga aureole. Nevertheless a type of metamorphism is here shown which has not yet been observed in the Cligga area, namely, the production of andalusite schist close to the junction with the granite. In the masses of debris on Wheal Coates and on the slopes of the Beacon tourmaline schist is of common occurence. A little may also be seen in situ in the big open work on Wheal Coates and also in the smaller one to the north ; and again at the southern end of the summit of the Beacon some occurs in situ ; but it must be remembered that in the first two cases, certainly and probably in the third also, the schist is associated with lodes, which, as already stated, are accompanied by this type of alteration in the killas at distances far away from the actual junction with the granite. METAMORPHISM. 49 The bleaching is not so well developed as in the Cligfga aureole. This apparently is due to the extensive mineralisation which the killas has undergone, resulting in pale tints of yeUow, red, purple, and brown. In the coombe leading down from the high land to Chapel Forth, however, and by To wan Cross, bleached shales like those in the debris on the Explosive Factory are seen in the dumps from the old shafts. In the cliffs at St. Agnes Head the shales at the top are distinctly altered ; but the shales and mudstones, which occupy the lower half of the cliffs, show hardly a trace of metamorphism. This, however, may be partly due to greater distinctness of the spotting, where the rock is weathered ; the rock at the foot of tlie cliff is more uniform in colour. The Beacon, which rises to a height of 629 feet, is composed of metamorphosed killas which there is reason to believe, from the debris lying on its slopes, is traversed by veins of granite. Here, as at Cligga, it is the altered killas, and not the granite, which makes the feature in the landscape. Spotting can be seen throughout the aureole of the St. Agnes franite, but in the zone of bleaching it does not reach such a evelopment as it does in the Cligga aureole. On the beach at Chapel Forth, where the killas is not noticeably bleached, the spotting is very dense. According to Dr. J. S. Flett, "the spotted killas from this locality is grey in colour, with rounded spots ranging up to a quarter of an inch in diameter, and sometimes pale needle-shaped bodies which resemble weathered chiastolite crystals. Microscopic sections show that the latter consist of small flakes of muscovite, pale brownish-yellow biotite, a small amount of quartz, iron oxides and many minute, well-formed short prisms of rutile. The cleavage has been only partly obliterated by the contact metamorphism, and in many of the slides traces of the ausweichv,n(jsclivage are still evident. Except for the spotting and the coarser crystallisation of the rutile the killas does not differ greatly from the unaltered killas along the shore to the west of Newquay. The relative proportion of muscovite and biotite varies considerably. "The spots are always rounded or elliptical in section, and in a few cases consist of zones of slightly different composition and colour. Their essential ingredient is a yellow or a brownish yellow biotite which is mixed with muscovite and with other scaly minerals, which sometimes give very low polarisation colours, and in fact are nearly isotropic. The knots in no way disturb the foliation or cleavage-banding of the phyllite, and the biotite of the knots may be easily distinguished from that of the matrix. " In two of the slides of rocks from Chapel Forth small crystals of pinkish andalusite were also seen, , but they were practically undecomposed, and are in no definite relationship to the rounded spots. At Wheal Coates, which is close to Chapel Forth and near 8934. D 50 GEOLOGY OF NEWQUAY. the outcrop of the St. Agnes granite, fine specimens of andalusite hornfels were obtained in the great open work of this mine. The andalusite is in crystals which are sometimes half an inch long and are easily seen in the hand specimens. They are pink where fresh, but weather to grey or white micaceous aggregates. In the microscopic sections the matrix is a mixture of dark brown biotite, muscovite and quartz, and is far coarser grained than unaltered killas of the same composition. It is entirely free from cleavage. The andalusite is rose coloured in irregular patches, which alternate with colourless areas. Where the colour is most intense the pleochroism is very marked, and the c ray has a green tinge not often seen in microscopic sections ; usually, however, the colours are carmine or rose-red and white. The andalusite is weathering into quartz and muscovite. A few grains of brown tourmaline appear in the sections, and there are also zircons, iron oxides and small prisms of rutile." South of Chapel Forth the spotting becomes very sporadic, and appears to extend beyond the limits of this map for a great distance over an area which is probably aft'ected by a hidden mass of igneous rock connecting the St. Agnes granite with the outcrops to the south-west. 51 CHAPTER VI. ELVANS OR QUARTZ-POKPHYRY. Throughout Cornwall numerous igneous dykes, showing a close affinity to the granite, have long been known as " elvans." The typical el van is a more or less vertical dyke or wall of felsite or quartz-porphyry, usually containing abundant large perfect crystals of orthoclase, doubly-terminated quartz, and more rarely of pinite. These dykes cut through both killas and granite, apparently without regard to the jointing seen at the surface ; and they usually hold fairly straight courses, varying ?;reatly in direction. Elvans are not found at any great distance rom the granite, but they do not radiate from the granite bosses now exposed at the surface, and in many cases their outcrop is discontinuous, though the dyke is probably connected below. They branch and anastomose, but not so freely as the later dykes ; much of the apparent branching being perhaps due to intersection of dykes of slightly different date, rather than to true division. There seems no reason, in this area at any rate, to consider the porphyritic and non-porphyritic dykes as belonging to two different dates. A porphyritic elvan has always a chilled margin, showing distinct fluxion-structure ; and this part of the dyke, which may be a few inches or several feet in thickness, is usually free, or almost free, from porphyritic crystals, so that it is indistinguishable from a non-porphyritic elvan. It used to be considered tnat the porphyritic crystals were formed at considerable depths and floated up to their present levels in the still-molten magma. But the occurrence of a non- porphyritic margin has lately been held to indicate that the large ciystals must commonly have been formed in place in the slower- cooling part of the dyke, or they would be found also at its margin.* This, however, does not necessarily follow. The opening and widening of the fissure was probably gradual ; the molten material at first welled up slowly through a narrow crack, which would tend to strain out the already formed crystals, and this first-chilled magma was probably partly consolidated before the fissure opened sufficiently for the free flow Of the ordinary porphy- ritic material. In this respect there is a curious contrast between the parallel-walled elvans and the irregular granite veins, which only proceed a short distance from the granite, and often show enormous porphyritic crystals actually touching the adjoining slate. The rocks surrounding the granite seem to have been * See L. T. Pirrson, " On the Phenocrysts of Intrusive Igneous Kocks," Aiiier. Joum. Sci., ser. 4, vol, vii., 1899, p. 271. 8934, • D 2. 51 GEOLOGY OF NEWQUAY. sufficiently hot not rapidly to chill the marginal granite, and the large irregular fissures seem to have been opened and injected at one stroke, so that the porphyritic crystals were only strained out in the narrowest parts, which are often microgranite. Though about a dozen elvans occur in the district, there is scarcely a trace of the parallel arrangement which is so marked in other areas. Three dykes only trend in the east-north-east direction which is so common elsewhere in West Cornwall. As the elvans do not fall into groups, iu will be most convenient to take them in order, beginning at the north and ending with those around St. Agnes. The first dyke met with is one which is seen in the cliff in Watergate Bay. It has an exceptional length and an unusual trend, running nearly 7 miles about south-south-east, and ending near Mitchell. South of the village of St. Columb Minor this dyke makes an angle and then recovers its original course — as though it were forking ; but no fork can be traced in actual connexion with the elvan that runs south-east to Quintrel Downs. There is again a break at Quintrel Downs between the south- east elvan and the curved dyke which gradually changes from east-south-east to due east near Penhale. Still the evidence is very strong that here we have a south-south-east dyke, which gives off a long branch curving towards the east, thus breaking down the distinction sometimes drawn between north and south, and east and west elvans. The elvan at Watergate Bay is unfortunately so altered by the replacement of certain of its constituents by deep-seated action, probably either hot water or vapour, that the rock there is in a very rotten state. It is kaolinised, tourmalinised, and in parts silicified. It well shows, however, the doubly terminated pyramids of quartz which are so characteristic of most of the elvans. The dyke is of moderate width (about 30 feet) and has a distinct hade towards the Vest ; but its decayed state causes it here to form a gash in the cliff, not a projecting feature. As a slight depression, it is also traceable to St. Columb Minor ; but here the stone becomes more sound, and is largely quarried for building purposes at Newquay. The rock is a quartz-felspar-porphyry, with pink orthoclase, in a micro-granitic matrix, and has a conspicuous chilled margin of finer grain. Dr. Flett reports that under the microscope the central part of this elvan proves to be granophyric, having a groundmass entirely composed of coarse micropegmatite! a structure sufficiently uncommon in Cornish elvans to be worth remarking. In addition to the usual phenocrysts of idiomorphic perthitic orthoclase and corroded quartz, the latter filled with fluid cavities in the form of negative crystals, there is a small amount of weathered biotite and much muscovite. The white mica does not form well-shaped crystals, but occurs as clusters and tuft- like aggregates of small flakes which must be largely of secondary origin. Plagioclase and tourmaline are not represented in the microscopic shde, but apatite, zircon and iron oxides are all EL VANS. 53 present. In the margin of the dyke the same porphyritic minerals occur, but in far smaller individuals, and the ground mass, which is very fine-grained, is beautifully micropoikilitic. Above the water-level it is a buff freestone, easy to work, but not occurring in large blocks. Below the water-level it is greyer and in larger blocks, but as yet has been little quarried, for the various quarries are isolated and have no connected system of drainage. The rest of the southward course of the Watergate el van calls for no particular remark — the dyke disappears about 2 miles south-east .of Newlyn East. Turning now to the south-east elvan which passes Quintrel Downs, we find that for the first mile of its course it is a narrow kaolinised dyke with much tourmaline, and is so rotten that it has been dug for making bricks. Then there is a gap of half a mile, across which this rotten dyke cannot be followed. South of the Gannel it reappears in a sounder form and undergoes a curious change as it is followed eastward. An excellent section will be found in a quarry a quarter of a mile east of Retyn, and similar rock is thrown out from the northern shaft at Penhale Moor Mine, beyond which this elvan cannot be traced. To the eye the stone from Retyn is a coarsely crystalline mass of porphyritic crystals of felspar, quartz, and occasional pinite, with unusally little groundmass ; its chilled margin is finer-grained, with more groundmass. Dr. Flett remarks of this rock that " the groundmass is microgranitic, consisting of quartz and felspar with scaly muscovite. The porphyritic felspar is perthite and contains occasionally tourmaline and quartz. The pheno- crysts of biotite are weathered to chlorite. Porphyritic muscovite. occurs in the chilled marginal rock." The next elvan seen in the cliff is met with in Hoblyn's Cove, near Penhale Manor House. This cove has vertical walls and is quite inaccessible without the aid of a rope ; but at low tide a branching 8 foot elvan can be seen on the foreshore. , One branch runs east and west, and another of about the same width runs west-south-west, and a spur can be seen in the cliff on the north. This spur, the only part which can be reached, is 10 feet wide, and consists of a fine-grained rock looking like buff sandstone. It is-non-porphyxitic and its felspar is mostly decomposed into secondary micaceous minerals. No trace of this elvan is found inland. Half a mile further south a more important elvan appears in the cliff close to the Gravelhill Mine. The main branch is from 20 to 30 feet wide and hades south, there is a smaller branch or spur immediately to the north. This elvan is abundantly por- pnyritic, with half- inch phenocrysts of pink orthoclase and many smaller double pyramids of quartz ; the ground mass is micro- granitic. It has a well-developed chilled margin a foot or two wide showing fluxion structure. After disappearing under the sand-dunes this elvan is again found at Ellenglaze, and runs con- tinuously to Cubert, disappearing just east of the Vicarage. A 5i GEOLOGY OF NEWQUAY. large and deep qii^ry will be found on the west side of the village, the elvan being 25 feet wide and exceptionally sound and massive — it has^not changed its character. Dr. Flett states that in the chilled margin the ground mass consists principally of radiats micropegmatite. Another elvan commences at Trebellan, half a mile south of the termination of the Cubert elvan, runs in an east-south-east direction more than two miles, nearly to Newlyn East, and is perhaps continued in the elvan that passes Trevilson. It is less porphyritic, but is otherwise very like the Cubert elvan, of which dyke it may in fact be a branch. A small porphyritic elvan seen in the low cliff east of St. Piran's Chapel cannot be traced inland ; it is mainly interesting for the exceptional width (5 feet) of the margin showing fluxion, and for its very pale colour. Dr. Flett finds that in the micro- scopic slides it has a microgranitic matrix and is almost free from inuscovite, primary or secondary. It contains neither biotite nor tourmaline. Of the elvans in the southern part of this map two only can be traced for any great distance : the St. Agnes elvan and the Perran- porth granitic elvan. The trend of these dykes is roughly north-east and south-west, a direction slightly oblique to the strike of both bedding and cleavage in the slates. As the Perran- porth dyke is of somewhat exceptional character, it will be most convenient to leave its description till the last. The St. Agnes elvan averages 15 feet in width and is first seen in the cliffs near St. Agnes Head. It is possible to land from a boat and examine the rock, which is washed by the sea at high tide. It is a fine quartz-porphyry of the ordinary type. At the top of the cliff the elvan has the same character, but is remarkable for enclosing a large fragment of greisen, similar to that in the St. Agnes granite mass, and, doubtless, caught up as the elvan made its wa^ to the surface. This shows that the date of intrusion was posterior to that of the alteration of the granite to greisen. The dyke can be traced across the open land to a big quarry on the edge of the cliff north of the Beacon. In this exposure it presents quite a different character from that observed south of the Head. The mass of the rock is very fine-grained, tough, in colour a dull grey, with abundant tourmaline m small rosettes. In it small blebs of quartz are not uncommon, but never reach any size ; and scattered irregularly throughout the mass are nests of felspar phenocrysts, the individual crystals reaching as much as two- thirds of an inch in length. The exposure here is as good as could be desired ; yet there did not seem to be any definite arrangement of these nests with regard to the centre or periphery of the dyke. The tourmaline is mostly blue, and appears to be an original constituent of the rock. The felspar crystals throughout this exposure are completely kaolinized ; and in the centre of the dyke is a seam of the rock which has been similarly atfected ELVANS. 55 in toio, ground mass and phenocrysts. Owing to the peculiar disposition of the felspar crystals in this quarry it is impossible to distinguish a " chilled margin." From this quarry the elvan strikes out to sea for a distance of seven-eights of a mile, where its outcrop would be particularly valuable for the purpose of verifying the throw of an important cross course in Wheal Kitty. However, without any apparent deviation from its regular course, the elvan re-appears in the cliffs between Trevellas Forth and Green Island. The unweathered dyke is excellently shown in an outlying rock which can be reached on foot at low tide. The felspar phenocrysts are of the same size as in the quarry mentioned above, but they are regularly dissemi- nated throughout the rock. Tourmaline and quartz also occur. Owing to the north-westerly hade of the elvan at this point, the exposures between Trevallas Forth and Hanover Cove are very good in the cliffs, and, as can be seen from the amount of the hade (30-40°), the dyke must crop out also on the ground behind the edge of the cliffs. But as tne upper part of the elvan has been so altered by weathering as to resemble in consistency a clay-bed, it is not until Wheal Frudence is reached that the original structure of the dyke can be properly examined. It must be noted that both in the Islet and in the cliffs a chilled margin varying from four inches to a foot can be clearly dis- tinguished as a band of very tough and fine-grained rock. Throughout its course along these cliffs towards Wheal Frudence there is ample evidence that numerous small branches are given off from tne parent dyke, and also that since its solidification the elvan has been disturbed by a number of faults with a north-east direction, corresponding to the miner's gossans and slides. Jn no case, however, is the throw sufficient to cause the elvan to be moved by more, than its own breadth. From Wheal Frudence to Hanover Cove the elvan is very clearly exposed, and shows thai: the northerly dip is approaching the vertical. Close to the ruined engine-house is a large quarry, where the rock has been worked in past years for a building stone. This has been possible owing in part to sUicifica- tion, which has also affected the surrounding killas, and in part also to the pneumatolytic process similar to that of the formation of greisen. This alteration took place during the cooling of the elvan, and was quite distinct from the alteration of the granite in point of time. The felspar has been completely removed, with the expection of a few phenocrysts, and rosettes of tourmaline;, and patches of limonite derived from pyrites are common in the ground mass, which consists entirely of granular quartz and scaly muscovite. In the walls of the remarkable hollow, known as the Old Frison, the elvan is twice exposed, with a steep dip to the north. Finally it enters the cliff on the east of Hanover Cove, where it is nearly vertical. In the Report De la Beche says : — " The same 56 GEOLOGY OF NEWQtfAY. elvan runs to Wheal Prudence, and apparently enters the granite of Cligga Point." This is really lar from being the case, since between the elvan and the granite there are 450 feet of meta- morphozed Idllas ; but it must also be remarked that in the old map this killas is coloured as granite. The inland continuation of this elvan need not be described in detail. In the railway cutting at Perran Coombe the hade is completely reversed, and is about 30^ to the south. Two quarries on either side of the old mineral railway near Deerpark Mine show good exposures. * Here again another aspect of the dyke is presented, for, in place of a chilled margin of the ordinary type, the edges show 'a beautiful flow structure, which results in a fine lamination, determined by the direction of flow. In the quarry on the west these planes lie parallel to the boundaries of the elvan and arc straight, in that on the east the planes are curved, owing to the fact that here the elvan does not reach the surface of the ground above the quarry, and in consequence we see the spot where the flowing movement of the molten mass was arrested. At the edges only is the elvan porphyritic, in the centre it is of an even grain like that of a very fine microgranite. The rock is further remarkable for containing a little biotite. Along the planes marking the direction of flow there seems to have been .some slight alteration of the original rock. In the quarry on the west of the rail the elvan is seen to be dipping at 35" to the north ; so that here the dip is reversed once more. There are two points in connection with the St. Agnes elvan which will bear emphasizing ; the first, that the date of the intrusion was subsequent to the formation of the greisen in the St. Agnes granite, but that a similar alteration may have affected the elvan during cooling ; the second, that the repeated reversal of the dip shows that the form of the intruded sheet is by no means a plane surface, but is curved along its length and depth. Several small dykes shown on the map, but traceable for a short distance only, call for no remark, and we will now pass on to the granitic elvan of Perranporth. Running parallel to the St. Agnes elvan, and not far removed from it, this dyke, nevertheless, differs from it considerably, in that its petrological character is distinct and remains constant over the whole of its visible outcrop. The elvan is first seen in a quarry on the Perran Sands, 250 yards east of Ponsmere bridge. To the west of this point there is no evidence of its behaviour. To the east it is next exposed in a quarry by the side of the road where it passes Wheal Budnick, and on the ground of this mine it can be traced through a series of pits. In the village of Rose it has been in former times quarried also, and after crossing a small stream in the Wheal Hope valley it is again exposed in a quarry in a field adjoining Hendra farm. East of Hendra it is not again exposed until the minerals railway is reached, where BlVan3, 57 for the first and only time the thickness and dip can be observed. The breadth of the outcrop is 20 paces and the dip 45° south ; so that the thickness is approximately 42 feet. The mass of this dyke is perfectly homogeneous, and has the characters of a fine-grained granite. The orthoclase is white and sometimes porphyritic, but never markedly so. The biotite is quite fresh, and the quartz has no crystal boundaries. A little tourmaline is probably present. Where the edge of the dyke can be observed, it is found to have the same appearance as a rather fine-grained quartz-p»i-phyry, similar to the commoner type of these dykes. There is no other elvan in this district of similar composition to the Pcrranporth granitic elvan, and one is naturally inclined to speculate why it should stand alone. None of the other type can be seen to cut, or be cut by it, nor, if any do branch out from it, as is quite possible in the case of the Duchy Peru elvan, can the point of junction be examined. This precludes any possibility of determining whether there is any difference in the date of intru- sion. Apart, however, from such a consideration, which might reasonably be followed up to explain the anomalous character of the dyke, the fact that the margins resemble an ordinary elvan, and the centre a fine granite, could be explained by a ditforence in the rate of cooling dependent on the relative thickness of the dykes. This alone, however, cannot be taken as sufficient explanation in the Perranporth elvan, because the difference in thickness is not enough to warrant its logical employment. Perhaps the theory which is most likely to meet the case, in the absence of better evidence, is that this dyke was inti'uded earlier than the others, may be, at the same time as the Cligga granite, and into rocks at a higher temperature than the later dykes. Were it not for the extraordinary length of the intrusive sheet, it might be spoken of as a granite vein ; but seeing that, in addition to its length, its course is parallel to that of the ordinary elvans, it -is considered better to retain it among those dykes. S8 CHAPTER VII. MICA TRAP OR MINETTE. A group of small dykes of Mica Trap or Minette forms a noticeable feature on the coast between Newquay and Holywell Bay, and traces of a similar rock have been met with near St.' Allen, near Colan, and at Halveor, in the valley below St. Columb Major. The St. Allsn exposure helps to connect these dykes- with the group near Falmouth. The behaviour of the mica-trap dykes is very different from that of the elvans ; instead of following straight Hnes of fracture they zig-zag irregularly along joint planed in the slates, widening and narrowing very abruptly. Their usual trerid is north-north- east. Though not seen anywhere to cut the granitic elvans, they are probably of much more recent date, and may perhaps bo connected with the volcanic outburst which formed the trap-rocks of the Exeter district, rocks which occur near the base of the NeAV Red Series. This connection has already been suggested more than once.* To commence with the coast-section near Newquay, we find between the town and Towan Head a group of small much- branching and irregularly anastomosing dykes, none of which is over 4 feet in width. Some of the best exposures of these will be seen in the cliff-face and outlying rocks between the Heuer's Lookout House and the Tea Cavern ; others occur close to Towan Head, where one of them, formerly worked, is represented by an open gash across the point. The section seen in the small quarry in the cliff face at High Place, which is at the north- eastern corner of the headland, is interesting also as showing clearly the chilled margin, of the dyke (with occasional small vesicles), in contact with slate which has been baked to the depth of several inches. The exceptional width of the altered band is, however, probably due to the ramifications of the dyke. The contact alteration shows clearly that the slate was thoroughly cleaved and contorted before the intrusion of the mica-trap. Along the shores of the Gannel dykes reappear, one of considerable size occurring below Pentire Farm, and two or three smaller ones further east. The Pentire dyke yields the rock in an excellent state of preservation, and also well illustrates its mode of occurrence. New roads were being made while the survey was in progress, so that this dyke could be followed to its termination northward.. It cannot be found in the clear cliff- * J. H. Collins and H. F. Collins, " The GeologiAil Age oKCentral and West Cornwall," second paper, Journ. R. Inst. Cmnivmll, vol. viii., 1884, pt. ii., pp. 162-205. B. Hobson, " On the Basalts and- Andesites of Devon- shire," Qiiart. Journ. Geol. Soc, vol. xlviii., 1892, pp. 496-50*7. .7. J. H. Teall, in " Geology of Exeter," Mem. Geol. Survey/, 1902, pp. 76-85. MiCA TraJ. 59 section of the south end of Fistral Bay ; but a hundred yards north of Pentire Farm a very thin dyke appears. The next road southward shows three thin dykes, respectively, two, two, and one feet in thickness. These seem to combine' amid the farm buildings, and on the shore of the Gannel they have expanded into a wide dyke quarried for road-metal just at the water's edge. This dyke is probably not so thick as it appears, for quarrying indications suggest that it may be a right-angled turn rather than an expansion to the width of 60 feet. A smaller dyke immediately to the east was driven along (in following a string of argentiferous galena), and proved to be only a branch of the Pentire dyke. The best specimens of the mica-trap can be obtained from the inside of the large blocks which occur in the middle of the Pentire quarry at the sea-level. The petrological description and analysis is given at the.end of this Chapter. This dyke reappears on the south shore of the Gannel with a thickness of forty-five feet ; but it cannot be traced far across the cultivated land. It may, however, be continued -in a dyko formerly worked close to the high-road half a mile west of Crantock Church, and in a 4 foot dyke seen 200 yards west of Treago Mill. Whether the somewhat wider dyke seen in the cliff- face 150 yards south of the Holy Well is part of the same is doubtful ; the connection is hidden by sand-dunes, and the strike does not correspond. The dyke in the cliff' has a hade of 70° towards the south-east; if the lower part of the Pentire Quarry happens to be hidden, the Holy Well dyke is the next best place to obtain specimens. The other inland exposures call for little remark. The wide dyke at Colan, which can be traced for half a mile, is thoroughly rotten. Many years ago it was extensively dug for manuring the land, and its value for this purpose may have been to some extent duo to the considerable quantity of apatite (phosphate of lime) that these mica-traps contain (.sy'^ analysis, p. 61). The decomposed rock is scarcely sufficiently sandy to have been valuable for its physical properties alone. No pits are now open in this dyke ; all that caii be seen is a peculiar soil, and a few of the harder fragments in ploughed fields. A trace of the dyke, apparently here very wide, is seen in the shallow railway-cutting. Another decayed dyke, about 15 feet wide, will be found at Lower Tresawle, near Halvcor, about a mile west of St. Colonib Major. Mr. J. H. Collins mentions also a mica-trap which can be proved by fragments to be picked up among the debris of Cargoll Mine, on Newlyn Downs. We found certain fragments which may represent weathered mica-trap, but no structure is preserved in them. The two jpica-traps recorded as crossing the road a little to th^north of Fiddler's Green cannot now be found. The dyke of Watergate Boy, described by Mr. Collins as a mica-trap, is an ordinary quartz-porphyry, nuich decayed there though well- preserved inland. 6() BIOLOGY OF NISWQTJAY. Peteological Description. By J. S. Flett. The Gannel Quarry minette is the only mica-trap within this sheet which will repay microscopic and chemical investigation ; all the others are very much decomposed and their biotite has entirely weathered to chlorite, epidote and other secondary minerals, while their felspar is often too turbid to be accurately identified. Corroded quartz xenocrysts occur in all the dykes except perhaps that from Gannel Quarry. It is a medium grained rock without conspicuous phenocrysts as a rule, though some of the specimens contain irregular plates of greenish brown biotite 2 or 3 mm', in diameter. In the slides the mica is the most conspicuous mineral, both on account of its abundance and its size. It forms large plates which have zig-zag borders made up of the angles of hexagonal sub-individuals. These crystals contain miiny lath-shaped felspars, but in spite of this their idioniorphism is often very perfect. Their vertical sections also seem made up of smaller rectangular biotite erystals grouped in parallel orcler, with enclosures of the surrounding minerals. In basal sections the dark borders characteristic of the micas of this group of rocks are visible though not very pronounced. The pleochroism is intense, rays vibrating perpendicular to the cleavage being very pale yellow or almost colourless, while the other rays are dark chestnut brown and differ little in colour and absorption. The mineral is very nearly uniaxial. Though often very fresh it is sometimes decomposed into chlorite, brignt yellow epidote and rutile. Brown hornblende, always idio- morphic in short prisms, is fairly abundant in. some of the slides but entirely absent from others. It is undecomposed, often simply twinned on the transverse face, has an extinction angle about 18°, and a pleochrism a-pale yellow, J[j-and t-dark brown.- It contains few enclosures, mostly grains of iron oxides and needles of apatite, and is rarely decomposed. A pale green variety of augite, in somewhat irregular crystals without perfect faces, is present in all the sections and is lined with chlorite along its cracks and on its surfaces. It frequently encloses prisms of weathered felspar find assumes an ophitic character. In polarised light many of the crystals show twih- ning on the orthopinakoid. Felspar and quartz together form rather more than one- half of the rock. The felspar is idiomorphic in short rectangular sec- tions. Much of it is orthoclase, but oligoclase and andesine appear also in the freshest samples of the rc^k, deconniosing into kaolin, calcite, muscovite, and epidote. The qu^tz, which though scanty is always present, is interstitial and 'is the only ingredient which does not show crystalline form. Hence the structure is that which has been described as " panidiomorphic." Apatite and magnetite are the common accessories. MICA TRAP. 61 The analysis of this rock (by Dr. Pollard) is appended and confirms the microscopic examination in all respects. The small (quantities of carbonic acid and combined water prove the essen- tially fresh state of the rock, for the members of this group are exceedingly liable to decomposition. The marked preponder- ance of potash over soda is due not only to the orthoclase felspar, but also to the abundant biotite. l^hosphoric acid yields a rather high result, but is not sufficient in itself to account for the use of the weathered stuff from the quarry as a fertiliser by the farmers of the neighbourhood ; probably this is in part accounted for by the physical properties of the decayed rock. Analysis of Specimen feom the Gannel Qcjaeey,Tentire, Newquay. Rock used for road mending and, when decayed, for agric id tvral purposes. SiOj 50-98 TiOa 1-25 AI2O3 16-13 Ci-aOs Trace. V2O3' Trace. Fefis 4-20 FeO 3-24 MnO -17 NiO Trace. UaO 5-50 SrO Trace. BaO -20 MgO 7-28 K2O 4-82 NaaO 2-99 Li,0 - Trace. Ha-Q-lOS" C. - -44 H,0 above 105° C. 1-46 FeSa (Pyrites) -43 P2O5 - -74 CI -07 CO2 -58 100-48 Less O for CI "02 Total - 100-46 62 CHAPTEK VIII. PLIOCENE. " After the formation of tlie rocks already dealt with, there came -a long period during which their upturned edges were smoothed and worn down for thousands of feet. Very little is known about this interval in West Cornwall, for all Secondary rocks have been destroyed, and the Tertiary are represented by nothing of earlier date than Older Pliocene. AVhether the singular contours about to be described are in part of early- Tertiary, or even of Second- ary, date we cannot yet say ; but the plateau may have originated long before the oldest of the deposits that now cover it. The surface may have been merely cleaned up and the features sharpened in Pliocene times. The topographical peculiarities to which we refer are very striking. In an area of high dips and of rocks of varying hard- ness, such as we have been describing, one would expect to find bold features and jagged outlines, like those of North Wales or of the Lake District. Instead of this we see a broad, smooth, gently undulating tableland, out of which rise boldly a few rounded hills. The outlines of these hiUs do not correspond Avith geological boundaries, nor do they show necessarily the limits of the harder masses. The tableland, though now a good deal trenched by valleys of more recent date, seems peculiar!}- Hat when we look across it ; its greatest altitude is about 4-20 feet above the sea, any land above that level rising in irregular dome-shaped masses. This platform is obviously an ancient sea- floor or plane of marine denudation ; and the hills rising out of it once formed scattered islands, like those of Scilly. Standing on St. Agnes Beacon (628 feet), or on DenzeU Downs (605 feet), one observes in the distance across the plain various of these islands ; but the only other one that comes within the area we are now describing is Newlyn Downs (490 feet). St. Agnes Beacon is formed of metamorphic slate, and Denzell Downs of hard sandstone ; but Newlyn Downs happens to be composed Gntirol y rif slate of similar character to the surrounding area : it has therefore suft'ered more from denudation and is less strikino- than the other hills. The only strata now remaining on this plateau are certain un- fos.siliferous sands and clays, which form an old shore-deposit still almost surrounding St. Agnes- Beacon. Adjoining areas, hovvc\-er, give further evidence, for a fossiliferous clay found at St. Erth yields a marine fauna certainly of Older Pliocene date, and this deposit seems to belong to the same period as the old beach of St. Agnes Beacon. The relations and geological position of the Pliocene strata can be more conveniently discussed in the PLIOCENE. 63 memoir which includes Wt. Erth,* here we need only describe those that are seen at St. Agnes. Judging by the sections and illustrations of the well known sands and clays of St. Agnes given by previous writers, it would appear that these beds are not so well exposed now as was the case formerly. Thus De la Beche, K. Hunt, and Mr. W. A. E. Ussher all either mention or figure the uneven killas svirface on which these deposits lie, whereas now there is no section in the field showing this, nor is there any section shewing such a varied succession as that given by De la Beche. Prestwich included these beds among the Pleistocene raised beaches of the South of England ; but thejr differ greatly from the raised beaches such as are met with in Cornwall, and they are of the same nature as the St. Erth beds, which are undoubtedly Pliocene. These sands and clays foriiv a semicircular belt fringing the northern part of the Beacon, and lie roughly between the 360 feet and 420 feet contours, with a gentle slope away fi-oni the higher ground. The exact limit nearer the Beacon is hidden by head, while nearer the sea it is confused by the fact that the sands and clays themselves have entered into its composition of the head. The best section to be seen in the summer of 1902 was at Higher Bal, where the following succession was noted : — Feet. Head - - - - 4 Grey and red mottled clay fi White sandy clay - 2 White, brown, and red sands 8 Another good section, but of the clays alone, occurs at Beacon Cottage. The clays were formerly dug for use in mines, to hold the candles, and the clays from St. Agnes were used all over Cornwall. The sands, which are in some places very loosely coherent, contain minerals which point to the local origin of the beds ; these are: — hismatite, tourmaline (brown, yellow, and more rarely blue), zircon, rutile, cyanite, audalusiie, topaz, and cassiterite. Of these, hasmatite can be seen in the " open-work " by Wheal Coates, brown and yellow tourmaline is abundant in the metamor- phosed killas ; andalusite occurs in the metamorphosed killas .of the St. Agnes District ; Wheal Trevaunance, when working, was a well known locality for topaz, which has been also found to occur abundantly in microscopic grains in the modified St. Agnes granite ; 'and cassiterite is abundant in several lodes trending east and west. Still better evidence than this of the local origin of these beds is the presence of blocks of conglomerate between Wheal Coates and Higher Bal, containing rolled pebbles of quartz and killas in a ferrugineous matrix, the killas being identical with that on which the sands and clays rest. Owing to the mask of * "Geology of the Land's End "; and see also "Pliocene Deposits of Britain," 1890, 64 GEOLOGY OF NEWQUAY. head this bed cannot be seen anywhere in situ, but there can be no doubt of its existence, and that it is the bed of pebbles mentioned by De la Beche as the base of the Tertiary deposits, and the hardened and iron cemented sand mentioned by Uavies and Kitto as occupying a similar position. Isolated pebbles are not uncommon in the sands: generally they are of quartz, distinctly water-worn, and varying considerably m size. All those recorded have been derived from the neighbouring rocks, and, but for the discovery from time to time of pebbles composed of almost pure cassiterite, of which a good specimen is now in the Miners' Institute at St. Agnes, do not require any further notice here. One curious point in relation to St. Agnes Beacon remains to be noticed. Shore deposits nearly surround a small island now represented by the Beacon ; the Beacon itself, however, is formed, not by the granite, but by the altered slate-rocks several hundred yards from it on its north-east side. Now the granite is sur- rounded on every side by a belt of very hard metamorphic killas, much harder than the slate outside the aureole. Such being the conditions, one would at first expect to find that the island corresponded with this mass of hard rock. In Pliocene times, however, the prevalent winds were probably south-westerly, as at the present day, and they would tend ultimately to reduce the island to its present condition. Firstly, the soft unaltered slates would be washed away all round ; then the metamorphic aureole would be attacked and slowly eaten into, but mainly on the windward side; at last the sea would cut into and destroy the central core of kaolinised granite, leaving finally, when marine denudation ceased through the rise of the land, a small island of metamorphic rock corresponding with the leeward or north-east side of the larger island. 65 CHAPTER IX. DRIFT. Though the time occupied by the Newer PHocene period is probably represented by much of the erosion of the valleys which now trench the plateau described in the last chapter, yet there are no known deposits of Newer Pliocene date near Newquay. Even the earliest Pleistocene strata are also missing, and we have only indirect evidence that beneath the sea there probably exists a marine glacial deposit with far-transported erratics. Certain peculiarities in the surface contours, older than the period of the raised beaches, also suggest an earlier cold period; but they are too slight to be discussed here ; the oldest deposits that we have to deal with are the well-known raised beaches, which fringe the coast here and there in sheltered localities. The raised beach is but poorly represented within our area, though traces of the rocky platform on which it once rested are more common. Towards the north end of Watergate Bay this platform is well seen in a broad ledge by which one can pass round the point into Stem Cove. This ledge is very irregular, as the rocks are of uneven hardness and have a high seaward dip ; but it is clearly recognisable as a shelf distinct from, and 15 or 20 feet higher than, that now slowly being cut by the sea. The situation bemg much exposed, all the beach deposits on this shelf have now been swept away. As we travel southward along the coast faint traces of this plat- form are met with here and there ; but it is not till Newquay is reached that anything more definite is seen, clear sections beginning immediately north of the Harbour. In the cliff face east of the Atlantic Hotel a broad fairly level shelf of kiUas will be found at a height 15 or 20 feet above the sea. This shelf has been worn, smoothed, and channelled in the same manner as the present shore, and on it are found patches of beach shingle, with large rounded boulders and a few shells of limpets, though in most places the fossils have entirely disappeared. The raised beach is only a few feet thick, and is composed mainly of local rock with a small admixture of hard grit like that north of Mawgan, and a few chalk flints. Above the 4 or 5 feet of beach about 20 feet of blown sand with snail shells is seen in one place ; but it is not clear whether any part of this sand is ancient ; it may be entirely modern, for, during heavy gales, sand still drifts right across from Fistral Bay. Fistral Bay shows an exceptionally fine section of the raised beach and overlying deposits. The low clifi" of kUlas rises 5 or 10 feet above the beach-level, and on it rests a well-rolled shingly beach, with, here and there, trace of much decayed marine shells, 8934. E 66 GEOLOGY OF NEWQUAY. the species recorded by Mr. S. R. Pattison being Modiola vulgaris, Cytherea chiove, Ostrea, Patella* The beach does not usually exceed 5 or 6 feet in thickness, and is succeeded upwards by a mass of rubbly head, often inter stratified with blown sand. Some of this sand is obviously very ancient, and belongs to the period of the head ; it has become cemented into a hard building stone, formerly a good deal used in Newquay. The main mass of sand dune, however, seems to be quite mod.ern, though in places it is quite impossible to distinguish between them. The raised beach of Fistral Bay yields a noticeable proportion of stones belonging to other districts, that is to say, of stones that could not have drifted into the bay under present conditions. The bulk of the beach consists, as usual, of vein-quartz and silicified slate ; but there is also a considerable mixture of metamorphic killas, a little granite, and schorl-rock, which may have travelled down the Gannel from the outskirts of the St. Stephens granite. There is also, as everywhere else in these raised beaches, even as far as the Land's End, much grey or dark- purple hard sandstone, like that which forms Trenance Point, bounding Mawgan Porth on the north. This rock seems, there- fore, to have travelled in considerable quantity against the prevalent south-west wind and round points which now completely stop the movement of the shingle. The other materials are rare fragments of greenstone, like that seen near the old chapel of St. Piran, and chalk-flints. Though most of the erratics are of small size, one seen on the beach towards the southern end of the bay is more striking. It is a block of greenstone 3 or 4 feet in length and weighing probably one or two tons (it is usually buried in sand and could not be properly measured). Such a block could not possibly have been brought by the ordinary action of the sea, and it is much too large to have been brought as ballast ; it is obviously an ice-transported erratic floated from a distance, and not many years since it was probably imbedded in the base of the raised beach, where most of the large boulders occur. These erratics at the base of the raised beach of Fistral Bay would seem to point to the formation of ice-foot or shore ice, such as would pick up beach stones and enclose fallen blocks in the winter, to float them to distant localities when the ice broke up in the spring. That such a period once existed seems clear ; but the little that is known of the fossils of the raised beach does not support the idea that the climate then was arctic ; the fossil mollusca both in Cornwall and all along our south coast point to temperate seas. The period when the erratics were drifted on rafts of ice was probably an earlier one, and the erratics now found in the raised beach have been merely washed out of an earlier deposit, perhaps still existing on the foreshore opposite, or just beneath the sea-level. * Trans. JR. Geol. Soc. Cornwall, vol. vii. 1848, p. 50. DRIFT. 67 The angular rubble-drift or head which overlies the raised beach suggests the recurrence of arctic conditions, during the reign of which the rocks were shattered by frost, and the material transported down gentle slopes in a way suggesting the agency of snow-slopes and rapid thaws. In short, the masses of head are perhaps more comparable to the " stone-rivers " of the Falkland islands and of Tierra del Fuego than to anything now forming in Britain. Though , Cornwall has, up to the present time, yielded no fossil arctic mammals or plants, arctic plants have been found at Bovey Tracey in Devon. The head, unfortunately, is so loose and porous that all organic remains in it tend to decay ; but careful search in any fine-grained clayey seams will probably lead ultimately to the discovery of arctic plants, like those of Bovey, or of arctic mam- mals, like those of Fisherton, near SaUsbury. The drift deposits in Fistral Bay are banked against an old buried cliflf of kiUas, now hidden under the dunes, except at its northern and southern ends. The upper part of this cliff was, however, exposed in 1903 in the sand pits close to some new houses at the southern end of the Bay. The part seen was vertical, and descended -from 80 feet down to 60 feet above ordnance datum ; but the raised beach itself, on the floor below, was not reached, and lay apparently several feet lower. Further building operations may expose the shore line; if so its exact height should be noted, for at present we do not know the maximum amount of the Pleistocene submergence in Cornwall. The highest Pleistocene beach yet found in Cornwall lies at 65 feet above present mean-tide level but has only been seen near Penzance. Before leaving Fistral Bay attention should be drawn to the curious cylindrical cavities seen in the cliff near the Headland Hotel (Plate 5). They are smooth-walled vertical pipes, often 2 or 3 feet in diameter, of sand cemented by carbonate of lime. Some of them still contain masses of loose decalcified sand, others are now empty; they are often perfectly round, and descend from near the surface to the floor of slate below. These cylinders seem to be formed in some way by percolating rainwater ; but it is not clear why the decalcification of one part and the cementing of another part by re-deposited lime should here have taken this unusual form. The raised beach on its rocky platform is traceable here and there round Pentire Point East ; but the highest level reached by the platform is only about 30 feet above high-water. On the south side of Crantock beach this feature again appears ; but beyond West Pentire we only find traces of the platform, without any beach material, and at Penhale even this is lost. Perhaps the sand-dunes of Perran Bay may hide an old buried cliff like that of Fistral Bay, but at present nothing is visible, and we have to travel several miles towards the south-west, beyond the district we are now describing, before it is again seen, 8934. B 2 68 GEOLOGY OP NEWQUAY. The sand-dunes of Perranzabuloe have long been celebrated' for their steady inland march. By this long since the British church of St. Piran was overwhelmed, to reappear after several centuries when the sand-drift had moved on. The dunes are well worthy of examination, from the point of view of the geologist as well as of the archaeologist, for with the connected area of Cubert Common they occupy about five square miles. These dunes rise to the exceptional height of 225 feet above the sea ; but the greater part of this height is made up of old buried hiUs of killas, overwhelmed by the advancing sands. It is doubtful whether the drift-sand itself is anywhere more than 150 feet in depth. The dunes, or " towans " as they are commonly called in Cornwall, form a billowy more or less desert region, bounded on the leeward side by two small streams, which stop the further advance of the sand by removing it particle by particle as fast as it is blown in. The sand is maiiuy shell-sand, in small dry porous flakes which rise and skim through the air far more readily than the heavier and rounder quartz - grains ; this extreme mobility is one of the most noticeable characteristics^ it and the sharpness of the flakes making it painful to cross the sands in anything but calm weather. Where free from vegetation, as near Ellenglaze (Plate 6) or on the seaward face, the sand is set in motion by the slightest breeze, and can travel up the slopes to an indefinite height, falling over grain by grain on the sheltered side. The soil formed by these dunes is by no means barren ; if the movement stops for a short time it soon becomes covered with vegetation, beginning with the creeping marram- grass on the dry parts and the creeping sedge Carex arenaria on the flatter and wetter ones. In a few years it is covered by turf, largely consisting of wild thyme. We have spoken of the wet parts of the dunes, for not all the area is dry. The dunes are full of basin-shaped hollows or craters scoured out by the wind, and these craters are often deepened by the eddies till the soil 30 or 40 feet below is laid bare, or till the water level is reached. Thus we find in the middle of the dunes numerous hollows without outlets, and in these hollows there is either a gently inchned stony waste, or a patch of marsh, sometimes with bulrushes. . The stony flats are interesting, for they represent the soil beneath the dune, and they give the only clue to the nature of the underlying strata. On them also are left stranded anything of weight lost in the dune above. Search was therefore made for relics which would give the date of the advance of the dunes ; but except around St. Piran's Chapel we only found hammer-stones, flint-flakes, a few bones of ox, sheep, and dog, numerous broken marine shells, and a bronze tool. The absence of pottery suggests casual traffic across the dunes, not overwhelmed settlements on any of the spots where craters occur ; but these are continually changing and are w.orth further examination. Stones found amid the dunes are so eroded and DRIFT. 6S polished that specimens have been placed in the Museum as examples of wind-erosion. Other smaller areas of sand-dune will be found at Crantock, Newq^uay, St. Columb Forth, and Mawgan Forth; but they are ot similar character, consisting mainly of shell-sand. Shell- sand is extensively used as manure, but freshly deposited sand is preferred to that of the old dunes. In all probabihty the considerable amount of organic matter in the fresh material makes it of greater value. In addition to the drift deposits of the coast, already described, there are fluviatile deposits in most of the valleys ; but the bulk of these strata lie beneath the water-level, and are seldom seen now that the alluvial tin has been entirely worked out. Though most of these deposits occupy flat-bottomed gently-sloping water- logged valleys, they do not usually consist of muddy alluvium, except in the upper part. They are in 'the main coarse and gravelly, containing abundance of large stones, too big to travel down such gentle slopes at the present day. The streams that come from the neighbourhood of the granite yield abundance of granitic and metamorphic detritus, and their alluvia have every- where been worked for stream-tin, even down to the tidal waters. The explanation of the singular coarseness of the deposits formerly brought down by these gently - flowing streams is twofold. In the first place, during part at least of Fleistocene times, and again during the period of the growth of the much later submerged forests, the sea-level was considerably lower than now, and the fall of the streams per mile was considerably greater. This, however, is insufficient to account for deposits like much of the coarse tin-ground or like the loamy gravel of metamorphic rocks seen on the foreshore of the harbour at St. Columb Forth. Such deposits, like the head, probably point to an arctic climate, which continually shattered the bare rocks, then unprotected by much vegetation, set free the grains of tin, and in the spring when the snows melted, allowed the detritus to be swept down the valleys in a way that only sudden rushes of water could compass. One stone from St. Columb Forth, however, must be accounted for otherwise. It is a pebble of silicified coniferous wood, picked up in the harbour by Mr. Cecil Robinson, of Newquay, and sent by him through Mr. Barratt to the Geological Survey. Microscopic sections were made, and were referred to Frof. A. C. Seward, who thinks that the wood belongs to a Cwpressinoxylon resembling a form from the Lower Green- san(^of the Isle of Wight. A good deal of Cretaceous material occurs in the raised beaches in Cornwall ; but it does not extend inland. The pebble is perhaps derived from an old raised beach at St. Columb Forth, of which no other reUcs remain, except a few indestructible pebbles in the modern beach. It is now very difficult to see anything of these old alluvial deposits, axcept in the heaps of coarse gravel thrown up by the 70 GEOLOGY O^ NEWQTTATf. old tinners ; even these heaps and trenches are mostly obliterated by detritus washed down from the stamps of the more modern mines. The washings from these mines, combined with the shell-sand, drifted in by the sea, have almost silted up the estuary of the Gannel, which can no longer be used for shipping. Opposite the mouths of several of the valleys ' submerged forests,' or old buried land-surfaces on which trees are rooted, have been recorded as seen between tide marks ; but unfortu- nately none of these could be examined during the progress of the new survey, as they are usually hidden by beach-sand. De la Beche mentions them as occurring at Mawgan Forth, St. Colomb Forth, and Ferran Forth. De la Beche's account ol the alluvial deposits of St. Columb Forth will be quoted, for it throws much light on the structure of the vaUey, and it seems to be the only detailed account now avail- able of the alluvium* in the Newquay district. After giving numerous detailed sections of deposits m other parts of Cornwall, which should be carefully studied as explaining this more obscure district, he writes as follows : — " In the valley extending from Lower St. Columb Forth by Treloy towards Tregoss Moor, and in which stream tin has been obtained, we have evidence that on the north of Cornwall, as well as on the south, tin-ground was covered by marine deposits to a certain height up the valley, judging at least from information which we obtained from respectable sources on the spot, for no part of the valley was worked for tin when the Survey was engaged upon that part of the district. Here, also, as on the south, a bed in which vege- table remains were abundant, chiefly oak-trees, the roots of which were described to us as standing in the position in which they appeared to have grown, rests upon the tin-ground towards the seaward termination of the valley. " We were informed by several respectable persons of a circum- stance observed in this valley, during the time it was last streamed for tin, which seems to throw some light upon the condition of at least a part of it, relatively to the level of the sea, anterior to the drift of the tin-ground. It would appear that in the direction of Treloy some beds of hard grauwacke traversed the bottom of the valley in such a manner that, if the whole detrital contents were now swept out, water running down would form a cascade over them to a lower level. Upon the higher part, above this bar of rock, the tin-ground became scarce, but beneath it was abundant, and intermixed with shells of the common mussel of the present coast, many of which were ia the position in which they were attached to the rock anterior to the accumulation of the tin-ground, this gravel appearing to have been readily brought to rest in a manner not to detach the mussels from their places at the bar of rock, but on the' contrary to bury them firmly, in consequence of the eddy produced behind the fall. Supposing this information to be correct, the sea would Drift. 7 1 have extended up the valley, as in a creek, to this bar of rock prior to the deposit of the tin-ground." It is unfortunate that no information is now obtainable as to the exact position or depth of the very interesting section mentioned by De la Beche. Treloy is nearly two miles from the sea and the surface of the alluvium there lies about 40 feet above mean tide. The valley is narrow and steep-sided. When the mussels lived on the rocky ledge there was probably a long winding arm of the sea extending for two miles inland. Other fjords in the district, like the Gannel, were probably even longer, so that we can picture a time when this coast possessed several good natural harbours, since almost entirely silted up. There is one question to which, though not purely geological, the geologist is perhaps in a better position than anyone else to give an answer. It is often asked what was the appearance of Cornwall in prehistoric or early historic times ? Was the country bare as now, or was it wooded ? As regards the earlier periods, when man co-existed with large mammals now extinct, we can at present say very little. But everything seems to show that at the time the " submerged forests " flourished the valleys at any rate were thickly wooded with oak, hazel, and alder. To this period we should be inclined to refer also the woodland snails, discovered by Messrs. Kennard & Warren at the base of an ancient sand-dune on Towan Head, Newquay.* We doubt the connection of this sand with the raised-beach below or with the head ; but it is certainly ancient and probably Neolithic. To get this evidence of the former existence of woodland in such an exposed situation as the north end of Fistral Bay is very remark- able ; it seems to suggest a former seaward extension of the land, so that this spot was out of reach of the sea and was probably flanked by a belt of wooded lowland, the dunes having at that period only begun to form. * "The Blown Sands and other Deposits of Towan Head, near Newquay, Cornwall." Geol. Mag., 1903, pp. 19-25. 72 CHAPTER X. ECONOMICS. Mining. Once an important mining region, at the present day the area described in this Memoir is deserted, except for a few mines at St. Agnes. The districts within which mines have been worked fall naturally into two groups. The first group contains the tin and copper mines, which are almost confined to the granite and to the metamorphic aureole surrounding the granite. Such mines are found m two areas, that of St. Agnes and Cligga Head, and that bordering on the St. Austell granite, close to the eastern limit of our district. The second group contains mines yielding lead, silver, and iron ; it shows no connection with the aureoles of metamorphism ; but on the other hand its lodes seem almost to be limited to strata which contains much calcareous matter. Placed in order of their former importance, the districts are approximately as given below. The yields are, however, only rough approximations ; exact statistics are impossible to obtain, for many of the mines were worked long before the date of accurate records. A considerable amount of stream-tin has also been obtained from the alluvial deposits in the valleys draining the granite area ; but the last of these stream- works has long been closed. Mr. MacAlister, from the best statistics available, has helped us to obtain the following estimates : — Appeoximate Yield and Value op Ores. St. Agnes. Tons. Value. Dressed Tin-ore - 50,000 £2,500,000 Copper-ore 200,000 1,000,000 Lead-ore - 600 Silver (from the lead) oz. 10,000 2,500 Zinc-ore - 35,000 Iron-pyrites - - - - 11,000 Small quantities of arsenic and wolfram have also been raised, and cobalt and pitchblende occur, though not in such quantity as to be worth working. Newlyn Downs and Chiverton. Tons. Value. Lead-ore . 125,000 Metallic Lead"| I 86,000 f-from the Lead-ore \ Oz. Silver * J (.2,410,000 £602,500 Tons. Zinc-ore 62,000 Iron-pyrites 2,000 Copper 520 Wheal Golden and East Wheal Golden. Tons. Value. Lead-ore - . . 2,570 Metallic Lead] f 1,760 [from the Lead-ore \ Oz. Silver j 124,380 £6,095 ECONOMICS. 73 Tin mines and stream works near St. Enoder have yielded considerable amounts in this area ; but no statistics are obtain- able. Park of Mines, which from a very small area yielded a large amount of tin-ore, lies just outside our district.- The amount of iron-ore raised from the mines situated in Sheet 346 is approximately 122,500 tons ; which consisted mainly of brown haematite, but there was also a good deal of spathic iron- ore and some red haematite. A little red ochre and umber have also been raised. Added together the value of the ores raised in this district must have amounted to somewhere about £4,000,000 or £5,000,000 ; but on the other hand a large amount of capital must have been sunk in works entirely unremunerative. Every- where one finds trial holes or small mmes which never paid their working expenses.* The village of St. Agnes has long been known as the centre of a considerable mining district, and the extent of the operations" may be judged by the immense heaps of debris brought up from the old levels, and which now disfigure the landscape. At the present day there are only two mines of importance working, both actually in St. Agnes, West Kitty and Wheal Kitty. Most of the other mines have been shut down for some time, but there are a few recently reopened and working for tin and copper on a small scale. The most distant mines on the map belonging to this district are those situated on the south side of Chapel Forth — Wheal Charlotte, Wheal Freedom, East Wheal Charlotte, and Charlotte United. North of Chapel Forth is situated Wheal Coates, which extends from the sea-shore as far as the slopes of the Beacon. This mine has not been worked of late years. It is stated that it has been worked spasmodically for many centuries. It is remarkable, not only for the well-known specimens of the replacement of orthoclase by cassiterite, but also for a very fine example of an open work extending from the cliffs back to the old count house. No definite, information can be obtained concerning this open work beyond the fact that it was worked for tin along the back of a lode. To geologists it is of great interest because it affords a good section of metamorphosed killas including andalusite schists. North of Wheal Coates is Wheal Bungay, which like Wheal Coates has been worked partly in the St. Agnes granite ; indeed, it was from this mine that the best specimens of the granite were obtained. Wheal Buiigay was worked for tin and copper; it also afforded some quantities of colourless and pale-green fluorspar, which can still be collected around the old shafts. According to Symons' map, the chief lodes worked here were the Bungay and north Seal Hole lodes. North of Wheal Bungay and also north of the St. Agnes elvan another lode has been worked, the North Tin lode. * In Appendix I. (p. 91) will be found an account of the different mines, compiled by Mr. D. A. MacAlister. 74 GEOLOGY OF NEWQUAY. North east of the Beacon is a large area covered with spoil heaps which mark the site of Polberro Consols, a very famous mine in its day. In addition to tin, a lode whs worked here for copper also. . Borlase, writing in 1758* thus describes it. " The richest tin mine I have ever heard of, as to the quality of the ore, is one in the parish of St. Agnes, near the Beacon, called Polberou. Several parallel and contiguous veins, mostly of large grain crystals, make the treasure of tin in such quantity, that, in the year 1750, they covild not get horses enough in the neighbour- hood to carry the tin from the mine to the melting-house, but carried it in ploughs, a very unusual sight. . . . Great part of the ore was so rich and pure that it needed not to be stamped, and the lode is so large that it affords vast rocks of tin ; one rock, in March 1750 . . . weighed 664 pounds, and it brought eleven and a half for twenty [i.e. 11 Jibs, metallic tin in 20 lbs. of ore] in the stone without stamping and dressing. I have since, been informed, that one stone . . . weighed 1,200 pounds." Closely associated with Polberro is Wheal Trevaunance, which was well known as a locality for topaz. On the west of the deep coombe which traverses the village of St. Agnes is West Kitty, which extends from the new Friendly shaft (named after Wheal Friendly, now incorporated in the West Kitty Sett) to the old Polbreen Mine, situated east of the southern extremity of the Beacon. The chief shafts of West Kitty are — the Friendly shaft a new venture, situated between the church and the sea ; Reynolds' shaft, close to the church ; and Thomas's shaft, situated almost on the high road leading from the church out of St. Agnes. In 1902 and 1903 West Kitty was one of the most productive mines in Cornwall, in consequence of rich btmches of ore being met with in the workings at the bottom of Thomas's shaft. On the east of the coombe mentioned above as dividing St. Agnes are situated Wheal Kitty, Penhalls, Bluehills, and Gooninis. Wheal Kitty has been working for many years, but on the whole has not experienced such good fortune as the sister mine, West Kitty. PenhaUs is on the north of Wheal Kitty, and has long been noted for the number of faults which disturb the lodes, much to the detriment of the working of the mine. Bluehills is in the coombe east of Wheal Kitty and Pen- halls, called Trevellas Coombe on the Ordnance map, but better known locally as Jericho. Gooninis is on the south of Wheal Kitty. It was started only a few years ago with the hopes of striking a known lode, but as this attempt failed, the mine was shut down. Three other mines should be mentioned, the New St. Agnes Mine, now incorporated with West Kitty ; Wheal Betsey, on the east of Bluehills, and Wheal Burrow and Butson, about one mile north of St. Agnes. The last mine was worked for copper and zinc. j^, * " The Natural History of Cornwall," fol. p. 188. ECONOMICS. 75 As in other tin mining districts so also in St. Agnes there are extensive works for saving the waste tin which is not caught in the dressing on the two mines, Wheal Kitty and West Kitty. In the case of the former mine "this is effected by a series of " frames " and " buddies " at the bottom of Trevaunance Coombe ; in the case of West Kitty the frames, etc., are situated in Tre- vellas Coombe, at the head of which valley are the stamps where the ore is crushed. The waste from these salvage works passes on to the shore in Trevaunance and Trevellas Coves respectively, and it is significant that it is found worth the trouble to wash the sand on these beaches for the cassiterite that has escaped the second dressing. At Perranporth again there are several mines, only one of which however is now working. This is the Good Fortvme mine. It is situated" on Messrs. Nobel and Co.'s Explosive Factory, and is worked in consequence of an arrangement between that company and the owners of the land. From this the value ot the mine may be readily gauged. The Explosive Factory was also the site of the Perran United Mines, which were worked for copper chiefly. Wheal Prudence is situated on the cliff's west of Cligga Head. In it three lodes were worked, one underlying north, the other two south. In the village of Perranporth itself and, it is said, connected with the Perran United sett, is the Wheal Leisure sett. This mine was also worked for copper. To the east of the Porth are three tin mines, situated on the sandhills, Wheal Ramoth, Wheal Vlow, and Wheal Budnick. The veins in the divisional planes of the granite at Cligga Head have been worked on a small scale for tin. They also con- tain a considerable amount of wolfram. One of the characteristics of the St. Agnes District is the coarse grain of the tin-ore above the sea-level, large brilliant crystals of cassiterite still being obtainable in narrow fissures at Cligga Head. The convenience of working in a cliff-face, and the readiness with which pure tin-ore could be picked out, make it probable that this was one of the first areas in which tin was obtained in pre-historic times. But up till now no direct evidence of such early working has been obtained. There is, however, a great tendency for later more extensive workings to obliterate all traces of ancient mining. .The Microscopic Steucture of Tin Lodes. In order to gain some idea of the arrangement of the mineral constituents of the tin bearing lodes in the St. Agnes district a number of sections were cut from specimens supplied by Captain Williams, of West Kitty, and also from specimens obtained from the Good Fortune Mine on Messrs. Nobel's Explosive Factory. A section was cut also from a very rich specimen of tin ore from Wheal Kitty. 76 GEOLOGY OF NEWQUAY. The chief constituents of the lodes are quartz, tourmaline, chlorite, and cassiterite. Blende and other sulphides are of fre- quent occurrence. Before describing the habit of these minerals it is necessary to give an account of the lodes as seen under- ground. The actual rock worked embraces not only the quartz- ose fillings of the fissures constituting the lode proper, but also a large amount of brecciated killas which has become mingled with the quartz, and in some cases a portion of the walls of the lode also, which are impregnated by the mineral solutions which passed along the fissures, and . are known as " capel."* That portion of the lode which is used as a guide to direct the driving of a stope is known as the " leader." The term is somewhat in- definite, as it may signify a bunch or a string of tin, the " peach " which will be described later, or the capel. Irregularly dissemin- ated throughout the lode are numerous crystals of iron pyrites, mispickel, and sometimes copper pyrites in workable quantities. The blende occurs more commonly in bunches, but in microsopic sections it is met with also in isolated crystals. In section the cassiterite is easily recognised by its high refrac- tive index and by its strong double refraction. The cleavage parallel to 100 is very distinctly shewn ; and twin crystals are not uncommon. The colouring of the cassiterite crystals also is very characteristic. Two distinct colours can be recognised ; a pale yellow, and a violet brown. Both colours are found to be distrib- uted unevenly ; and rarely the cassiterite in section is nearly colourless. Generally the crystals form well defined prisms with traces of terminal faces. It occurs, however, in other forms. Thus it is not uncommon in the West Kitty specimens to find the tin oxide in the form of perfect spherules composed of thin prisms of cassiterite radiating from a centre. The prisms are so slender as to allow of the black cross of perfect spherulites appearing when the Jiicols are rotated. Again, it may occur in the form of minute granules massed together. Sometimes these granules form botryoidal masses. In the Good Fortune speci- mens the cassiterite was found to have yet another habit. Some of the crystals in this lode were found to be terminated as an ordinary prism of cassiterite at the one end, but at the other to be frayed out into numerous acicular prisms, each with terminal faces. A similar habit is very frequent in tourmaline ; but no other specimens from this district have shown it in cassiterite. The tourmaline occurs as minute prisms, either brown or blue in colour. Sometimes the colour is so faint that it is hard to distinguish. The brown tourmaline occurs often in dense masses of distinct crystals which undoubtedly represent frag- ments of brecciated killas. On the periphery of these masses it * For account of Cornish tinstones and capels, see J. H. Collins, Journ. Min. Soc, vols. iv. and v. Also Flett, Summary of Progress of the Geological Survey for 1902, p. 1.54. ECONOMICS. 77 is not uncommon to find the tourmaline prisms to be blue. In some slides the felted masses of brown tourmaline are seen to be traversed by veinules of quartz bearing blue tourmaline, showing that after the brecciation of the walls of the lode fresh disturbances and infilling with quartz took place. Isolated crystals of brown tourmaline are sometimes found among the blue ; and in one of the West Kitty specimens in which the tourmaline was better developed than usual the prisms were found to display zonary bands of brown and blue. At one spot in this slide (E. 3597j the tourmaline prisms form a distinct wall against the killas with their long axes pointing to the centre of the lode and at right angles to the killas wall. In the specimen from Wheal Kitty dense masses of very minute and pale blue tourmaline prisms were found mingled with minute flakes of chlorite.. This mixture of tourmaline and chlorite is one of the forms of '" peach " — so called because of the bloom it exhibits in a hand specimen. It would appear from specimens from other districts that peach may be composed of olue tourmaline alone, or of chlorite. With regard to the sequence of crystallization, there can be no doubt that part of the blue tourmaline crystallized before the cassiterite. This can be best seen in the Good Fortune specimens, where prisms of an unusually deep blue can be easily detected enclosed in the cassiterite. In the Wheal Kitty speci- men the chlorite would seem to have solidified at the same time as the blue tourmaline ; but in one of the West Kitty specimens it has certainly crystallized after the cassiterite. It should be added that in the peach of the Wheal Kitty specimen minute granules of cassiterite occur also. The chlorite is sometimes very abundant. This can be seen best on the beach at Chapel Forth, where there is a lode consist- ing almost entirely of brecciated chlorite enclosing pyrites and fragments of killas. A slice of this rock was cut, and was found to contain some muscovite, besides the chlorite and pyrites. In some of the specimens from Good Fortune mine the chlorite is very well shown and can be studied under the microscope. The commonest mode of occurrence is in perfect spherulites of some size. VermicuHtes, however, are not unfrequent. But the most remarkable form is another in which one part forms the half of a hexagon, the other a spherulitic mass describing an arc of a circle. The colour is either green or light brown. The interference colours are generally bluish, but some of the spheru- lites give higher colours than others. The hexagons give a good figure, which is apparently uniaxial. The quartz forms irregular mosaics with ■inclusions of fluid in which vibratile bubbles are common. It has crystalUzed last of all the minerals described. In one of the West Kitty slides hexagonal sections of quartz were seen in a mass of cassiterite granules. These are the oidy examples of clearly 78 GEOLOGY OP NEWQUAY. idiomorphic quartz seen. They may have been derived from the walls of the lode by brecciation. The sections from Good Fortune mine were taken from the indurated killas on one side of the lode to that on the other. Thus several sections were obtained which illustrated the microscopic character of capels formed in killas. The killas beyond the reach of the influence of the lode material has been altered by the granite mass at Cligga Head, showing both bleaching and spotting. Specimens taken from within a few inches of the edge of the lode show that the mass of the rock, which consists of quartz grains, muscovite, and zircon, has been traversed by small veins of quartz, and has also disseminated through it a few grains of brown tourmaline. Judging from the killas outside the metamorphic aureole the muscovite probably owes its origin chiefly, if not entirely, to the shearing movements that took place before the intrusion of the granite. As the lode is approached the brown tourmahne, which sometimes has a tinge of green, is found to increase greatly in quantity. In some specimens a great deal of chlorite also was found, forming pleochroic halos around dark inclusions, or around zircons. Finally, the killas bomiding the lode itself is a good example of a brown tourmahne schist. Quartz veinules are abundant ; and sometimes they are rich in muscovite, which would answer to the nests of " gUbertite " in the larger veins in the granite of Cligga Head. Occasionally in the tourmahne schist grains of rutile can be detected. Cassiterite occurs some- times in veinlets in the killas at West Kitty, Penhalls, and Polberro. The Lodes of Cligga Head. C. le Neve Foster has said that the chffs of Cligga Head are an ideal spot for studying the formation of mineral veins.* The veins in question are in the centre of the greisen bands described in earlier pages, and mark fissures which were formed roughly parallel to the surface of the killas into which the gi-anite was intruded owing to the contraction consequent on the coohng of the igneous mass. The advantage in studying these veins in preference to those in the killas is that owing to the difference m origin there has been no brecciation of the walls of the fissures whatever, so that the veins are very clearly defined, which cannot be said of those in the killas. The matrix of each of these veins consists of irregular grains of quartz with abundant fluid cavities. The metalliferous minerals which it contains are cassiterite, mispickel, wolfram, iron pyrites, decomposition pro- ducts of copper p3^-ites, and, it is stated, bismuthine. Haematite occurs also in places; and the non-metalliferous minerals are blue tourmaline, kaolinite, a lithia mica, gilbertite, topaz, and a * " Kemarks on some Tin Lodes in the St. Agnes District," Trans. B. Geol. Soe. Cornwall, vol. ix., 1877, p. 205. ECONOMICS. 79 felspar. The last four have been described elsewhere. (See above pp. 43, 44). The cassiterite occurs in large crystals, the greatest size observed being nearly one inch in length. No tin in a fine state of division has been found here, as is commonly the case in the lodes in the killas, especially at great depths. The crystal faces are well defined and lustrous. The colour is deep brown. The mispickel is not common and does not require further notice. The same may be said of the iron pyrites and the copper ores. The wolfram is in some of the larger veins very abundant. It forms large masses of a lustrous black appearance, especially where the cleavage faces are exposed. The tourmaline varies greatly in quantity, in some of the veins it appears in a hand specimen to be entirely absent, while in others it is so abundant as to render the whole vein quite dark in appearance. There is reason to believe that it is associated with chlorite in parts. Although no strict parallel can be drawn between the mineral veins in this granite mass and those in the killas, on ac- count of their different mode of origin, nevertheless there are one or two comparisions which may be profitably applied. It has been described in another place how the- lodes of Cligga Head are parallel to one another'; but it was also mentioned that sometimes the greisen bands were confluent. So also it has been observed that sometimes one quartz vein is connected with another by a short quartz vein which answers to the " caunter lodes " in the killas. Again, the veins are frequently found to be heaved by faults. Thus, at the bottom of the path leading down from the Factory to the beach by way of the chasm in the cliff there is an artificial cave in which a comby quartz vein can be seen with an approximate north and south trend heaving one of the tin bearing veins and greisen bands for the distance of a few inches. This comby quartz vein is, according to definition, a small " cross course," such as are known in some of the mines not far off to heave the lode manj^ fathoms. For instance, the cross course in Wheal Kitty may be quoted, which heaves the lode 35 fathoms. Again, the lodes at Cligga Head are seen to be heaved by faults trending east and west. Thus, in the centre of the cliff section, that is about midway between the two paths leading up the cliff, a quartz vein of greater size than is usual is seen heaTed "down on the north" about 6 feet by a fault dipping to the north. This fault corresponds to one of the slides in the St. Agnes mines ; but cannot be compared to the gossans because those faults are said generally to dip to the south. But the most striking lesson that can be learned from these lodes is the distribution of the tin, especially as this bears so directly on economics. It is well known that in tin lodes the ore tends to occur in bunches which are very rich while they last, and which give way to tracts of poor or barren vein stuff, sometimes 80 GEOLOGY OF NEWQUAY. bringing disaster to the mine. This bunchy character of the tin IS excellently shown in the Cligga Head lodes, which can be studied m broad daylight instead of in the obscurity and dirt of underground workings. It is impossible to give exact measurements of any of the bimches of cassitente ; but a short description of a bunch discovered by the Survey Officers in the summer of 1903 will serve as an illustration. A recent fall of the cliff, certainly not earlier than during the sharp frosts in the beginning of the year (1902), was found to have exposed a portion of a quartz vein about 3 inches thick which was exceptionally rich m tin. Part of the vein was shown in an enormous boulder on the shore containing perhaps 25 square feet of the lode. The rest was in place in the cliff, so exposed that only the edge of the lode could be seen. The tin was all in large well formed crystals, sometimes grouped together in twos and threes, but often lying isolated in the quartz matrix. The average size of these crystals was perhaps a little more than an eighth of an inch in length. Associated with it was a quantity of wolfram in large, shapeless masses, jet black, but lustrous on the cleavage faces, and numerous acicular prisms of blue tourmaline could be seen disposed irregularly in the quartz. It was impossible to judge from the part of the lode in situ in the cliff how far the bunch might extend. The find was duly reported to Captain Turner, who sent some miners from Good Fortune to brmg up all the tin to be obtained, and it is significant in connection with what has been said about the sporadic occurrence of the cassiterite, that although a considerable portion of the cliff was broken down so as to expose more of the lode, no more tin was found than that which was visible when the bunch was first discovered. On account of the sporadic distribution of the tin in the lodes of Cligga Head extensive workings of value have never been carried on. There are, however, signs that the " old men " thought it worth while to work among some of the lodes, as can be seen by the numerous levels which have been exposed in section by the falling away of the cliff. - Some of these are said to be of comparatively recent date ; but others again are said to date back beyond any records of mining in the immediate neighbourhood. A little tin is still raised by one man during the winters from coarse quartz sand which can be found between the big boulders on the shore, and this is derived from the granite, greisen, and lodes. In view of the high price of wolfram it might be thought that it would be worth working this mineral commercially ; but here again the sporadic nature of its distribution makes it impossible to be sure of a profit, in spite of the richness of some of the bunches. If ever the tin and wolfram should be worked here there should be no difficulty in separating the two minerals, as both occur in masses of such a size that hand picking would be quite effective. The magnetic separator also now makes it possible to deal with mixed ores. 8] Lead and Iron Mines. In the uoighbourhood of Chiverton and Newlyn Downs extensive lead mining operations were once carried on, but have now ceased entirely. The chief mines were Wheal Albert, near Goonhavern, West Chiverton, Great South Chiverton, Wheal Frances, Chiverton Moor, Wentworth Consols (also worked for zinc) ; New Chiverton, Wheal Constance, CargoU (worked for lead, zinc, and copper). Shepherds and East Wheal Rose (worked for silver lead). Wheal Golden and Penhale Mine in Cubert were also worked for lead rich in silver. The lode runs north-north-west and south-south-east and crosses a series of points and small bays in such a way as to be clearly seen in section in the clitfs and on the foreshore, the lode is vertical, or hades to the east, and it cuts the Perran iron-lode next to be described. Running from the northern end of Perran Beach in a south- easterly direction is a series of mines on a big iron-lode. None of these mines are now being worked, and the following account is partly compiled from Hunt's " British Mining" (pp. 799-801) and W. W. Smyth's " The Duchy Peru Lode."* The lode appears in the cliff's at the northern end of Perran Beach, whence it can be traced by workings in a direction slightly south of east for over three miles. The mines along this lode, all of which have now ceased to work, are Gravelhill, Mount, Treamble, Great Retallack, Duchy Peru, and Deerpark Mines. Beyond Deerpark Mine no ore of value has been raised. At the time when R. Hunt wrote (1884) the lode had been worked for about twenty years. It has been worked chiefly by mining, but there are one or two large open works, for instance that at Mount, and smaller workings of a similar sort on the Deerpark Mine. At the cliff on the western extremity of the lode the Wheal Golden lead lode crosses it ; and at Treamble also, promising lodes of argentiferous galena were found to cut the iron lode in two quarries. At Great Retallack some lead is stated to have been raised from similar lodes, and at Duchy Peru silver lead of great richness was raised. The ore from which the iron was extracted is chalybite, which has at the surface become oxidized to haematite, limonite, and partly to magnetite. W. W. Smyth gives the following minerals as recorded from these mines : chalybite, haematite, magnetite, pyrites, copper pyrites, blende, galena, pyromorphite, melanterite, copper vitriol, common garnet, and boldly crystallized horn- blende, of the radiated " strahlstein " character. The lode dips south-west at an angle of 50°, and it is stated on the authority of Mr. Argall that the iron affects the footwall, while the central portion contains a large amount of blende, which increases with depth. Thus R. Hunt states that zinc was * TroMS. B. Geol. Soc. Cornwall, vol. x., 1882, p. 120. 9834. F 82 GEOLOGY OF NEWQUAY. found for the first 25 fins, in Great Retallack, and that at a greater depth the blende increased, so that for some time 500 tons per m.onth were sold. The thickness of the lode varies greatly, at some spots it is only a few inches wide ; while at others, as for instance at Great Retallack, it is several fathoms thick. These great masses of iron ore seem to occur where the lead lodes cross the iron lode, and it is also worthy of note that there also the lead was found to be particularly rich in silver. In one case, on Duchy Peru, the silver was found in pure, visible threads. Masses of pyrites were also met with which caused great difficulty in working the Duchy Peru mine on account of the heat and foul air caused by its oxidization. Hunt states that in this mine the temperature in Vallances shaft was as high as 124° F., and that the air was so foul that a candle would not burn. The Perran Iron Lode is, however, chiefly interesting - on account of the enormous brecciation it has undergone. This can be seen in almost any of the still existing dumps of ore lying round the mines, where the thin quartz veins in the chalybite are broken up into minute fragments so that no trace of the direction of the veins remains. But to gather an adequate idea of the extent of this brecciation it is necessary to turn to W. W. Smyth's account of the lode in the Duchy Peru Mine, where he describes a breccia twelve feet thick containing blocks of blende weighing as much as a ton. The significance of this enormous brecciation has been discussed in his paper.* At the eastern hmit of our area, in St. Enoder, Penhale Moor Mine lies close to the metamorphic aureole which surrounds the St. Austell granite, for though the slate in the spoil-heaps shows no spotting it seems to be more or less bleached. This mine was worked for tin ; but we cannot ascertain its yield. The valleys near it have been streamed for tin, and apparently yielded con- siderable quantities of ore, though the workings have been so long closed that it is impossible to obtain any particulars. In a small copper mine, Wheal Trugo, two miles to the north, "a small vein of cobalt was found from 4 -to 6 inches wide ; it was estimated as worth £60 per ton. The other mines scattered over the district seem never to have been of much importance. Chalybite was worked north of St. Columb Perth, in a lode running east-south-east through Flory Island, where specimens of the crystalUsed ore can still be obtained. Numerous small workings and trials for lead will be fouijd around Newquay ; but none of these were successful, for though the lead yields an exceptionally high percentage of silver, it only occurs in thin strings or lenticles." One of the strings is stated to have yielded as much as 200 ozs. of silver to the ton of * " The Duchy Peru Lode, Perranzabuloe," Trans. Roy. Geol. Soc Cornwall, vol. X., 1892, p. 120. t Hunt, " British Mining," p. 184. ECONOMICS. 83 lead. A lode in Stem Cove is interesting, for it coincides with an overthrust fault which forces the Lower Old Red rocks over marine Lower Devonian. As regards ores found in the alluvial deposits, stream-tin occurs, and has been dug, in each of the valleys which drain the metamorphic aureole, but none is found in the other valleys. Thus the river gravel at St. Columb Forth is full of meta- morphic material, and this valley has been systematically worked all the way across our area, though the tributaries from the north and south are barren. The valley of the Gannel has also been streamed, for it drains the tin district containing Park of Mines and Penhale Moor Mine. Stream-tin has also been obtained from the valley running southward to Ladock, and in this valley grains and small nuggets of gold were found. Gold has also been noticed in the raised-beach of Fistral Bay. The St. Agnes stream works have already been alluded to ; the valleys there are short and steep, and have not yielded much tin. Building-stone. The building-stone in use is commonly of local origin, for though there is nothing worth sending into other districts, yet nearly everywhere material can be found sufficiently good for local purposes. The stones naturally fall into two groups, first the kiUas or slate, which is quarried in jointed blocks flat above and below, and second, the elvan or quartz-porphyry, which comes away in irregular masses without beading or parallel joints, and has to be dressed with a hammer, or often is treated as freestone and used for facing. Perhaps the most convenient way to deal with the building-stone will be to take the strata in order, beginning with the oldest, which occur in Watergate Bay. The Old Red Sandstone series consists of silty strata alterna- ting with hard platy or flaggy slates. The silty beds do not seem to have been used, except for field walls, and they are probably too porous for houses. The flaggy slates have been quarried in several place at the edge of the cliff and also inland near the Watergate Bay Hotel and further east. They yield good impervious stone of two colours, dark grey and dark reddish- purple. As most of the killas isd ark grey (except the weathered upper part, which is paler and often very porous) this purple slate might be used where a warmer colour is desired. Quarries in it will be found a quarter of a mile east of the Watergate Bay Hotel (where it is a good deal disturbed) and near Penvose. It has not been much used, for it occurs some distance from the villages, and grey stone is to be had nearer. Selected bands in the platy slates around Newquay have been extensively quarried and yield good building-stone, especially if set with bedding sloping slightly outward. Often vertical joints are selected lor the outer face of the wall, and these being coated with quartz or ochre, give a lighter and warmer tint 8934. F 2 84 GEOLOGY OF NEWQUAY. than faces of the dressed stone; they are also less porous. Newquay is mainly built of this platy killas, with facings of elvan from St. Columb Minor, or sometimes of granite. Pentire Point quariy yields a stone harder than usual, but irregularly bedded. The Staddon Grit in the northern part of our area is too hard for building and is mainly used for road-metal. The standing- stones and cromlechs are made of this rock. The kUlas in the south of this map, on account of the ease with which it an be dressed in large flat blocks, is a very useful build- ing stone, and in general use throughout the district. The best materal for houses, etc., is derived from the mudstones and fine- f rained grits, which are more durable than the shales, and ave, according to local information, the property of hard- ening after dressing. Body's quarry in Trevellas Coombe, near St. Agnes, is an excellent example of the value of this rock, most of the building material in the nouses of St. Agnes having been taken from it. Higher up the same Combe the Great Western Railway Company has quarried the same stone for the construc- tion of a big viaducton the new Newquay and Truro Railway. The shales associated with this stone, and the Perran shales, being more easily cleaved, are not used in important work, but are commonly to be seen in the hedges. In St. Agnes, besides the sandstones and grits, roughly dressed blocks of metamorphosed killas are built into the walls in many houses, and the same material is largely used in the hedges. The altered granite on the west of St. Agnes Beacon has also been utilised for facing some of the houses in the village, being the most durable stone in the neighbourhood. Unfortunately its limited outcrop and the difficulty of dressing it have prevented its more general use. The Cligga granite has been used to some extent in past years for facing buildings and as gate posts. At the present day, however, it is not in use because of the difficulty of access to the clifl", which is the only place where it is exposed. The elvans which intersect the kiUas in various directions jdeld stone varying greatly in character. Where the dyke is much altered, as at St. Columb Minor, it may yield a white or buff free- stone which looks and works very like a sandstone ; while an unaltered dyke may show either a close-grained rock, without porphyritic crystals, a similar rock with scattered crystals of quartz or felspar, or a purple granitic-looking rock like that found north-east of Perranporth, or north of St. Enoder. Elvan is often excellent building stone ; but the dykes are so much and so irregularly jointed that it is seldom possible to obtain a squared block two feet in length. As each dyke tends to retain its own character for a considerable distance it ^vill be convenient to describe them one by one. The Watergate Bay elvan where it reaches the coast is too much and irregularly decayed to be of any value. At St Columb Minor, however, it is extensively quarried and is about 40 feet ECONOMICS. 85 thick, which thickness it seems to retain southward nearly to Trerice. It then again becomes rotten and thinner, §nd is only traceableby small overgrown quarries and fragments ploughed up. This elvan is usually a white or pinkish granular rock, with doubly-terminated quartz crystals and a good deal of schorl. It was originally a quartz felspar-porphyry, but the porphyritic felspar is scarcely recognisable, having gone into a granular mass like the matrix. A dyke, probably connected with that just described, run- south-eastward from St. Columb Minor. For the first mile or two it seems to be like the Watergate Bay elvan, but it is so decayed that it has only been worked for bricks. At Ketyn, however, this elvan (or perhaps a new elvan in nearly the same line) takes on a totally different character. It is a highly porphyritic rock, with crystals of quartz, orthoclase, and tourmaline, and is quarried in large blocks. This quarry might yield a very hand- some porphyry for polishing. The same exceptionally porphyritic character is noticeable where the dyke is lost near Penhale Moor Mine. Not far from Cubert Church a deep quarry will be found in a porphyritic elvan about 25 feet wide ; but this elvan is not trace- able eastward, though westward it runs under the dunes to the coast. Another elvan runs eastward from Cubert nearly to Newlyn East. It is fine-grained and sparingly porphyritic ; but it doe- not appear to be wide enough to be of much value. A tough granitic elvan, quarried a mile north-east of Perran- porth for road-metal, is a handsome rock, and would be valuable if it could be obtained in blocks of sufficient size. With the exception of the portion of the St. Agnes elvan ex- posed in the quarry at Wheal Prudence the elvans of the district are of little use as a first class building stone, since the irregular jointing makes it impossible to dress them in large enough blocks. At Wheal Prudence this jointing has been, for some reason, either non-existent or obliterated, and as the stone after quarrying becomes very hard and durable, it has been used for facing buildings in the parish of Perranzabuloe, even as far as three miles from the quarry. It has been noticed, however, that in spite of the presence of these materials the Great Western Kailway Company has found it advisable to bring dressed granite blocks from other districts for use as coping-stones on the bridges of the new railway. Clay and Bricks. The Pliocene beds at St. Agnes occupy a distinct position in the economic geology of the district. Many years ago the clay was used for the manufacture of tobacco pipes ; but the discovery of more fitting material elsewhere has led to the abandonment of 86 GEOLOGY OF NEWQUAY; this industry, and now the clay is solely used in the mines as a handle by vhich to hold the candles. Messrs Davies and Kilto wrote in 1877 concerning these deposits :— " The main deposit of sand and clay extends as a broad belt around the north and east sides of the Beacon. Its length is about If mile (1;250 fathoms) ; its width and thickness vary very considerably. Besides this there is a smaller deposit on the western side lying on the decomposed granite; the former rests on the killas. Generally speaking, we may say it is a bed of sand resting upon the rock, having upon it a bed of clay, the whole being covered by ' head/ or overburden. " The clay is of two kinds, candle-clay and fire-clay. The former is of a blue colour, and when of good quahty is almost entirely free from grit, is plastic, adhesive, andT very tough. It sells for about seven or eight shillings a ton at the pits ; and a stock is raised in summer to last over the winter, when rainy weather makes it difficult to get it up."* Bricks are httle used in this district : but some have been made from the decayed elvan already mentioned. Chiverton House, the residence of Mrs. Peter, was built many years ago of bricks made from the clayey "head." on the estate. Good tile clays have not been dug, slates being in common use for roofing. The slates come from Delabole or North Wales, none of the local slates have a cleavage sufficiently perfect. Lime. At one time a little lime was burnt near Newquay and St. Columb Forth ; but as the limestone occurs in sheared lenticles, which seldom exceed two feet thick it cannot be worked with Erofit. The limestone is also very impure, and, unless carefully umt, tended to fuse into a slag, instead ot burning into lime. Sand. The supply of sand is mainly obtained from the dunes, the best for building being found where the deposit has long been subject to the dissolving action of the percolating rain-water, For use as manure, however, the best sand is always that just washed up by the sea. The decayed mica-trap dyke near Cosworth was once used as dressing for the land, probably in place of sea-sand, for it does not seem to have much chemical value. The Pliocene sands of St. Agnes, which are often unstained by limonite, are largely exported to other parts of England, for use in pottery works and other purposes. Ihey do' not seem to have ever been used in the manufacture of glass. Messrs. Davies and Kitto mention that " The fine white sand is used by gardeners in potting, .and is delivered in Truro at 17s. 6d. per ton. Much of it is shipped to London. The coarser is used.by crucible manufacturers. The * Trans. Roy. Geol. Soc. Cornwall, vol. ix., 1877, p. 196. ECONOMICS. 87 sand is also in request for mixing with mortar for building purposes, and for strewing over the lime floors of the cottages in the neighbourhood." Rf) AD-METAL. The-road metal used on the main road around Newquay is largely obtained from outside the district, in the neighbourhood of Roche ; it is apparently a calcareous slate baked into hornstone by the granite. A great deal of el van is also used, and the mica- trap dyke of Pentire is also quarried. A much tougher rock is the altered greenstone near Trebudannon and Trugo ; but we are informed that it is little used, owing to the expense of breaking. In the southern half of the area, road material is abimdant and of excellent quality. The two best rocks for this purpose are the fine-grained St. Agnes elvan from the quarry north of Polberro Mine, and the fine conglomerate from the "parishes of St. Allen and St. Erme. The former is not being used very extensively at the present time, but the road surveyor for the parishes of St. Agnes and Perranzabuloe, Mr. John Retallack, considers that there is no stone so good for standing the wear and tear of the traction engine traffic, which is considerable in this part of Cornwall. The fine conglomerate is the only stone used m the neitj;hbour- hood where it occurs, with the exception of rounded pebbles of greenstone brought from the south coast for the purpose of filling up depressions. Far away from the outcrop of this con- glomerate also one meets with it in the roads north of Truro. The chief quarry where it is worked in this map is at Bissick, in the Ladock Valley. In the neighbourhood of Perranzabuloe the Perranporth elvan is largely used in the roads, the stone being worked at Wheal Budnick, on the sandhUls. In the bye roads the stone of the locality is generally used ; and if there should be no quarries the stones off the fields or mine dumps are utilised. Thus in the vicinity of Summercourt, the metamorphosed killas and altered granite of the St. Austell mass are employed ; while in localities not so well provided the shaly killas is the only available material ; this, although making an elastic even surface, requires frequent attention, and becomes very muddy in wet weather. In places on the high roads, but more generally on the bye-roads and lanes, vein quartz from the fields has been used with indifferent results ; for if the traffic is only ordinary it is speedily ground to sharp edged powder, and if the traffic is light, and in consequence the roads rarely mended, the irregularly sized blocks make the surface too rough for comfort. Water Supply. Water supply is a matter of considerable difficulty, though the rainfall is heavy, averaging at Newquay 33'5 inches for the last ten years.* Much of the area is occupied, by impervious clay-slates, * From Dr. Vigurs' Report to the Urban District Council for 1904. 88 GEOLOGY OP NEWQUAY. into which the rain does not readily sink, but rapidly flows away The matter is further compUcated by the old mines and adits, which tend to drain many parts more quickly and thoroughly than would be the case under natural conditions. Besides this, the removal of the woods which once clothed the country must greatly have hastened the drainage, for an oak wood, even on a clay soil, parts with the water far more slowly than does an open field. It might be thought that the abandoned mines would be specially valuable as sources of supply, and this is sometimes the case. But, on the other hand, many of the mines jdeld waters contaminated by copper or lead, rendered undrinkable by iron, or containing an excess of lime. Over the areas where sandy strata occur at the surface, there is no difficulty in obtaining a supply of pure water of moderate hardness, and perennial springs are- often to be fomid. Throughout the area mapped as Meadfoot Beds springs are more uncertain and the water is usually hard. The water obtained from wells in the immediate neighbourhood of Newquay is objectionably hard, and contains a good deal of lime and chloride of sodium. An old mine-shaft on Mount Wise (deepened to about 167 feet), is used as a supplementary source for Newquay, when the supply from the main wells is insufficient for the town. * An analysis of this water made for the local authority by Mr. Benedict Kitto, dated 17th July, 1905, is as follows : — Chlorine - -' 5"6 Nitrogen (in nitrates) 'ISa Ammonia, free - '0028 Ammonia, albuminoid - "0021 Oxygen absorbed fromHn 15 minutes '010 Permanganate at 80°F./in 4 hours '019 Total solid matters in solution - 37 "8 Solid matters reduced by ignition to - 34"4 Poisonous metals - - absent Hardness - 9| degrees Appearance in 2 feet tube - good colour and clear The main sujpply of Newquay, however, is obtained from better sources, at Ruthvoes Tunnel, from an old disused mine ; and from an old mine adit near the Indian Queen. Both these sites are on the baked_ killas surrounding the St. Austell granite ; and each is about a mile east of the border of our map. In these altered rocks the lime is locked up in insoluble minerals, and the water is there- fore always much softer than that obtained from the calcareous slates. The character of this water is excellent, the following analysis of the combined waters by Mr.. Kitto having been made frdm a * The particulars as to the water-supply of Newquay have been" taken from information kindly communicated *y Dr. Hardwick, the Medical Officer of Health, and by Mr. Bullmore, the manager of the water company ECONOMICS. 89 saijiple taken from the discharge pipe, before emptying into the Reservoir at Quintrel Downs : — Chlorine - - - 1'95 Nitrogen (in nitrates) - -035 Ammonia, free - - 'OOIS Ammonia, albmninoid - •0017 Oxygen absorbed from\in 15 minutes '005 Permanganate at 80°F. Jin 4 hours "009 Total solids in solution - 7"2 Solid matters reduced by ignition to 5"2 Poisonous metals (lead and copper) - absent Hardness - _ - If degrees Appearance in 2 feet tube - good colour and clear Though scarcely belonging to the question of water-supply, the Holy Well which lies about three miles south-west of Newquay may be referred to here. This celebrated well will be found m a sea-cave at the northern end of Hoi well Beach, in the next cove beyond the mica-trap dyke. On entering the cave rounded bosses of tufa will be seen, and the deposition of this tufa has formed a series of shelves and small basins, which receive the water in succession as it overflows. This exceptional mass of tufa is derived mainly from the calcareous matter dissolved out of the wind-drifted shell-sand on the cliff above. Smaller masses of tufa are often to be found on this coast, but the slate alone seldom yields water so saturated with lime as to deposit it in this form. The supply of water at Holy Well is but small, and the water has no other properties than excessive hardness. St. Agnes is supplied with water from springs in the vicinity of Mount Hawke. This is pumped up from the vaUey to a tank on the high gi'ound behind the village, whence it is conducted by pipes. A certain amount of water is derived from an old adit running eastward from the Beacon by means of a shallow well which taps it at a short distance below the surface. At Perran- porth the Explosives Factory is making use of the cold water collected in the deserted mines in order to maintain a low temperature in dangerous processes. As a whole this part of the country is well watered, and there is no difficulty in obtaining good drinking water in wells, wherever they are sunk. Nevertheless, the supply is not so ample as to enable the inhabitants to look on the prospect of a long drought with indifference, as can be gathered from the fact that in 1887, a particularly dry suimmer, the whole of St. Agnes had to draw its supplies from one small spring near Wheal Butson. It is on occasions like this that the enormous accumulations in the old mines would be invaluable, were there some simple and inexpensive method of bringing the water to the surface. It is only necessary to walk along the cliffs north of St. Agnes to realise the amount of splendid fresh water which flows daUy into the sea from adits. The abundance of small streams in the deep coombes has proved to be invaluable to the miners, as thereby a constant 90 GEOLOGY OF NEWQUAY. supply of water is assured them for washing the ore preparatory to smelting. A few mills are also utiHsing this supply. Through the courtesy of Mr Hansford Worth, of Plymouth, seven analyses of St. Agnes water hare been sent from the Chemical Laboratory of the Municipal Buildings.* No. 1 is from the Wheal Trevaunance adit, to the north of the village ; out of 100,000 parts this water afforded 39 parts of solid matter ; there are 15-2 parts of chlorine. No. 2 is from the Gooninis adit, east of St. Agnes ; this water contains 21-9 parts of solid matter, and 10-6 of chlorine. No. 3 from Wheal Lawrence, near Chapel Forth, contains 207 parts of solid matter, and there are 55 parts of chlorine. No. 4 is from the same locality, and shows much the same proportions of chlorine. No. 5 is from Gover Well, near Mount Hawke ; it contains 1-5 parts of solid matter, and 9 2 parts of chlorine. No. 6 from Penhallow Well in the same neighbourhood shows 9-5 parts of solid matter ; there are 7-6 parts of chlorine. No. 7 is from Penhallow adit, and shows 11-4 parts of solid matter, and 7-6 parts of chlorine. There are two points in connection with these analyses which are of interest besides the proportion of carbonate of lime, namely, the high proportion of chlorine and the absence of poisonous metals", which might very well be expected in this district. In the analysis of the water from Penhallow adit No. 7, and also 5 and 6, it is expressly stated that special search was made for arsenic, copper, and lead, but no trace of any of them was found. The high proportion of chlorine shows that the influenpe of the sea makes itself felt for some distance inland, if, as it is' supposed, that is the source of this ingredient. Soils. Most of the area shows slate near the surface, but passing up- wards into shattered rock, which shades into head or soil. Over the plateau, however, a sheet of clay mixed with vein-quartz has accumulated, often to a depth of several feet. Whether the soil is open or impervious depends on the occurrence of vein-quartz or of thin grits, the slates themselves, even over the sandy areas, form a stiff soil. As most of the land is undulating, it is well drained, except over the flat valley-bottoms. The soil is fairly good, especially where mixed with the material from the igneous rocks. It is difficult at first to realise, however, how much depends on rainfall and moisture. The Cornish saying is true, that " the land can do with a shower every day and two on Sundays." A short period without rain suffices to parch the soil, for slope and im- pervious rock combine to shed the water very quickly. If Corn- wall had a climate like that of Essex, most of it would be arid waste. * These analyses have been deposited for reference in the Geological Survey Office. 91 APPENDIX I.. By D. a. MacAusteb. General Disteibtttion of the Mines. The principal mining district extends from Forth Towan through St. Agnes to Cligga Head and Perran Bay, and stretches for some distance inland. This area has yielded only tin and copper ores but has been pro- ductive in both (Fig. 1.) Chiverton and Newljm are noted for lead, silver, and zinc. In some parts outside these mineral centres there occur isolated Fig. 1. Sketch Map showing the distribution of the Minerals. mines, yrorked. mainly, fpr silver and lead. At the eastern margin of the map are tin mines, which belong to the St. Austell mineral area. In addition to these ores, iron has been raised, principally from the Perran Iron Lode. But although the bulk of the ore has been raised from this lode, iron is found also in other places, for instance, in Watergate Bay. The outputs of the mines -will be found in the table appended. 92 GEOLOGY OF NEWQUAY. The mines situated round the village of St. Agnes are almost exclusively tin producing, the principal being West Kitty, Wheal Kitty (both active), Polberro, Penhalls, Blue Hills, Wheal Betsy, Polbreen and Trevaunance The lodes of this district have a general bearing E. 26° N., but some of them strike in a more east and west direction, about E. 10°N. The lodes of Wheal- and West Wheal Kitty, Polberro, Trevaunanoe, Blue Hills, etc., have a characteristic low hade, some of them approaching a horizontal position. The county rock is, in some cases, ramified through with ore-bearing strings and veins, which have made it profitable to extract a considerable portion of the rock ; but generally speaking the lodes are narrow and rich. The remarkable tin and wolfram lodes of Cligga Head will be described later. Proceeding south-westwards from St. Agnes towards Porth Towan the lodes from being almost exclusively tin-bearing become productive in both tin and copper, while at Porth Towan the lodes were practically only worked for copper. The lodes in this district have a general southerly underUe and an average strike of E. 20° N. Between St. Agnes and Cligga Head is situated Wheal Prudence, a mine principally' wrought for copper ore. The lodes may be regarded as belonging to the series worked in the well-known Perran St. George and Wheal Leisure at Perranporth, striking E. 20°N. The mines situated on the dunes beyond Perranporth were mainly tin producing and have a bearing about E. 10°N. The Lead and Zinc Mines. — The lead lodes are thinly distributed over a comparatively wide area in the parishes of Perranzabuloe, St. Erme, St. Allen, and Newlyn. Among the principal lead and blende mines are those of West and Wheal Chiverton, the particulars of which are given in the de- scriptions of individual mines. On Newlyn Downs are the celebrated Mines Cargoll and'East Wheal Rose, the lodes of which have various directions. Half-way between these mines and Perranporth is Wheal Albert, the lodes of which have an east and west bearing. The other lead mines occurring in the region can be found by reference to the tables at the end of the section. Tlie Iron Mines. — See Perran Iron Lode in " Description of Individual Mines." Miscdlaneons. — At Wheal Trugo, near St. Columb Majdt, cobalt and bis- muth have been worked.* Gold has been found in detrital tin ore in streams of the parishes of Probus, Kenwyn, Ladock, etc. Faults and Cross Courses. — ^With the exception of the remarkable jointing at Cligga Head, the fissure systems of the St. Agnes district can be grouped under four heads according to the classification proposed by Mr. A. T. Davies.f Although there is no direct evidence that the lodes of tlus region are faults, there are good grounds for believing them to be related to the folded structure of the rocks, and it is probable that the actual fissures in which the minerals were deposited are fractures along lines of weakness determined by the structure. The miner in speaking of faults, however, refers to fissures formed subsequently to the lodes, and which cut across and dislocate them. Each district has its own peculiar terms in speaking of the various kinds of fissures, and in this region the word " gossan " has not the ordinary meaning, but is used for veins which underlie south, and strike in the same direction as the lodes. These veins consist mainly of quartz. As a rule these " gossans " are actual faults. Thus in West Wheal Kitty there are several gossans, the principal of them forming a natural boundary between it anJl the old Wheal Friendly on the north, and dislocating the West Kitty Main lode at the 84 fathom level. In a similar manner the north-underlying tin lodes of Polberro, Blue Hills, Penhalls, Seal Hole, North Seal Hole and Trevaunance are traversed by such gossans {see Kgs. 2, 3 and 4). • A. W. Tooke " Mineral Topography of Great Britain," Mining Review, 1836, p. 263. t " Heaves and Faults in the St. Agnes district," Rep. Roy. Corn. Poll/. Soe., 1889, p. 2. APPENDIX I. Fig. 2. Blue Hills Mine. 93 S. ^ Fig. 3. Blue Hills Mine. 'tO.rm Lewi. Fig. 4. East Blue Hills. V fraTT\,9Urfc S. 3^ N. orSO'fms. si- % • . ^ 4-0 finabeio>vAdJjL_ 94 GEOLOGY OF NEWQUAY. Both the lodea and gossans are traversed by the cross courses, which, according to Hen wood, have an average bearing in the district of N. 39° W, They are similar to those of other parts of the county and are fairly numerous, but certain of them are well known on account of the amount of faulting which accompanies them. Thus the lodes of East Wheal Leisure on the east side of Perranporth are the same as those in Great St. George and Wheal Leisure, but they are dislocated by a cross course which passes through the valley. A well-known cross course is that seen in the cUff of Perran Bay, north of Wheal Ramoth. It is known as the B3Ton Cross Course, and although it consists only of quartz and a little ferruginous material it is said further south near New Wheal Chiverton to be' a lead lode. A cross course in Blue Hills Mine traversing Trevellas Coombe dislocates the lodes several fathoms. There are several cross courses traversing Wheal Kitty and West Kitty in a direction roughly parallel to Trevaunanoe Coombe, which heave the lodes in varying amounts. The Wheal Golden and Penhale Lead lode and that of the Phoenix Mine are veins having the same general bearing as cross courses and must be regarded as such. Here and there the north and south lead lodes are seen to intersect most of the other lodes, and in origin it is difficult to separate them from this same system of fissures. Finally, there is another group of faults called " slides " which are generally regarded as being dislocations entirely subsequent to the other series of veins. There appears to be no direction particularly favoured by them, although in this region the bearing is generally in an east and west direction, more or less hke that of the lodes and gossans. As a rule, like the fluccans of other districts they do not contain minerals, . but consist mainly of clay with occasionally some quartz. Good instances of the complicated faulting which maybe effected by a combination of gossans and slides in a mine are those at Penhalls, Blue Hills, Friendly and West Pink, etc. In West Kitty there are two main slides which outcrop one on each side of Rejmolds Shaft. The more southerly imderlies south 33°, dislocating the lode 12 fathoms. The other underlies south 47°, dislocating the lode 12J fathoms; and joins the other sUde at about the70 fathom level. The total throw of the two slides is therefore 24J fathoms. Another slide further south in the same mine dislocates the lode 6 fathoms. It should be noticed that in some cases recent movements have taken place in the planes of the lodes, crushing and squeezing out the mineral contents and producing slickensides. Like the slides they were produced by comparatively recent movements of adjustment in the district. i Description of Individual Mines. Btjdnick, Wheal. — The mine yielded lead, copper and tin ores, but mainly the last. The lodes are partly in elvan and partly in kUlas. Tlie nature of the ore in the elvan has been described by Mr. Collins* who says that it con- sists of cassiterite, quartz and a green chloritic mineral in cracks; and as a cementing material in brecciated elvan. The following notes are from Henwood. Lead Lode. — Bearing E. 30° N. The lode varies in underlie from N.W 6° to N.W. 30° from the 34 to the 74 fathom levels and varies in width from an inch to 2 feet. The lode is partly in elvan and partly in slate and contains, in addition to fragments of these rocks; blende, galena aqd copper pjrrites. Some cassiterite also occurs The elvan is from 4 feet to 20 fathoms in width Gaunter Lode. — Bearing E. 35° S. At the 54 fathom level the lode varies from vertical to an underlie of N. 10° and is 2 to 4 feet in width. It is mainly in elvan and contains tin, blende, copper and iron pyrites and galena. Nmth Lode. — E. 35° N. At the 54 fathom level the lode is vertical to N. 10° and contains quartz and tin ore. * "Cornish Tinstones and Tin-capels,"JoMra. Min. She. 1880, p. 8. APPENDIX I. 95 Sovih Lode. — At the 54 fathom level the lode varies from J to 3 feet in width and consists of an irregular mass of dark blue slate and cassiterite. The lode which at Wheal Golden jdelded so much galena is seen in this mine striking in a north-westerly and south-easterly direction, but consists of quartz only. It is faulted 6 feet by the lead lode. Chiverton, Wheal — The lodes were worked under Chiverton House, which at one time was the Count-house of the mine. When the mine was abandoned the eastern part was poor, but westwards at the 78 and 86 fathom levels the ore ground was good.* The country consisted largely of yellowish soft shaley beds passing from a sand to fine conglomerate. CoaGA. — The face of the granite clifi which is 300 feet high is worked into by numerous drivages which were made by the " old men " in search of tin ore. The rook is traversed by a countless number of veins varying in width from a mere crack up to 6 inches or more, some of which are very close together. The county rock on either side of the veins is altered to greisen, the width of which depends to some extent on the size of the vein. The minerals oc- curring are wolfram, cassiterite, chalcopyrite and molybdenite and other rarer compounds. The lodes are not now being worked, but tin ore and wolfram are sometimes collected on the shore from rock fallen from the cliff. The most remarkable feature of the veins is the curved form they take, which was described by Sir C. Le Neve Foster as an anticline followed by a synoline. Foster regards the veins as shrinkage cracks similar to some of the veins in the Zinnwald. The curved form of the veins is due to the general shape of the granite margin and consequently of the cooling surface shortly after the intrusion of the granite, t On the cliff above and behind the granite mass mining has been carried on on a large scale. Wheal Coates. — The adit level of the mine is about 5 fathoms above sea level, and below this level the mine has not been much worked. The mine has been referred to by Henwood, Foster, Collins, Tweedy and others who make mention of the well known pseudomorphs of cassiterite after orthoclase. Foster says that in 1878 it was the Towanrath Lode which was being wrought. This lode strikes E. 24° N. and underlies S. 10° and is seen out- cropping in the cliff. It varies in width from 2 to 12 feet and consists of quartz with red and brown haematite in patches, and some clay. Most of the ore was derived from the small veins and strings of clay and tin ore in the killas varying from \ inch to 1 inch in width. The killas occasionally turned into a hard capel of quartz and schorl. The lode as a whole is an interlacing mass of tin veins averaging throughout about 1\ per cent, in black tin. Some of the veins are in soft decomposed granite or elvan and it was in one of these that the pseudomorphs occurred so plentifully. They were in a vein of an average width of 3 inches which owing to its sandy nature was called the sand lode. This decomposed rock was also aggregated into lumps in which tin ore was found. Mr. A. W. Tooke states that car- bonate of bismuth was found (see Fig. 5). Deerpabk Mine. — Situated on the part of the Perran Iron Lode nearly a mile east of Duchy Peru Mine. There are three lead lodes traversing thi sett as well as the iron lode. The lead contained on an average after smelting from Iff to 30 ozs. of silver a ton (see " Perran Iron Lode "). * H. C. Salmon. Mining and Smdting Mag, 1864. Vol. v. p. 272. t Remarks on some Tin Lodes. Trans. R. Oeol. Soc. Cornwall. Vol. IX. 1864-1878 ; and seeWso above pp. 40 — 46. 96 GEOLOGY OF NEWQUAY. Dbvonshieb, Wheal. — Situated in the group of mines between St. Agnes and St. Agnes Head. In the adit level an elvan is seen which is recognised as being the same as that in the Seal Hole Mine. Henwood states that the Cand Lode has a bearing B. 24° N. and underlies from 14° to 22° N. Fig, 5. Wheal Coates. S. Adit LerreJi 80rm. varying in width from IJ to 2 feet. At the 50 fathom level it consists largely of fluorspar but other minerals present are chalcopyrite, oassiterite and pjT^ites. DtrcHY Pebtt Mine. — Situated on the part of the Perran Iron Lode where it changes its strike from a direction E. 30° S. to E. 10° S. There are several workings on the back of the lode. The mine has been simk to a depth of 70 fathoms or 30 fathoms below sea level. For a depth of 20 fathoms from surface the lode, for a width of over 10 fathoms, consisted of brown haematite below which was a quantity of blende in irregular masses up to 6 or 7 fathoms in width in which galena also occurred. Below this at a depth of 40 fathoms from siu-face was a quantity of marcasite, while at the 50 the lode was all of chalybite. At the 60 fathom level the lode consisted of a breccia 10 or 12 fathoms width. The workings on the Peru Lead Lode are down to a depth of 50 fathoms. This lead lode is only a few inches in width but has yielded silver-lead ore containing 2,000 ozs. per ton in which part of the ore was native silver. At one time as much as 900 tons of zinc ore were raised per month {see " Perran Iron Lode "). East Wheal Chablottb. — The lode has a general bearing of 12° to 13° N. and imderlies S. 20° to 40°. It varies in width from 10 laches to 4 feet and consists of black copper ore with quartz and iron pyrites with fragments of the country rock at the 42 fathom level. ■ East Wheal Rose. — This mine was in the height of its prosperity about 1850. According to Henwood*, during twenty- two years of working, £799,600 were received for sale of ore, the costs and dues on which were £525,000. The junction of the lodes of Wheal Rose and Shepherds takes place in this nrine {fee Fig. 6). Good Foktttne Mine. — Part of the old St. George and Droskyq Mine situated near Chgga Head. The workings are almost entirely in killas, but an elvan traverses the sett. The main lode branches at the hauling shaft into north and south parts, called respectively the north and south lodes. At the 23 fathom level the south part is in elvan. Both lodes underlie north. * Address. Roy. Inst. Cornivall. Vol. IV. 1871 and 1873, p. 37. APPENDIX I., 97 The ore occurs in a lode a little over a foot broad of a strong gossany char- acter. Tin ore, copper pyrites and mispickel occur with much oxidized ferruginous matter. The mine is active. Fig. 6. EaRt Wheal Rose. ■> Uil / s ni / 13 «5 m \130fm. Gravel Hill. — Near the surface the ore is brown haematite, but near the adit it is a mixture of brown haematite and iron carbonate. At the 13 fathom level the lode is a mass of brown cellular iron ore about 9 fathoms in width (see " Perran Iron Lode"). Gbeat Retallack. — This mine was worked for iron, silver, lead and blende. The lode generally is several fathoms iu width and at the 60 fathom level it is said to be 240 feet wide, but this in aU probability is not a measurement taken at right angles to the lode. Near the surface the lode contained brown haematite and blende, the latter becoming of more and more importance with increasing depth. Below the 60 fathom level copper ore occurred. Near its intersection with the Peru lode it contained rich argentiferous lead ore. (See " Perran Iron Lode.") Gbeat St. Geobge and Wheal Leisitke. South Lode. — Bearing E. 5 ° N. From the 36 to the 46 fathom level the lode underlies S. 30 ° to 50 ° and varies in width from 2 to 5 feet. The lode consists of earthy brown iron ore, black and vitreous copper ore and iron and copper pyrites with quartz. Calloway's Lode. — Has an E. and W. bearing. From the 26 to the 46 fathom levels the lode underlies N. 45 to 60 ° and is 1 to 2J feet in width, consisting of quartz, iron and copper pyrites with purple and vitreous copper ore. Kernick's Lode. — Bearing E. 20 ° N. From the 26 to the 46 fathom level it underlies 8.4° to 50 ° and varies in width from J foot to 12 feet, consisting of quartz, copper pjTites, black and vitreous copper ore with iron pyrites and zinc blende. The lode is heaved 3 feet by a cross course* (see Figs. 7 and 8). Kitty, Wheal. — This mine is active. There are four distinct lodes in the sett, all of which underlie N. The most southerly is Pryor's Lode, the adit level of which is about 66 fathoms S. of Vottle Shaft. It varies in strike from E. 17 ° N. to E. 30 ° N. Li the upper levels it has an underlie of about 50° but gets flatter and flatter in depth until at the bottom of the mine (near the 180 fathom level measured on the underlie) it joins the Wheal * Henwood, Trans. Roy. Oeol. Soc. Cornwall. Vol. V. 1845. 8934, G 98 GEOLOGY OF NEWQUAY. Kitty Old Lodo and is here almost horizontal. The next is the Wheal Kitty Lode which strikes E. 32 ° N., the adit level of which is about 60 fathoms south of the Holgate Shaft. The two lodes are connected m the neighbour- hood of the New Shaft by a Gaunter Lode which is very nearly vertical and Fig. 7. Great St. George. Fig N. Great St. George. S. N. -^ // M fn-LLsy-el, strikes a few degrees E. of N. This lode has been extensively worked for tin ore, but contains in addition copper and iron p3Trites and blende. Further east, near Vottle Shaft, between the Wheal Kitty Old Lode and Pryor's there is another lode called Vottle Lode, which strikes E. 35 ° N., underlying N. about 1 foot in a fathom. It is intersected by the Vottle Shaft, has been extensively worked and contains quartz, chlorite, blende, cassiterite and copper pyrites. North of the Wheal Kitty Old Lode there is another, the upper part only of which occurs in this mine. It is known as the Wheal Pink Lode. The productive part of the lode in Wheal Kitty, known as the leader, varies from a soft peach to a highly quartzose veinstone included between smooth, slickensided walls. The lode is frequently accompanied by capel, which is a very much silicified slate traversed by lenticles of quartz which follow the contortion and gnarling of the slate, and by strings of quartz or tin ore. Wheal Kitty Old Lode varies in width from 6 feet down to a few inches and has an average of 18 inches to 3 feet. Accompanying the cassiterite, the produce of which is about 2J per cent, there occurs pyrites and blende while chalybite, apatite and fluor have been recorded. Wheal Kitty is on part of the site of the old Goonlaz and Pink Mines men- tioned by Pryce,* MoiTNT AND Teebisken. — The ore raised was mainly brown haematite and the workings were not carried sufficiently far to strike the spathic ore. The lode has been worked to a depth of 10 fathoms for a distance of about 200 fathoms, but although the lode is about 6 fathoms in width the best of it is confined to a width of 3 fathoms, the other three fathoms consisting of a breccia or killas and quartz cemented by iron ore. The iron lode is intersected by the TVebisken and Trebellan Lodes which contain sprigs of silver with galena.. At about 20 fathoms from the point of intersection with the Trebellan Lode a rich deposit of native silver with galena was found. Penhale and Baeton. — Situated near the Park of Mines sett. There is an elvan, 8 fathoms in width, on each side of which is a lode. Both elvan * " Mineralogia Cornubiensis," 1778, p. 107, APPENDIX I. 99 and lodes underlie south. The south lode varies in width from 1^ to 6 feet and carries tin ore. The north lode is about 5 feet in width and contains both tin and copper ore. There are also several tin bearing caunter lodes. The mine has been worked to the 80 fathom level. Penhale Iron Mine. — The lode is 60 or 70 feet in width and composed of red haematite which has been worked for a length of 70 fathoms and to a depth of 12 fathoms. It narrows down in depth to 4 feet below which it was sunk on for 8 fathoms, lead, blende and iron pyrites being met with {see " Perran Iron Lode " and " Gravel Hjll Mine"). Penhalls Mine. — The Pink Lode is the main lode of the mine and the old Pink Mine is part of the Penhalls sett. The main lode strikes about E. 35° N. and underlies N. 35° to 65°. Le Neve Foster described the character of the lode as seen at the 45 and 60 fathom levels.* The capel of the lode is killas altered into a dark quartz and schorl rook, these minerals being arranged in streaks along original lines of stratifi- cation of killas. In addition, the capel is fiiU of short lenticular veins of quartz intersected by numerous little strings of cassiterite and chlorite, and copper pyrites. The main part of the lode is a rich vein of cassiterite containing, in ad- dition to tin ore (some of which is " Toad's-eye " tin), quartz, chlorite and bismuthine. Alongside of this is a vein containing blende, tin ore, chlorite and iron p3Tites, on one side of which is a narrow vein of copper and a lode of quartz with tin ore. Mr. Collins has also described the veinstone, f The average produce of the mine in 1877 was 53 lbs. of black tin per ton {see Pigs. 9 and 10). Fig. 9. Penhalls Mine. N. /IcUX Fig. 10. PenJmlls Mine. S. N, Zci^e.l' // 50 Cm. Penwinnick Mine. — There are several lodes traversing the sett, including a copper lode supposed to be the Great Wheal Charlotte lode. The other * " Remarks on some Tin Lodes in the St. Agnes District," Trans. R. Oeol Soc. Cornwall, Vol. IX., 1864-1878. t " Tinstones and Capels," Min. Mag., 1880-1881. 8934. G 3 100 GEOLOGV OF NEWQUAY. lodes contain tin. The main lode bears E. 40° N. and underlies S. 8° to 22°, varying in width from an inch to 4 feet from the 22 to the 42 fathom level. The lode consists of slate, quartz and iron and copper pyrites. The mine has also been called Great West Kitty. Perean Ibon Lode. — This lode has been described by many writers, the principal of whom are Warington Smjrth,* Captain N. Bryant,t Mr. J. H._ Collins, J and Mr. Charles Parkin. § This remarkable lode is said to have been traced from the coast at Perran Bay eastwards to the parish of Grampound, a distance of 12 mUes, but it does not appear to have been seriously worked further east than Deerpark Mine, although the lode is of great width, varying from a few feet to many fathoms ; it is not very regular either as regards the distribution of the iron ore or in its general course from east to west. From the coast to the Duchy Peru Mine the lode has a bearing of E. 30° S., and from the Duchy Peru Mine eastwards the lode is nearly east and west. It has a general southerly underlie of 40° and has been worked to 70 fathoms from surface. The mines and trials situated on this lode, taken in order from the coast eastwards, are : — Gravel Hill (Penhale Iron Mine), Halwyn (shaft sunk to 20 fathoms from surface). Mount and Tribisken, Treamble, Great RetaUaok, Duchy Peru, Deerpark and Penhallow Moor (trial). The lode in addition to its great width is characterised by the large amount of brecoiated material which it contains, while in some places further evidences of the lode being a line of considerable disturbance is shown by the branches thrown off by it, as, for instance, in the eastern pit at Treamble, where several branches are thrown off north-eastwards. Some of the north and south silver-lead lodes which occur in the district are seen in a few of the mines situated on the iron lode. Thus the Wheal Golden and Penhale silver and lead lode is said to traverse the iron lode at the cliff. The lead lode (containing horn and native silver) of Wheal Mexico is seen in Treamble. There are lead lodes at Great RetaUack. The Peru and Wheal Hope lodes are seen in Duchy Peru. In Deerpark the Shepherds lode is seen and at Penhallow Moor the CargoU lodes. According to Mr. Collins, the minerals found in the Perran iron lode are brown ' and red haematite, chalybite, pyrites, melanterite, marcasite, zinc- blende, galena, chalcopyrite, native silver, argentite, cerussite, pyromorphite, pyrolusite, quartz, cassiterite (Duchy Peru), axinite, hornblende (Great Retallack), garnet (Gravel HUl). With regard to the quality of the ore, Mr. Charles Parkin states that there has been a good deal of prejudice against it owing to its siliceous nature near the eutcrop. From various published analysis the brown haematite contains from 68 to 78 per cent, of peroxide of iron. Erom 4 to 12 per cent, silica, and from -24 to 1-84 per cent, phosphoric acid. The spathose iron contains 51 to' 56 per cent, of protoxide of iron (EeO), 35 to 37 per cent, carbonic acid, -64 to 1-74 per cent. sOicia, and no phosphorus. An analysis of some first class ore gave 91-4 per cent, peroxide of iron, a little over 1 per cent silicia and -072 phosphorus with scarcely any Ume or magnesia, the rest of the contents being mainly moisture. Some of the ores contain magnesia, which renders the gangue easily fusible. Near the surface the ore is all oxide and frequently 'it is siliceous or mixed with cellular or cavernous quartz. At * Trans. B. Oeol. Soc. Cornwall, Vol. VII., 1858, p. 332; 013. cit Vol X 1882, p. 120. t 38th Ann. Rep. Roy. Corn. Poly. Soc, 1870, p. 99. J Rep. Miners Assoc. Corn, and Devon, 1874, No. XLIV. ; Journ. Boy Inst. Corn., 1892, p. 80. J North of England Institute of Mining Engineers, 1878, p. 131, APPENDIX I. 101 a depth of from 10 to 30 fathoms spathose iron ore makes its appearance, and the change from oxide to carbonate can be noticed in various stages, as some of the oxide masses are seen to contain nuclei of carbonate of iron and occasionally also a little iron pyrites. Zinc blende, occasionally brec- ciated, also occurs in the lode and was particularly plentiful in Great Retallaok. The brecciated part of the lode is generally a few feet in width ; the rest pf the lode consists of iron ore jdelding 50 or 60 per cent, of iron. In the cliff at Perran Bay the lode is in two parte — one consists of iron ore traversed by strings and veins of quartz about. 40 feet in thickness, and the other is iron ore mixed with quartz on either side, but fairly clean ore in the middle, about 15 feet. Between them the kiUas is 45 feet thick. PoLBBBRO. — The lodes in common with those of the rest of the neighbour- hood have the characteristic low hade. The following details are abstracted from Henwood. Pye Lode. — Bearing E. 30° N. Varies in underUe from 40° to 45° north, and at the 68 fathom level it is from 1 inch to 1 J feet wide, consisting of quartz, slate and cassiterite (and wood tin). The lode extends through into the Friendly and West Pink Mines. South Home £oie.— Bearing E. 28° N. Underlies south 60° to 80° and varies in width from 2 to 3^ feet, consisting of quartz, slate, oxide of tin and iron pyrites. This lode heaves the Pye lode'3 fathoms and is itself heaved 2 fathoms by the Eastern Cross course. Great Gossan ioie.^— Bearing E. 28° N. At the 68 fathom level it is 1 to 2J feet wide and tmderlies S. 30° to 40°. It consiste of quartz, earthy brown iron ore, and iron and copper pyrites. It is heaved 2 fathoms by the Eastern Cross course. Trevaunance Lode. — Bearing E. 30° N. At the 68 fathom level the lode is 10 inches wide to 1| feet and underlies N. 65° to 80°. It consists of quartz, slate (capel), oxide of tin, and 'iron pyrites. It is heaved 2 fathoms by the South House Lode and 2^ fathoms by the Great Gossan Lode. Much of the Trevaunance Lode is merely country rock traversed through and through with veins of tin ore. Toad's-eye tin occurs. South Branches. — E. 25° N. At the 60 fathom level the lode underlies N. 50° to 60°, and is 1 to 4 inches in width, consisting of quartz, slate and cassiterite. North Seal Hole Lode. — Bearing E. 25° N. At the 60 fathom level it is 2 to 3 feet in width and imderlies N. 12° to 30°. Consists of quartz, slate, earthy brown iron ore and copper and iron pyrites, heaved 9 feet by the Eastern Cross course (see Pigs. 11, 12, and 13). In Fig. 12 the shaded part represents the ground removed in working the lode. Fig. 11. PolherTo Consols. 102 GEOLOGY OP NEWQUAY. Fig. 12. Polhe'h-o. Fig. 13. St. Agnes Consols. Peimeose, Wheal. — Several lodes belonging to Polberro and Penhalls Mine pass through this sett. The Polberro main lode, underHes south and intersects the Pink Lode. In this mine the Pink Lode is characterised by the number of its branches and strings of tin ore which penetrate into the country rook. Mr. Collins states that the tin occurs as fine needles em- bedded in quartz and that the so-called silicate of tin supposed to be pseudomorphous after quartz are really quartz crystals filled with minute groupings of heavy opaque tin particles.* Pkttdbncb, Wheal. — Situated on the coast about 1^ miles east of Tre- vaunance Cove. The el van seen on the cUflf is the- same as that seen in Seal Hole Mine at Adit level. North £oie.— Bearing E. 35° N. Prom the 80 to the 110 fathom level the underMe varies from N. 10° to N. 22°, and the width from 6 inches to 2 feet. The lode consists of quartz, slate, copper and iron pyrites with some blende and, cassiterite. An elvan 10 fathoms in width dipping N. 45° is seen at the 110 fathom level. The lode is heaved 9 feet by a cross coiirse. * « Tinstones and Capels," Min. Mag., 1880-1881, p. 115. APPENDIX L 103 SorahLode—Be^Ting E. 30% N. From the 47 to the 110 fathom level the lodeimderhes S. 5° to S. 22°, and varies in width from IJ to 10 feet It consists of quartz, fragments of slate, iron and copper pyrites, and blende and a httle cassiterite. OaunlerLode-Be^Tmg E. 20° S. At the 47 fathom level the lode dips b. 5 to 10 and is 1 foot to 18 inches in width. The lode consists of quartz, copper pyrites, etc. (Henwood.) (See Pigs. 14 and 15.) Fig. 14. Wheal Prudence. Fig. 15. Wheal Prudence. South Polbeeeo.— The mine is bounded on the West by Great Wheal Charlotte and on the east by Polbreen. The Dorcas lode of Polbreen Mine 104 GEOLOGY OF NEWQUAT. passes through the sett and the lodes generally have proved productive in their upper levels. The killas is full of strings of tin ore. Treamblb.— Situated between Great Retallack and the Mount Mine. There are two open works on the iron lode. A lead lode belonging to the E«tallack Mine crosses the iron lode and at the junction galena was proved to occur to a depth of 7 or 8 fathoms. In 1873 the iron lode was opened to a depth of 17 fathoms. The ore near the surface for a width of about 6 fathoms was a hard compact brown iron ore of inferior quaUty, but in depth was spathic. (/See "Perraji Iron Lode.") West Chivekton.— This mine in 1864 was yielding a profit of £1,000 a month. There are three lead lodes, all underlying south. Blende occurred in the lodes in addition to galena. The lodes have a general bearing of E. 27° N. William's Lode.— Ks-wkes Shaft, which is sunk vertically to the 80 fathom level, crosses the main lode at the 70. In the upper levels the lode was quartzose, and in general il is large and carries ore throughout. The workable ore ground at the 40 fathom level, was 30 fathoms in length while at the 50 it it was 60 fathoms long. Valpy's Lode. — A branch of William's Lode on the south side. It strikes off from the main lode at the 50 fathom level in a downward direction. It is said to drop into William's Lode again at the 90 or 100 fathom level. The lode is more compact than William's. Elizabeth's £orfe.— Situated north of WiUiam's Lode. It is of a more flucoany (clayey) character, and contains rich silver lead ore.* West Kitty. — This mine is one of the most profitable at present working in Cornwall. It is situated on the western side of the Combe, which runs from PetervUle to the sea, and-has lately taken in the old Wheal Friendly sett. The West Kitty Lode extends eastwards into Wheal Kitty, where it is known as Pryor's Lode. In the northern part of the West Kitty sett Reynolds shaft intersects the Rock Lode, which underlies north at about 15° from the ver- tical. Another lode called the Top Lode Kae been intersected at adit level by Thomas shaft. It has a northerly underlie of about 60°, and is not of much value as yet. The country rock of the mine is entirely kiUas, which is a fine- grained clay slate, varying from a black carbonaceous rock to a light-coloured spotted slate with well pronounced cleavage. There are several systems of fissures traversing the mine, and this has led to a classification of them. West Kitty Lode. — The underlie of the lode is 65°, near the 60" fathom level, but beyond this the lode gets much flatter, and is practically horizontal in the furthest workings. . The productive part of the lode is confined to a persistent leader generally carrying quartz and soft blue peach, and varying in width from an inch or 80 to 2J feet. The leader is sometimes hard and quartzose, but the richer parts are generally oeEular or drusy. A typical specimen of the rich ore is to be seen in the Museum at Jermjnn Street. It consists of a mass of well formed oassiterite crystals with quartz. When such rich ore occurs it is simply prized out with a drill or crowbar and saved on a piece of sacking or a mat. The capel is frequently well developed, and is similar to other capels of the district (Wheal Kitty, Penhalls, etc.) A little copper ore occurs, but only a few tons are sold annually. Sulphide of tin and^copper has been recorded from Wheal Rock (part of West Kitty) (see Fig. 16). * Salmon, Mining and Smelting Magazine, vol. v., 1864. APPENDIX I. Fig. 16. West Kitty. 105 L&KcL West Pink Mine. — The mine comprises the old Friendly and Primrose Mines. The following notes are abstracted from Henwood's description. The Tin Lode varies in width from 1'5 to 5 feet and in underlie from N. 38° to 68°. The lode consists of quartz, slate, copper and iron pyrites, tin stone, fluor spar. The lode is heave between the Friendly and Primrose Mines, a distance 40 fathoms, by the Gossan Lode. Carrow Gossan Lode. — Bears E. 22° N., and from the 25 to 66 fathom level it underlies S. 14° to 28°, and varies in width from 1 to 2 feet. The lode con- sists of quartz, earthy brown iron ore, and iron and copper pyrites. It heaves the tin lode 7 fathoms. Or eat Gossan Lode. — Bearing E. 25° N. in the Friendly part. At the 90 fathom level the lode underlies S. 10° to 20°, and is 2J to 3 fathoms in width, consisting of brown iron ore, quartz and clay. Lead Vein. — In the Primrose part this lode has a bearing N. 20° E. and from the 26 to 69 fathom level underlies E. 1§° to 26°, varying in width from 4 inches to IJ feet. It consists of quartz and galena (see Kg. 17). Fig. 17. Friendly and 'Wheal Pink Mines. 106 GEOLOGY OF NEWQUAY. Miscellaneous Ceoss Sections. Fig. 18. North Wheal Ghiverton. Fig. 19. TrewoUach Mine. N. |i |l>^ S 4ar . E*ST PART or MINE Fig. 20. Perran United. Fig. 21. Wheal Frederick. Fig. 22. Wheal Liberty. Fig 28. Cam Perran. ll^ N. -30/m. APPENDIX I. 107 List of Mines Situated in 1-inoh Sheet 346. Mino. Parish. I Mine. Parisli. Albert, Wheal. Perranzabuloe. Liberty, Wheal. St. Agnes. Betsy, Wheal. St. Agnes. Mary, Wheal. Perranzabuloe. Blue Hills Mine. »j Metha Sett. Newlyn. Budniok Mine. Perranzabuloe. Morganna Mine. St. Columb *Bungay, Wheal. St. Agnes Minor. Burrow and Butson. 3, Mount Mine. Perranzabuloe. Callestock Vean. Perranzabuloe. New Chiverton. »> CargoU Mine. Newlyn. New Wheal Char- Carn Kief. Perranzabuloe. lotte. St. Agnes. Charlotte, Wheal. St. Agnes. New Kitty. „ Charlotte United. ,, New St. Agnes. jj Chiverton Mine. Perranzabuloe. North Blue Hills. ,, Chiverton Moor Mine • North Budniok. Perranzabuloe. ChivertonWhealRose . Crantock North Kitty. St. Agnes. Coates, Wheal. St. Agnes. North Retallack. Perranzabuloe. Coit, Wheal. ,, North Wheal Rose. Newlyn. Constance, Wheal. Newljm. North Seal Hole. St. Agnes. Creeg, Wheal. Perranzabuloe. North Towan. j» Deerpark Mine. Newljrn. Ocean, Wheal. Devonshire, Wheal. St. Agnes. Penoorse Consols. St. Enoder. Duchy Peru Mine. Perranzabuloe. Penhale Mine. Perranzabuloe. East, Wheal. ,, Penhale Moor Mine. St. Enoder. Bast Blue Hills. St. Agnes. PenhaUow Moor Mine. Newlyn. East Budnick and Penhalls Mine. St. Agnes. Mount. Perranzabuloe. Penwinniok. ft Bast Wheal Char- Perran United. Perranzabuloe lotte. St. Agnes. Perran St. Gteorge. >> East Chiverton. Perranzabuloe. Perran Consols. j» East Wheal Fortune. Peru Mine. East Wheal Leisure. / Phoenix Mine. Perranzabuloe. East Polberro. St. Agnes. Pink, Wheal. St. Agnes. East Wheal Rose. Newlyn. Polberro. St. Agnes. Prances, Wheal. Perranzabuloe. Polbreen. »» Freedom, Wheal. St. Agnes. Polglaze. Perranzabuloe. Friendly, Wheal. »» Prince Royal Mine. jt Friendship, Wheal. Perranzabuloe. Prince Albert Consols. ,, Garras, see Gwarniok Primrose Mine. St. Agnes. Golden, Wheal. Perranzabuloe. Providence, Wheal. »j Good Fortune Mine. ») Prudence, Wheal. 't Goonhavem. J) Ramoth, Wheal. Perranzabuloe. Gooninis. »j Reen, Wheal. »j Gravel Hill Mine. >» Rock, Wheal. St. Agnes. Great Callestock Rose, Wheal. Perranzabuloe. Mine. )3 Seal Hole Mine, see Great Retallack. North Seal Hole. Great St. George anc Shepherds. Newljfn. Droskyn. ,, South Great Chiver- Gwamick. St. Allen. ton. Perranzabuloe. Halwyn Sett. Perranzabuloe. South Wheal Leisure »» Hope, Wheal. »> South Polberro. St. Agnes. Jane, Wheal. »j South Wheal Rose. St. Enne. Kitty, Wheal. St. Agnes. Toleame Mine. St. Columb. Leisure, Wheal. Perranzabuloe. Minor. 108 GEOLOGY OF NEWQUAY. List of Mines Situated in i-inch Sheet 346- Mine. Parish. Mine. Treamble. Trebellan. Trebisken Mine. TrefuUock. . Treslow. Trevaunance, Wheal. Trevellas Downs. TrewoUaok Mine. Tniro Consols. Virgin, Wheal. View, Wheal. Perranzabuloe. Cubert. >) St. Enoder. Perranzabuloe. St. Agnes. St. Agnes. St. Columb. Minor. Perranzabuloe. Parish. Wentworth Consols. „ West Polberro. St. Agnes. West Chiverton. Perranzabuloe. West Wheal Hope. „ West Kitty (formerly Wheal Rock). St. Agnes. West Pink, see Friendly and Primrose Mines. West Polbreen. „ Widden, Wheal. Perranzabuloe. APPENDIX I. 109 List op Mines gbouted according to the Parishes in WHICH they are situated. Sheet No. 6-inch Map J Sheet. No. of 25-incli Map. Crantock, Parish of : * Chiverton Wheal Rose XXXIX. N.E. 3 Cubert, Parish of : Trebellan Mine XXXIX. S.W. 14 TrebiskenMine' XXXIX. s.w. U Newlyn, Parish of : Cargoll Mine XLVIII. N.E. 8 Constance, Wheal XLVITL N.E. 4 Deerpark Mftie XLVIII. N.E. a East Wheal Kose XLIX. N.W. 1 Metha Sett - XL. S.W. 13 North Wheal Rose - XLIX. N.W. 1 Peiihallow Moor Mine XLVIII. N.E. 4 Shepherds XLVIII. N.E. 8 Perranzabuloe, Parish of : Albert, Wheal XLVIIL N.E. 7 Budnick Mine (and Rose) XLVIII. N.W. Callestook Vean XLVIIL S.E. n Chiverton (or Cornubian) Mine XLVIII. S.E. 15 Creeg, Wheal, see Wheal Vlow. Cam Kief XLVIIL S.W. 10 Chiverton Moor Mine - *- XLVIII. S.AV. 14 East Chiverton, part of Chiverton. East Wheal Lfeisure Deerpark Mine, see Parish of Newlyn. Duchy Peru Mine XLVIII. N.E. 3 East, Wheal, see St. George Mine. East Budnick and Mount XXXIX. S.W. 14 East Wlieal Rose ,• XLIX. S.W. fl Frances, Wheal XLVIII. S.E. 11 Friendship, Wheal Golden, Wheal XLVIIL S.W. 9 XXXIX. S.W. 9 Good Fortune XLVIII. N.W. 5 Goouhavern - XLVIII. S.E. 11 Gravel Hill Mine (formerly called Pen- hale Iron Mine) XXXIX. S.W. 10 Great Callestock Mine - Lvn. N.W. 2 Great Retallack XLVIIL N.E. 3 Great St. George and Droskyn XLVIIL N.W. 5 Hahvyn - XXXIX. S.AV. 14 Hahvyn Sett XXXIX. S.W. 10 Hope, Wheal - xLvni. N.W. 2 Jane Wheal - XLVIII. S.W. 9 Leisure, Wheal XLVIII. N.W. 5 Mary, Wheal XXXIX. S.W. 14 Mount Mine XXXIX. S.W. 14 New Chiverton Mine XLViir. S.W. 10 North Budnick, see Wheal Vlow. North Retallack - XLVIII. N.W. 2 Penhale Mine - XXXIX. S.W. 13 Perran United XLVIII. N.W. 5 Perran St. George Mine - XLVIIL N.W. 5 Perran Consols, see Wheal Vlow. Peru Mine XXXIX. S.E. 15 110 GEOLOGY OF NEWQUAY. List op Mines grouped aoco'eding to the Parishes in WHICH THEY, ARE SITUATED — continued. No. of Sheet No. 6-inoh Map 25-inoh \ sheet. Map. Phoenix Mine « XXXIX. s.w. 10 Polglaze or Treslow xLviir. S.W. 9 Prince Royal Mine - XLvm. S.w. 9 Prince Albert Consols see Wheal Albert. Kainoth, Wheal XLVIII. N.W. 1 Been, Wheal XLvm. N.W. 2 Rose, Wheal - XLVIII, N.W. 2 South Great Chiverton XLVIII. S.W. 15 South Wheal Leisure XLVIII. s.w. 9 Treamble Mine XLVIII. N.W. 2 Treslow, see Polglazp. • Truro Consols, see South Wheal Leisure. Virgin, Wheal Lvn. N.W. 9. Vlow, Wheal XLVIIL N.W. 2 Wentworth Consols XLVIII. S.E. 15 West Chiverton Mine XLVIII. s:e. 15 West Wheal Hope XLVIII. N.W. 2 Widden, Wheal XLVin. N, W. 1 ,S7. Agnes, Parish of : Betsy, Wheal XL VII. S.E. 12 Blue Hills Mine xLvn. S.E. 12 Bungay, Wheal XLVIL S.E. 15 Burrow and Butson, Wheal LVIL N.W. 1 Charlotte, Wheal - LVI. N.E. 3 Charlotte United LVI. N.E. 3 Coates, Wheal LVI. N.E. 3 Coit, W^heal - XLVIL S.E. 16 Devonshire, Wheal XLVIL S.E. 15 East Blue Hills XLVIL S.E. 12 East Wheal Fortune XLVIIL S.W. 9 East Wheal Charlotte - LVI. N.E. 3 East Polberro, see Wheal Betsy. Friendly, Wheal XLvii. S.E. 16 Freedoin, Wheal LVI. N.E. 3 Gooninis - XLVII. S.E. 16 Kitty, Wheal - XLVII. S.E. 16 Liberty, Wheal New Kitty XLVIL S.E. 16 New St. Agnes XLVII. S.E. 16 New Wheal Charlotte North Seal Hole Mine XLVII. S.E. 15 North Kitty - XLVII. S.E. 16 North Blue Hills XLVII. S.E. 12 North Towan LVL N.E. 3 Ocean, Wheal Penhalla Mine- XLVII. S.E. 16 Penwinniok LVI. N.E. 4 Pink, Wheal XLVI. S.E. 16 Polberro Mine - XLVII. S.E. 16 Polbreen Mine XLVII. S.E. 16 Prudence, Wheal XLVIL S.E. 1-2 Providence,Wheal XLVIII. S.W. 9 Primrose, Wheal XLVII. S.E. 16 Rock Wheal, see West Kitty. Seal Hole Mine, see North Seal Hole. South Polberro XLVIL S.E. 16 APPENDIX I. Ill List oi Mines geouped according to the Parishes in WHICH THEY ARE SITUATED — continued. Treslow, see Polglaze, Parish of Perran- zabuloe. Trevaunance, Wheal Trevellas Downs West Pink, see Friendly and Primrose Mines. West Polberro West Polbreen West Kitty St. Allen, Parish of : Gwamick Mine (formerly the Garras) St. Erme, Parish of : Cargoll Mine • South Wheal Eose St. Enoder, Parish of : Pencorse Consols Penhale Moor Mine TrefuUock St. Colomh Minor, Parish of : Morganna Mine Tolcarne Mine Trewollaek Mine Sheet No. IXLVII. XLVII. XLVII. LVI. XLVII. XLVIII. XLVIII. XLIX. XLIX. XL. XLIX. XXXIX. XXXIX. XL. 6-inch Map J sheet. S.E. S.E. S.E. N.E. S.E. S.E. N.E. N.W. N.W. S.E. N.E. N.E. N.E. N.W. No. of 26-lnch Map. 15 12 15 4 16 16 2 15 3 112 GEOLOGY OF NEWQUAY. Mineral Statistics. I. Output of copper ore and copper from 1815 to 1904 and OF black tin from 1852 TO 1904. These statistics are compiled from records of annual sales published in the Transactions of the Royal Geological Society of Cornwall ; OryU's Annual Mining Sheets ; General Reports and Statistics prepared by the Home OfSce ; The Miners' Manual, by Phillips and Darlington, and from other publications. The Returns prior to 1882 are approximate only, so that the figures representing the total output of minerals for years before 1882 should 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 differ according as the returns were made by the Stannaries, Public Tioket- ings, or Inspectors, etc., but much of the ore was sold by private contract, and such sales were not recorded. In addition to this, statistics for a number of the early years are unprocurable. The sales of ore from stream works are not included. For information relating to the total sales of tin and copper in Cornwall, and the prices of these metals, the reader is referred to the Memoir on Sheet 352 (Camborne and Falmouth). Note. — In the following table, when two figures occur, one above the other, the larger is the total yield for the period stated, while the smaller is the largest output for any one year during that period. Name of Mine. C°PP':'- : copper Remarks, Betsy, Wheal Blue Hills - Budniok Consols anil Budnick Mine Cam Perran CargoH Mine Charles, Wheal - Charlotte, Wheal Coates, Wheal - Coit, Wheal Coit, Wheal, and Friendly Devonshire, Wheal Duchy and Peru East Blue Hills - East Budnick East Wheal Cliarlotle East Wheal George East Wheal Leisure East Polberro East Wheal Rose Tons. 95 2,020 142 1,100 263 700 101 340 310 10 Tons. I Tons. In 1839 and between 1856 and 1861. Between 1870 and 1896. 200 i 35 Copper between 1832 and 1834 ; tin in 1837, 1838 and 1839, arid between 1866 and 1904. 800 ; 50 Between 1844 and 1847. 315 55 Between 1864 and 1871. 4,360 285 Between 1821 and 1834 (Phillips and Darlington). 23,010 1,950 Between 1820 and 1856 (Phillips and Darlington). 335 30 j In 1839 and between 1861 and 1889. Between 1855 and 1875. In 1885. 35 i 2 In 1832 and 1833. 185 6 In 1862. Between 1881 and 1893. Between 1888 and 1892. 90 6 ! In 1828, 1829 and 1862. 450 32 ! In 1853, 1854 and 1855. 700 35 I In 1833 and in 1851 and 1852. In 1863 (see Wheal Betsv). 160 20 In 1850 and 1851. APPENDIX I. 113 I. Output of coppee ore and copper from 1815 to 1904 and OF BLACK TIN FROM 1852 TO I90i— continued. Name of Mine. Black Tin. Copper Ore. Copper. Remarks. Tons. Tons. Tons. Friendly, Wheal 440 160 16 Tin between 1855 and 1895 ; (Friendly Mines) 39 Copper between 1823 and 1825. Good Fortune - 45 4 Between 1900 and 1904, Great Wheal Charlotte 2,800 200 Between 1834 and 1836 and in 1838 and 1840. Great St. George and Droskyn 80 71,000 4,650 Copper ore yielded between 1824 8,055 480 and 1838 in ] 839 and 1840; black tin between 1886 and 1894. Phillips and Darlington state that 73,705 tons of ore containing4,909 tons of copper were sold Letween 1815 and 1810. Great Wheal Leisure 27,400 l,36o Between 1832 and 1836, and in 7,479 370 1852 and 1853. Kitty, AVheal 6,780 (?) 950 90 Between 1853 and 1904. 239 115 10 Leisure, Wheal - 29,900 2.870 Between 1829 and 1832 and 9,627 782 in 1840. See Great Wheal Leisure. Phillips and Darling- ton state that 51,807 tons of ore containing 3,549 tons of copper were sold between 1827 ar.d 1810. Liberty, Wheal - 700 32 In 1835, 1836 and 1837. New Wheal Charlotte 3 In 1870. New St. Agnes - 1 25 3 In 1877. North Hallenbeagle - 65 5 In 1862 and 1863. North Seal Hole 1,740 130 Between 1815 and 1827. Phillips and Darlington state that 2,030 tons of ore containing 147 tons of copper were sold between 1821 and 1828. Penhale, Wheal 100 8 In 1849. Penhalls 3,610 234 25 3 Between 1859 and 1884. Penwinniok 630 40 Between 1832 and 1834. Phillips and Darlington state that between 1831 and 1833, 673 tons of copper ore containing 41 tons of copper were sold. Perran Consols 220 Between 1869 and 1874, 3 tons in 1894 and 1895. Perran, Wheal 20 3,200 2C0 Black tin between 1862 and 1864 ; copper between 1834 and 1842. Perran and Great Wheal Leisuie 4,550 2,799 145 83 In 1851 and 1855. 8934. H 114 GEOLOGY OF NEWQUAY. I. Output of coppeb, oee and copper from 1815 to 1904 and OF BLACK TIN FROM 1852 TO IQQi— continued. H&me of Mine. Black Tin. Copper Ore. Perran St. George Perran United Perran Wheal Virgin Polberro Polbreen (New Wheal Kitty) Primrose Mine Prince Albert Consols Prince Royal Prudence - Pye, Wheal Ramoth (and Ramoth Barrows) Reen, Wheal Rook, Wheal Rose, Wheal Rose United St. Agnes Consols St. Enoder Consols - St. George South Charlotte South Prudence Towan, Wheal - Trevaunance, Wheal Trevaunance Consols Trevaunance United - Trugo Tywarnhayle Turnavore - - - Vlow, Wheal (North Budnick) 16 4,300 520 52 10 5 1 10 4 'l2 305 15 100 20 45 550 36 510 Copper. Tons. 32,125 3,775 7,700 2,785 4 1,055 250 45 160 7,000 513 100 1,100 6.360 2;357 220 530 350 26,100 1,160 800 43 32,400 6,500 10 120 1,800 230 250 87 i 60 15 11 400 24 5 70 435 149 12 25 30 1,465 53 60 2i 1,745 380 Kemarks. Between 1845 and 1860. Phillips and Darlington state that 30,398 tons of ore con- taining 1,724 tons of copper were sold between 1845 and 1856. From 1853 to 1857. In 1871. In 1837, 1838, and 1839, and from 1849 to 1895. Black tin in 1839 and between 1858 and 1887 ; copper in 1829 and 1836 and 1840. In 1822. In 1853 and 1854. Tin in 1887 ; copper in 1826. Copper between 1821 and 1865 ; tin between 1874 and 1879. In 1837. In 1861, 1879, 1882, and 1902. In 1832 and 1836. From 1815 to 1822 and 1833 to 1835. Phillips and Diirlington state that 1,493 tons of ore containing 84 tons of copper were sold between 1820 and 1835. Black tin in 1867. Between 1873 and 1835. Copper in 1846 ; black tin in 1872, 1873, and 1875. In 1838. In 1815 and 1816. In 1852, 1855, and 1859. In 1882 and 1885. Between 1815 and 1835. Between 1861 and 1883. Between 1843 and 1844. In 1884 and 1887. In 1881. Between 1848 and 1869 ; a little in 1903. Phillips and Darlington state that 21,726 tons of ore containing 1,264 tons of copper were sol 1 between 1848 and 1856. In 1857 and 1858. In 1864, 1865, and 1866. Appendix i. 115 I. OtiTPUT OF COPPER OKE AND COPPKR FROM 1816 TO 1904 AND OF BLACK TIN FROM 1852 TO 190i— continued. Name oJ Mine. Black Tin. Copper Ore. Copper. Kemarks. Tons. Tons. Tons. Valley, Wheal 270 15 In 1826. West Budniok 5 Between 1878 and 1882 and in 1904. West Chiverton 16 1 In 1874 and 1876. West Kitty - 8,190 467 121 12 Between 1863 and 1904. Sett adjacent to West Kitty - West Pink 180 Between 1887 and 1890. 280 15 Between 1832 and 1835. West Poberro 10 205 10 Between 1855 and 1859. West Polbreen 10 Between 1872 and 1889. West St. George 220 10 In 1867 and 1868. 116 GEOLOGY OF NEWQUAY. a 03 O t-i N ■i •—* "n a 5 0)^ 00 CO "o . * — Id HI t44 00 0) OO til ;-( tS -'-Q i ^H o TS .t3 -Td 13 a ^ > 0) c5 CO ^(M C-l ^ 2 en n;:S 00 CO e ^^. □ »''!i^ 0) tr~ 1? -* :3 ■f. oo g: f. 00 r^ M tiipq m 3Ph a^ aij3 e ^*J ■" .2 fl 'rt -iJ o . n H u CO do oj , 00 p o JD -j-t; ft c) rt S ^ s ^ a; 0) o ^ .2 ■* o e tio (M cd cd o S^ ^ o o pT w Ph o o Q !zi 00 o t-H 1 CD05 •y\ CO I I I OICC OfMOlOOOXOCO (M -* O — 1 1:^ o ■* to -^ I M otT-s'io' (yTrtco'cM" £ H & o I 050iH r-H QO 00 OW30^00XlC100rH 0(M oooco i-H oo (30 «oo Ol— 03inO(MOiHOCi5 if5(MfOO»^'^-«*cqo QOCOrHlO r^ CD{>)W3 !2i a ffl T! ' a N1 fc O ;:^ o n t4 tin s crt rl MOO a o ■e ;a o a o o ^ o oo f-i c fci 2^ on APPENDIX I. 117 ■^ i:.5M -: P5 fl el a 0} v 9i 03 (D V V 00 fe ^ p; ■^ -U -*i +3 -, a> a:> 0) CD - 'qj go rt oj g 'O.-e 3 5 rt C t t- 00^ £ Td o (B -4^ N (U A O^ J ^ rH miUS -=-^5 J3 S.2 2 •s ram. ofm ore 1 8 owt lead, tive si from lode ran G e. **-< 03 n:3 > *j 2 od o 2 s^l-^-s^S ton 000 spatl hydr 9 « 5i: o 1 S 1 J § „ a :S o ts oja S CO SB ^^ U -»:> I— 1 -*>m >-H 1— I I III I I MM I 0(N 1 1 O lA 1 1 TPtD 850 609 O0)O« 1 1 S) lOtoS I:~IM oto (NOO 0(N I I I I I I III MSI I I I I I' fsrl O C ^ ce ^ CS '3 cd Id a Tt< 3 00 CO £ PCD OS lO 'J T3 CO ^ CD TJH lO o © tH ■* w -1^ >, t~- 00 GO 00 OjCO 00 00 w oo S a .S . cj C B CO 1— t c I-H o w o I-H a I-H © oc ^ ^ 05 © CO S'S © a) © CO CD t^ a s S l-~. ■^ ^ CD © t-- +3 o ■5 © c © o ^ CDCD lO p ^ 00 1-H sa 25 00 -5 2 ^ -u 5 5 2^ I-H 00 aooo o ^ lO I-H t~ E- « -^ CD CO 1 1 1 IT- 1 1 1 1 1 1 1 o CI 0(N rH 1 1 1 1 1 1 1 1 1 1 t> O .9 H tS] o o o to OO o lO oo o oc OO t4* t^% 1 I ^-^ 1 IC CD IQ CM 1 1 1 1 1 00 CO ? 1 1 CDOJ 1 «DCT 1 -( -* OiOS 1 1 1 1 1 Bl i;^ o^ CQCO ofio cc t-^CM'cM m T~^ • O O H«»0 ITS ifS ■<* O ■* ^_, O 00 u^ o o r*> o^oOi O -d l'^^ Tt • m 1 "o tn a g f ID 13 .b 2 ;g .g-s 1^ ^ © 1^ 1 i 1 CO 1 § o Si 'eg ai ©(HO O OS o 1 o 3 ^ ^ ^ M (4 © © © s n a Q^ V m ^CLia; APPENDIX I. 319 s -Sill l-^^^B- cilt'"'^- '^ CO 00 C CO a S '*'-5 Ed ^?2„'^° ^ C-rt ^ a o oS ^ a S^ 6^-s -F js w a . . f pi s » o o ^ .-a e 5 > ^ 3 1 "-S o 1 2 ffiO PM S^« a H ^ 120 APPENDIX II. List of Peincipal Works on the Geology of the District. 16V5. Anon. The Improvement of Cornwall by Sea Sand. Phil. Trans., vol. x., p. 293. 1 758. BoELASB, E.EV. W. The Natural History of Cornwall. Fol. Oxon. 1817. CoNYBEAEE, J. J. Memoranda relative to the Porphyritic Veins, etc., of St. Agnes, in Cornwall. Trans. Geol. Soc, vol. iv., p. 401. 1820. Sedgwick, A. On the Physical Structure of those I ormations which are immediately associated with the Primitive Eidge of Devon- shire and Cornwall. Trans. Cambridge Phil. Soc, vol. i., p. 89. 1829. Oeynhausen, K. von, and H. von Dechen. On the junction of the Granite and the Killas Kocks in Cornwall. Phil. Hag. and Annals, ser. 2, vol. v., pp. 161 and 241. 1830. Anon. Mineral Pitch near St. Agnes. Edinburgh Journ. of ScL, ser. 2, vol. ii., p. 374. 1832. Davey, S. Notice on the Pseudomorphous Crystals of Oxide of Tin found in Huel Coates Mine, in St. Agnes, in the year 1828. Trans. Roy. Geol. Soc. Corn., vol. iv., p. 484. Hawkins, J. On a very singular deposit of Alluvial Matter on St. Agnes Beacon, and on the Granitical Rock which occurs in the same situation. Trans. Roy. Geol. Soc. Corn., vol. iv., p. 135. 1838. Henwood, W. J. Granite of Cligga Head, and the Elvan Course of the same neighbourhood. Wth Ann. Pep. Roy. Inst. Corn., p. 29. 1839. De la Beche, [Sir! H. T. Eeport on the Geology of Cornwall, Devon, and West Somerset (Geological Survey). 8vo. London. 1343. Henwood, W. J. On the Metalliferous Deposits of Cornwall and Devon. T'rans. Roy. Geol. Soc. Corn., vol. v., p. 93. 1844. Whitley, N. Notes on the Geology of the neighbourhood of Perran Porth, with a map and sections. 25(<, 100, 107, 109, 118. Shore deposits, Devonian, 34, 35. Silification of elvan, •")2, 55 ; slate, 47, 48. Silicified wood, 69. Silver-ores, 2, 16, 72, 81, 82, 01, 92 96-98, 100, 104, 116-119. Slaty cleavage, 3, 7, 8, 20. Slickensides, 94. Slides, 55, 94. Smyth, Sir W. W., on mines, 27, 81, 82, 100, 120, 121. Snail-shells in sand dunes, 65, 71. Soils, 1, 2, 59, 61, 86, 90. South Cargoll Mine, 119. Charlotte Mine, 114. Chiverton Mine, 119. Great Chiverton Mine, 107. PolberroMine,]03,104,107,110. Prudence Mine, 114. Wheal Rose, 107, 111, Speedwell, Wheal, 119. Spoil-heaps, 2. Staddon Grit, 30-35, 84. Standing-stones, 31. Statistics, mineral, 72, 112-119. Ste(/aiiodictyum, 11. Stem Cove, drift of, 65 ; mine in 82 ; slates of, 3, 4, 8, 9, 18, 21, Plates, 1,2. Point, Pteraspis at, 8. Stephens, F. J., mines at Perranza- buloe, 122. K 180 INDEX. Stone-rivers, 67. Strain-slip, 8. Strase Clilf, Fterasjm at, 8. Stream-tin, 69-73, 82, 83. Strike- faults, 10. Strike of the slates, 1, 2. Submerged forests, 69, 70. Summercourt, road metal at, 87. Sweden Rock, Old Red near, 5. Symons' map, 73. Tableland, origin of the, 62. Tamblyn, Capt., on Cligga granite, 41, 42. Tea Cavern, mica-trap near, 58. Teal], Dr. J. J. H., on mica-trap, 58 ; on rocks of Mevagissey, 32; Preface by, i. Tertiary strata, 62-64. Thickness of strata, 5-7, 8, 12. Thomas, Capt., on Cligga granite, 41. Dr. I., on Ortfiis, 35. Thrust planes, 3, 5-7, 9, 10, 12, 17. Tides, 4. Tierra del Fuego, stone-rivers of, 67. Timber, destruction of, 2. Tin, alluvial, 69-73, 82, 83. Tin-lodes, 2, 36, 72-78, 91, 92, 94-99, 104, 105 j microscopic structure of , 75, 76. Tin-ore, yield of, 72, 112-115; re- placing orthoclase, 39, 46, 95. Tinners Point, Old Red of, 7. Titanium, 38. Tithy Cove, slate of, 16. Toad's-eye tin, 99. Tobacco pipes, 85. Tolcarne, microscopic character of rocks from, 23, 24. Bay, slate of, 15, 16. Merock, grit of, 21. Mine, 107, 111. Tonkin, Capt., on Cligga granite, 41. Tooke, A. W., on ore deposits, 92, 95. Topaz, 37, 38, 44, 45, 63, 74, 79. Tourmaline, 28, 34, 37-39, 44-47, 50, 52-55, 57, 63, 76-80, 99. schist, 47, 48,_ 78. Towan Cress, metamorphism at, 49. Head, mica-trap of, 58 ; woodland snails at, 71. Towans, 65-69, 71, 86. Towan, Wheal, 114. Town Beach, slate of, 16. Traffal, slate of, 23. Traquair, Dr R. H., on iish of "Watergate Bay, 7, 8, 11. Treago Mill, mica-trap of, 59. Treamble Mine, 81, 100, 104, 108, 110,119. Trebellan Mine, 54, 108, 109. Trebisken Mine, 98, 108, 109, 117, 119. Trebudannon, greenstone of, 21, 22, 87. Trees, destruction of, 2. Trefronick, grit of, 33, 34. Trefullock Mine, 108, 111. Tregony, cherty carbonate of, 32. Tregoss Moor, tin-ground of, 70. Treliver Mine, 119. Treloy, alluvial deposits of, 70, 71. Trembleath, slate of, 21. Trenanoe, grit of, 19, 30, 66. Trenissick, greenstone of, 23. Trenithick, slate of, 33. Trerice, elvan of, 85 ; slate of, 33. Tresithny, slate of, 22. Treslow Mine, 108, 110, 111. Trevarrian, grit of, 21 ; slate of, 10. Trevaunance Coombe, cherty carbon- ate at, 32 ; mining, 75, 94. Cove, slate of, 32 ; mining, 102. , Wheal, 63, 74, 90, 92, 108, 111, 114. Trevelgue, slate of, 13. Trevellas Coombe, mining in, 74, 75,. 84, 94. Downs Mine, 108, 111. Porth, elvan of, 55 ; slate, 32. Trevemper, grit of, 21. Trbvilson, elvan of, 54. Trewheela and Benallack Mine, 119. TrewoUack Mine, 106, 108, 111. Treworgan, grit at, 34. Treworthen, slate of, 23. Trewothall, greenstone of, 23. Trowlesworthite, 38. Trugo, greenstone of, 22, 25, 27, 87, Wheal, 82, 92. Truro Consols, 108, 110. Museum, 35. Tubby's Head, granite of, 36. Tufa, 89. Tuflf, 12, 14, 15, 17, 19, 24. Tungsten, 2, 44, 45, 72, 75, 78-80. Turnavore Mine, 114. Turner, Capt., on lodes of Cligga, 80, Tweedy, W. M., on pseudomorphs of cassiterite, 95, 120. Tywarnhayle Mine, 114, 119. Umber, 73, 116. Uranium, 2, 72. Ussher, W. A. E., on Devonian rocks 20, 122 ; drift, 63, 121. Vallances shaft, temperature in, 82. Vallentin, "R., Pteraspis found by, 8. Valley-erosion, 65. INDEX. 131 Vallevs, trend of, 1. '-, Wheal, 115. Vegetation, character of, 2. Vigiirs, Dr. C. C, on rainfall, ^7. Virgin, Wheal, 108, 110, 114, 118. Vitreous copper- ore, 97. Vlow, Wheal, 32, 47, 75, 108, 110, 114. Volcanic ash, 12, 14, 15, 17, 19, 24. Warren, S. H., on blown sand, 71, 1-2-2. Warren, The, grit of, 21. Watergate Bay, elvan of, 52, 84 ; iron-ores of, 91 ; Old Ked rocks of, 2, 3, 5-11, 83 ; raised beach in, 65. Water-supply, 87-90. Wave-erosion, Pliocene, 64. Wentworth Consols, 81, 108, 110. West Budnick Mine, 115. Chiverton Mine, 104, 108, 110, 115, 119. Kitty Mine, 73-77, 92, 94, 104, 105, 108, 110, 111, 115. Pentire, raised beach of, 67 ; slate of, 17. Pink Mine, 94, 105, 108, 111, 115. Polberro Mine, 108, 111, 115. WestPolbreen Mine, 108, 111, 113. St. George Mine, 115. Wheal Hope, 108, 110. Wheal, see name of mine. ^Miite Cross, greenstone of, 22. Whitley, N., on Perranporth, 120. Widden, AVheal, 108, 110. Williams, Capt., on tin-lodes, 75. Wind-action on sands, 68. Winds, prevalent Pliocene, 64. Wolfram, 2, 44, 45, 72, 75, 78-80, 92, 95. Woodlands, ancient, 2, 71. Woodward, Dr. A. S., on Devonian fish, 8. Dr. H., on Devonian fish,. 121. Worth, H. water-analyses, 90. Wyatt-Edgell, E., on Devonian fish, 121. Zacry's Islands, Old Ked of, 5, 6. Zaphrentis, 13. Zinc-ore, 2, 27, 28, 72, 74, 76, 81, 82,, 91, 92, 94, 96-98, 100, 116-119. Zinnwald, lodes of the, 95. Zinnwaldite, 45. Zircon, 37, 39, 44, 50, 52, 63, 78; Si fcJO > o O r2 0. ^ 55 r. cc o > o 0) fli ,•••'5 GENEBAL UEUOIRS. SUMMARir OP PKOGRESS of the GEOLOGICAL SURVEY for 1897, 1898, 1899, 1900, 1901, 1902, 190S, 1904 & 1906. Each U. PLIOCENE DEPOSITS of BRITAIN. By C. SBID. 6«. 6d. CRETACEOUS ROCKS OF BRITAIN.— VOL. I. 6AULT AND UPPER GREENSAND OF ENGLAND. 9«. Vol. U. LOWER AND MIDDLE CHALK. 10». VOL. III. UPPER CHALK. 10«. By A. J. JOKBS Browne and W. Hal. JURASSIC ROCKS OF BRITAIN.— Vol. I. YORKSHIRE, 8». M. Vol. H. YORKSHIRE, Fossils, 12». By C. For- StkanqwAIS. Vol. m. LIAS OF ENGLAND (Yorkshire excepted). 7«. 6(2. By H. B. WOODWARD. Vol. IV. The Lower Oolitic Backs of England. 108. By H. B. Woodward. Vol. V. The Middle and Upper Oolitic Rocks of England. 7«. 6d. By H. B. Woodward. BRITISH ORGANIC REMAINS. DKOADES L to Xni., with 10 Plates each. Price 48. 6d. each 4to ; 28.6d. each 8ro. MONOGRAPH I. On the Genus PTERYGOTUS. By T. H. HnxLEy and J. W. Salter. 78. MONOGRAPH II. On the Structure of the BELEMNITID^. By T. H. Huxley. 28. Od. MONOGRAPH III. CROCODILIAN REMAINS found in the ELGIN SANDSTONES. By T. H. HUXLET. 148. 8d. MONOGRAPH IV. On the CHIM^ROID FISHES of the British Cretaceous Rocks. By £. T. Newion. 68. VERTEBRATA of the PLIOCENE DEPOSITS of BRITAIN. By E. T. NBWION. 4». Hvteum Cataloguet, Jsc. :— HANDBOOfc to BRITISH MINERALS. By F. W. RUDLER. Is. HANDBOOK to the MUSEUM of PRACTICAL GEOLOGY. M. FOSSILS :-CAMBEIAN and SILURIAN, 28. M. ; CRETACEOUS, 2«. M. ; TERTIARY and POST-TERTIARY, 1«. Sd. GEOLOGICAL MODEL OF THE BLE OF PURBECK, GUIDE TO THE. By A. STRAHAN, 6d. SISTSICT HEUOISS. MEMOIRS of the GEOLOGICAL SURVEY OF GREAT BRITAIN. Vol. L ESSAYS by De LA BECHE and Others. 21* Vol. II. Fart 1, MALVERN HILLS. By J. PHILLIPS. 218. Part 2, ESSAYS. 21«. Vol. III. N. WALES. By Sir' A. C. RAU8AT. App., by J. W. Salter and R. Ethbridqe. 2nd Ed. 21>. CAMBRIDGE. By W. H. Penning) and A. J. J17EEB-BR0WIIE. 4<. «d. CORNWALL, DEVON, AND WEST SOMERSET. INDEX to De LA Beohe'8 Report on. By C. Reid. l8. DERBYSHIRE, NORTH. By A. H. GREEN, C. LE Neve Foster and J. R. Dakths. 2nd Ed, By A H. Green and A. STRAHAN. 6>. M. FENLAND. By S. B. J. SKERTCHLT. 368. 6