CORNELL UNIVERSITY LIBRARY BOUGHT WITH THE INCOME OF THE SAGE ENDOWMENT FUND GIVEN IN 1891 BY HENRY WILLIAMS SAGE ENGINEERING L/BRAKr I n Y{^0'), hydrous sesquioxide of iron, is a brown or yellow mineral sometimes very earthy, but in its pure form having a hardness about equal to that of steel. A number of mineralogical varieties are commonly included under this mineral, the entire series of hydrous sesquioxides of iron (including gothite, turgite, bog iron ore, etc.) being called brown hematite by miners. The series can be told from other ores of iron by the fact that their powder is yellow or yellowish brown, and this is best seen by testing the " streak " which is obtained by scratching the mineral on a piece of rough porcelain or white quartz. Hematite (Fe203) differs chemically from limonite by the absence of water, and there is accordingly every grada- tion between the two, the rust of hematite being limonite. The red colour of soils is due to a hematitic iron, as the yellow colour is to limonitic iron. Hematite is harder than limonite, has a metallic lustre, and varies in colour from red to brown, or even black. Its streak is reddish brown, and this serves to distinguish it from limonite and magnetite, the streak in the latter mineral being black. There are four common varieties of this species, — (1) specular hematite, which has a brilliant metallic lustre, and which is called micaceous hematite when the structure is foliated; (2) columnar he- matite, where the structure is radiating and the lustre less metallic ; (3) red ochreous hematite, where the colour is red and the structure earthy ; and (4) argillaceous hematite (clay iron stone), when the earthy form is mixed with clay. Miners include under the name red hematite all those vari- 20 ECONOMIC GEOLOGY OF THE UNITED STATES. eties having a red streak, and according to the form of the ore they give different names, such as flaxseed ore, fossil ore, etc. Magnetite (FcgO^) is always black, with a black streak, a metallic lustre, usually with a granular structure and con- choidal fracture. In hardness it cannot be scratched with the knife. A feature which distinguishes it from the other ores of iron is its magnetic property. Franhlinite is almost identical in form and appearance with magnetite, but it is not magnetic, and differs chemi- cally in the possession of both zinc and manganese in addi- tion to iron. In this country it occurs in only one locality as an ore, and that is at and near Franklin Furnace, Sussex County, New Jersey. Siderite, the carbonate of iron (FeCOg), is readily scratched with the knife, is light compared with other iron ores, and in colour varies from gray to brown. It very closely resembles a discoloured calcite, which in reality it frequently is, the calcium being replaced by a certain per cent of iron, and in pure siderite being completely replaced. Gold occurs in the earth in only two mineralogical forms, so far as known, one in association with tellurium, the other native, the latter being its typical occurrence and the one from which the gold in use is obtained. While we speak of it as a native ore, this is not strictly true, since gold is nearly always alloyed with other metals, chiefly silver, in greater or less proportions. It is found mixed mechanically with other minerals such as iron pyrite, copper pyrite, and silver ores, and much of the gold is obtained from the last two sources, being a by-product in the extraction of the other metals. COMMON ROCK AND VBIN-FOEMINU MINERALS. 21 Platinum occurs as an ore in the native form, but, like gold, usually alloyed with other metals, chiefly iron, iridium, and osmium. It is found in irregular lumps, usually of small size, is steel-gray in colour, has a metallic lustre, can be scratched with the knife, and has an extremely high specific gravity. Silver is found in much greater variety of chemical com- binations than the two last metals, since it is much more readily attacked by the ordinary mineralizers. Native silver is less common than the mineralized species, but it is, never- theless, not uncommon. It also occurs native as an alloy of gold, copper, and other metals, and much silver is annu- ally obtained from these sources. A large part of the supply of silver of this country comes from the sulphide of lead, where silver at times replaces some of the lead. There are numerous ores of silver, but only three are of marked importance. Argentite (AgjS) is a blackish lead-gray mineral with metallic lustre, and distinguishable from the other ores of silver by its malleability. The argentiferous lead sulphide may be considered a mixture of this mineral and lead sul- phide, the richness in silver varying with the proportion of argentite. Pyrargyrite, or ruby silver, is a sulphide of silver with antimony and sometimes arsenic. Its colour is black, some- times a very deep red, and always with a ruby-red streak. The lustre is very brilliant metallic. Oerargyrite, or horn silver (AgCl), is extremely soft, and can be cut with a knife like horn. The colour is usu- ally gray, and the lustre resinous. With a very low heat the chlorine is driven ofE and native silver left. This ore is 22 ECONOMIC GEOLOGY OF THE UNITED STATES. found in the Cordilleras, Mexico, and South America, in the latter place, particularly in Chili, occurring with a bro- mide and iodide of silver. Copper is found native in this country chiefly in the Lake Superior region. Its most common occurrence, however, is as the sulphide, chalcopyrite (CuFeSj), or copper pyrites, which is in reality a sulphide of iron and copper combined, the proportion varying from an exceedingly cupriferous variety (chalcopyrite) to pure iron pyrites. The former is golden yellow in colour with commonly an iridescent tar- nish; the latter is brassy. Another sulphide, chalcocite (CugS), is lead-gray and rather soft. The oxide cuprite (CujO) is red in colour and translucent, with a metallic lustre, sometimes brilliant, sometimes earthy. Chrysoeolla, the silicate (CuSiOg 4- water) is green to bluish green, the colour of copper rust. The lustre is vitreous, the specific gravity low, and the mineral soft. There are two carbo- nates of copper, — malachite (CugCO^+water) and azurite (CugCgO^ + water), — the first being green in colour, the second blue, and each with brilliant vitreous lustre, of low specific gravity, and with a hardness such as to admit of its being easily scratched with the knife. Ores of copper are usu- ally more or less oxidized at the surface, and can generally be told in such places by the characteristic green or blue rust. lead does not occur native, but is most commonly found in the sulphide galenite, or galena (PbS), a lead-gray mineral, with a metallic lustre and well-defined cleavages. The knife scratches it easily. Galena is very commonly argentiferous, and a considerable percentage of our silver is extracted from this ore. The sulphate of lead, anglesite (PbSO^), is white, yellowish, or grayish, soft, and has a resinous lustre. COMMON EOCK AND VEIN-FORMING MINBKALS. 23 Oerussite, the carbonate (PbCOg), has usually a white or grayish colour with a brilliant vitreous lustre, and is easily scratched with the knife. Both the sulphate and the carbonate are commonly the result of the decomposition of some other form of lead ore, usually galena, and all of the lead ores are frequently marked at the surface by a peculiar pale yellow rust. Zinc occurs most commonly as zinc blende , or sphalerite, a sulphide (ZnS), called by miners black jack. It varies markedly in colour, but is most frequently brown or yellow ; it has a peculiar resinous lustre which is quite distinctive ; it can be scratched with a knife, is rather light for an ore, and has very marked cleavage. There are two oxides of zinc, franklinite (already described under iron) and the red oxide of zinc, zincite (ZnO), which has a red colour, usually of a deep shade, though sometimes being orange- yellow, a brilliant vitreous lustre, and a hardness within the touch of the knife. Zinc as an ore occurs as a silicate in two forms, the hydrous and the anhydrous. The latter, willemite (ZugSiO^), is usually yellow with a vitreo-resinous lustre and a conchoidal fracture. As in most silicates, the specific gravity is low for an ore. The hardness is not great. Calamine, the hydrous silicate (ZngSiO^-l- water), is white in colour, but otherwise resembles willemite, except- ing that it is lighter on account of the contained water. Smithsonite, the carbonate (ZnCOg), is usually white or grayish, with a vitreous lustre inclining to pearly, and a hardness and specific gravity about like that of willemite. It effervesces with acids, as do many of the carbonates. All of the above ores of zinc, with the exception of franklinite, are translucent, or in some pure specimens transparent. A 24 ECONOMIC GEOLOGY OP THE UNITED STATES. whitisli rust is frequently present in zinc ores which have been exposed to the action of weathering. Mercury occurs as an ore in the form of the sulphide cin- nabar (HgS), although sometimes native mercury is formed by the decomposition of this ore, the affinity of the two elements being very slight. Cinnabar is very soft and heavy, has a brilliant lustre, is red in colour, often of a deep shade, and breaks with an uneven fracture. When heated carefully, the sulphur is driven off and metallic mercury is left ; but if heated too high, both the mercury and sulphur disappear. This ore is used not only as a source of metallic mercury, but also as a mineral for vermilion. Manganese occurs in many rocks as a black or purple stain, and it is an oxide of this metal which forms the arborescent stains called dendrites, which are so common on cleavage and jointed faces in many rocks. It is found very com- monly with iron in greater or less quantities ; and, as it is in iron-working that the chief supply of manganese is used, much of the metal is mined in this form and never sep- arated. There are, however, several ores which are mined for manganese, the principal being the three oxides, — pyro- lusite, psilomelane, and wad. Pyrolusite (MnOg) is usually black or dark steel-gray, with a metallic lustre, rather soft, and not very heavy. Psilomelane is a mineral of doubtful composition, being essentially an oxide of manganese and barium with water. Its characters are almost exactly like those pyrolusite, but it is much harder, and the knife scratches it with difficulty. Wad, or bog manganese (MnOg-l- water), is usually impure, just as is the case with bog iron ore and for the same reason. It is extremely soft and earthy, not heavy, and varies in colour from dull black COMMON EOCK AND VEIN-FOKMING MINERALS. 25 to bluish or brownish black. The ores of manganese usually rust to this mineral under the action of weathering. Aluminum, although one of the most abundant of the metals, is also one of the most difficult minerals to extract from most of its ores, since it is firmly held in chemical combination by its mineralizers. It is found in all the silicates of alumina, of which there are many, and is present in all feldspars and in the clay or kaolin which results from their decay. Ordinary Jcaolin (H3Al2Si208 + water) contains an inexhaustible supply of this metal, but it cannot at present be economically extracted. Corundum (AlgOg) is a possible source of alu- minum, but is not now used, because it is more valuable for other purposes. Cryolite (NagAl2Fj2) is one of the chief sources of aluminum. It is usually pure white, though sometimes coloured, has a vitreous lustre, is translucent, brittle, easily scratched with the knife, and has a rather low specific gravity. It is fusible in the flame of a candle. The mineral bauxite (or beauxite) (AlgOg+iron and water), also used as a source of aluminum, is white or brown in colour, and occurs as concretions in clay. The colour and hardness vary with the per cent of iron. It is a comparatively light mineral. Tin is obtained entirely from the oxide oassiterite (Sn02), which is usually brown or black, with a brilliant lustre, a hardness too great to be scratched with a knife, and a high specific gravity. With the blowpipe, it can be reduced on charcoal with soda to metallic tin. The ore is found both as tinstone, in coarse granites or pegmatites, and as stream-tin, in river gravels, where, by the decay and removal of the tin- bearing rock, it has accumulated, owing to its high specific gravity and chemical indestructibility. 26 ECONOMIC GEOLOGY OF THE UNITED STATES. Nickel is obtained from the two sulphides, millerite, niccoli- ferous pyrrhotite, and the arsenide niccolite. Millerite (NiS) is a brass-yellow mineral, usually with a gray iridescent tarnish, a metallic lustre, and a moderately high specific gravity. It is brittle and can be scratched with a knife. Niccoliferous pyrrhotite is a sulphide of iron (Fe^Sg), with more or less nickel, and this ore is the principal source of nickel. In colour, it is bronze-yellow and copper-red, usually tarnished, and in specific gravity, hardness, and brittleness, it resembles millerite. In a fine powder it is attracted by the magnet. Niccolite (NiAs) is harder and heavier than either of the other two ores of nickel, being scarcely scratched with the knife. The colour is pale copper- red, with a gray or blackish tarnish, and a metallic lustre. Associated with nickel are the ores of cobalt,^ and one of these ores, smaltite, contains nickel in varying proportions. Antimony and its compounds are obtained from the mineral stibnite (SbjSg), a soft, sectile mineral of medium specific gravity, a metallic lustre, and a lead or steel-gray colour, with a blackish or iridescent tarnish. It is soluble in hydro- chloric acid. The above summarized description of minerals gives only those tests which can be applied roughly in the field without the use of exact methods, and includes those features which are present in ores, omitting the more purely mineralogical characters. The object of the summary, however, is less the presentation of the mineralogical than the geological features. There are many other minerals which one is liable to en- counter in the mines and quarries, some of them of economic value, but the above include the most common species, and 1 Described above, p. 13. COMMON KOOK AND VEIN-FOEMING MINERALS. 27 the ores which are most liable to be met with frequently in economic work. Without a thorough mineralogical study, a more complete list or a more thorough statement of the features of the minerals would be useless ; but such a study is very desirable, indeed necessary for one who wishes more than an elementary knowledge of economic geology.^ ^The most complete text-book on mineralogy is Dana's System of Mineralogy, thougli the essential features are given in the Text-Book or the smaller Manual of Mineralogy by the Same author. Brush's Blowpipe Analysis gives the blowpipe tests for minerals. While there are numerous other text-books, these are the standard works and best adapted to the needs of the American student. CHAPTER II. BOOKS OF THE EABTH's CETJST. The earth's crust, so far as it has been exposed to view by the processes of erosion, or by mining operations, is found to be composed of rocks of different characters, but all alike in the fact that they are composed of minerals. Sometimes a rock is composed of one mineral, but more commonly several combine to make up the rock-structure. Not only do they differ widely in mineralogical composition, but they differ both in form and in origin, and upon the latter basis we divide ■ the rocks into three groups — Sedimentary, Eruptive, and Metamorphic. Sedimentary Rocks. — There is no single term which can properly be applied to those rocks which are neither eruptive nor metamorphic. The term sedimentary, strictly used, includes only those rocks which are formed as sediments, and excludes a large group of rocks subaerially formed. Stratified refers to those which are formed in strata or layers, but many metamorphic rocks are truly stratified ; and, on the other hand, the glacial deposits are, in large part, neither sedimentary nor stratified. The terms fragmental or clastic might be used were it not for the fact that they exclude certain chemically deposited rocks, as well as those of organic origin, which are truly stratified. Of these several terms, sedimentary is, per- haps, the best general name, and in this treatise it will be used to include all rocks which do not fall into the other groups, 28 ROCKS OF THE EARTH'S CRUST. 29 and the most important of which are both stratified and sedi- mentary. The material forming these rocks is of secondary- origin, being derived either by mechanical or chemical means from pre-existing rocks. According to the nature of the material composing these strata we have a basis for classification. A conglomerate is composed of pebbles rounded, generally by water action, and cemented by finer, usually sandy particles, and some chemi- cally deposited mineral, such as calcite or iron oxide. The pebbly beaches are composed of material which might readily become consolidated into a hard conglomerate. When the pebbles are angular, as, for instance, when they have not been transported far from their source, the rock is a breccia. The name fault breccia is given to a similar aggregate of angular fragments found in a fault plane, and caused by the crushing of the rocks. As upon a beach there is every gradation from a mass of coarse pebbles to a fine-grained sand, so among the sedimentary rocks there is every gradation between con- glomerates and sandstones. The particles composing the sandstone are usually quartz, for the reason that this is the most durable of common minerals, and outlasts both the chemical disintegration and the mechanical wear to which the less durable minerals succumb in the process of weather- ing and transportation. Sandstone grades into clay rocks, which are composed of the finer parts of rock decay and of mechanical destruction. When consoUdated these may become clay stones, or shales if they split easily in the direction of the bedding, and these may be sandy, or, on the other hand, of exceedingly fine grain. Since there are these gradations, it may be difficult to say whether a rock is a shale or a sandstone, and then it may be necessary to introduce 30 ECONOMIC GEOLOGY OF THE UNITED STATES. a compromise term, such as shaly or argillaceous sand- stone, or sandy shale, according to the predominating constituent. These rocks are deposited in water, and in all bodies of water they are now being formed. The rivers, lakes, and oceans are repositories of these various materials, which are derived from the waste of the land. Frost and the agents of weathering cause the rock to disintegrate, the wind and moving glaciers grind the material finer; rain, gathering into rills, rivulets, and powerful rivers, sweeps this material toward, and finally into, the sea. Here the waves and currents work it over, grind it finer, and assort it, transporting the finer particles out to sea and depositing the coarser fragments near the land. The waves beating upon the shore batter off other fragments which are placed with those furnished by weather- ing and river erosion, and these all go to make up the sedi- mentary deposits of the ocean. These fragmental rocks are furnished by the land waste, and their source may be other sedimentary, or eruptive, or metamorphic rocks. Chemically Precipitated Rocks. — When rains fall upon the land, a part of the water sinks into the ground, while the remainder gathers into streams. The former, and to a slight extent the latter, takes from the rocks a certain store of soluble mineral which it carries away. In places, notably in inland seas, where this mineral matter becomes concentrated by evaporation, the water becomes overcharged, and is forced to precipitate some of the dissolved mineral. Carbonate of lime, particularly the magnesian carbonate, gypsum, and salt, are the chief deposits of this nature. In the neighbourhood of hot springs siliceous rocks and deposits of carbonate of lime may be precipitated ; but this class of rocks, since they ROCKS OP THE EAETH'S CEUST. El are very local, is of scarcely any general importance in a consideration of the structure of the earth's crust. Organic Rocks. — Far from land, where rock fragments are rarely transported, the ocean bottom receives practically nothing but contributions of organic remains, excepting such fragments as may be transported by ice, or such bits of pumice as may float to that point. Minute lime-secreting animals furnish the greater part of this supply, and, therefore, in great ocean depths there is a muddy ooze, composed principally of their tests or shells, and this is called glohi- gerina ooze, from the predominance of species of animals belonging to this genus. The chalk of England is a deposit of very nearly this character. In still greater ocean depths, even this small supply is not furnished; for here, owing to the great pressure of the water, the lime composing these shells is dissolved as they drop toward the bottom. Here a red ooze is formed, which is composed of the insoluble residue, and is therefore of extremely slow growth. Among the sur- face rocks, we have as yet failed to identify any similar stratum. Organic contributions to the strata are, however, more numerous than' this. Practically, every sedimentary rock contains some relic of organic remains, even if no more than an indistinguishable powder of lime, resulting from the grinding up of calcareous shells. From this there is every gradation to pure limestone, when the entire stratum is made up of animal remains. Upon tropical coasts, where marine life attains a luxuriant development, there is frequently nothing furnished to the sea in solid form, excepting frag- ments of shells, corals, or other calcareous remains built up of carbonate of lime extracted from the sea-water by the 32 ECONOMIC GEOLOGY OF THE UNITED STATES. marine animals. Such conditions prevail in coral-reef regions, where limestone beds are at present being deposited. There are conditions under which the limestone may be deposited in an impure form, as, for instance, by the addition of clay, forming an argillaceous limestone, or of magnesia, which produces a magnesian limestone. Certain minute animals (Infusoria) and plants (Diatoms) extract silica from the water for the construction of a siliceous test, and under certain conditions, chiefly in fresh- water deposits, these may be accumulated into a layer of infusorial or diatomaceous earth. Of coals little need be said here, since these strata will serve as a special topic. They have resulted from vegetable contributions to the earth's crust, under conditions favouring rapid burial and protection from destruction. Coals are of importance from an economic standpoint, rather than from their value as parts of the earth's strata; but, when carbonaceous shales and limestones are taken into account, it is found that vegetable contributions to the earth's crust are of much importance. Conditions of Accumulation. — These several deposits, most of which are extremely important in the structure of the earth's crust, although being formed in all bodies of water, are being most rapidly deposited in the ocean, where also they are most widespread. Hence it is that the sedimentary strata of the world are most commonly of marine origin. That this is true we know from- their fossils, which are usually the relics of marine animals. Furnished by the decay of the rocks, or the death of animals or plants, these deposits are gathered in the sea and accumulated, often to great depths, before finally being raised above its surface. The earth's crust is ROCKS OF THE EAETH's CRUST. 33 changing in form: certain areas are slowly rising and others sinking. This we know partly by direct observation, partly by inference from the present position of sedimentary rocks on the very crest of mountains. If a coast line is suffering a gradual downsinking, the accumulating sediments may gather into a great thickness of strata, one deposited upon another. In places, thousands of feet of sediments have been thus accumulated. Those which are beneath become consolidated by pressure, and by a cement deposited from solution, by percolating water, and when finally the series of strata is elevated above sea-level, what was once an unconsolidated stratum of sand has been transformed into a hard sandstone. This, in general, is the way in which our sedimentary series has been formed and placed in the present position as a part of the land. In the ocean the fragments, being deposited by gravity, tend to build up layers of nearly horizontal strata, thicker and coarser near the shore, and thinning out as well as becom- ing of finer texture in a seaward direction. They vary from horizontality only when the irregularities of currents or waves cause a local variation of position, or when the form of the ocean bottom is uneven. Such cases are, compara- tively speaking, both rare and local, and it is a safe state- ment to make, in general, that sedimentary layers are originally horizontal. Yet, when these strata are found upon the land, they are scarcely ever perfectly horizontal, and are frequently tilted at a high angle. The same cause which brought about the depression and elevation of the ocean bottom, and which is still taking place, — namely, the contraction of the earth, — has caused the crust to wrinkle, the layers to bend and break, and mountains to form. Hence 34 ECONOMIC GEOLOGY OF THE UNITED STATES. it is that we find the strata so often thrown out of the hori- zontal and cast into folds, or broken and faulted. Igneous Rocks.i — Rocks which have been formed by the cooling of molten material coming from within the earth are known as igneous. In some parts of the earth they are extremely abundant, while in others they are practically absent. Thus in the United States the Cordilleras abound in igneous intrusions and extrusions, while in the Central States they are very rare. In general, it may be said that igneous rocks abound in highly tilted strata, and are liable to be rare in those which are nearly horizontal. The same thing may be stated in another way ; namely, that igneous rocks are most abundant in mountainous regions, or in regions where mountains formerly existed but have been destroyed by erosion. Of the former the Cordilleras furnish an illustration ; of the latter. New England. Igneous rocks vary greatly in character in two ways: chemical composition and physical structure. On the one hand there are some having from sixty to seventy per cent of silica, on the other, forty per cent or even less, while between these two extremes there is every gradation in chemical composition. Accompanying this variation there is naturally a wide difference in mineralogical composition. There are, for instance, granites which have orthoplase feld- spar, quartz, and some other minerals; syenites containing the same minerals with the exception of quartz ; diorite car- rying hornblende and plagioclase feldspar ; and many other species, as will be seen in the accompanying table. In structural features these vary from glassy to coarsely 1 A scientific treatment of the igneous rooks will be found in Kosenbusch's Mikroshopische Fhysiographie cler Massigen Gesteine. ABSTRACT OF A "TABULATION OP THE IGNEOUS EOCKS BASED UPON THE SYSTEM OP PEOPESSOE H. EOSENBUSCH " By F. D. Adams {Canadian Becord of Science, December, 1891, pp. 463-469). At.kat.t "Pp.T.nppA^ EOCKS. Orthoclase, Mlcroline, Anorthoclase, Albite. Alkali Feldspar Nepiielink (or Leu- cite) KOCKS. Leucite Eocks. irEPHELINi; EOOES. Melilite Eocks. Lime Soda Feld- spar Nepheline (or Leucite) Eocks. Lime Soda Feldspar Eoora. eockb containing no Feldspar Constituents (Feeb from Alkalies). With Mica, Amphftole, or Pyroxene. With Mica, Amphibole, or Pyroxene. With Hornbleiide or Mica. With Augite, Diillage, or Hypersthene. Pyroxene Eocks. OUvine Eocks. With Quartz. Without Quartz. Without OUvine. With Olivine. Without Olivine. With Ohvine, Without OUvine. With OUvine. With Quartz. Wilhout Quartz. Without OUvine. With OllYuie. Abyssal (Plutonic) Books. Granular structure GRiNITE. Biotite granite Hornblende granite Muscovite granite Syenite. Mica syenite Augite syenite Hornblende syenite El^olite syenites Leucite syenites TheraUte Quartz diorite DldRITE. Mica diorite Hunlblende di(|rite Gabbro and Horite Olivhie gabbro and OUvine norite Pyroxenite Peridotite Effusive (Volcanic) o 1 § o Quartz porphyry Quartzless porphyry . Quartz porphyrite Porilhyrite Diabase. Augite porphyrite OUvine diabase Melaphyre Picrite porphyrite Porphyritic structure Liparite Ehyolite Trachyte Phonolite Leucite phonolite Leucitite Leucite basalt Nephelin- ite Nepheline basalt Melilite basalt Tephrite Basantite Dacite Andesite Basalt OUvhie basalt The mineralogical character varies upon coohn^ according as the chemical composition of the molten magma varies. On the one extreme of the table the rocks are very acid, aud the percentage of silica is very great. Accordingly free quartz occurs in these rocks, as, for Instance, in the granites. From this extreme there is every gradation to the very basic rocks, of which the non-quartz and feldspar-bearing peridotites are illustrations. The granites frequently contain as high as seventy-five percent of silica, and sometimes more, whereas the rocks of extreme basic nature contain as little as thirty per cent. Since there is every gradation between these two extremes, it is natural to expect every gradation in mineralogical character, and such is the case ; for granites grade into syenites, and diorites into gabbros. All chemical varieties of rock between these extremes are extruded from the earth, and upon the basis of this variation the fundamental principles of the Eosenbusch classification depend. But some rocks reach the surface and cool rapidly, while others come to rest at considerable depths and cool slowly, and between these extremes there is every gradation. Granite, quartz porphyry, hparite, and rhyolite have essentially the same chemical composition, but they are given diflFerent names because their mineralogical characters vary. Granite cools slowly and has coarse .crystals, quartz porphyry cools under conditions favouring the formation of porphyritic crystals, and liparite may even be a natural glass so rapidly cooled that no crystals were formed from the magma. These are the principles upon which the above table is based. The dike rocks, considered by Eosenbusch intermediate between effusive anil plutonic rocks, are omitted here, because there appears 1^ be no espocial basis for this division. The division into older and younger eflusive rocks is also of doubtful value. ,, . , , Many siMi™ions, such as the division of the andesites Into mica hornblend.1 hypersthene, and augite andesites, as well as a number of comparatively rare rocks, are omitted in this abstract. ROCKS OF THE EARTH'S CRUST. 35 crystalline. Certain rocks are natural glasses, others have a glassy groundmass with large, quite perfect crystals, por- phyritic crystals, scattered through it, still others have a fine-grained granular structure called cryptocrystalline, and many are holocrystalline, or of a coarse-grained granitic structure. All of these various physical differences may be possessed by rocks having essentially the same chemical com- position, and, indeed, all may be present in the same mass. This difference in structure is largely the result of a differ- ence in the rate of cooling. A surface lava, cooling rapidly, may become a natural glass, because the minerals had not time to crystallize out of the molten magma, while the same lava, cooling slowly, might assume a granitic or holocrystal- line structure. Upon these two characters the following classification ^ is based. Those in the vertical columns are of essentially the same chemical composition, while in the horizontal rows the chemical variation is indicated by the change in minera- logical character. The position of these igneous rocks in the earth's crust varies. They differ from the sedimentary strata princi- pally in the lack of uniformity and regularity. So far as the chemical character is concerned, there is no uniformity of occurrence which can be predicted. Acid and basic lavas may be found intimately associated in the same region ; or, on the other hand, only one kind of lava may occur. Also, the igneous masses may all be of uniform structure, or there may be holocrystalline, cryptocrystalline, porphyritic, and 1 Adapted from Adams' table, which is based upon the Rosenhusch clas- sification of igneous rocks. This table differs from the Adams table only in the omission of certain comparatively unimportant groups. 36 ECONOMIC GEOLOGY OF THE UNITED STATES. glassy, all in the same region. This variability is the result of causes which cannot be discussed in detail here. In general, it may be said that lavas are derived from a portion of the earth some distance beneath the surface, and are an expression of an effort of this molten material to escape. If they are successful in this effort, they flow out upoa the surface, cool rapidly, and tend to become glassy or crypto- crystalline in structure ; but if unsuccessful, they cool slowly, and become well crystallized. Their variation in chemical composition is apparently the result of a variation in source of supply, although it is difficult to explain why neighbour- ing volcanoes send forth different lavas, and 'still more diffi- cult to understand why the same volcano may at different times erupt different lavas. In the effort to attain the surface, some igneous rocks escape from the earth, and issue as lavas from a volcanic vent, or from a fissure. These extruded or effusive rocks may flow out quietly as lava, or, by the explosive violence of the contained water, they may be blown into fragments of volcanic ash or pumice. In both these cases there is a tendency to build up a cone about the vent, although, where the vent is a great crack or fissure, large areas of country may be flooded and no cone constructed. An ordinary volcano erupts lava which solidifies within a radius of a few miles from the vent, and its influence is therefore local ; but volcanic ash, rising high in the air, may float great distances either in the air or on the water. Later these deposits may be destroyed by denudation, and their fragments distributed in the ocean as sedimentary deposits ; or, on the other hand, they may themselves be buried without change, and become a part of a bedded series of sedimentary strata. BOOKS OP THE BAETH'S CRUST. 37 While vast quantities of lava escape to the surface, vast quantities, also, are unsuccessful in their effort to escape. Such rocks are often found solidified in the other rocks into which they have been intruded. The volcanic vent, when the activity ceases, becomes clogged with the contained lava, andihere is a plug or volcanic neck of solidified lava extending deep down into the earth. At times, the lavas find it easier to raise the strata in an arch than to break through them, and a laccolite, or well of lava, is formed. Intruded sheets of lava are found between the sedimentary strata, and at times these are rent asunder and masses of molten rock forced into them, forming great areas or bosses, such as the granite masses. These various rocks are said to be intruded or intrusive, and those like granite, which are intruded at great depths, are called plutonic or deep-seated. They are revealed only after the thick overlying layers have been removed. From all of these igneous masses, dikes, or narrow sheets of lava, may extend, sometimes as feeders, sometimes as off- shoots, and where the volcanic history has been complex, there may be a great complexity in character and position of the igneous rocks. They may cut each other, or traverse any of the groups of sedimentary or metamorphic strata. Some- times their boundaries are sharply defined and regular, but more commonly they are irregular, and even at times in- definite. It is more common for them to traverse the sur- roimding rocks in a more or less vertical sheet, but cases are numerous where such intrusions are nearly horizontal. For a study of that part of economic geology which deals with ore deposits, some knowledge of igneous rocks is neces- sary, for the reason that many such deposits are in greater 38 ECONOMIC GEOLOGY OP THE UNITED STATES. or less degree due to their presence. By direct contact, these heated intrusions have, in some cases, caused an ac- cumulation of valuable ore. Still more commonly have they furnished the ore which has been gathered together in the vein; for nearly all, if not all, igneous rocks carry a certain percentage of the metals which, by the decay of the min- erals, may become a part of the sedimentary series, or which may be taken directly by percolating water and gathered into a vein. MetamorpMc Eocks. — The third great group is classed as metamorphic. Originally these were supposed to mark an early stage in the history of the earth, possibly the original crust of the earth, and for some this may still be true, since they lie beneath the oldest known sedimentary strata, and when these were formed had their present character. They are the oldest known rocks, but to assume that they actually are the oldest is going farther than the facts warrant. Of late years, studies of these metamorphic districts have tended to withdraw from the old Azoic or Archean group many areas which were formerly supposed to be of this age. It is found that both sedimentary and igneous rocks may be made to lose their characters and become metamorphosed. This may happen* by contact with large masses of plutonic igneous rocks, as well as in the centre of mountain chains, where the strata have been folded and crushed. The first is called contact; the second, regional metamorphism. As a result of this change, it happens that strata of much younger age than the true Archean may have very nearly the struc- ture of the Archean series. Parts of the New England hills, long classed as Archean, are now known to be of much later age. Whether the real Archean rocks owe their structure ROCKS OP THE EAETH'S CRUST. 39 to the same cause, or whether the resemblance is one of coincidence, we are hardly in the position at present to state, although the tendency of the recent studies is toward the belief that they are the same in cause as well as in character. There is a wonderful variety of structure in the meta- morphic series. It might be said that every consolidated sedimentary layer is more or less metamorphosed. There is every gradation from the incoherent accumulation of coral debris to limestone and marble, from sandstone to its meta- morphic representative quartzite, and from clay shale to its representative among the metamorphics, slate and phyllite. These, in turn, grade into crystalline rocks so greatly meta- morphosed that the original condition cannot be determined. Leaving out of consideration these three groups which can be easily traced to their source, the crystalline metamorphics may be divided in general into two groups — gneisses and schists. A crystalline structure, often neaily as marked as in igneous rocks, is a common feature of these two groups, and they are alike also in the possession of schistose structure. In the schists proper, it is present in such a marked degree that the rock cleaves with facility in a given direction, while in the massive gneisses it is present only as a banding of some of the minerals, so that they frequently resemble very closely a granite. Other distinctions than that of schistosity are difficult to maintain, although it is common to find in schists a greater predominance of mica. A great number of sub-varieties of these metamorphics are known. We have, for instance, quartz schists, amphibole schists, mica schists, chlorite schists, hornblende gneisses, augite gneisses, and a large number of others ; but in all the foliated structure is the uniform and general feature. The 40 ECONOMIC GEOLOGY OE THE UNITED STATES. minerals are arranged in bands, in strings, or, in some cases, simply with their major axes oriented in parallelism, and this gives the gneissic structure. Shales and slates are found passing over to chlorite schists, conglomerates and granites to gneisses or mica schists, and in all cases the direction of the schistose structure is at right angles to the direction of the pressure which is causing the metamorphism. Upon a study of the rock it is found that there are several ways in which this gneissic or schistose structure may orig- inate. It may be the result of the crushing of the com- ponent minerals and their arrangement in parallel bands; or it may be due to the stretching of some of the minerals which are so nearly plastic that they do not crush ; or, finally and most commonly, it may be due to the development of new minerals, the result of heat, pressure, and attendant con- ditions. These facts may be verified by observation and study, and in many cases it is possible also to observe the cause for the metamorphism, as, for instance, when the strata occur in the core of a mountain chain. Both the igneous and sedimentary series furnish the material upon which metamorphism acts, and it is found that the same kind of metamorphic may be produced from sources as opposite in character as igneous and sedimentary rocks. This result, which at first thought seems an anomaly, is easily under- stood when we consider that a conglomerate may have the same chemical composition as a granite, or a shale as a diorite. Metamorphism takes account of material available rather than the particular form of this material, — of the chemical rather than the structural features. While it is possible that the old Archean series may rep- resent the original crust of the earth, either in its original EOCKS OF THE JBAETH'S CKTJST. 41 condition or else altered by metamorphism, yet, since the same kinds of metamorphics are known to be produced by simple and easily studied and comprehended changes in known rocks, it is natural that one should be skeptical of an explanation which has for its support merely hypothesis. It seems probable that the great mass of Archean strata will be found to be metamorphosed sediments and eruptives, just as many similar but more recent gneisses and schists are known to be, although so far all efforts to prove this have been futile. Geological Age of Rocks. — In a study of the rocks and their relations one to another, it is necessary to have some- thing more upon which to base our studies than their mere chemical and physical characters. It is desirable to be able to refer to them according to age, and to differentiate between a shale formed in the first ages of the earth's history and one formed in more recent periods. It was at one time thought that such a classification in general was possible upon a mineralogical basis ; but more extended studies have shown that there is no uniformity of this sort, but that in any age strata of the same mineralogical composition are liable to be formed. Age of MetamorpMo RoeJcs. — Naturally the basis for a classification of rocks according to age must be a study of their relations one to another in the field. If one sedimen- tary layer is found resting on another, it seems probable that the lower layer is the older. In the case of eruptives and metamorphics this is not necessarily so. The bedding of a metamorphic rock may be mere schistosity of secondary ori- gin, and hence of no value in determining the relative age of the layers. In the true Archean rocks a certain time- 42 ECONOsnc geology of the united states. classification has been made out in places ; but it is of local value only, and so far no valid grounds for extending it have been found. This much is known, however, that a certain por- tion of the metamorphic series, the greater part apparently, belongs to the lowest and oldest geological period. So far as we know no fossils exist there, no sedimentary layers are found among them, and all known sedimentary and fossil- bearing strata are of later origin. Age of Uruptive Rocks. — With eruptive rocks, we are in no way better able to construct a chronology. Locally, it is possible in most cases to determine the relative age of associated eruptives, or of the erupted rock, and the one through which it passes ; but this cannot be extended beyond the locality where it is observed, because in any part of the earth's crust, or in any period, any kind of an igneous magma may have been erupted. Still, if the igneous mass cuts a certain other rock, it is the later of the two, and so far we have a chronology ; but only a hundred years ago, a dike may have cut an Archean series, and to-day we would be unable to tell whether it were a hundred years old, or many ages. Sometimes, by a careful study of a region, it is possible to determine quite accurately the age of an igneous mass. Thus in the eastern United States great dikes of an igneous rock, diabase, are found cutting the strata of all ages from the earliest down to the time of the Triassic period, but nowhere crossing the later layers. The age of these lavas is, therefore, Triassic. At times, an igneous rock is in such a position in the stratified series that one is unable to tell whether it was formed at the same time as these, or later; that is, whether it flowed out as an extrusive lava sheet, while the sediments were being formed, or whether it EOCKS OF THE EAETH's CEUST. 43 were later intruded between the layers. If intruded, it may follow the bedding planes very closely, though it may cut from one layer to another, which would not be the case if extruded. An intruded sheet would show the effect of heat at both the upper and lower contact, and would be liable to intrude dikes into the overlying layer. An extruded lava would nqt produce these effects, but the sedimentary layer above would probably contain fragments of the lava. These are about the only means of determining the age of an eruptive, although it may be added that if a rock is coarsely crystalline and granitic, it is usually old, for such masses are intruded into the earth at considerable depths, and are not revealed until the overlying layers are removed, which is usually a slow process. In very high mountain regions, where erosion is rapid, and in the case of thick lava flows, there are exceptions to this rule, so that it is only of very general application. Age of Sedimentary Rocks. — There is a much more satis- factory chronology for the sedimentary strata, the rocks which, so far as revealed, predominate in the earth's crust, although in years we can make no estimate at all approximating the truth. By the folding of the mountains in Pennsylvania, and by the erosion of the streams which have breached them, there are found to be revealed not far from 40,000 feet of sedimentary strata, one layer upon another. These were all deposited in water, and apparently under the same laws which govern the accumulation of sedimentary deposits to- day. This must have represented a vast lapse of time, yet there are represented here less than one-half of the total thickness of the geological column from the Archean to the present. Evidently this period of time must be estimated in 44 ECONOMIC GEOLOGY OF THE UNITED STATES. millions of years, but how many it is impossible to say, and those who have hazarded guesses have made estimates ranging from ten to several hundred millions of years. There are no facts upon which to base such an estimate, because the conditions are too variable, and our knowledge of them entirely too obscure. Knowing, however, that one layer is above another, and is hence later, we have a valuable local indication of relative age and, as far as a given stratum, or a group of strata, can be traced, the chronology is correct. But it is possible to extend this chronology even beyond the limits possible by directly tracing a given series of layers, for it is found that in these sedimentary strata there are fossils, relics of animal and plant life of the time when the rocks were formed. The fauna and flora of the world to-day are marked by a general uniformity of character, certain groups of animals and plants predominating, which give character to the life of the period as compared with those which preceded. Assuming that this has been the case in the past (and this is more than a mere assumption, for it is verified by a study of the fossils), an examination of the fossil contents gives us. a chronology which, in its broadest features, is of world-wide application. Before a certain series of rocks was deposited, there were no vertebrated animals, then fishes appeared, then reptiles, and mammals, and birds. If, now, in a certain stratum the petri- fied bone of a bird is found, it can be affirmed definitely that this stratum belongs to a period later than the time of appearance of the first birds. A knowledge of the exact species of the bird might even indicate the exact period. Certainly, this, taken together with a knowledge of other fossils from the same bed, would furnish a means of identifi- cation of this bed as a part of a general group. EOCKS OP THE EAETH'S CRUST. 45 The knowledge upon which our ability to make these determinations is based has been slowly acquired by a long and careful study of many different fields, and, as far as the general groups are concerned, it is a safe statement to make that ordinarily a knowledge of the fossil contents will serve to place a certain stratum in its proper position in the geological time-scale. This study has proved that there has been a development, an evolution of forms, from simple to more complex, and that, in each succeeding age, the prevailing types of life are progressively higher. In some places, the divisional line between two ages is indefinite and difficult to draw, but generally it is sufficiently well defined for the purposes of division. New types seem, at times, to have developed rapidly, and to have displaced the older types, in a period of time so brief that the gradation is not marked. Yet, in various parts of the earth, every gradation, generally speaking, is found. The division into ages is usually based, however, upon fields where no gradation exists, but where the dividing line is sharp, and these places are generally regions where for a time sedimentation was interrupted. That is to say, a region of marine deposit was transformed to dry land for a period of sufficient duration to admit of the development of new types, and then a submergence brought these animals into the condition of fossils in beds above the earlier ones^ (Fig. 1). Having been demonstrated for such a place, the observation can be extended to other areas. For the minor details of the geological time-scale, the classification is less satisfactory. Just as at present the fauna of Australia is widely different from that of America, so in the past, contemporaneous deposits, even when not far iThis is known as an unconformity. 46 ECONOMIC GEOLOGY OF THE UNITED STATES. removed geographically, may have entombed widely different species. While the presence of certain types of mammals, chiefly man, would serve to indicate the general contem- poraneity of the deposits of Australia and America, it is quite unlikely that, from a study of the fossils alone, the two deposits, of exactly the same age, would be placed in the same minor subdivision in the scale. Recognizing this, geologists rarely attempt to correlate the subdivisions of an age in different regions, but confine their use to local areas. Fig. 1. — Unconfokmitt. The inclined strata were deposited and tilted before the horizontal strata were laid down. Between the time of deposit of the tilted strata and that of the horizontal, several geological ages may have elapsed. Thus the term Silurian is used in all countries, but the sub- division Niagara is a local Ncav York term, and indicates a part of the Silurian, whose position in the New York column is perfectly definite, and whose fauna is practically uniform. How far such a term can be extended, even on the same continent, depends upon a variety of circumstances, but, generally speaking, its use is local. The stratified rocks are divided, according to these features, into a chronological series of large divisions of a general nature, and subdivisions of local nature. In the table which follows, the American terms are given, and no attempt is made to correlate these with their probable equiv- alents in other countries. EOCKS OP THE BAETH's CRUST. 47 2 QUATERNARY i Recent o (Age of Aran) Plktstocenb o TERTIAET = (Age of Mammals) Pliocene Miocene o KOCENE 3 o CRETACEOUS Lahamie Ui'PEE Cketaceous Lower Cuetaceotts a^M JUEA-TEIAS JUUAbSK^ s TRIA9SI0 * CAEBOMFEEOUS (Age of Plants) Permian Coal Weasures Lower Cabbonifeeous or Sub-Carboniferous DEVONIAN (Age of Fishes) Catskill ClIEMUJJG Chemung Portage Hamilton Genesee Hamilton Marcellus COKNIFEEOUa Corniferous Schoharie o Canda-Galli N f ■< s UPPER SILURIAN Oriskany '^ Lower Helderbbeg ^ Sallna NlAGAEA Niagara CUiiton Medina LOWER SILURIANS Trenton Cincinnati Utica Trenton Canadian Chazy Quebec Calciferoua CAMBRIAN Upper CAiiBRiAN^ Middle Cambrian Lower Cambrian ALGONKIAN Keweenawan 8 Upper HuKONLiN Lower Huronian AECHEAN Laueentian (Fundamental Complex) ^ There is a tendency in some directions to substitute the term Pleistocene for Quaternary. 2 The United States Geological Survey adopts the term Neocene to include the PUocene and Miocene. 2 In Europe, the subdivisions of the Tertiary are particularly well marked, and a fourtli division, Oligocene, is recognized as occurring between the Eocene and Miocene. * The term Newark is now used by the United States Geological Survey to include the strata of the eastern states, which were formerly called Triassic. The Jurassic and Triassie periods are not well developed in America, (For continuation of notes, see following page.) 48 ECONOMIC GEOLOGY OF THE UNITED STATES. The above table gives the best recognized names for the most prominent members of the geological column. Minor subdivisions are introduced only in the case of the New York Devonian and Silurian. Each period contains many minor subdivisions based upon local studies, and, in the Cretaceous, for instance, the names for the minor subdivisions of the Atlantic coast series differ from those of the central western states, and these in turn are different from the names applied to the Cretaceous strata of the Pacific coast. The subdivisions are therefore of local value only, and will be learned by a study of localities. Disturbance of the Rocks. — While in places the surface of the earth is composed of sedimentary rocks in orderly suc- cession, one above another, and in a very nearly horizontal position, there are large areas where they lie in very much disturbed positions. The earth is apparently losing heat and, in consequence, contracting, the outer crust endeavour- ing to accommodate itself to the constantly decreasing size of the interior. It is, consequently, wrinkling very much as an apple wrinkles by the loss, of water as it dries. Speaking broadly, and without entering into the discussion of the various theories, this seems best to account for the con- tinental and mountain folds of the earth's crust. ^ Some of the minor divisions or epochs of the Devonian and Silurian are introduced here, because they are well developed and well worked out in New York state. 6 In England, the term Ordovician is used as the equivalent of Lower Silurian, and the name Silurian is confined to the upper division, but this has not been generally adopted in this country. ^ This division of the Cambrian is more perfectly developed in Europe than in the United States. ^ This division of the pre-Cambrian rocks is based on the Lake Superior region, where these strata are better exposed and more fully studied than in any other part of the country. The Archean includes those rocks "^^hich show no sign of clastic origin, and have no indications of organic remains. Algonkian includes the strata between the true Archean and the true Cambrian. They show signs of sedimentary origin, and, when more carefully explored, may yield fossils. The rocks are distinctly older than the Cambrian, and also markedly younger than the Archean, which may be in part the original crust of the earth. BOCKS OF THE BARTH's CEUST. 49 As a result of this process, portions of the land are rising, others sinking, with reference to the datum-plane of sea- level. It is because of these changes that the great thickness of sedimentary rocks is possible. Of the 40,000 feet of such strata in the Pennsylvania column, the greater number are rocks formed not far from the shore lines. Such a vast accumulation under such conditions proves a long-continued sinking of the sea-bottom at this point. The fact of the existence of these marine rocks at present above sea-level points conclusively to a subsequent upheaval. A study of the region has proved that, from the Cambrian to the close of the Carboniferous period, the sea-bottom sank; then followed an elevation, and since that period this elevation has been maintained and even added to, although the actual elevation has been reduced by the long-continued erosion to which the area has been subjected. Such changes in relative position of land and sea are among the most common phenomena with which the geologist has to deal. Not only have they taken place in the past, but, even at the present time, they are being registered along the coast lines, as slow movements of the land, just as in the past. The presence of peat bogs and submerged forests beneath sea-level, and of beaches and wave-cut cliffs above the present shore line, is recorded on many coasts; and if more evidence is needed, it is necessary to state merely that, on the coast of Sweden, man himself has recorded the pres- ence and amount of these changes by actual observations upon fixed bench-marks. At times the land is bodily uplifted, forming plains or plateaus, according to the amount of uplift. In such cases, although elevated above sea-level, the rocks retain their 50 ECONOMIC GEOLOGY OP THE UNITED STATES. original horizontality. If the uplift is unequal, the rocks may break along a given plane, and upon one side move hi_gher than on the other, forming a fault, — a dislocation of the rocks accompanied by differential movement. The fault plane may be vertical, or it may dip, or hade, one way or the other. The side which is the higher is called the upthrow side, that which is lower the downthrow, without regard to which side has actually moved. A fault in which the hade is toward the downthrow is called a normal fault (Fig. 2) ; where toward the upthrow, a reverse fault (Fig. 2), and here a vertical shaft will pierce the same stratum twice, N V R Fig. 2. — Cross-section showing normal fault (N), vertical fault (F), and reverse fault (jB). AB, downthrow ; BC, lateral throw. once on each side of the fault plane. Where the fault plane is nearly horizontal, or nearly parallel to the bedding, it is called an overthrust fault, because by this means earlier strata may be thrust over upon later strata. When the horizontal direction of a fault plane is in the direction of the dip of the strata, the fault is a dip fault ; when at right angles to this, a strike fault (Fig. 3). Folding of strata is even more common than faulting, for even the most rigid of rocks may bend when the pressure of the overlying rocks is sufficient to prevent them from breaking. A simple upfold of the rocks is an anticline EOCKS OF THE BAKTH S CKUST. 51 (Fig. 3) ; a downward fold is a syneline (Fig. 3) ; and a single rise, followed by a horizontal or nearly horizontal condition of the strata, is a monocline. The direction in which the rocks pitch into the earth is the dip, and the angle of dip is the angle made by this plane with the horizontal. The strike is a horizontal line at right angles to the dip and in the plane of the dip, or the strike is the horizontal direction of the outcropping stratum. Folding of rocks in mountains may be of one or all of these simple types, or it may be complicated by faulting, or the folding itself may be extremely complex. At times the rocks are Fig. 3. — Section showing anticlinal (A) and synclinal folds {B), overturned folds ((7), and a strike fault (D). 1-2, direction of dip. folded so far that they become overturned, in which case older strata appear to lie upon younger, and a careful study is necessary to detect the cause. The folds themselves may be folded, and all of these complications added to the in- trusion of igneous rocks, the metamorphism of sedimentary strata, and the subsequent erosion of the area, gives to us an extremely complex maze of rocks. It is in such places that mines are commonly located.^ 1 This brief statement of .such geological facts and principles as seem absolutely necessary for a comprehension of the elements of economic geology might be advantageously supplemented by a thorough course in geology. The reader is referred to Geikie's Text-Book of Geology, Geikie's Class-Boole of G-eology, Jukes-Browne's Physical Geology, Dana's Manual of Geology, or Le Conte's Elements of Geology, for a complete presentation of the subject. CHAPTER III. PHYSICAL GEOGEAPHY AND GEOLOGY OF THE UNITED STATES. Thbee are five geographical zones in the United States : (1) the southern coastal plains; (2) the mountains of the eastern states ; (3) the inland plains and plateaus of the central western and southern states ; (4) the Lake Superior hilly region, a southern extension of the Canadian Highlands; (5) the Cordilleran region, including the Rockies, Sierra Nevadas, and Coast ranges, with their enclosed plateaus and basins. These are capable of much more minute subdivision, but this will serve as a general classification upon which to base the summary which follows. Coastal Plains. — There are several distinct parts to this area, all of which, however, are marked by the possession of the general features of a plain extending inward from the coast line, and composed of recent strata. The Quaternary Coastal Plains, or coastal plains proper, a subdivision of this general region, are the most recent additions to this country ; being, in fact, old sea-bottoms, so recently elevated above sea-level that in many places the fossils entombed in their strata are the same as the living species in the neigh- bouring ocean. The rocks here are horizontal, or nearly so, and consist of the usual materials formed along shore lines. Sandstones, clays, and conglomerates predominate, and while in some places the strata are partly or completely consoli- dated, for the most part they are still incoherent deposits. 62 PHYSICAL GEOGKAPHT AND GEOLOGY. 53 Their origin has been partly from the action of waves upon the old shore line, partly from river deposits assorted and distributed by the oceanic waves and currents. Just such a deposit is being formed near the shore in these same regions at present. The coastal plains, which exist in New Jersey as a narrow strip and are not found north of this state, increase in size toward the south, until in Texas they have a width, in places, of from forty to fifty miles. It is proper to include here, also, the delta and lower flood plains of the Mississippi, which are in part the elevated deposits of this river, formed in a great estuary, in part the flood plain deposits of the river formed since the elevation of the region. In topography, these plains are extremely simple. Where they attain their best development, in Texas, they are exceedingly young, so young, in fact, that a perfect system of drainage has not yet been established upon them. There is a monotonous stretch of dead level plain, relieved only here and there, where some stream, extending out from the interior, has sunk its channel to a slight depth in the strata, and furnished a drainage sufiicient for the growth of trees. Between the streams there are flat-topped divides, swampy, and occupied by a growth of un nutritious swamp grass, because undrained. A few small streams have begun to develop in the areas between the extended streams, but as yet very little progress has been made. Skirting this plain on the seaward side is a strip of varying width, in which new land is being made. Bars are being thrown across the river mouths by the combined action of tides, waves, and winds; lagoons are being formed, and these are being filled with sediment and by the growth of marsh vegetation. 54 ECONOMIC GEOLOGY OE THE UNITED STATES. This region is at present of very little economic impor- tance, for the reason that it is inaccessible. What stores of clay there may be below the surface, or what local deposits of iron, or even of lignite, where streams have brought down vegetable matter, can only be conjectured by a comparison with the similar deposits formed in the age immediately pre- ceding this, and at present existing in the region immediately to the landward. At present the only economic products in the region are the sands along the shore. Florida Plains. — Florida, which forms a part of the general region under consideration, is a unique geographic unit. It is a region of Tertiary, essentially calcareous rocks built upon a submarine bank whose origin is not clear. Being situated in the warmer waters, coral growth was possible; and in this respect it differs from the other por- tions of the coastal plains, where the ocean water was freshened and clouded with sediment by the influx of river water. As Florida was, at the time of its construction, practically unaffected by land water, so also to-day we find no land streams extending across it. The drainage is that of newly developed streams, and the short time that they have been in possession of the land, together with other causes, has prevented them from draining the peninsula perfectly, and, consequently, immense swamps and shallow lakes exist as a feature of this geographic form. Since the streams of the Florida region are practically sediment- free, coral growth is still possible upon the shore and upon the off-lying banks, so that, by this means, added to the influence of the mangrove tree, which grows with its roots in the salt water, the coast of Florida is growing outward. Tertiary Coastal Plains. — While the coral beds of the PHYSICAL GEOGRAPHY AND GEOLOGY. 55 Florida peninsula were being developed, the coast line of the southeastern states was some distance farther inland than at present. This condition did not exist in New England, excepting in the off-lying islands ; but from New York, southward to the Rio Grande, the land was lower, and, in general, the submergence increased to the south- ward. The submerged strip in Texas reached inland nearly as far as Austin, the present lower course of the Rio Grande was a great estuary, and an extensive embaj^ment extended well up the valley of the Mississippi. Apparently the coastal conditions were not unlike those at present pre- vailing, and the deposits are just what we know to be forming along the present shore line. These strata have been uplifted without folding or extensive faulting, but are inclined gently seaward, giving a slight tilting with an in- creasing elevation inward. Cretaceous Coastal Plains. — In the immediately preceding period, the Cretaceous, the geography of the country was vastly different from the present, the Rocky Mountains not having then been formed, and their area being, in large part, occupied by oceanic water. The far west was separated from the east by an arm of the ocean, and in all these areas of water Cretaceous deposits were formed. There is no genetic difference between the plains formed in the west and those which are found skirting the eastern base of the Appalachians, but it will be necessary to divide these two areas and include the Texas Cretaceous with the other central and southern plains, and for the present consider only the Cretaceous deposits east of the Mississippi. The eastern coast line was still lower than in the Tertiary, which followed, and coastal plains were formed, remnants of which 56 ECONOMIC GEOLOGY OF THE UNITED STATES. are still found skirting the inner margin of the Tertiary Coastal Plains at Martha's Vineyard, Long Island, in "parts of eastern New Jersey, in central Alabama, and north- eastern Mississippi, as well as elsewhere along this line. They are, for the most part, scarcely more disturbed, though slightly more consolidated than the Tertiary. In these Tertiary and Cretaceous plains, the clays are usually still plastic, and the sands frequently only partially consolidated ; but the coral rocks of the Florida region are more indurated, because calcareous rocks are easily consoli- dated by the action of percolating water. This series of rocks is prolific in certain classes of economic deposits. The clays of the Cretaceous and Tertiary in New Jersey and elsewhere, and the phosphate deposits of the South Carolina and Florida districts, are of primary importance ; and in Texas there are extensive beds of lignite and of iron ore, while in Louisiana valuable salt deposits occur. Triassic Coastal Area. — Between these two plains and the mountains, there are two intermediate areas, one composed of the older Palseozoic strata, forming the foot hills and the eastern plateaus of the Appalachians, the other an area of Triassic strata, which may be considered under the general division of the eastern plains, although, in reality, they belong to a type of their own. What the conditions were in Triassic times, it is not easy to say, nor can it be stated how extensive the Triassic deposits were. The strata existing at present are chiefly sandstones and conglomerates of shore line, or, as in the case of the Connecticut valley area, of estuarine origin. Local areas occur in the south; there is an extensive area in Pennsylvania and New Jersey, forming, in the latter state, the undulating plains between the High- PHYSICAL GEOGRAPHY AND GEOLOGY. 57 lands and the Cretaceous plains ; and in the Connecticut valley there is an area extending from the Sound to the northern part of Massachusetts, narrowing toward the north, where, in the Triassic period, the head of a bay was situated. During Triassic times, and also shortly afterwards, there prevailed in the region under consideration a period of volcanic activity, the last one to which the region east of the Mississippi has been subjected. Great flows of lava were poured out upon the surface in the Connecticut valley and New Jersey ; and, both at this time and later, dikes of trap or diabase were intruded across the strata as well as between them. The period of volcanic activity was widespread, and the character of the erupted material moderately uniform from North Carolina to Nova Scotia. Not only were the Triassic strata themselves cut by these traps, but all the older rocks in the neighbourhood were also traversed, even to a considerable distance from the Triassic. With the beginning of the Cretaceous age, these eruptions ceased. The trap hills near Patterson, New Jersey, the Palisades of the Hudson, East and West Rock at New Haven, the Hanging Hills of Meriden in Connecticut, and Mt. Hol- yoke in Massachusetts, are all witnesses of this period of vulcanism. Partly on account of the great age of the strata, partly as the result of the volcanic intrusions, and partly because the rocks have been subjected to folding and faulting, the sand- stone of Triassic age is compact and well consolidated. When the texture is even, and the colour reddish brown, owing to the presence of iron, the sandstone of this age is of value for a building-stone; and its importance for this purpose is greatly increased by its nearness to the market. 58 ECONOMIC GEOLOGY OP THE UNITED STATES. There are also metalliferous deposits in the Triassic at the contact of the igneous rocks, but these are usually of but very little value. Moimtains of the Eastern States. — This area is divisible into two important geographic units, the Appalachians and the older Archean mountains of New England, which also extend southward, east of the Appalachians, and northward into Canada. The Eastern Archean Mountains. — This area is a region of hills and low mountains, worn down to their very core, and consisting of rocks chiefly of metamorphic or of igneous origin, with here and there areas of Palaeozoic strata. The region has had an exceedingly complicated history. It, together with a large portion of eastern Canada, consists chiefly of Archean rocks which, before the beginning of the Palaeozoic era, were folded into a series of mountain folds of extremely complex structure and attitude, being even then composed of metamorphic and igneous rocks of the same character as the strata which at present constitute their mass. Since then they have been again folded so as to include Palaeozoic rocks. This was a part of the land which furnished the sediment out of which the rocks of the Appalachians are constructed, and in this area must be included, not only much of eastern Canada and New Eng- land, but also the Adirondacks, the Highlands of New Jersey, and the low Archean hills east of the Appalachians in Pennsylvania, Maryland, and the more southern states. The exact history of this area cannot be presented, but it is composed of distinctly igneous rocks (diorites, granites, syenites, etc.), and of metamorphic rocks, whose origin is uncertain, but which may be, in part, altered sedimentary PHYSICAL GEOGRAPHY AND GEOLOGY. 59 strata. At the beginning of the Cambrian period, not only were these rocks much folded, faulted, and metamorphosed, but also they were much denuded. The old Cambrian shore line can still be traced in places, as in the Adirondacks and on the western margin of the New Jersey Highlands. A new period of mountain growth occurred during the Palaeo- zoic, presumably at the time of the growth of the Appa- lachians, for all the rocks included in these mountains are included here also. Apparently the folding was more intense in New England than in the Appalachians, since, by its action, the Palaeozoic strata have in places been meta- morphosed almost beyond recognition, while in the Appa- lachians they have not lost their character. It is probable also that the mountains were higher here, and that igneous rocks were again intruded into the mountain cores, and in places caused to flow out upon the surface. Be this as it may, we have, in the New England area and the northern and southern continuations of it, an extensive mountain region worn down to its very core, and revealing to us rocks which are apparently as old as any on the earth's surface. Owing to its complex history and structure, there is, in this region, a great diversity of economic deposits. There occur here great areas of granite, of marble and slate, deposits of iron, and, in small quantities, practically all the metalliferous deposits. For reasons to be suggested later, the metalliferous minerals are not generally accumulated here in great abundance. Appalachian Mountain Region. — The Appalachians proper are folded rocks of Palseozoic age. No later strata are in- cluded, because the mountains had practically ceased growing when these were deposited ; and no earlier rocks are found 60 ECONOMIC GEOLOGY OF THE UNITED STATES. in the Appalachians proper, because erosion has not been carried to a sufficient depth to reveal the underlying plat- form, excepting to the east, where the Palaeozoic strata were perhaps thinner and the mountains higher. Both to the north and the south the folds of the Appalachians die out, and on the western side they become lower, and finally merge into the plateau of the central states. In these mountains, the topography is dependent upon the rock structure. The strata have been thrown into great waves or folds, sometimes sharp, sometimes broad, and usually pitching in the direction of their axes, which are nearly parallel to the trend of the mountains. The rocks are alternating sedimentary strata, with varying hardness and with a variable dip, usually at a considerable angle to the east or the west. Owing to the long continued erosion to which these mountains have been subjected since the close of the Carboniferous, the variations in hardness have had a marked influence in determining the topographic featiu-es. Where hard sandstone or conglomerate beds outcrop there are hills ; and the valleys are usually located in the lime- stone belts, although some streams flow directly across the strike of the strata, and cut at right angles both the hard and the soft layers. The hills are linear, with their axes parallel to the mountain folds, and they often follow the irregularities of the outcropping strata, as these turn in passing from one fold to another. This district furnishes us with much building-stone, slate, marble, iron, petroleum, nearly all the anthracite, and much of the bituminous coal of the country, as well as many other valuable materials in smaller quantities. The importance of mountainous districts, as producers of valuable ores, is due PHYSICAL GEOGRAPHY AND GEOLOGY. 61 chiefly to the fact that the rocks are folded, so that erosion reveals a great variety of strata, and that in mountains the conditions which favour the accumulation of such deposits are present; namely, the formation of cavities and the presence of eruptive rocks. The Appalachians are sur- prisingly free from eruptive rocks, while faults and cavities are much less frequent there than in the Rocky Mountains, so that the greater importance of the latter region as a producer of metals is easily understood. It is possible that the old New England mountains, at the time of their greatest development, simulated more closely the Rocky Mountains than do their smaller neighbours the Appalachians. Central Plains. — Very nearly one-half of the country is included in this area. Commencing at the western margin of the Appalachians, where the rocks cease to be thrown into waves or folds, there is a series of plateaus and plains extending westward to the base of the Rocky Mountains and southward to the Gulf of Mexico. Already those portions of the plains which form the marginal and coastal areas of the east have been described. The portion which remains consists of Cretaceous and Palaeozoic strata chiefly, although in Nebraska and vicinity the rocks were formed in a great inland sea of Tertiary age. Considering the area as a whole, the strata are very nearly horizontal, and the country a plain scored and eroded to a greater or less degree in different places, so that at times its character as a plain is almost destroyed. The geology is by no means as simple as might be inferred from this statement. At different points, rocks of nearly all ages outcrop at the surface, and the present condition is the culmination of a complex history of elevation and sub- 62 ECONOMIC GEOLOGY OP THE UNITED STATES. mergence. The essential features of the entire region are the almost complete absence of igneous rocks, and the fact that the strata have been uplifted without marked disturbance. These statements must, however, be qualified, since in several places the strata are disturbed and igneous rocks are present. There is a broad gentle fold, in Ohio and the neighbouring states, known as the Cincinnati arch. In Missouri, a knob of igneous rock projects through the Palseozoic strata at Pilot Knob. A large area in Indian Territory and Arkansas has been extensively folded and subjected to igneous intrusion ; and the same is true of a smaller region in Central Texas, northwest of Austin. The Black Hills also form an igneous and folded area in the midst of the plains, and there are other similar areas elsewhere. Some of these disturbed regions, as those of the Black Hills and Indian Territory, are actual disturbances in the plains ; but others, as Pilot Knob, are islands of pre-Palseozoic age. These regions, though considerable in number, are small in extent when compared with the plains as a whole. Properly, they should be con- sidered separately; but, in this generalized statement, they need only be mentioned as disturbances in the great area of almost universally horizontal rocks. These strata, being practically undisturbed by folding, faulting, or volcanic intrusion, are not such as would be expected to 3deld up large stores of metallic wealth, yet much zinc and lead and some iron come from this area, while salt, gypsum, coal, petroleum, and gas, are found in great quan- tities in various parts of the region. The major part of the rocks are well-consolidated limestones, sandstones, and shales, so that in this area there is an almost inexhaustible supply of the non-crystalline building-stones. PHYSICAL GEOGRAPHY AISTD GEOLOGY. 63 Lake Superior Region. — In northern Michigan, Wisconsin, and Minnesota, there is a region of metamorphic rocks, a southern extension of the Canadian series, which, like those of New England, have had an extremely complicated his- tory. Here there is a central core of complex Archean sur- rounded by later rocks, among which are late Archean, Algonkian, and Cambrian strata. This has been a moun- tainous region ; but, unlike New England, it has not been subjected to intense Palgeozoic folding, although since the first period of mountain-building there has been considerable folding and faulting, accompanied by the intrusion and extrusion of igneous rocks. It is now a hilly region, much less mountainous than New England, but, like this province, is an old mountain worn down to its roots. From here are obtained immense quantities of copper and iron, and in this area there are large stores of building-stones. Cordilleran Region.^ — Toward the close of the Cretaceous there existed, in the area now occupied by the Cordilleras, a great sea with archipelagos, and perhaps even continuous masses of land, composed of older rocks. An extensive dis- turbance of the strata, which has not yet ceased, was then initiated. This disturbance extended from Alaska to southern South America, and, although in places the moun- tains are still growing, the disturbance has now passed its maximum, and is declining. In the course of its develop- ment the rocks were extensively faulted and folded, igneous rocks were intruded into the strata, and numerous volcanoes poured out floods of lava and quantities of volcanic ash 1 Only for the purpose of a general statement can such a comprehensive term be allowed. This is in reality a very complex province, composed of several geographic units. 64 ECONOMIC GEOLOGY OF THE UNITED STATES. upon the surface, while during all this time erosion was at work attempting to wear away that which was elevated. The present Cordilleras have resulted from this complex interaction of forces. All ages of strata, from the Archean to the Pleistocene, are included in this region, and very nearly every variety of rock is found there. By the folding, chains and ranges were built, and valleys formed between them, some of these being great basins and extensive plateaus. At first many of these valleys, including parts of the Great Basin, were partially enclosed seas, and finally lakes with an outflow to the sea ; but, as the enclosing mountains grew higher and the climatic conditions changed, these became transformed into interior basin lakes, then salt lakes, and in many cases they eventu- ally became completely desiccated. The deposits of these seas and lakes were in part incorporated in the later moun- tain folds, but the most recent of them still remain hori- zontal strata of gravels and clays, forming great flats between the mountains, often with no drainage to the sea. In this region there exists very nearly every economic product of the earth's crust. There is probably no region of similar extent in the world where such a variety and abundance of mineral wealth is stored. Already in develop- ment it exceeds any other portion of the earth in the output of many metals, and its resources are only partly understood. The more valuable and better known substances only have been discovered, and of these there undoubtedly remain many yet to be found. There is, also, in this province a vast store of mineral wealth known to exist, but at present undeveloped on account of its inaccessibility and remoteness from the market. Among these may be mentioned building PHYSICAL GEOGRAPHY AND GEOLOGY. 65 and ornamental stones, clays, gypsum, salt, coal, and iron. The metals, such as gold, silver, lead, and copper, which are of sufficient value for transportation come chiefly from this region, and their output is increasing every year. Nature seems to have conspired to produce here the proper conditions for the accumulation of a great variety of valuable minerals in great abundance; and what would otherwise have been an uninviting and sparsely populated region has become, in consequence of this prodigality of nature, a well- populated region. Summarized Q-eological History of the United States. This in general states the geological features of the several provinces of the country. The history of its development may be inferred from this statement, but it seems well to supplement it by pointing out the main steps of this evolu- tion ; to put in a summarized form the sum of our knowledge of the geological evolution of the country as a whole and of the grander geographic features. What the condition of the country was during the earliest geological ages is only obscurely understood ; but since that time the history becomes progressively more clear. That there was land, however, is shown by the fact that sedi- mentary rocks were formed. It is evident that there were land areas in the eastern seaboard states, in Canada, the Lake Superior province, and in parts of the Cordilleras ; but how extensive, or exactly where they were, cannot be stated. Besides these there were probably other Archean land areas, now destroyed, and buried beneath the later strata. In Canada, and in some of the seaboard states, such as 66 ECONOMIC GEOLOGY OF THE UNITED STATES. New Jersey, the Archean seems to be divisible into two dis- tinct groups of rocks, an older and a younger, the latter being derived from the former ; and in places there is some ground for a still further subdivision. There is no part of the Archean in the country which is better understood than that of the Lake Superior province. Here there is a central core of Archean of great complexity, an old mountainous land area, from which were derived immense quantities of sedimentary material of pre-Cambrian age, which, although since then greatly folded and faulted, is still much less dis- turbed than any area of similar age in this country, so that its true and original composition can still be determined. It is, therefore, of great' value as an indication of the condi- tions of that period. From a study of these rocks it is found that, as in many areas of more recent strata, both sedimen- tary and eruptive rocks occur, that a vast lapse of time was occupied in their formation, and that during this time moun- tain-folding and other orographic changes were in progress. Probably the history of this region was not distinctly unlike that of other Archean areas less easily studied. At the close of the Archean, there were many land and probably mountainous regions in the country. There was a very large area extending from Labrador to Lake Superior, and thence northwestward toward the Arctic, besides certain areas in this country, as mentioned above. At present, the rocks of Archean age outcrop where they have been uncov- ered from beneath later strata, or perhaps, in places, as in some parts of Canada, where they have never been buried. Where they are now found we know that they existed ; but how far they extended, and how many extensive areas of former land are now buried beneath the ocean, or beneath PHYSICAL GBOGEAPHY AND GEOLOGY 67 later rocks, will probably never be known. The Archean rocks were bigbly metamorphosed in most places even in pre-Palseozoic times, though they have undoubtedly under- gone some changes since then ; and into these strata granitic and other igneous rocks were intruded in Archean as well as in later periods. Around the margins of this land Cambrian sediments were accumulated. Such places show that shore lines existed not far from the seaboard of New England and also on the west- ern side of the New Jersey highlands, indicating an island of considerable linear extent extending southwards from New England. A shore line skirted a part of the Adiron- dacks; and there were shore lines on the southern margin of the Lake Superior Archean region, in Texas, and in parts of the Cordilleras. The probable geographic condi- tions, indicated by these shore lines, were a series of islands, mountainous and generally linear, marking, in a very rough way, the merest outlines of the developing continent. The backbone of the Laurentian highlands in Canada was the most prominent land area ; and linear islands or groups of islands extended along the eastern coast and in the Cor- dilleras, their greatest length being, in general, parallel to the present mountains of these two regions. Probably other islands existed, and perhaps the extent of the islands just described was really much greater than has been stated. It is an interesting fact that the present valley of the St. Law- rence was then a strait between New England and the Laurentian Archean land areas, the valley being thus early indicated. It is also worthy of note that the present valley of the Mississippi was a sea partly enclosed on three sides, as at present, and that the eastern and western enclosing areas 68 ECONOMIC GEOLOGY OF THE UNITED STATES. sketched, roughly, the present though much later-formed mountains. During the remainder of Palseozoic times, — that is, until the close of the Carboniferous, — the event of chief impor- tance was the accumulation of vast quantities of sediment in the seas surrounding these land areas and furnished from their destruction by weathering and erosion. There must have been a slow and long-continued subsidence of the sea and a long-continued and vast destruction of the land areas. The sediment was furnished to the sea, where now the Appa- lachians exist, from a land area which probably extended seaward beyond the present eastern coast line. In the Cor- dilleras the events are less well determined. Toward the close of the Palaeozoic, much of the region of the Appalachians and of the central states became shallow water and marshy land, upon which the coal vegetation flourished ; and the same is probably true of some parts of the Cordilleras. Immediately following this came the great revolution which culminated in the formation of the Appalachians and the elevation of the central states above sea-level, — an eleva- tion which has been maintained since then, with occasional oscillations, but continuous elevation above the sea. The Jura-Trias ages were of little importance in the evolution of the eastern part of the continent, although some changes took place in the Appalachian district, the most important being an increased elevation accompanying the volcanic out- bursts which caused the traps of the Palisades, the Connect- icut valley, and elsewhere. In the west, however, this period was marked by the growth of the Sierra Nevadas and the addition of much land to that part of the continent. At the beginning of the Cretaceous the outline of the PHYSICAL GEOGRAPHY AND GEOLOGY. 69 continent was tolerably well determined, and only finishing touches were necessary to complete its present form. The Pacific bathed the base of the Sierras, the Coast Range not then being formed ; and along the eastern margin of the con- tinent the ocean covered the eastern part of all the states from New Jersey to Georgia. Florida, the greater part of Alabama, Texas, and Arkansas were beneath the ocean, and an arm of the sea extended northward, along the line of the Rocky Mountains and the states east of them, beyond the confines of this country. Islands existed in this mediter- ranean sea, in Texas, Arkansas, Indian Territory, Dakota, and probably elsewhere, while in the Sierras arms of the ocean formed estuaries, or in some cases had been shut in to form lacustrine basins. The country east of the Mississippi was nearly completed, excepting for the addition of the coastal plains; but the western region was yet to be per- fected. During the Cretaceous period sediment accumulated in these inland seas and along the continent margin ; and at its close the great inland sea was transformed to a dry land area with many lakes. The Coast Range was not then formed, nor were the Rocky Mountains more than begun. To the eastern coast a slight addition was made, but the Tertiary plains were yet unformed, and the Gulf of Mexico extended as an arm of the sea up the valley of the Missis- sippi for a considerable distance. During the Tertiary period the Coast Range was devel- oped, and vast floods of lava were poured out upon the surface. The Rocky Mountains were also formed then, and by these mountain-foldings great lakes were caused, partly in the Cordilleras, partly on the eastern margin. In 70 ECONOMIC GEOLOGY OF THE UNITED STATES. the Rockies also vast quantities of lava were erupted, and this period of volcanic activity is only just now, within recent geological times, brought to a close. The great Cordilleran lakes existed even into the Quaternary period, but most of them have been drained, while some were destroyed by mountain-folding and the lake sediments built into the mountains. Even now, however, some of the lacustrine basins exist as interior basins, although because of the aridity of the climate, they are not now occupied by water. The Great Salt Lake is a shrunken remnant of such a lake in a great basin. By the close of the Tertiary period the southern and east- ern coast was nearly completed, though in Quaternary times a slight addition has been made, particularly in the south. Two notable areas have been added to this coast, one the delta and flood plain of the Mississippi, the other the Florida Peninsula. Both of these areas, which form a part of the coastal plains, were formed partly by material deposited and partly by the elevation of the land. At the close of the Tertiary period the land, in the north at least, was considerably higher than at present, and during the immediately succeeding period, the Pleistocene, the northern part of the continent, as far south as New York and Cincinnati, was covered by an ice sheet which has some- what modified the topography and the drainage, partly by its erosive effect, but chiefly by means of the detritus which it has left scattered over the surface. This period, like all which preceded, has had its effect upon the economic resources of the country. It has given to us many of the brick clays, it has changed the character of the soil, often disastrously, and it has given us the lakes and waterfalls PHYSICAL GEOGRAPHY AND GEOLOGY. 71 which abound north of the southern margin of the glacial drift. Accompanying its presence there was a subsidence of the land in the north, which has transformed pre-existing river valleys into the estuaries and harbours which have been so influential in giving the northern states such importance in commerce. This is, briefly, and without entering into details or proofs, the general evolution of the continent. Its form was roughly sketched in the very earliest period and it has been slowly perfected, although undoubtedly many changes yet await it. No adequate mention has been made of the effect of erosion during all this time, but this is of prime importance. Old lands have been worn down and the ruins deposited in the water to afterwards be again built into land and perhaps again transformed into sediment. Erosion and sculpturing have been ever-acting, and the present form of the continent is the resultant of the conflict between the two opposing forces ; the one tending to build up, the other to tear down. CHAPTER IV. ORIGIN OP ORB DEPOSITS. Original Condition. — Deposits of ore are accumulated under certain conditions which favour the gathering together of like kinds of minerals in concentrated form. It will be found, as the later pages are studied, that there are many diverse ways in which this accumulation is brought about, and that it is possible to offer a classification of ore deposits based upon origin. What the original condition of metals and metalliferous deposits may have been cannot be said. There are some who believe that the interior of the earth is, in part at least, composed of unoxidized metals, and that the ores which we find in the rocks are, in reality, the form assumed by these elements when they reach the surface, and come under the influence of the surface conditions, where oxidizing com- binations are prevalent. Be this as it may, igneous rocks, which bear to the surface the substances existing below the surface, contain in their mass a greater or less proportion of metals in mechanical or chemical combination. It requires no careful analysis, nor even a microscopic study, to detect iron and, frequently, manganese, in the form of their oxides, in these eruptive rocks. Sometimes, copper salts and other metalliferous compounds are present in sufficient quantities to be detected by the eye. Analyses have for a long time shown that rarer metals are present in small quantities in 72 OKIGIN OF OEE DEPOSITS. 73 many eruptive rocks ; and very careful analyses of certain rocks, made for the purpose of determining the point, have shown that rare and precious metals are present. They seem to be more prevalent in the complex basic bisilicates, such as augite and hornblende, and hence the basic rocks (diorites, diabases, etc.) are more prolific producers of these metals than are the acid rocks. It is to Sandberger ^ that we owe the first proof of these facts, although his experiments have been repeated and extended by others. Previous to the time of his observa- tions, analyses of rocks had not revealed any but the more common metals ; but by separating the olivine, hornblende, mica, etc., and analyzing these, he proved the existence of iron, nickel, copper, lead, zinc, tin, cobalt, and other metals. Since this study, nearly all metals have been found in the common minerals in appreciable quantities. Nearly all lithia micas contain tin ; muscovite, although poor in other metals, usually contains copper ; and black micas carry many metals. Sandberger also found the disseminated metals in slates, and he proved also that the veinstones might all be derived from the common rocks ; for even fluorine is found in mica and barium in feldspar, while the other necessary elements are common enough. Sedimentary strata, being all formed from material either directly or indirectly derived from igneous rocks, naturally contain these metals also, and the same holds true for meta- morphic rocks. In other words, metals are disseminated through all rocks, being much more prevalent in some than in others, but generally being in such small quantities that only very careful analyses serve to prove their presence. 1 Sandberger, Untersudmngen uber Erzgdnge. 74 ECONOMIC GEOLOGY OF THE UNITED STATES. Removal of Original Ores. — In order to bring these metals into concentrated form, some agent is necessary to act as a carrier, and this agent is usually the ever-present water. All rocks contain water. In the quarry, it is shown by the loss of weight when the quarried block is exposed to the dry air; in the volcano, its presence is proved by the clouds of steam which rise from the lava stream, and the vesicles and cavities which it causes in the lava by its expansion. This water was partly built into the rocks when they were formed; but partly, probably chiefly, it comes from the surface. During every rain, a part of the fall flows off as surface water; a considerable portion creeps through the soil and reappears in springs; but a small portion starts on an underground journey, during which it often penetrates to great depths, traverses hard and soft rocks alike, and is ever present as interstitial water in the microscopic crevices in the rocks. Cold water, free from impurities, has little solvent power except for the most soluble minerals, such as salt, gypsum, or calcite ; but very little of the underground water is pure. As it passes through the soil and the surface coating of vegetable matter, certain acids and gases are absorbed. These give to the water an increased solvent power, and as it descends it may eventually become so strongly acid, or so alkaline, that even the most insoluble substances are taken into solution. The temperature of the earth progressively increases as the depth is increased, and hence water at con- siderable depths attains a temperature often high above the boiling-point, so that its power as a solvent is vastly in- creased. Even ocean water carries in solution small quan- tities of gold, silver, and most other metals, and it is probable ORIGIN OF OEE DEPOSITS. 75 that, under conditions of great heat, the percolating water of the earth becomes a solvent of as great power as many of our acids and alkalies. Its effect is expressed not alone by the material carried in solution and subsequently concentrated, but also, in many places, by alterations of the rock-forming minerals by the extraction of certain parts, or the addition of others. This form of change sometimes results in the com- plete destruction of one mineral and the formation of another. Origin of Cavities. — Granting, as we must, that the im- prisoned water of the earth bears ore in solution in many cases, there remains to be considered the more difficult subject of the manner in which this ore is concentrated. Many of the ores occur in cavities where they have been deposited from solution. Sometimes these cavities are only partly filled ; at times they are completely filled ; and it is not uncommonly the case that the cavities are not only filled but enlarged, the force which causes the mineral to be deposited being so great that the walls of the cavity are spread apart by the growing deposit. Joint Planes (Plate II.). — The most numerous cavities are those formed by joint planes, cracks extending across the rocks in given directions and breaking them into blocks without any sensible motion or displacement. Joint planes are of two kinds, — incipient, or those whose presence is shown only when weathering develops them, and normal joint planes, which, even without the aid of weathering, are present as dividing planes in the rocks. They are of the same origin apparently, and differ merely in the amount of development. In igneous rocks there are joints of cooling, the result of contraction by the loss of heat. The basaltic columns and the concentric, nearly horizontal joint planes of 76 ECONOMIC GEOLOGY OF THE UNITED STATES. granite are illustrations of these. Sedimentary rocks are crossed by joints of contraction, due, perhaps, to the loss of water; for when these rocks are formed, a certain amount of water is built into their mass between the fragments, and this may be lost, causing a considerable contraction, when the strata are raised above sea-level and drained by erosion. There is, also, in these rocks a possible contraction due to the loss of heat; but whether this is often sufficient to account for joint planes is a question. The most common b Fio. i. — Horizontal strata crossed by an irregular fault line, ab, which upon faulting produces cavities as in Fig. i a. cause of these divisional planes in sedimentary and meta- morphic rocks, and even in some igneous rocks, is contortion or folding, which causes stresses that are relieved by a frac- turing or jointing ; and hence all folded rocks are crossed by joints. These are generally nearly vertical; and two sets are commonly present, forming rhomboidal blocks, with angles frequently approaching the right angle and rarely very acute. Mineral veins are sometimes formed along these joints, which are channel-ways of easy passage for water ; and even where veins are absent, small deposits are frequently found. ORIGIN OF OEB DEPOSITS. 7T Fault Planes. — During the folding of rocks there are often formed faults or dislocations where one side slips past the other. These faults, being of deep-seated origin, often extend to great depths, and serve as passage-ways to the surface for the heated waters from below. If the fault plane were a perfectly straight line, the cavity would not be very great; but most commonly the fracture plane is irregular, and a series of cavities are thus often pro- duced where two concave walls come to rest opposite Fig. 4o. — The same as Fig. 4, showing the result of faulting along an irregular fault plane, producing alternate cavities and closed spaces. each other (Figs. 4 and 4 a). By the motion of the rocks the uneven walls, rubbing against each other, tear off frag- ments, and produce in the vein a crushed substance, a fault breccia, which is common where two projecting parts of the vein are in contact. At times the faulting amounts to actual crushing, and the rocks are very badly brecciated. Such a series of cavities furnish an easy channel for the passage of water. Solution Cavities. — Water, percolating through soluble rocks, such as limestone, dissolves the minerals, and forms cavities or caves which may later be filled with ore. Such 78 ECONOMIC GEOLOGY OP THE UNITED STATES. cavities are formed independently in some regions, but very frequently they have their beginning in joint planes ; and in faulted regions the vi^ater, which later served to fill the vein with mineral, may at first have dissolved cavities in the enclosing rocks. Minor Cavities. — Cavities exist in lava where there was a lack of supply of material, or, more frequently, where super- heated water expands into steam, and produces a pumiceous or scoriaceous lava. So, also, in sedimentary rocks there may be original cavities (usually on a small scale) where there was a lack of material, or where some soluble portion may have been dissolved after the formation of the rock, as, for instance, in or around fossils. The contact of sedi- mentary and igneous rocks, or of two diverse series of strata, owing partly to the difference in character of the two, and partly to the presence of minute cavities, is a plane of weakness, along which the underground water finds a pas- sage. Also the more porous rocks, such as sandstone, form channels, as is proved by the fact that artesian wells are found in such strata when bounded above and below by more impermeable layers. Besides these, there are numerous other cavities of small size and minor importance. Classification of Ore Deposits. — There have been many clas- sifications of ore deposits offered, and attempts have been made to classify them upon each of the three following bases : (1) mineral contents, (2) form of deposit, (3) origin of deposit. The first, that based upon mineral contents, is far from satisfactory, since the ores of silver, copper, zinc, and many others are all found in the same form of deposit derived in the same manner. It is not scientific ; and yet in any economic study this must serve as a primary basis for ORIGIN OP OBE DEPOSITS. 79 classification. An attempt to study ore deposits upon any other basis would involve much confusion, since it would be necessary to consider the veins of one class, as iron, for instance, then for the other metals in succession; and the study of any one metal would be scattered throughout various chapters. Therefore, as the primary basis for our study, we must adopt the metal. The more scientific clas- sification would discard the above and consider the relation of the ore deposit to its surroundings ; for if we have a vein of a particular form and origin, why should it be important whether it is one of lead or of copper, since both may be formed in the same way, and may even be present in the same vein? The great majority of classifications, apart from the eco- nomic, have been based upon the form assumed by the deposit rather than upon the origin. This, it seems, advances a matter of secondary importance to the first rank, and in the classification which is given here origin has been considered as of prime importance, and form of secondary importance.^ Carrying this scheme out to the end, and losing sight of 1 Other classifications are discussed in various books upon economic geol- ogy and upon ore deposits, and will not be considered here. Some of the subdivisions in this scheme are taken from Whitney's classification, which is most currently accepted in this country, and is by far the best of any based upon the form of the deposit. The classification here given had been used for two years by the author in the class in economic geology at Cornell University before hrs attention was called to the fact that a similar classiflcation was in use at the Houghton Mining School in Michigan. Its author, Dr. M. E. Wadsworth, published this classification in the early part of 1893 (Eeport of Michigan State Board of Geological Survey for 1891-92, p. 144. It was previously published in the Catalogue of the Michigan Min- ing School at Houghton) , and so far as it coincides with this classification Dr. Wadsworth has priority, both of use and publication, although in the two cases the scheme was originated independently. 80 ECONOMIC GEOLOGY OF THE UNITED STATES. the economic bearing, the character of the ore itself would be considered as of third importance. The following is the classification based primarily upon origin and secondarily upon form : ^ — I. Eruptive II. Mechanical m. Chemical (a) Disseminated. (b) Massive. (Sedimentary). (a) Precipitated. (6) True veins (c) Replacement. (d) Impregnation. (e) Concretionary. (/) Segregated. i. Chamber deposits, ii. Gash veins, iii. Fissure veins, iv. Ore channels. (^r) Contact {«: i. By sublimation. By concentration. I. Eruptive Deposits. — Already the eruptive deposits of original disseminated nature have been described, and it has been stated that nearly all eruptive rocks contain ores in 1 This classification might be much more minutely subdivided, but this seems hardly necessary for our purpose. Various classifications of ore deposits will be found in the following works : Report of Michigan State Board of Geological Survey for 1891-92, p. 144 ; Davies, Metalliferous Min- erals and Mining, p. 8 ; Phillips, Ore Deposits, p. 3 ; Whitney, Metallic Wealth of the United States, p. 34 ; Newberry, School of Mines Quarterly, 1880, p. 337 ; Raymond, Mining Statistics for 1870, p. 448 ; Pumpelly, John- son's Cyclopedia, 1886, VI., p. 22; Geikie, Text-Book of Geology, v- 5SQ; Le Conte, America7i Journal of Science, Vol. XXVI., 1883, p. 17 ; Le Conte, Elements of Geology, p. 234 ; Emmons, IT. S. Geol. Survey, Monograph, XII., p. 368. Classifications of ore deposits are also found in the German text-books of Von Cotta, Grimm, Serlo-Lottner, and Von Groddeck. Since this went to press a comparison of the various classifications has been published in Kemp's valuable treatise on Ore Deposits of the United States, pp. 42-65. This author also presents a classification of his own. ORIGIN OF OEB DEPOSITS. 81 greater or less quantities, though not in sufficient abundance to be classed as ore deposits without the intervention of some agent of concentration. The other subdivision of eruptive deposits, the massive, is almost equally unimpor- tant. There is no deposit of ore, known to be of eruptive origin, which is at present worked, although the deposit of native iron in Greenland, occurring in a basalt, is sufficiently rich to pay for extraction, provided its location was more favourable. This group may therefore be dismissed, its only importance being as a source of metalliferous substances for concentration under other conditions. II. Mechaiiical Deposits (Figs. 16 and 17). — When a rock containing metals is disintegrated by weathering, the products of disintegration go o£E, partly in solution, partly as mechanical sediment. It is chiefly in this manner that disseminated deposits become introduced into sedimentary rocks. Usually metalliferous minerals are easily decom- posed, and frequently, as a result of their decomposition, soluble salts are produced, or a very fine powder of hydrated and oxidized ore, which may be disseminated through fine- grained rocks. When, however, the mineral is compara- tively indestructible, as in the case of gold, platinum, and oxide of tin, it outlasts many of the other minerals of the disintegrating rock, and may become concentrated. Where the chemical durability is combined with mechanical strength, as in gold, which is not brittle and not easily worn down, this concentration is favoured; but under ordinary circum- stances this would hardly attain economic importance, were it not for the high specific gravity of some of this class of minerals. Gold, for instance, is disseminated through cer- tain rocks, but in such small quantities that by their mere 82 ECONOMIC GEOLOGY OF THE UNITED STATES. decay, without the assorting action of water, it would hardly be accumulated. Given, however, a rapid stream, the lighter minerals are carried off, while the heavy gold accumulates in pockets where the currents are less rapid. Such deposits are of the mechanical type, including not only the accumu- lations in stream gravels, but also those in talus deposits and those which more rarely accumulate along shore lines, where conditions are favourable. When the three metals, tin, plati- num, and gold, are excluded, this class of metalliferous deposits becomes unimportant. III. Chemical Deposits. — This group of ore deposits in- cludes all which come into their place by chemical action, and in it are included the vast majority of metalliferous deposits. There are a number of ways in which this form of mineral concentration is brought about, all of which, with the exception of some of the contact deposits, are caused by the intervention of water. (a) Precipitated Deposits. — Precipitated deposits, in the sense used here, include those which are formed by precipi- tation from solution, at the surface, when the liquid which carries the minerals loses its power to hold them, either as the result of the loss of some of its properties, or by the accession of some substance which causes a precipitation. The simplest illustration of this class of mineral deposits is that of bog iron ore, where water which has carried in solu- tion the hydrated sesquioxide of iron, obtained from the soil or the rocks, is, in the presence of certain vegetable acids, unable to maintain the solution, and the ore is precipi- tated frequently in a bog. Moderately extensive beds of impure iron are thus sometimes formed, and, being buried beneath other strata, become truly bedded deposits (Fig. 5). OEIGIN OF OKE DEPOSITS. 83 Practically the same class of deposit is formed about an iron spring, where the iron-bearing water, rising from the earth to the surface, loses some of its gases, and hence some of its power as a solvent, and is forced to deposit the iron about the spring. Applied to non-metalliferous minerals, the pro- cess finds illustration in the stalactites of caverns and the siliceous sinter about hot springs. In some cases true veins illustrate very nearly the same principle ; but probably other Fig. 5. — Bedded deposit of iron (a) . causes enter, and this group is so distinct in form and char- acter that they will not be classed here. (6) True Veins. — The term true veins is here given to those occupying pre-existing cavities where the mineral deposits have been placed by the agency of water. That percolating water is constantly active in its effort to fill cav- ities is shown by the study of fossils, such as Ammonites (shells allied to the chambered Nautilus of the present), where the chambers are filled with calcite, or silica, or even ores. The same is true of the gas cavities in lava flows, where geodes or amygdules are formed from the wall of the cavity toward the centre. The term true vein applied to such deposits is perhaps a trifle irregular, although there is no genetic difference between deposits from water in small 84 ECONOMIC GEOLOGY OP THE UNITED STATES. cavities and those in the type of the true veins, — the exten- sive fissure veins. i. Chamber Deposits (Figs. 21 and 23), or cave deposits, are closely allied to these small cavity deposits. Here the source of the mineral is usually local, often from the same stratum in which it is accumulated. The process is allied to segregation, excepting that a cavity furnishes a place for accumulation. On the other hand, some chamber deposits are so nearly allied to precipitated deposits that they might very well be classed in that group. Stalactites furnish instances of this form of accumulation, and in some of the chamber deposits true stalactites of ore are formed. ii. Crash Veins (Figs. 20 and 21) are comparatively rare and very local. The rock is cracked and spread apart, forming a local fissure, usually confined to one layer or stratum; and in these, as in the chamber deposits, the supply of ore is evidently local. Both chamber de- posits and gash veins are illustrated in the lead^zinc mines of the Mississippi Valley. iii. Fissure Veins. — The type of fissure veins (Fig. 6) Tig. 6. — Fault plane occupied by a vein is perhaps the most COmmOD — a true fissure vein. . ., . , ,^1, j- x- of all veins. The distm- guishing feature of such accumulations is that they occur in a fault or fissure in the earth. Such veins are frequently of great extent both vertically and horizontally, but their width is relatively small. Usually the bounding walls are distinct, although sometimes they are crushed and penetrated by ORIGIN OF OKE DEPOSITS. 85 the vein-forming mineral ; or the solid wall may be impreg- nated by the ore (as described below), either of which con- ditions tends to make the bounding wall indistinct. There is in these veins evidence enough, in many cases, to prove that the mineral deposits came from water which passed through the vein, apparently from below upwards. This evidence is present in the banding of the minerals forming the vein, the same minerals being found in succession on each side of the centre. That is, if quartz is found next to the country rock on one side, this mineral is found in the same position on the opposite side ; and if copper pyrite is found next to this on one side, it is present in the same position on the opposite side.i This banding is often very complex, and at times the cavity is completely filled, while in other veins the process of deposition was interrupted before the filling was complete. It is possible to explain this process satisfactorily by assuming that heated water, either acidic or alkaline, was escaping from the heated parts of the earth's crust toward the cooler surface portions, and that as the water rose it lost in heat, and perhaps also in its acid or alkaline contents, and hence in its power as a solvent. Deposition from the super- saturated solution might then be made necessary. Under uniform conditions of temperature and foreign contents there would be a uniformity of deposit at a given place ; and in proceeding from below upwards there would be a progres- sive change in the character or amount of deposit. A slight change, either a loss or an accession of heat or of contained substances, would bring about a change in deposit at differ- ent parts of the vein. These changes might occur vertically at the same time as the water ascended and lost heat, or 1 See Fig. 12, p. 98. 86 ECONOMIC GEOLOGY OF THE UNITED STATES. horizontally at different times as the conditions at a given point changed. It is highly probable that some of the hot springs which are found in various parts of the country are the points of escape of metalliferous-bearing waters which are at present engaged in the formation of mineral veins.^ There are certain peculiarities, found at times, not only in fissure veins, but in other mineral deposits as well, which call for a modification of this general statement. The verti- cal variations in the character of the ore are not always those which can be accounted for by the mere vertical change in the character of the ore-bearing solution, but in some cases these changes are apparently due to the influence of the surround- ing rock. This has led to the theory that mineral veins are, in some cases, either supplied with mineral, partly or wholly from the enclosing rock, by lateral secretion,^ or that by some electrical influence the character of the ore deposit is modified by the presence of some particular rock. It seems probable that both of these processes act, but that the chief cause of these mineral veins is the ascension of ore-bearing water from below and the deposition of the mineral without the intervention of these outside agents. iv. Ore Channels is a term given to those planes of weak- ness which exist between two series of rocks, either between two eruptive rocks, or an eruptive and sedimentary or meta- morphic rock, or along the unconformable contact of two 1 A definite instance of this process is found at the Sulphur Bank Quick- silver Mine in California (see chapter on Mercury). 2 Sandberger's experiments on the metalliferous contents of common rocks (described above, p. 73) have given much support to the theory of lateral secretion. These experiments have proved that these sources may supply ore, and have made it probable that they sometimes do ; but the proofs are not sufficient to warrant the widespread application given the theory by some. ORIGIN OF ORE DEPOSITS. 87 series of sedimentary strata. These planes furnish channel- ways for the comparatively easy escape of subterranean waters. The remarks made in speaking of the fissure veins hold almost equally for these, excepting that the water is less liable to come. from great depths, the channel-way is less distinct, and the influences which bring about deposit are more apt to resemble those of the more superficial deposits, such as those in chambers. It must, however, be borne in mind that even at shallow depths the earth may be highlj'- heated by the intrusion of igneous rocks, and hence a supply of heat be furnished to subterranean water channels of com- paratively superficial origin. (c) Replacement Deposits. — Certain minerals seem par- ticularly liable to solution and replacement by a gradual Fig. 7. — Bed of limestone, (a) being replaced by iron, particularly in the synclinal troughs, 6, 6, 6. molecular transfer, after the manner of petrifaction of wood. Under the proper conditions, this process may take place in any mineral ; but the mineral calcite seems particularly sus- ceptible to the change. In the rocks, fossils are thus re- placed by a great variety of minerals (silica, iron, copper, and many others), one molecule being dissolved by the per- colating water, while another is put in its place, until the transfer is either complete, or is in some way interrupted. By this process of replacement entire beds of limestone are sometimes dissolved away, and one of the oxides of iron put in their place (Figs. 7 and 15). Other minerals are acted 88 ECONOMIC GEOLOGY OP THE UNITED STATES. upon in the same way, and pseudomorphs — that is, a mineral of one kind with the form of another — are not uncommon in nature. (JT) Impregnation Deposits (Fig. 8). — During the forma- tion of fissure veins, and indeed of other veins as well, it fre- quently happens that the ore- bearing solutions enter the vein walls and impregnate them with metalliferous deposits. These are at times replacements of pre-existing minerals, and at times the result of an accumula- tion of the foreign ore between the minerals of the country rock. Impregnation deposits, therefore, even in the same vein, may be of several kinds of origin : they may be concretion- ary, or replacement, and their source may be from the solu- tions which are filling the veins, or perhaps they may even be the result of a lateral secretion from the country rock toward the vein. They do not form iinportant deposits by them- selves, but are usually a leaner ^'t®;';'3'^if?°n°^ ^'\°^^ ^* part of a true mineral vein. Bast Hull Lovell in Cornwall, a, a, '■ leader OT divider. (After Phillips.) A form of mineral deposit ORIGIN OP ORE DEPOSITS. 89 known as Stock werk possibly belongs here. It is found in the Cornwall district, and is typically a series of small rami- fying veins and irregular bunches of ore, sometimes connected with fissure veins, but very frequently separate. (e) Concretionary Deposits (Fig. 9). — It is easy to under- stand how deposits of ore accumulate in gravels, and in what manner minerals are chemically precipitated. The process of replacement is analogous to well-known phenomena, and the formation of mineral deposits in pre-existing cavities pre- sents no inexplicable phenomena, or, at least, we are able to form a conception of their method of origin; but the two Fig. 9. — Concretions in strata, a, a, iron-stone concretions in shale; c, flint con- cretions in limestone. groups of deposits included under the headings concretionary and segregated are much less easily understood. A study of the chalk beds of England shows that there are nodules and layers of flint which have been formed by the accumulation of silica, originally disseminated through the chalk, but now gathered together about a common centre, or along a common line or plane, and a similar condi- tion exists in many beds of limestone. In slates, originally deposits of clay or fine-grained fragments of disintegrated rocks, it is not uncommon to find crystals, and bunches of crystals, of iron pyrite, which have been formed by the gathering together of the sulphide of iron from the surround- ing dense rock, and its concentration where there was no pre-existing cavity. The iron-bearing clay rocks frequently 90 ECONOMIC GEOLOGY Of' THE UNITED STATES. contain concretions of limonite, or of hematite of the same origin. How does this happen ? By what force are particles of like nature drawn together from a given area to a grow- ing concretion, forming a space for itself often in a compact rock ? These are questions which the author has never seen explained in a satisfactory manner. (/) Segregated Deposits (Fig. 10). — If it is difficult to answer these questions in the case of concretions, it is still a Fig. 10. — Segregation of iron (a) in schistose strata. more difficult to answer them when asked about the formar tion of the much more extensive segregated deposits. These occur most commonly as veins, often of considerable extent, though usually small and non-continuous, one beginning and fraying out, while another starts in the same general direction as if it were a non-continuous extension of the first. Sometimes they seem to have started in small cavities, or along planes of weakness ; but with even greater fre- OKIGIN OF OKE DEPOSITS. 91 quency, the entire space which they occupy seems to have been formed by the growing accumulation. They are gener- ally parallel with the bedding or structural planes of the rock. Segregated deposits occur most commonly in metamorphic rocks and, indeed, much of the metamorphism of strata seems to consist in segregation. Starting, let us say, with a clay rock of complex composition, the resultant of the decay of feldspar and hornblende, pressure and heat begin to act, and this, with the aid of the enclosed water, commences an alteration of the rock. The old decayed minerals commence to assume a more permanent and definite chemical com- position and, indeed, to revert to their original composition. New feldspars and hornblendes and iron oxides are formed, and these different minerals by metamorphism tend, in many cases, to arrange themselves in bands which are at right angles to the direction of pressure. Actual melting does not take place, the new minerals are slowly evolved, and, as they develop^ minerals of the same kind, tend to form in clusters; in this case, in linear clusters. Thus, bands of hornblende, of iron, and of feldspar are formed, rarely strictly pure, but tending toward purity. How far segregation accounts for ores it is difficult to say. Some ascribe to this process a very great importance, while others are inclined tcr consider it of minor importance ; and it is true that the evidence of segregation is often obscure. Nevertheless it is a cause, and an important cause, par- ticularly in metamorphic rocks. In sedimentary strata, it rarely expresses itself in any other form than that of con- cretion, and in unmetamorphosed igneous rocks the tendency to segregate is shown in the banding of minerals, and in the spherulitic concretions in lavas. 92 ECONOMIG GEOLOGY OP THE UNITED STATES. When asked what segregation is, one can answer only that it is a force which causes like minerals to gather together, and is merely another form of concretion. We know that, by some form of attraction, molecules of a given substance will accumulate to form a mineral crystal, each particle that can be drawn to the crystal being added to it. There is here certainly some attractive force — " chemical affinity." In segregation, perhaps, the same force is at work. Its attractive power is strong, for it draws material from con- siderable distances ; and, once started, its force seems to be increased until a neighbouring area is leached of all the desired mineral that is in a form admitting of transfer. Heated water seems to increase the tendency, and the initial presence of cavities appears frequently to give an opportunity for a beginning, though by no means is this a necessary starting-point. In true mineral veins, the same tendency of accumulation is shown under more favourable circumstances of supply and opportunity. What the attractive force is cannot be told. It is a force, and it acts in the above man- ner, and we therefore have a name and a definition, which is perhaps as satisfactory as if we attempted to assign it to a place among some of the slightly understood forces of nature. It might be called an electro-chemical process, as indeed it has been, and, in spite of denials, this seems still a not unreasonable explanation. (jg'y Contact Deposits (Fig. 11). — By the contact of igne- ous rocks, highly heated and molten, the surrounding layers may be markedly modified, particularly when large masses or bosses of igneous rocks are intruded at considerable depths. Such masses take many years, probably centuries, to cool, and during all this time they are tending to alter the OBIGIN OF ORE DEPOSITS. 93 surrounding rocks, not alone by their heat, but chiefly by the aid of the aqueous vapour or superheated water, which is present in abundance in all lavas. A zone of contact meta- morphism is thus produced, in which to a distance of many yards the surrounding rocks are often altered past recog- nition, by the development of new minerals both from the material in the country rock and from the gases furnished by the lava. In such positions mineral deposits formed in several dif- ferent ways are not uncommon. By sublimation, as in the Fig. U. — Contact deposits (a), between and in shale (6), and diabase (c). case of mercury and sulphur, mineral deposits may be formed at or near the contact as the result of condensation, from the gaseous condition of substances emanating from the igneous rock. More commonly the presence of the lava serves to concentrate minerals along the contact, partly from the igneous, partly from the cold enclosing rock, by a process of segregation. All deposits along the contact of igneous rocks must not, however, be considered as contact deposits ; for, by a subsequent process of segregation or con- centration, mineral veins may be formed along these planes of weakness by the solution of the ore contained in the igneous or in the country rock and its deposition here. This 94 ECONOMIC GEOLOGY OP THE UNITED STATES. is the origin of a great many of the apparent contact deposits ; but, nevertheless, true contact veins, both of con- centration and sublimation origin, actually exist. Distribution of Ore Deposits. — It will be noticed in study- ing the distribution of ore deposits in any country that they are more common in certain parts of the region than in others, and this is the direct result of cause and effect. Omitting the mechanical deposits which may occur in any place where the supply of ore is sufficient and the condi- tions of weathering and deposition favourable, the precipitated deposits which may also occur anywhere, segregated and re- placement veins which are typical of nietamorphic or the older sedimentary rocks, and the only important groups of mineral deposits remaining are the true and contact veins which include by far the greater number of mineral deposits, if iron, manganese, and stream-gold are excluded. These two groups of metalliferous veins are associated in origin with either cavities or heat, or both combined. Geo- graphically they are associated most commonly with moun- tains, and usually with mountains of recent formation. The reason is apparent, for in such places there are numerous fractures and fault planes, and abundant volcanic and intru- sive igneous rocks, — in fact, all the conditions necessary for the formation of such deposits. Moreover, in high moun- tains erosion has penetrated to considerable depths, and hence has revealed to us more of the hidden stores of the earth's crust. Geologically, in this country the mineral wealth is chiefly stored in the less ancient rocks ; that is, in post-Archean series, and in many cases in post-Palseozoic strata. This is due largely to the fact that these rocks form the greater part ORIGIN OF ORE DEPOSITS. 95 of the recent mountains of the Cordilleras. One might con- sider it remarkable that the older strata, which have for a longer time been exposed to the action of subterranean water and other agents of change should be comparatively so unim- portant as mineral producers. There seem to be at least two probable causes for this. In the first place, the lower rocks being buried beneath a great thickness of overlying strata, when subjected to mountain-forming forces tend to fold rather than to break, while the less compressed layers nearer the surface become more fractured. Fewer cavities, there- fore, exist in these older rocks. Besides this these deeply buried strata are subjected for long periods of time to a leaching of percolating waters which escape toward the surface and deposit their dissolved mineral in the cavities of the overlying strata. They are robbed of their mineral con- tents for the benefit of the overlying layers. If this be true, then in older mountains, such as those of New England, there may have formerly existed mineral deposits which have since been destroyed by erosion. The discrepancy between the Appalachians and Cordilleras is also, as has already been stated, due to the conditions prevailing during their formation. Thus the Appalachians seem to have been formed more by folding and less by faulting than the Rockies ; and, also, the former were practically without volcanic activity, whereas in the Cordilleras volcanic conditions were marvellously developed. These differences seem sufficient to account for the marked difference in distribution of ore deposits in this and in other countries, showing the intimate relation which exists between geologic conditions and mineral wealth. CHAPTER V. MINING TEEMS AND METHODS.^ Mining Terms. — A mineral may be defined as an inorganic substance having theoretically a definite chemical composi- tion and frequently a definite geometric form. It is usually a combination of elements, though sometimes a single element, as gold, sulphur, etc. Miners use the term mineral as a synonym of ore, which is, according to the economic standpoint, a metal, usually mineralized, occurring in sufficient quantities and in such combinations as to be economically valuable. Elements are of two kinds, metals and metalloids, though some have properties common to both groups, and the dis- tinction is much less sharp than was at one time supposed, before all the elements were carefully studied. The typical metal has certain definite characteristics, being basic rather than acid in its properties, having a considerable specific gravity and a metallic lustre. In the arts the metals serve different purposes, depending upon their physical characters, some being bright, beautiful, and not easily tarnished; some 1 That part of this chapter which refers to mining methods is necessarily brief and generalized, and refers only to the more important processes. There are text-books which give in detail information upon this subject; but the only way in which such knowledge is properly obtained is by a study of the mines themselves. A good short account of mining terms and methods will be found in the last part of Davies, Metalliferous Minerals and Mining, and other treatises are referred to in the list of books of reference at the close of this work. 96 MINING TEEMS AND METHODS. 97 having hardness, or ductility, or malleability, or a low or high melting-point, etc. The metals which we know best, such as gold, silver, iron, copper, etc., are, with the exception of iron, comparatively rare, while the most common metals, such as aluminum, calcium, magnesium, etc., are comparatively rare in the arts. Of the metalloids, oxygen, silicon, and carbon are the most common. As has already been stated, these elements combine in different proportions to produce minerals, some of which are ores. In the mineral vein there are not only ores, but also very frequently foreign minerals which make the veinstone or gangue, a foreign, mechanical mixture of minerals which are of no economic value. Thus, not only are calcite and quartz considered to be gangue, but also such metalliferous minerals as iron p3'^rite, which have to be separated from the ore by mechanical processes. When minerals combine to form a fixed and essential part of the earth's crust, a rock is formed, and these may result from crystallization by meta- morphism, or from solution, or from a molten condition, or they may be produced by the mechanical destruction of pre-existing rocks and the accumulation of the fragments. Ordinarily the term rock is applied to a solidified accumu- lation of minerals, but in reality it should be made to include unsolidified deposits as well, since there is every gradation between the unsolidified and solidified sometimes in the same bed. There is some difference of opinion as to the propriety of including veinstones under the term rock; but it seems better to consider them as minerals, although miners some- times speak of the veinstone as vein-rock. A vein, as well as a rock, is said to outcrop where it appears at the surface in a natural exposure, — or whei'e ECONOMIC GEOLOGY OP THE UNITED STATES. it crops out. In California the outcrop of a vein is fre- quently called a ledge, since the outcrops for which the prospectors of that region were most anxiously looking, being of hard quartz, formed a ledge. For the same reason, the term reef is used in Australia, this name being suggested, no doubt, by the resemblance to the coral reefs of that region, which project above the ocean. Instead of a ledge- FlG. 12. — Section of mineral vein sliowing ribbon or banded structure and sym- metrical disposition of the various mineral bands. A, country rools; B, fluccan; C, comb structure; 1, iron pyrite; 2, calcite; 3, quartz; 4, mag- netite; 5, barite; 6, cbalcopyrite ; 7, galena; 8, quartz. like outcrop, it is more common for many mineral veins to be marked by a depression caused by the weakness of the ore or the gangue, or both. In such cases the ore is often hidden and discovered by accident, though its position may be indi- cated by loose boulders, or by a stain or rust characteristic of the metal. The Cornish miner calls this gossan, while in France and Germany it is called the iron hat,^ because of the characteristic iron stain. For a vein the term lode is some- times used meaning a deposit which the miners are following 1 Chapeau de fer and eisener Sut. MINING TERMS AND METHODS. 99 in the expectation of finding something valuable, — the deposit which is leading them, hence sometimes called a lead. In the vein, one of the most striking features, provided it is a true fissure vein, is the handed structure (Fig. 12), due to the regular arrangement of the various layers on either side of the centre. At times the vein is completely filled ; but it is frequently the case that it is only partly filled, and the projecting points of the crystals last formed produce a serrated surface known as the comh structure (Fig. 12) . Frag- ments of foreign rock, included in the vein, are called horses or riders (Fig. 13), and these are usually broken from the neighbouring or enclosing country rock or country (Fig. 12 and 13), though sometimes they are included between two veins. The country rock is sometimes sharply defined, forming the vein wall; and since nearly all veins are more or less inclined, the two walls are called respectively hanging and foot walls (Fig. 14), according as they are overhead or beneath the feet. Between the vein and the country rock there is fre- quently a clayey substance, elay selvage, fluccan^ or gouge ' This, like many of our mining terms, is a Cornish name, for from this district we have obtained not only many of our mining methods, but also much of" our mining nomenclature. Fig 13 — Vein of blende and galena (A) in a gangue of quartz and calcite (B), including horses (H) of the country rock (C). (From Davies.) 100 ECONOMIC GEOLOGY OF THE UNITED STATES. (Fig. 12), -which is sometimes the result of decay, sometimes of faulting and crushing by a movement between the vein and wall. It is of value in mining, because it is easily removed, it enlarges the vein, gives a smooth firm wall, and is, moreover, a good sign, since it is more common in fissure veins than elsewhere, and such veins are more liable to be permanent. By this subsequent movement in the vein the walls, and even the different parts of the vein, are often polished and grooved or slicJcensided. A careful study of slickensides frequently shows where to look for the continua- tion of a vein which has been lost by being moved out of position by a cross-fault. During the formation of the fissure in which the vein is located the country rock is some- times crushed and brecciated, and during the formation of the vein these fragments may be cemented by either gangue or ore. Subsequent movements may again open the vein, either causing a new fissure or crushing the vein-rock to a breccia. The horizontal direction of the vein is called its strike, or by miners very frequently the run or course. Veins rarely extend vertically into the ground, but generally dip or hade at a greater or less angle. In geology, the dip is measured in degrees from the horizontal ; but in some mining districts it is measured from the vertical, the one being then the com- plement of the other. In some of the English districts this angle is called the underlie. Besides the dip there is some- times present a pitch, a term which refers to a dip of the entire vein or pocket in the direction of the strike. The relation of the ore to the surrounding rock, together with the strike, dip, and position of the vein, is shown by means of various plans and sections. A geological map gives in MINING TEKMS AND METHODS. 101 horizontal plan the various rocks which enclose the vein ; and if it is desired to show the horizontal appearance of the vein, or of its tunnels at different depths, ground plans are made to show these features. Where it is desired to show the linear extent of the vein and of its tunnels, and the position of the shafts, a longitudinal section or plan is made parallel with the plane of the vein. A cross-section is one made at right angles to the strike of the vein, and shows its dip, the position of the enclosing walls, and also the position of the shafts and tunnels in the line of the section. The geological map and the cross-section show most clearly the geological structure, but the ground plan and longitudinal section are the most valuable in showing the position and number of the tunnels. Variation in Veins. — During the process of mining there are often found to be variations in the character or position of the ore. The vein varies in width, swelling and pinching, sometimes by original irregularities, at times as the result of an actual squeezing in of certain parts of the vein, forming alternate pinches and swells. The walls roll, the miners say, since they seem to form waves. Actual faulting may cut off the vein, and the miner finds the ore ending abruptly against a wall of barren rock. These faults are sometimes of small extent, in which case the vein is readily found again ; but in some cases valuable veins are completely lost. In a given district veins have a prevailingly uniform direction, fre- quently parallel to the direction of the strike of the rocks or of the mountain range. Yet, on the other hand, they may be very irregular in direction, and in the same district two or more sets of veins may exist. In such cases the veins of one set are usually richer than those of another, and they 102 ECONOMIC GEOLOGY OF THE UNITED STATES. may be widely different in character, one set being perhaps barren of ore. These veins frequently intersect, the older being crossed by the younger, and being displaced by the disturbance which formed the vein cavity. A great variety of confusing conditions are encountered by miners in con- sequence of these intersections of veins ; but a careful study of the geology of the district will usually aid in the solution of the problems thus presented. On the other hand, veins are frequently lost by becoming gradually more and more barren, or sometimes by branching at either end, and thus becoming smaller and more difficult to work, and in these cases the ore is usually permanently lo3t. From the main vein branch-veins are frequently sent off, and these are called droppers oi: feeders, the latter name being given because they are supposed to furnish the vein material, though in reality these offshoots diminish the quantity of mineral in the vein. The ore often varies both in quantity and quality in different parts of the same vein. This variation may occur even in the same enclosing walls, or it may at times be dependent upon a change in the character of the country rock showing the influence of the enclosing rocks upon the vein material. The variation may amount to a complete change in the kind of ore as in the Przibram district of Bohemia, and in Cornwall, where the influence of the rock is very marked, the ore sometimes changing from copper to tin. Change in the character of the ore in a vein is, however, most commonly the result of an alteration due to the effect of weathering. Below a certain line in the earth there is permanent water, the rocks being saturated. This water line varies greatly in position according to the climate, being in some parts of the arid regions many hundred feet beneath MINING TERMS AND METHODS. 103 the surface. Above this line the minerals are subjected to conditions of alternation from dry to moist, and conse- quently if they are not permanent combinations, to changes in character. Most ores are comparatively unstable, and under these conditions are altered in composition. Thus galena, the sulphide of lead, becomes altered above the water line to the sulphate anglesite, and many sulphides become carbonates, or oxides, usually of hydrous varieties. Moreover, by the solvent power of the percolating water metallic salts may be dissolved and carried away leaving the ore above the water line more porous. The effect which these alterations have upon the richness of the ore is very different under different conditions. Thus the native gold of California is found enclosed in iron pyrite in quartz rock, but by weathering the iron pyrite is removed, and it was supposed in the early days of the mining industry of Cali- fornia, that the gold became less abundant as the depth of the mine increased ; but with the present methods the gold is easily extracted from the pyrite. On the other hand, instead of carrying away the gangue in solution, the perco- lating water may destroy the ore and thus make the vein above the water line less rich. This, however, is often more than compensated for by the increased difficulty of mining or reducing the unweathered ore from below the water line. For different ores and gangues and for different climates the conditions of weathering vary so that no general statement can be made, but each district may have a peculiarity of its own. Mining Methods. — In order to obtain a metal, there are usually four processes which must be used, — mining, dressing, concentration, and reduction. The first three processes are 104 ECONOMIC GEOLOGY OF THE UNITED STATES. mechanical, the fourth depends upon chemical reactions. In mining, the first step is naturally to find the vein, and for this, very different methods are in use in different parts of the world and for different kinds of ore. The Cornish miners speak of shading, shodes being fragments of veins increasing in size as their source is approached ; and shoding consists in tracing these fragments to their source. American miners have invented for this process of ore-finding the term prospecting, a prospector being one who is in search of a prospect upon which to base future work. At the time of the development of the gold fields of California in the years succeeding 1848, a horde of people of all classes turned prospectors, and even at present there are thousands of such people in the Cordilleran region, now, as then, for the most part barely eking out a living, though ever in hope of finding some prospect which shall yield them a fortune, as some of their numbers have already done, in some cases several times. The original prospector confined his attention to the streams, washing the gravels here and there, in search of placer deposits. When this field became fully occupied and less paying, the attention of many of the prospectors was turned to other deposits, and these men have, in many cases, developed a wonderful degree of skill in the detection of ore deposits, — a skill which the trained mining engineer may well covet. Their methods consist chiefly in the appli- cation of a wide experience, by which they are able to tell where not to look for ore, and what is the surface appearance of various common metalliferous deposits. The characteristic rust of a metal, as the green of copper, or the yellow of lead, the crumbly, disintegrated appearance of the outcrop of an MINING TERMS AND METHODS. 105 ore, and the appearance of characteristic vein minerals, all serve as guides. More scientific methods, which are some- times possible, the prospector does not usually possess ; but the vast majority of mines in the west have been discovered either by pure chance or by the application of these methods. Having found a surface indication of ore, the next step is to develop in order to see if there is a "show," and if so, to give the property a market value. If the outcrop is not already fully revealed, enough work is done to see in which direction the vein strikes ; and then, in order to test its extent, cross-cuts are made at right angles to the strike, the earth being removed down to the bed rock until the vein is encountered, and this is continued at intervals of a few yards until the miner is convinced of the probable direction and extent of the vein. Since most of the newly discovered ore deposits in the west are situated upon government land, the miner must then locate his claim at a government land office, and then, within a specified time, do a sufficient amount of work to become the absolute owner of the land. If the deposit is of much value, it is usually not long before others have located claims near by, and the whole region is crossed by these claims, often in such inextricable con- fusion that long-continued litigation results, and the profits of the mining operations are diverted. Subsequent development depends largely upon the local conditions, the character and position of the ore primarily, as well as the probable future of the mine. The immediate purposes, or even, in some cases, the permanent development, of the mine may be best served by opening the deposit as a pit or as a quarry, although the most common method is to open a mine, or a series of shafts and tunnels. In the 106 ECONOMIC GEOLOGY OF THE UNITED STATES. serious development of a mine, the most important thing to be taken into consideration is drainage, and this gives to miners more trouble than any other single need. The simplest possible condition is to commence the mine upon a Fig. 14. — Diagram showing usual method of exploiting a vein. V, vein or lode; H, hanging wall ; F, foot wall ; D, intrusive diabase ; Sh, shale ; SS, sand- stone; Cg, conglomerate; S, shaft; A, adit level; C, C, C, cross-outs. valley side, and drain it into the valley, as the work of development .progresses, using the lowest tunnel for a drainage way. Where this is impossible, it is frequently found economical to extend a horizontal shaft, tunnel, drive, MINING TERMS AND METHODS. 107 or adit level (Fig. 14), as it is variously called, to some neighbouring valley, and this is often done at an immense expense, the expenditure of years in construction, and the formation of a tunnel sometimes several miles in extent.^ When this is impossible or impracticable, pumping is resorted to, but this is an extremely expensive process in deep mines. When the vein is vertical, a shaft may be sunk in the vein and the material removed made to pay the expense of con- struction ; but most veins are inclined, and then one of two things is possible, — either to work on the incline and hoist the ore on inclined tracks, or to construct a vertical shaft which shall intersect the vein at a considerable depth and be connected with it by a number of short horizontal tunnels ; and in well-developed mines this is usually done. The width of the shafts and tunnels varies with the amount of work to be done. In working along the vein or lode, horizontal tunnels or " drifts " are made through which the ore is hauled to the shafts, where it is hoisted to the surface. Usually there is more than one shaft, often a number, connecting dif- ferent levels or drifts, these being used partly for hoisting ore, partly for ventilation (" winzes "), which every well- developed mine must take into account. From the drifts and small shafts the ore is worked or " stoped " out, some- times by overhand, sometimes by underhand, stoping ; that is, from above or below. In this stoping, secondary di-ifts and partial shafts (" mills ") are constructed to facilitate the process of ore extraction. During the process of mining the lode is completely honey- ^The Sutro Tunnel of the Comstock Lode in Nevada is 20,489 feet in length, and meets the Lode at a depth of 1900 feet. Its cost was 1 2,000,000. 108 ECONOMIC GEOLOGY OP THE UNITED STATES. combed by these various excavations.^ In old-fashioned or in poorly developed modern mines, the excavations are irregular and the tunnels rudely constructed, being confessedly tem- porary ; and when one part of the mine is worked out, it is abandoned to its fate. Where better and more permanent methods are used, pillars of ore are left to support the roofs of the tunnels, and the shafts and tunnels are carefully tim- bered to prevent collapse. For this purpose, not only is much valuable ore left behind, but often millions of dollars are expended in timbering, particularly in some of the larger mines of the Cordilleras, where timber is scarce and difficult to obtain. This timber is a danger in one respect, since it is liable to be burned and cause a temporary abandonment of the mine as well as great expense in retimbering. During the development of the Comstock Lode, a novel difficulty was encountered which all large mines, extending to great depths into the earth, are liable to encounter in time. This is intense heat, which, in the Comstock, was encountered at a point unusually near the surface, owing, no doubt, to the proximity of heated rocks of igneous origin. Floods of hot water burst through the walls, and flooded the mine, heating the air so that work was well-nigh impossible. It was neces- sary to pump cold air into the galleries, and even then slight physical exertion was nearly impossible, so that eventually the lower tunnels of the mine had to be abandoned. Excepting for the general direction of operations, the process of mining in itself is purely mechanical. One fun- damental principle is followed, — to leave below as much of 1 In 1880 there were more than one hundred and fifty miles of shafts and galleries in the Comstock Lode, and since then these have been somewhat increased. MINING TEEMS AND METHODS. 109 the gangue as is possible. Hence each miner directs his labours so as to avoid barren areas, and, where possible, to make them serve as supporting pillars. The ore is drilled, blasted, or picked, according to its nature ; and in selecting material to be sent to the surface, the fragments are roughly- assorted in the mine in order to send out of the mine as little valueless mineral as need be. For transportation from the point of mining to the shaft, various methods are used, such as wheelbarrows, horse railroads, cable, gravity, or even, at present, electric roads. Having reached the shaft, it is hoisted to the surface by a method depending upon the scale of operations adopted in the mine, this varying from hand power to electricity. The mines in Europe are frequently owned and operated by the government; but in this country they are in the hands of private owners, who usually direct all operations, although in some of the western mines a method of working known as the tribute system is in operation. Certain parts of the vein, and at times the entire mine, are turned over to individual miners or groups of miners to develop on shares. This method is usually adopted in mines where the amount of ore varies greatly, and where rich pockets occur in great areas of barren gangue, or in mines which have been aban- doned because of the average poverty of the deposit. It is probable that the average result of this system is far from profitable to the miner, but the element of chance and the possible riches which are sometimes won is a sufficient incen- tive to many miners to enter into the tribute system. The owners risk very little, but this system is usually bad for a mine, since the tribute miners generally leave it in a bad condition, and not properly timbered or ventilated. 110 ECONOMIC GEOLOGY OF THE UNITED STATES. Concentration of Ores. — When the ore has arrived at the surface, the mechanical process is still farther pursued in separating the ore from the gangue. This is often done, first by breaking the fragments into smaller pieces, generally by hand, and then by the separation, also by hand, of the very lean ore and gangue from the richer fragments. The ore is now in a fairly concentrated condition, but is still in combination, mechanically with some of the gangue, and chemically with the mineralizer. The methods used for the extraction of the metal from these associations are extremely varied, depending both upon the character of the ore and the development of the mine. A few of the more important methods only are briefly described here. The first thing to be done in gold-bearing quartz and some other ores is to crush the ore so that even the finest particles of foreign, mechanically associated mineral may be removed by water. This is done by means of the stamp, an apparatus so old that the time of its invention is not known. There are many kinds of these, the most improved being the piston stamps in which a heavy head, weighing in some cases a ton, is raised to a height of from twelve to fourteen inches and then dropped. In some of the better equipped mills not only do the piston stamps work automatically, but the ore is fed in the same manner, and one may pass through such a mill, where many stamps are at work, without seeing any other workmen than the watchmen. In the placer gold, platinum, and stream-tin deposits nature has performed the duties of the stamp mill in disin- tegrating the rock which contained the ores ; and to a cer- tain extent, also, the duties of the cencentrator by the assorting power of running water. This same principle is MINING TERMS AND METHODS. Ill made use of in much of the separation of ore from gangue. Placer miners separated the heavy gold from the admixture of gravel by means of a pan or some similar contrivance, simply giving to it a peculiar shaking motion which caused the heavy gold to accumulate in the bottom of the pan, while the lighter gravel was washed out. The introduction of the cradle, an inclined board with riffles, was an advance in method which was followed by the sluice, an apparatus in which nature's process of concentration is closely imitated. This consists of a long box with a rapid slope, built in the river valley, into which the gold-bearing gravel is washed by streams of water. The gravel rushes down through the box, while the heavy gold drags near the bottom and tends to collect behind the riffles, or cross-pieces nailed across the bottom of the box, just as it does in the streams where the current is slackened by a boulder or some other obstacle. Two things are necessary : a plentiful supply of water and a rapid slope. In some parts of this country, and of other countries as well, there are extensive deposits of gold-bearing gravel which might be worked by this hydraulic process, if water or slope were present. Indeed, in most of the placer regions of the west the water supply has presented difficult problems, for the solution of which vast sums of money have been expended in the construction of canals and water pipes for the carriage of water often from one drainage basin to a,nother. Even under these circumstances hydraulic mining was very successful, and gravel with very little gold was worked over with profit. In the case of gold-bearing quartz and other ores in which the gangue is abundant, the ore is crushed to a pulp or " slime," and under different circumstances different methods 112 ECONOMIC GEOLOGY OF THE UNITED STATES. are used for the separation. An ingenious contrivance for this purpose is the pointed box, an apparatus consisting of several V-shaped boxes of varying size with small apertures at the apices. A stream of water passes from one to the other, keeping the water in them in circulation, and " slime " is fed into the first box, the heavier parts sinking and pass- ing out of the opening at the bottom, and the balance being carried into the next, where, the current being less strong, still more of the heavy particles drop through the aperture. Beneath each box there accumulates a pile of material ; pure ore beneath the first, pure gangue (" tailings ") beneath the last, and beneath the intermediate ones an admixture which may pay for further concentration. Frame, tye, or huddle, are names given to an inclined board upon which crushed ore is fed, together with a current of water which carries the lighter material downward, while the ore remains near the top, and in the middle there is an admixture of ore and gangue which may need to be passed again over the frame. A man standing near with a rake assists the separation by stirring the slime. Machinery works faster, but produces no better results than this rather crude method. When jarred by machinery the frame be- comes the percussion table, of which there are numerous modifications. A constantly moving belt of corrugated rub- ber, the vanner, upon which the ore is fed, serves to con- centrate it in a similar manner. The jiff or jigger, also used for this purpose, consists of a box with small holes in the bottom. Slime is placed in this, and a jigging motion given to the box either by hand or by machinery (^piston jigger'), by which there is a separation of the minerals into layers according to specific gravity, the ore seeking the MINIKG TEEMS AND METHODS. 118 bottom. One of these pieces of apparatus, or some modifi- cation of it, is used for nearly all ores where the percentage or character of the gangue is such as to call for a mechanical separation further than that of selection at the mine. Some ores of iron and other metals are sufficiently rich when ex- tracted to go directly to the smelter without concentration. Other ores are in such combinations, as, for instance, with some mineral easily disposed of in smelting, or with some heavy mineral which cannot be separated by water, that con- centration is either not necessary or not possible. Reduction of Ores. — For the chemical reduction of ores, a few words of the most general nature must suffice. Each different ore is treated in a different manner, but in general three methods are used: amalgamation, smelting (the dry way), and metallurgy (the wet way). The process of amal- gamation is used chiefly for the extraction of gold and silver. In the case of gold it is used to remove the metal, which is mechanically mixed with impurities. Mercury placed in the sluices in hydraulic mines, remains behind the riffles and greedily seizes all gold which comes within its grasp, forming an amalgam with it. Practically the same is done with the gold extracted from the quartz rock by crushing and con- centration. From the amalgam the mercury is easily driven off by heat, and, being collected by condensation, is ready to be used over again. For the extraction of gold from its silver and other alloys, finer methods are used. The affinity of mer- cury for other metals is also made use of as for instance in the extraction of silver from certain of its ores. Several processes are used, but in general they consist in the use of mercury, the crushed ore, and some salt, which are all stirred together, in the Mexican mines by driving mules back and forth over 114 ECONOMIC GEOLOGY OF THE UNITED STATES. the ore, but more commonly by machinery. A chemical reaction, not very well understood, takes place ; the silver is freed from its chemical combination, and enters into an amalgam with the mercury, from which, as in the case of gold, it is obtained by heat. So important is the use of mercury in the extraction of gold and silver that the greater part of the supply of this metal is used for that purpose. Ores differ very markedly in the strength of the affinity which binds the metal and mineralizer together. The chlo- ride of silver can be extracted by a very gentle heat, the chlorine being driven off and pure silver left. With other ores a high heat does the same, and, again, by the use of some other mineral as a flux, upon the application of high heat the metal is driven from its mineralizer, which enters into combination with the flux, while the metal remains free. Some ores have to be smelted again and again, and some are so difficult to obtain that they are not mined. Every year adds to our knowledge of metallurgical processes, or gives us some new way of smelting by which it is possible to extract the refractory metals more economically. As an instance of this the Franklin Furnace zinc mine' of New Jersey, originally worked for iron, is now kept open chiefly for the zinc. Formerly the zinc contained in the oxide zincite, the silicate willemite and the oxide of iron and zinc franklinite, was considered to be in too refractory combi- nation for separation. Before smelting some ores it is necessary to either calcine them — that is, to allow them to decompose in the air at ordi- nary temperatures — or to roast them. This serves to drive off a part of the sulphur, or arsenic, or other elements which have strong affinities for the metals. The ore is then MINING TEEMS AND METHODS. 115 smelted and the metal obtained. For more detailed state- ments concerning the processes of smelting or of metallurgy, recourse should be had to some of the treatises upon the general subject, or upon special ores or metals.^ 1 Some of these are referred to in the bibliography at the end of the book. Paet II. METALLIFEROUS DEPOSITS. CHAPTER VI. IKON.^ General Statement. — The ores of iron are, (1) brown hemch tite (including all varieties of the hydrated sesquioxide, — limonite, gothite, bog ores, etc.) ; (2) red hematite (the anhydrous sesquioxide, including specular, micaceous, fossil hematite, and other varieties based upon physical character- istics) ; (3) magnetite ; and (4) the carbonate (FeCOg, in- cluding spathic ore, blackband, siderite, etc.). Native iron is found in meteorites and in basalt rock, in Greenland, but it is not known as an ore. The sulphide, iron pyrite, is mined, not for its iron, but for the sulphur which it contains. An iron ore, in the present state of the iron industry, must occur in a very favourable position as regards market, it must be of good quality, in considerable quantity, and favourably situated for extraction and smelting. The presence of sul- phur or phosphorus in an ore makes it valueless unless the quantity is very slight. Iron is now so cheap that, where mining operations are difficult, as, for instance, where the mine is deep, the vein narrow, gangue abundant, or trans- portation difficult, it cannot be mined. There are a suffi- cient number of good iron deposits in this country to make selection possible, and consequently many of the older mines are being abandoned because of the development of these 1 A very complete account of the iron industry of tliis country is found in Vol. XY., Tenth Census, pp. 1-601. 119 120 ECONOMIC GEOLOGY OP THE TJNITBD STATES. more profitable mines. For reasons of this sort, the New- Jersey region, for instance, which was once an important iron-producing section, is becoming abandoned ; and whereas only a few years ago there were many score of profitable mines in that state, now there are very few. As this ore is chiefly magnetite, and some of it of a very high grade, it is possible that the use of electricity in the separation of the ore, which is now being experimented with, may revolution- ize the iron industry of that state. The most favourable situation of an iron ore for profitable extraction is near good coking coal for smelting and lime- stone for a flux, as in the Birmingham district of Alabama ; and in such a situation even low-grade ores can be worked profitably. Unless this is the case, iron ore cannot be exten- sively mined excepting under conditions of great abundance and economical methods of transportation, as in the Lake Superior district, where thick and remarkably uniform beds of good ore occur in such a position that water transporta- tion to the market is possible. Where these conditions do not exist, iron-mining is feasible only on a small scale for the local market. Thus, in the Rocky Mountains, there are almost inexhaustible supplies of iron, often of high grade, which are at present of no value whatsoever. Brown Hematite Ores. — The brown hematite ore (hydrated sesquioxide), of which limonite is the most important vari- ety, produced, in 1891, 18.9 per cent of the iron ore of the country. Of the total output of 14,591,178 tons of iron ore, 2,757,564 tons were of brown hematite. While in 1880 this ore was third in rank of importance, in 1891 it held second place in the production of iron. Hydrated sesquioxide of iron occurs abundantly in most IKON. 121 soils as a yellow stain, and nearly all percolating water takes it into solution. From this it is frequently precipitated in bogs, forming bog-iron ore, which is common in New England and the northern states generally. Here it was mined in the last century and used for iron; but at present, partly because of its impurity, partly on account of its local nature, this source is not exploited. At present, the greater part of the supply of brown hematite comes from the southern states, chiefly from Virginia, Alabama, and Georgia, where it occurs typically as beds in the nearly horizontal sandstones of recent age and in the older slates and limestones. The first mode of occurrence is typically illustrated in the iron mines at New Birmingham, Cherokee County, Texas, where flat-topped hills of erosion, or "buttes," stand up above the surrounding country, and in these beds of iron occur capped and under- lain by a partially consolidated ferruginous sandstone. The ore, which varies in colour from brown to black, and is usu- ally granular or semi-compacted, is of the bog-iron variety, and is distinctly bedded with the sandstones, having appar- ently been precipitated in shallow lakes or lagoons along the shore line before the region was elevated in Tertiary times. After scraping away the loose or semi-compact sandstone covering, the ore is easily removed by picks, and the mine worked at a low cost as an open work or pit. There is much of this class of ore in eastern Texas and other parts of the Tertiary plain, although at present it is very slightly developed. In northeastern Alabama brown hematite occurs in pockets, often of large size, from which it is extracted by means of a steam shovel. Pennsylvania is an important producer of this ore. In Lehigh County it occurs in slates, 122 ECONOMIC GEOLOGY OF THE UNITED STATES. apparently the result of the decomposition of pyrite, or else of concentration by deposition from percolating water. There is a more or less continuous band of limonite, often associated with manganese, in the limestone belt of early Palaeozoic age which extends from Vermont to Alabama. Mines in this belt are located at Brandon, Vermont; Richmond, Massa- chusetts ; Lehigh County, Pennsylvania ; Shenandoah valley, Virginia, and elsewhere. Whether originally precipitated or subsequently concentrated, perhaps by replacement, is still a disputed point. On the Pacific slope the most important iron-producing region is a limonite bed near Portland, Oregon. Here, in the Prosser mine, the limonite is found in hollows in a basaltic lava flow which has been buried beneath a later flow of lava. These hollows seem to have been lakes and swamps, as indicated by the association of tree trunks and vegetable remains. The supply of iron came no doubt from the basalt, from which it was leached by water and precipitated as bog ore in the swamps, and later buried beneath lava. The value of brown hematite, as an ore of iron, consists less in its richness or its purity than in the- ease with which it can be exploited and smelted. Nearly all the mines of this mineral are open works, and the ore is soft. It is, however, usually local in distribution, and not generally found in large masses ; but since extensive plants for its extraction are not necessary, this is not a vital objection. The future of this ore seems good; for, with the develop- ment of the southern states, a large, undeveloped supply will no doubt be drawn upon. Red Hematite Ores. — This mineral, which in 1880 produced but 1.5 per cent more ore than magnetite, and only 5 per IRON. 123 cent more than brown hematite, in 1891 produced 63.9 per cent of all the iron ore of the country. Out of a total of 14,591,178 tons of iron ore produced in 1891, 9,327,398 tons were red hematite. This remarkable increase is due chiefly to the development of the Lake Superior and Alabama districts, while at the same time, and for the same reason, the output of magnetite decreased. One of the most remarkable deposits of iron in the world is the Clinton ore bed which occurs in a horizon in the upper Silurian, known as the Clinton, because of its typical occurrence at Clinton, New York. This bed is not always ore-bearing, but in many parts of the outcrop it is a lime- stone interstratified with shales and limestones. On the other hand, it is frequently iron-bearing. It occurs in New York state, extends southward, following the folds of the Appalachians to Alabama, and is found outcropping in Wisconsin, Ohio, and Kentucky. Throughout its extent it occasionally furnishes iron mines. The ore varies in character, being at times oolitic, when it is called flaxseed ore, or, in other places, replacing fossils, and then being called fossil ore. There is some question as to the origin of this remarkable ore-bearing stratum. It has been held that the ore was originally precipitated during the formation of the stratum, and the oolitic character of certain parts of the bed seem to prove this. On the other hand, fossils, which were originally calcareous, are now composed of hematite, which shows that, in these cases at least, the ore is a replacement, and hence secondary. At Atalla, Alabama, the Clinton limestone, two hundred and fifty feet from the surface, carries only 7.75 per cent of iron, while at the outcrop it has 57 per cent of 124 ECONOMIC GEOLOGY OF THE TTNITBD STATES. iron, and this seems to prove that here the ore is concen- trated by the action of weathering, which has rfemoved some of the calcite. Probably in different places the ore has originated differently. It is not unlikely that, for some reason, during the time of deposit of the Clinton bed, abun- dant iron was precipitated, producing a ferruginous lime- stone and, in places, even an oolitic iron bed. Later, perco- lating water removed some of the iron, and a replacement of fossils and limestone took place, partly from this source and partly from an outside supply of iron. The replacement may have been at first siderite and later hematite. Thus the bed varies in character and richness from place to place, owing to the local concentration, and perhaps, also, as at Atalla, as the result of the concentrating effect of weathering. The Lake Superior hematites are even more important than the Clinton ore bed, but their occurrence is less simple. There are several districts in Michigan, Wisconsin, and Min- nesota. In the Marquette district of Michigan, the ore occurs in strata of quartzites, schists, banded jasper, and limestones of Huronian age (a division of the Archean). There are several types of occurrence, but all are apparently bedded with these strata. As to their origin, Foster and Whitney^ considered them eruptive, Brooks and Pumpelly^ called them altered limonite beds ; and the last geologists to study the ore, Irving and Van Hise,^ ascribe the origin of the ore deposits in part to concentration by percolating water, in part to a replacement of limestone. This view 1 Report on the Geology of the Lake Superior Land District, Part 11., 1851, pp. 66-69. 2 Geological Survey Michigan, 1869-187-3. ' The Fenokee Iron-bearing Series of Michigan and Wisconsin, Tenth Annual Report United States Geological Survey, pp. 341-508. IRON. 125 seems tKe most probable, although it is possible that other explanations may account for some of the deposits. The Menominee district in the same region has a very similar mode of occurrence. Owing to the studies of Irving and Van Hise, the occurrence of the ore in the third district, the Penokee-Gogebic, is well understood. Here the rocks are cherty^ limestones, slates, quartzites, etc.. Fig. 15. — Diagram showing mode of occurrence of iron ore in Penokee region, o, quartzite stratum; b, dikes; e, iron ore, replacing ferruginous chert, e; t, drift. (Modified from Irving and Van Hise.) dipping at a moderate angle and crossed by trap dikes. It has been shown by these authors that beds of dolo- mitic limestone, originally stratified with the series, have been replaced by red hematite, and that the ore occurs most commonly in the troughs formed by the intersection of the dikes with the impervious strata beneath the replaced lime- stones (Fig. 15). The water apparently percolated through 1 Chert is impure flint. 126 ECONOMIC GEOLOGY OP THE UNITED STATES. the limestone, but its progress was retarded by the nearly impermeable quartzites with which the limestone was bedded and by the dikes which crossed the strata. The water being forced to stand here, the limestone was slowly replaced by the iron obtained by solution from the rocks through which the water had percolated. A part of the same general series of iron ores is found in Minnesota, in the Vermilion Lake and Mesaba Range dis- tricts. Here, as in Michigan and Wisconsin, although the ore is sometimes magnetite, it is chiefly hematite. The prob- able origin of these ores is by replacement, as in Michigan, although Winchell,^ who has studied the district carefully, believes them to be originally precipitated, together with many of the associated rocks, from an ocean of pre-Cambrian age when the waters were in a transition stage from the heated primary ocean to the cold sea of geologic times. This theory, while very enticing, does not seem as yet to be suffi- ciently supported by facts for its general acceptance. One of the most interesting deposits of iron in America is the famous iron mountain of Missouri. Here is a hill of porphyry, rising, dome-shaped, through the much younger Silurian rocks. In the porphyry there are veins of hematite, probably of secondary origin, although some have held that they are an original part of the erupted rock. The ore sup- ply comes, however, from the base of the hill, where it occurs as a conglomerate cemented by limestone and resting upon the porphyry. It is overlain by limestone, and the entire series dips away from the mountain as if deposited upon a sloping surface. No other satisfactory explanation seems 1 The Iron Ores of Minnesota, Bull. No. 6, Minnesota Geological Survey, 1891. IKON. 127 possible than that suggested by Pumpelly,i which is, that this hill of porphyry was, in the Silurian period, covered by a soil of disintegration, in which the pebbles of iron, obtained from the veins, remained while the porphyry was decayed to a clay. As the sea which formed the Silurian strata encroached upon this hill or island, the clay was removed and the iron pebbles formed into a conglomerate at the shore line and later covered with other sediments. The ores of hematite are all apparently bedded. This appearance is either due to actual bedding by deposition, or to the subsequent alteration of some previously bedded iron ore of another character (such as limonite), or to the con- centration of the ore by some process, usually by replace- ment. These deposits are frequently lens-shaped, and often attain a considerable thickness in the centre of the lens. Frequently the hematite mines are open works, although where the beds are of a more permanent character, tunnels and shafts are constructed, generally in continuation of previous open-work mining. Magnetite Ores. — In 1891, 15.88 per cent of the iron ore produced in the country was magnetite, or out of the total of 14,591,178 tons of ore, 2,317,108 tons were of this nature. At present magnetite is the third most important ore of iron, while in 1880 it held second place, and was only a little over one per cent behind the leading ore, hematite. In distribu- tion, the magnetite is found chiefly in the metamorphic rocks of New York, Pennsylvania, New Jersey, and Michigan. Practically all of the New Jersey ore is magnetite, and in both New York and Pennsylvania this is the most important of the iron minerals. 1 Geological Survey of Missouri for 1872, Part I. 128 ECONOMIC GEOLOGY OP THE UNITED STATES. Magnetite is found in nearly all eruptive and metamor- phic rocks, as an accessory constituent, in small grains origi- nally formed with the other minerals. It rarely occurs in eruptive rocks in sufficient quantities to pay for mining, although a deposit of titaniferous iron ore, which has been worked at various times, is found in an eruptive rock in Rhode Island. The usual mode of occurrence of magnetite as an ore is typical. It exists as lenses in metamorphic rocks, frequently in the Archean, and often associated with limestone. This mode of occurrence is fully illustrated in New Jersey, in the Archean Highlands, where there is so much magnetite, both as disseminated particles and beds, that the ordinary compass is of no use in the region. These mines have been developed since the last century, and there are thousands of prospect and mine holes, of great and small size, where the dip-compass has indicated the presence of magnetite and encouraged exploration. The beds of iron are associated usually with black hornblendic bands and appear to be bedded with the gneiss, although the apparent bedding of both the gneiss and the iron may be secondary. In the mines the strike is quite uniformly to the northeast and the dip usually southeast, though sometimes northwest, and generally there is, in addition to this, a " pitch " in the direction of the strike, as if the rocks had been folded across the strike. The ore is very irregular, occurring sometimes in pockets, swelling and pinching, and at times being faulted. Some of the veins, as for instance the Hibernia mine of the central Highlands, are remarkablj^ uniform and extensive, but many are so local and irregular that it has been neces- sary to abandon them. Owing to the distance from coal, the irregularity and uncertainty of the iron deposits, and the ERON. 129 fact that the largest and most uniform have already been worked to a considerable depth, these New Jersey magnetites are rapidty losing in importance ; and unless by taking advan- tage of the magnetic properties of the ore, some process of concentration is perfected, the iron industry of New Jersey must continue to decline. The peculiar occurrence of frank- linite on the western border of the Highlands is described under zinc. At Mineville, Chateaugay, and other mines in New York, the occurrence of the magnetite is very similar to that of New Jersey. In the Chateaugay mine, as is often the case in the Archean ores, the magnetite grades, by an increased admixture of gangue, into the barren gneiss of the country. The Mine- ville deposit which has been worked to a depth of three hun- dred feet has, since it was opened in 1824, produced up to the close of 1889 over 9,500,000 tons of ore. In this mine the variation in character of the ore, which is even more marked in some other magnetite mines, is well shown. Practically all of the Archean magnetite, unlike the brown or red hema- tite, is hard and granular, or semi-crystalline. The iron percentage is high and varies in the Mineville ore from 55 to 70 per cent. In the New Bed of this mine a good Bessemer ore is found in which the percentage of phospho- rus does not exceed 0.025 per cent; but in one of the old openings the amount of phosphorus varies from 0.5 to 2.5 per cent, owing to the presence of apatite. There is practi- cally no sulphur in this ore, but in some magnetite deposits there is so much sulphur, usually in the form of iron pyrite, that the ore is not mined. Where magnetite is free from both sulphur and phosphorus, on account of the high per cent of iron, it is a valuable ore. 130 ECONOMIC GEOLOGY OP THE UNITED STATES. To account for these deposits of Archean magnetite, vari- ous theories have been offered. An intrusive origin has been suggested at various times, and certain facts have been stated which seemed to corroborate this view ; but, without discussing this theory, it may be stated that there are no facts connected with magnetite deposits which cannot be easily explained by other theories, and that there are numer- ous objections to this hypothesis which have not been an- swered. A second theory is that the magnetite beds are, in part at least, altered beds of limonite deposited with the original materials out of which the gneiss has been pro- duced, and metamorphosed to magnetite when the gneisses were formed. While it cannot be denied that this is a pos- sible source of some of these deposits, it may yet be said that it does not seem to be a general explanation. Moreover, the gneisses are so much altered that their original character has never been determined, and without proof this explanation can be called little else than a guess. That some of the Archean magnetites are replacements of limestone beds seems certain, and in some cases is proved; but even this plausible explanation, when applied to the New Jersey mag- netite, does not seem to be of general application. A fourth theory, and the one which, taking into consideration all the facts, seems to the writer most probable, is that of segre- gation ; but in advancing it there is no intention of denying absolutely the other explanations. The proofs upon which this belief rests can hardly be stated here. It may be noted, however, that magnetite is present in grains throughout most of these gneisses, and that it is gathered together into strings, bands, and even beds, just as is the hornblende and augite of the gneisses. There seems to be every gradation IKON. 131 from the magnetite grain to the magnetite bed, and it appears to be the result of metamorphism and the gathering together of like minerals from the surrounding rocks during their alteration ; that, in other words, it is merely an expres- sion of metamorphism of rocks rich in iron; but whether these rocks were originally limonite-bearing shales or diabase, we cannot in the present state of our knowledge determine. A very peculiar deposit of magnetite is found in Cornwall, Pennsylvania, occurring in an entirely different position from the above. Here an extremely wide regularly stratified deposit of iron, with a width of more iJian 400 feet, rests against a trap rock, which has protected it at this point from destruc- tion by weathering, forming a series of hills instead of the valleys which would normally have resulted in this soft de- posit. Whether it was originally a pyritiferous shale which has been altered, or a brown hematite metamorphosed to magnetite, seems a question. ^ It is a phenomenal example of cheap mining, the ore being soft so that very little explosive is needed, and the mine being entirely an open-work. Walls of ore eighty feet high are blasted with dynamite. Owing to the great width of the deposit, it can be exploited in a series of retreating terraces at the base of which temporary tracks are laid for its removal. Already, up to 1891, 11,508,990 tons of ore have been won from this deposit, which was first opened in 1740 ; and there are no signs of exhaustion, but on the contrary boring showing that the ore extends below the water line. Magnetite is typically a metamorphic mineral. As this ore by rusting alters to the hydrous forms of iron ore, so 1 Professor Lesley states that the deposit is a replaced lime-shale. Sum- mary, Final Eeport, Vol. I., Pennsylvania Geological Survey, pp. 351-357. 132 ECONOMIC GEOLOGY OP THE UNITED STATES. they by metamorphism lose their superfluous constituents and become magnetite. Thus, in whatever original position other ores of iron are found in sedimentary strata, magnetite is also found in the same mode of occurrence in the meta- morphic rocks which are altered from these sediments. It has, therefore, the appearance of bedding, and sometimes really is bedded, though more often this appearance is the result of replacement or concentration, by the process of segregation, during metamorphism. Carbonate of Iron Ores. — This is the least important of the ores of iron, and in 1891 out of the total output of 14,591,178 tons of iron ore, only 189,108 tons, or 1.3 per cent, of the ore of the country was carbonate. In 1880 the carbonate of iron produced 11.57 per cent of the total out- put, or, during the year, 823,471 tons. At present the only important carbonate-producing state is Ohio, which in 1891 had an output of over 100,000 tons ; New York, Kentucky, Pennsylvania, and Maryland being the only other producers of this ore. The carbonate, siderite, may be considered to be a combina- tion of iron and calcite in which the percentage of iron varies even to the point of complete replacement of the calcium. It occurs as concretions of clay ironstone in beds of calcare- ous clay ; but in this form it is usually too disseminated for mining in this country, although in Europe it is extensively mined. As an ore it is found stratified with slates and sand- stones in the Burden mine, near the Hudson, in New York, and it is quite universally found stratified in the other mines, being apparently most frequently a stage in the replacement of limestone beds. The blackband ore of Ohio and Kentucky is a stratified carbonate, coloured black by bituminous matter. lEON. 133 An exception to this general statement is found in a mine at Roxbury, Connecticut, now abandoned, where the ore is found in a fissure vein with quartz, galena, and calcite, — quite an exceptional mode of occurrence. Foreign Occurrences. — Foreign occurrences of iron illus- trate the same general features as those described above, and very little need be said about them. The greatest iron- producing country in the world, next to the United States, is Great Britain, which, up to 1889, was a greater producer than this country. At the time of the Roman conquest, iron mines were opened in the Forest of Dean and else- where, and some of these mines are still worked. Through- out the United Kingdom iron ores occur bedded in regular strata, or gathered together along contacts, or in hollows. These ores are chiefly red and brown hematite and the carbonate. They occur in the Carboniferous or mountain limestone, and in the coal measures chiefly; in the latter place being found in the form of clay ironstone concretions, which sometimes coalesce into partial beds. Brown hema- tites are found also in the Mesozoic strata. Many of the iron ores of the United Kingdom are of very low grade, and are capable of being profitably mined only because of the close association with coal, the coal and iron ore being at times hoisted to the surface through the same shaft. In 1860 the United Kingdom produced 8,155,749 metric tons ^ of iron ore, and the output increased to 1880-1882, when the annual production amounted to over 18,000,000 metric tons. Since then the output has been steadily decreasing, until in 1891 it amounted to only 12,987,159 metric tons. 1 The metric ton is 2204 lbs. ; the long ton, 2240 lbs. ; the short ton, 2000 lbs. 134 ECONOMIC GEOLOGY OF THE UNITED STATES. Germany, the third in rank as an iron-producer, had an output in 1891 of 10,657,521 metric tons of ore. These ores, which sometimes occur in thick beds, are found chiefly in the Devonian and Jurassic strata in the form of limonite, hematite, and the carbonate. The typical occurrence is bedded, but the ore also occurs in veins often at contacts. Spain, which in 1892 produced 5,465,150 metric tons, is a producer chiefly of brown and red hematite which occurs in Cretaceous rocks. The most important district of this country is Bilbao, which in 1890 produced 4,326,933 metric tons, or nearly the entire output of the country. In order to show the importance of our own iron-producing regions, it may be stated that, in 1890, the total output of Spain, the fourth iron-producing country in the world, was more than 650,000 tons less than the output of the one state of Michigan. Austria, which has been an iron-producing country since the Roman invasion, illustrates very nearly the same occur- rence as the above, and in 1891 produced 1,231,248 metric tons. Belgium also produces hematite, limonite, and clay iron-stone, which is bedded in and below the coal. In 1891 the output was only 202,204 metric tons. Both Norway and Sweden produce considerable iron, chiefly magnetite, the ore from the latter country being remark- able for the very low percentage of phosphorus, that from Dannemora containing only 0.003 per cent, and from other provinces, varying up to 0.05 per cent. This makes a remarkably good Bessemer steel, and the output of iron ore from Sweden in 1891 was 987,405 metric tons. In both Norway and Sweden, as in other parts of Europe where the rooks are metamorphic, the occurrence of the iron ore is IRON. 135 in lenses, apparently of segregated origin, very nearly the same as the ores of New Jersey and the Adirondacks. Both Italy and Portugal have large stores of iron, but owing to the fact that there is no coal at hand, very little is mined in these countries, Italy having an output in 1891 of only 216,486 metric tons. Canada has iron in modes of occur- rence similar to that of the United States, although, owing to the great areas of Archean rocks, it is probable that magnetites predominate over the other ores. There are undoubtedly great possibilities in store for the iron industry of Canada, although the general absence of coal over large areas must always interfere with its development. At present, Canada produces very little iron, the output for 1891 being only 62,594 metric tons. The iron ores of Africa, Asia, Australia, and South America are practically unde- veloped, not from a lack of supply, but because of the lack of industrial progress. The countries of these continents allow their stores of iron to remain undeveloped, obtaining only a very little for pressing local needs, and depend upon the United States and Europe, Great Britain chiefly, for the greater part of their iron supply. China, which produces not far from 500,000 tons a year, is an exception to this statement. General Mode of Occurrence. — Iron ores occur dissemi- nated through all rocks, being usually magnetite in the igneous and metamorphic rocks, and hematite, limonite, or carbonate in the sedimentary strata. From one or another of these sources it is taken into solution by water and either precipitated (bog-iron ore), or segregated (some of the New Jersey mines), or caused to replace other rocks (Penokee- Gogebic region), or, under some circumstances, formed into 136 ECONOMIC GEOLOGY OP THE UNITED STATES. beds by disintegration and mechanical deposition (Iron Mountain, Missouri). Under all of these circumstances an actual or apparent structure of bedding, either original or secondary, is typically given to iron-ore deposits. Varia- tions from this type of occurrence are distinctly rare. Fre- quently the beds of pre are very wide, and, unlike most of the ores to be considered, the process of mining is usually by open works instead of in true mines. Uses of Iron. — The uses of iron are so varied and im- portant that civilization depends upon it more than upon any other mineral product of the earth. Indeed, without a plentiful supply of iron the civilization of the present could hardly have been attained ; and, where iron is not present, a high degree of advancement in art and industry is not quickly reached. How much England and the United States owe to their supplies of iron can probably never be told. The value of iron in the arts depends upon the fact that it is both abundant and cheap, and that, by subjecting it to different processes, it can be made either brittle or malleable, either soft or extremely hard, and either comparatively fragile or extremely tough. Not only can its properties of hardness be varied by heat and tempering, but also, by alloy with such metals as chromium or nickel, a steel of extreme hardness can be produced. The melting-point may also be varied. If iron melted as easily as lead, or was as refractory as platinum, it would be of but little use, yet, for some pur- poses, it is desirable to have a comparatively low, or, on the other hand, a high, melting-point, and this can be accom- plished within a certain range, by different processes. Iron can in one form be cast, thus making it very valuable in IKON. 137 a certain class of work, but in another form, where more durability is desired, it is worked by hammering and weld- ing instead of by casting. There is one great fault in iron, and that is the ease with which it rusts ; but by painting or coating with some less easily oxidized metal, as tin or zinc, to exclude the air, this is not so serious an evil as it might at first thought seem to be. The uses of iron are being extended every year with the advance of civilization and the decrease in cost of iron and iron-working. No single industry has called for a greater supply than the railroads, and now steel vessels are demand- ing an increasing quantity. These, with bridges and great engineering works, are the largest uses for iron ; but in the smaller articles for household, farming, and other similar pur- poses, great quantities are also used. It is hardly probable that the marvellous increase in demand for iron, which has taken place in the past twenty-five years, will be repeated in the next quarter of a century, although there is little doubt that there will still be a decided increase. Distribution of Iron Ores. — The ores of iron are widely dis- tributed in this country, yet the areas in which mines are located are extremely limited. East of the Mississippi and a line projected northwards to the Lake of the Woods, the output of iron ore in 1889 amounted to a total of 96.73 per cent of the entire product of all the mines in the country. If this eastern division be divided by an east and west line extending along the Ohio and Potomac, the product of the northern portion, according to the census of 1890, is 76.82 per cent of the total output of the United States. While this rather remarkable distribution is in part due to the geo- logical conditions, it is chiefly the result of the fact that the 138 ECONOMIC GEOLOGY OF THE UNITED STATES. industrial progress of this section has been greatest. Un- doubtedly the two conditions have been interacting, the increase in industrial demands calling for more iron, while, on the other hand, the presence of the supply has without question aided in the progress. Ten years ago this division was much more marked, and already the centres of the iron supply are moving southward and westward ; and, as these sections develop industrially, their stores of iron will be more and more called into use. Carrying the consideration of iron-ore distribution to a still smaller division of areas, one is impressed by the fact that workable deposits are extremely local. The four iron-bearing ranges of the Lake Superior region are all included in a semi- circle, with a radius of 135 miles and a centre in Lake Supe- rior, the greater part of the mines being near the periphery. Li 1889 this district produced 7,519,614 tons^ of ore. A parallelogram sixty miles in length and twenty miles in width would include all the mines of the Lake Champlain district of northern New York, from which, in 1889, 779,850 tons of ore were won. A circle of fifty miles' radius, em- bracing portions of Alabama and western Georgia, included mines which, in 1889, produced 1,545,066 tons of ore, and a single locality, Cornwall, Pennsylvania, contributed 769,020 tons. From these districts- alone, 10,613,550 tons, or 73.11 per cent of the entire output of iron ore of the United States, were obtained in 1889.^ During the year 1891 the four states, Michigan, Alabama, Pennsylvania, and New York, each produced over 1,000,000 1 Long tons are used in the statistics for the United States. 2 The facts in this paragraph were obtained from the volume on Mineral Industries of the Eleventh Census Reports, p. 9. IRON. 139 tons of ore ; and Michigan had an output of over 6,000,000 tons ; Minnesota, Virginia, Wisconsin, Tennessee, and New- Jersey each produced over 500,000 tons, and less than 1,000,000 ; Georgia, Colorado, Missouri, and Ohio each pro- duced between 100,000 and 500,000 tons. Thus thirteen states only may be considered important iron-producing states, and of these only one is in the Cordilleran region. Reviewing hurriedly the output of each of these states, it is found that Michigan has, in 1891, decreased its output over 1,000,000 tons since 1890, but still produces 41.99 per cent of the iron ore of the country. Of this ore, 88.87 per cent was red hematite, 7.47 per cent brown hematite, and 3.66 per cent magnetite. More than one-half of the red hematite of the country comes from Michigan. The several districts which produce this ore are situated on the peninsula between Lakes Superior and Michigan ; and more than three- fourths of it comes from nineteen mines, five of which, in 1891, produced over 300,000 tons each, four between 200,000 and 300,000 tons, and ten between 100,000 and 200,000 tons. The development of the iron industry in the various dis- tricts of the Lake Superior region since 1883 is shown in the table on page 140. Alabama, the second state as an iron-producer, continues to increase its output, and in 1891 the production was 1,986,830 tons, or 13.62 per cent of the iron ore of the country. The ore is chiefly red hematite, although about one- fourth was brown hematite, and in both the red and brown varieties it is the second most important producing state, its output of red hematite being 16.35 per cent of all produced in the country, and of brown hematite 16.76 per cent. There are six mines in Alabama which produced over 140 ECONOMIC GEOLOGY OP THE UNITED STATES. r/i M < W tH i^i w H R t/j < Kl ^ K H W o fH m P<4 U} ^ 1-1 g o c^ W CM W tl v o ^ M o o M H 1— ( rt « S y Hi « H W Hi 1^ O |Zi O M H O O P5 1^ CO CO T^ lO CO rH o ■* -1*< t^ t- 4 (M o^ *^ ^« cq^ -r tH" 00 t^ CO CO ■ CD t- r-t Ol CD <>l rH o^ CM (M" o 1-^ CO CO Ol o O U3 00 cq_ ^ rH OS^ oo TtT co" °. ^ 00 - ■rt^ CO G^ CO co T-H -^ t-"^ J ^ ^ T*< tH (N (N I— I ^ o o CO 1-1 CO 00 >— 1 co" o" I '^»" co" 00 -rt< OS CO o iH 1-H CO lO o o ■M I-H 52 "*- ^« co_ 00 lO Ir- a o <0 bo a pQ . h n o ^c^rc'77-?rT>v a\iw/>>^fe tf >ywta^'/vrt Fig. 20. — Ideal section showing mode of occurrence of lead in Wisconsin, a, a, lead-bearing stratum. lead and zinc are found, free from association with the pre- cious metals, in the ores galena and blende. The region is one of slightly disturbed sedimentary rocks, of an age vary- ing from Cambrian to Carboniferous. Certain strata of lime- stone, of a dolomitic character, are ore-bearing, those in the upper part of the region being the Galena limestone of Lower Silurian age, and in the lower part strata of the Keokuk group of the Lower Carboniferous. When the Mis- sissippi valley was first explored, lead was found in boulders on the surface, and this added zest to the early explorations for the precious metals, which, however, were never found 230 ECONOMIC GEOLOGY OP THE UNITED STATES. in this region. The early settlers in the valley found this lead of great value in the manufacture of shot and bullets, since the transportation of this heavy metal, from the sea- shore through the wilderness, was a very difficult task. At first the lead was smelted by very primitive methods and moulded into the required form, but before the beginning of the present century, a shot tower was erected there. Actual Fig. 21. — Ideal section showing forms of "openings" and ore deposits in the Galena limestone, Wisconsin, a, vertical crevice opening; b, cave opening; c, gash vein; d, d, d, flat openings. (After Chamberlain.) mining was first begun near St. Louis, but it was not long before mining operations were extended into the neighbouring states. The ore occurs in the nearly horizontal limestones in flat openings parallel with the bedding, in gash veins of variable size at right angles to this, and in caves in the limestone. Fossils are not uncommonly found replaced by galena or LEAD AND ZINC. 231 blende, and in the caves actual stalactites of galena occur. These facts show that the ore has been gathered together since the formation of the limestone ; and as it is confined to single strata over wide areas, it is certain that its origin is either from the ore-bearing stratum or from the strata immediately above or below, probably the former.^ As we proceed in the study of lead-zinc deposits, it will be found that this is a common mode of occurrence in various Fig. 22. — Section showing flats (a) and pitches (c) in Galena limestone, Wisconsin. (Modified from Chamberlain.) parts of the world, and it must be granted that, in certain limestones, usually dolomitic limestones, there was a store of disseminated zinc and lead, which, under favourable circum- stances, was accumulated into these deposits. Sea-water contains these metals, and they may have been precipitated from solution, or certain animals may have extracted them 1 Recent studies show that there are small fissures connected with these deposits and that they have in part influenced the ore accumulations ; but this does not essentially modify the above conclusions. 232 ECONOMIC GEOLOGY OP THE UNITED STATES. from the water and built them into their calcareous skeletons. A plausible and rather attractive theory is that the source is from sea-weeds, which at present are known to contain these metals. This theory assumes that in the sea, over the point where the ore-bearing limestone was being deposited, a Sargassum sea existed, as is the case in the central North Atlantic and other oceans, in the swirl en- closed by oceanic currents. The Mississippi valley, in the Palseozoic, was occupied by a great ocean bounded by land areas on the north, east, and west, and such a condition may well have existed there. If such an accumulation of sea-weed did exist in this region, the constant decay of the vegeta- tion might have furnished to the ocean bottom a supply of both these metals, but it must be admitted that this is merely hypothesis. The facts are that in some way zinc and lead were incorporated into these strata, and later segregated, but by just what means we cannot say. Even from the very first, these deposits have been worked by individuals or small companies as superficial open-work mines. The conditions do not favour the formation of large companies, because the mining operations are simple, very little machinery is called for, drainage is easily obtained, and no deep or extensive tunnels and shafts are needed. More- over, the ore is found in irregular accumulations, sometimes yielding large returns, but often being absent. These con- ditions have led to the general adoption of this system, each Fig. 23. — Section showing gash vein (a), cave opening (6), and flat opening (c) , in the Galena limestone. (Modi- fied from Chamberlain.) LEAD AND ZINC. 233 land-owner working his own area or leasing it to others on shares. Recently, however, the mining operations have been extended by the discovery of the ore, in borings, at consider- able depths, and even beyond the limits of the original lead- producing belt. By these means the district is becoming more productive. Colorado Lead Mines. — The Leadville silver-lead vein, in the Mosquito Range, at the head-waters of the Arkansas River, has been one of the remarkable lodes of the country ; and this gave to Colorado its first important start as a mining state. From an area of about a square mile the output of silver has been, for a number of years, greater than that of any foreign country, with the exception of Mexico. During the same period the production of lead has been nearly equal to that of England, and greater than any other European country excepting Spain and Germany. In 1860 a placer deposit of stream-gold was found, in a gulch near this lode, and several million dollars' worth of this metal was ex- tracted, causing the establishment of a flourishing town called Oro, which, however, soon lost its importance when the gold began to be exhausted. Not until 1875 was the carbonate of lead, which has since been so important, ac- tually recognized. There are several modes of occurrence in this vein; but the typical one (Fig. 24) is between a bed of blue-gray dolo- mitic limestone of Lower Carboniferous age, for a foot wall, and a sheet of porphyry for the hanging wall, the dip being extremely variable, from steep to very gentle. The upper wall is sharp and distinct, but the ore passes by gradual transition into the underlying limestone. Argentiferous ga- lena, bearing native gold, is the actual ore, but above the 234 ECONOMIC GEOLOGY OE THE UNITED STATES. water line this is weathered to the carbonate and sulphate. The gangue is limestone, barite, and chert, with ores of anti- mony, molybdenum, copper, bismuth, zinc, etc. Through this the ore is distributed irregularly, the lead ore being chiefly in the limestone, the copper and gold in and near the eruptives and crystallines. Mr. Emmons,^ who has studied this vein, has arrived at the conclusion that the ore was deposited in the form of sulphides in the overlying quartz porphyry, Fig. 24. — Cross-section of Evening Star Mine, Carbonate Hill, Leadville, Colo- rado, a, recent deposits; 6, porpiiyry; c, white porphyry; eJ, white lime- stone; e, vein material in blue limestone stratum; /, fault; o, ore; t, quartz- ite ; V, blue limestone ; x, lower quartzite. (After Emmons.) and afterwards leached from this by percolating water. The strata are faulted ; but since ore is not found in the faults, the necessary conclusion is that they were formed after the accumulation of the ore. An easy passage-way for the metalliferous solutions was furnished along the contact plane of the porphyry and limestone ; and this served as an ore channel, in which the minerals were deposited, and from which they penetrated both the porphyry and the limestone, 1 Monograph, U. S. Geol. Survey, Vol. XII., 1886, Geology and Mining Industry of Leadville, Colorado. LEAD AND ZINC. 235 but particularly the latter, replacing it atom by atom. Ac- cording to this explanation, the vein is, therefore, partly an ore channel, partly a replacement deposit, and not a contact vein, as might at first appear probable, although there seems every reason to believe that the intrusion of some of the igneous rocks in the neighbourhood furnished heat to the percolating waters. The Leadville mines have exhausted the best of their easily mined carbonate ; and in the future the output from this district will probably continue to decrease, as it has in the past few years. However, other mines are in operation, and new ones continually being opened. What permanent effect the recent fall in price of silver will have upon these mines cannot at the present time be stated; but it will not be surprising if it serves to close many of the lead-silver mines, and to reduce the output of lead from these sources. Other Western Lead Mines. — The lead veins of the west are practically all argentiferous galena ; and the description of the Leadville mine, together with that of the Eureka and other mines in the chapter on silver will serve to illus- trate these modes of occurrence. Utah is next in impor- tance to Colorado, and some of the mines of this territory, as weU as of Idaho, have already been mentioned. Idaho is producing large quantities of this metal, principally from the famous Coeur d'Alene mine, which, in 1891, had an output of about 66,000,000 pounds of lead from a low-grade silver- lead sulphide, which exists in great quantities, and promises in the future to increase in importance. The ore occurs in metamorphic quartzites and schists which have been folded and faulted, and the gangue is siderite. Montana, Arizona, 236 ECONOMIC GEOLOGY OP THE UNITED STATES. and New Mexico also produce lead from their argentiferous galena mines ; and, in smaller quantities, this metal is obtained from the other states of the Cordilleras. Foreign Lead Mines. — Spain is the leading lead-produc- ing country of the world, and here, as in the United States, there are two sources, — ■ the argentiferous and the non-argen- tiferous ores. The most important non-argentiferous galena district is in the province of Jean, which produces nearly two-fifths of this class of Spanish ore. Here the lead occurs in true fissure veins, which traverse a series of nearly hori- zontal Triassic sandstones, and an underlying granitic mass. A very little silver and some blende occur, the gangue being quartz. Of even more importance than this district is the province of Murcia, where the ore is found in nearly vertical fissure veins traversing Silurian slates, limestones, and intrusive trachytes. The ores are partly argentiferous, partly non-argentiferous galena, in a gangue of quartz, calcite, and barite. A third important mine is in the province of Almeria, where galena, chiefly non-argentiferous, occurs in metamorphic rocks. Portugal has deposits not unlike those of Spain, but of much less importance. Germany produces lead, usually argentiferous, from the famous veins which have already been mentioned under silver, in the Harz, Erzgebirge, etc. (Clausthal, Rammels- berg, St. Andraesberg, Freiberg, etc.), and also from the Rhenish provinces, particularly Westphalia. Here galena occurs in nodules and grains cementing a Devonian sand- stone ; and near Cologne in Silesia lead sulphide, accom- panying blende, is found in limestone. The most important source of this metal is in the fissure and segregation veins of the great mining districts, already referred to, where LEAD AND ZINC. 237 copper, zinc, silver, lead, and other metals all occur together. In Europe, the next most important lead-producing country (Mexico and New South Wales are more important) is Great Britain. Both the Cornwall and Devonshire districts are lead-producers, but they are losing importance in this respect. Twenty-five years ago Devonshire had an annual output of over 1000 tons of lead, and Cornwall over 6000 tons, but now the output is much less. Elsewhere in England galena is found in fiats and fissures in limestone. In north England two sets of fissure veins cross the Carbo- niferous limestone, and from these there are branching flats, which sometimes lead to caverns, these being connected with the fissures by thin stringers or leaders. The gangue is calcite and quartz, and it also contains some blende. Nearly the same occurrence is noticed in Yorkshire, and lead is also found in Wales, Scotland, and Ireland, in nearly the same modes of occurrence as in England. In Italy and Belgium galena is found associated with zinc blende in modes of occurrence which are described in the latter part of this chapter. On the mainland of Italy galena also occurs in gneiss with very little blende, and in Belgium a lead vein crosses both the Carboniferous limestone and the Coal Measures and sends branches between the contact of the two. Austria-Hungary produces both zinc and lead, from the large veins, already mentioned in a previous chapter, and from a deposit of dolomite. Neither Russia, Sweden, nor France are of marked importance in the production of this metal, but each produces some. The supply from Russia is obtained partly from argentiferous galena veins and partly from the Polish zinc-lead deposits. Sweden produces argentiferous galena from the metamor- 238 ECONOMIC GEOLOGY OF THE UNITED STATES. phic rocks, and France also has argentiferous lead veins crossing metamorphics and eruptives. Important deposits of lead occur in New South Wales, but we know little about the mode of occurrence there, excepting that the supply comes chiefly from silver-lead mines. Mexican lead ores are partly smelted in this country, and our knowledge of the position of the industry, as well as the occurrence of the ore, is obscure. Origin of Lead Ores. — Like all metals, the original source of this one was probably igneous rocks, although it has come into its present position in a variety of ways. The metal easily oxidizes, and forms soluble salts, which readily find their way into sedimentary rocks. It may be said that lead deposits are found in three principal- modes of occurrence : first, in fissures or other cavities through which metalliferous solutions pass ; secondly, in segregated veins where rocks are metamorphosed ; and thirdly, in local deposits derived locally from mineral originally disseminated. The first two are generally argentiferous, while the third is usually associ- ated with zinc. These occurrences are more fully described in the chapters on silver and zinc. Uses of Lead. — This metal finds numerous uses in the arts, and these are being extended and increased every year as the output increases. White lead, the carbonate, to be used in paint, still continues to be the most important use of lead, and lithai-ge, the oxide of lead, is also made into paint; but much of the supply of this metal is manufactured into pipe and sheet lead for plumbing and various other purposes. These latter uses of the metal are favoured by its low melting-point, its softness, the ease with which it can be soldered, and the fact that it does not rust extensively. LEAD AND ZINC. 239 An alloy of lead and arsenic^ makes lead harder, more fusible, and gives to it the habit of assuming a spherical form when dropped through the air. This alloy is used in the manufacture of shot, and this industry calls for large annual supplies of lead. Other alloys are used for various pui-poses, but the only very important combination is the type metal alloy, which is a mixture of lead and antimony, at the ratio of 76 to 24.^ This reduces the melting-point below the average of the two, makes the alloy harder than lead, and gives to it the power of expanding on cooling so that it can be cast, a power which lead alone does not possess. The manufacture of type metal is a delicate proc- ess, since, if too much antimony is used, the alloy is too hard, and it becomes too soft if the proportion of antimony is too low. Under the heat of melting to form the alloy, the antimony may be partly oxidized and lost, and this has to be avoided by careful methods. The price of lead has steadily decreased, with some fluc- tuations, since 1870, when it was 6.25 cents a pound, to 1892, when it averaged 4.09 cents for the year, but in December was 3.80 cents. During this time it has never been above 6.55 nor below 3, but has averaged about 5 cents. Production of Lead. — The available statistics for this metal are not so complete as for those previously considered, nor is the metal of as much importance. Since the lead is so frequently smelted from other ores, and since much of it is made into white lead, it is difficult to estimate the value of the industry. The following tables will, however, serve to illustrate the distribution of lead and the changes in 1 Three parts of arsenic to 700 parts of lead. ^ There are numerous varieties of type metal of varying composition. 240 ECONOMIC GEOLOGY OP THE UNITED STATES. output of the different districts, and this is the chief ohject of the tables of statistics in this treatise. PRODUCTION OF LEAD IN THE UNITED STATES. Short Tons (2000 Lbs.). States. 1873. 1875. 1880. 1885. 1890. 1891. 1892. Colorado 56 818 85,674 55,000 54,500 64,000 61,600 Utah IS.OOO 19,000 15,000 28,000 18,000 28,000 30,000 Idaho-Montana 15,000 83,000 40,000 36,500 Mississippi! valley .... 22,881 24,780 27,690 21,975 31,351 84,000 37,000 Nevada . . . . 16,690 8,600 2,000 2,500 2,500 Arizona-California . . . 4,000 1,600 2,000 2,000 Total . 42,540 59,540 97,825 129,412 143,876 178,133 178,392 The remarkable increase in the output of Colorado is note- worthy, although since 1889 there has been a considerable decrease. Utah has steadily increased, as has also the Idaho- Montana production. This comes principally from Idaho, and the decrease in 1892 was due to the disastrous strike in the Coeur d'Alene mine, which caused the suspension of mining operations for several months. Nevada shows a marked falling off in lead production, as indeed it does in nearly all industries. During the year 1892, in addition to the output above enumerated, 9392 tons of lead were pro- duced by other states and territories, chiefly from New Mex- ico, and about 39,608 tons were produced from Mexican ores smelted in this country. 1 The estimate for the Mississippi valley includes all of the non-argen- tiferous ores ; hut most of them are from the states in the lead-hearing dis- trict of the Mississippi valley, although a small amount comes from the Appalachian states. LEAD AND ZINC. 241 The following table from the census statistics, based upon a study of the mines and an estimate of the lead contents, shows the distribution of the lead production by states : — LEAD PRODUCTION IN THE UNITED STATES, 1889. States. Short Tons (2000 Lbs.). Value at Place OP Pkoduotion. Colorado Missouri Idaho Utah Montana New Mexico Kansas Arizona Nevada Wisconsin 70,788 44,482 1 23,172 16,675 10,183 4,764 3,6171 3,158 1,994 1,6781 2,101,014 1,571,161 1,042,629 763,329 456,975 170,754 103,236 98,747 72,653 64,062 PRODUCTION OF LEAD BY THE UNITED STATES. Years. Short Tons Mexican Ore Total Value at (2000 Lbs.). smelted in U.S. New York. 1825 1,500 1835 13,000 1845 30,000 1855 15,800 1865 14,700 .... 1870 17,830 1876 64,070 1881 117,085 $11,240,160 1886 135,629 12,667,749 1889 157,397 25,570 16,137,689 1890 143,876 18,124 14,266,703 1891 178,133 23,867 17,574,000 1892 178,892 39,608 17,917,000 1 Lead ore. 242 ECONOMIC GEOLOGY OP THE UNITED STATES. With some fluctuations the United States has thus steadily- increased its output since 1825 ; but between 1870 and 1880, when the mines of the Cordilleras became of importance, there was a very striking increase. In 1892, 142,087 tons of the total lead product came from desilverized ores. PEODUCTION or LEAD IN THE WOKLD. Metric Tons (2204 Lbs.) ake used for All but the United States AND Mexico, where Short Tons are used. Countries. 1885. 1887. 1889. 1890. 1891. Spain 78,986 119,932 162,000 163,838 235,000 United States . . . 129,412 145,212 157,397 143,876 178,133 Germany .... 93,134 94,921 100,601 101,781 95,615 Mexico 1 ..... 15,488 25,570 18,124 23,867 New South "Wales 2 . 194 85,146 41,996 56,304 Great Britain . . . 38,899 38,411 36,189 34,139 32,731 Italy 16,461 17,795 18,165 17,768 18,500 Austria- Hungary . . 10,625 9,605 10,608 9,552 8,683 Russia 714 988 578 838 900 Sweden 282 254 310 299 Canada . . . . • 93 75 51 267 ' Mexican statistics are not obtainable, because part of the ores are smelted in this country. Eecently smelters have been established in Mexico which The Mineral Industry estimates will produce in 1893 about 45,000 tons of lead, having smelted something like 35,000 tons in 1892. The statistics for Mexico are based upon the lead product from ores smelted in the United States, and are therefore far below the truth. 2 No statistics are at hand for the output of lead in New South Wales, the estimate given above being the exported lead, and it is consequently less than the actual production. The United States includes only lead of domestic production, excepting in 1885, when Mexican ores are included. LEAD AND ZINC. 243 A remarkable increase is noticed in the Spanish pro- duction, which has exceeded that of the United States, and given to Spain the first place, which the United States held for awhile. The rapid increase in the production of New South Wales and the steady decline of the British production are also striking. Mexico should probably hold fourth place in the table, although exact statistics cannot be given. The total production of lead in the world in 1891 was probably about 650,300 tons. Zinc. General Statement. — Zinc is found chiefly in the ore sphalerite, or blende, the sulphide of zinc ; but in nearly all mines of this metal other ores, chieily weathered forms, are found, the most important of these being willemite, the silicate ; calamine, the hydrous silicate ; and smithsonite, the carbonate. In the New Jersey mines the ore is the red oxide zincite, and willemite, with the zinc-iron oxide franklinite. Blende occurs usually in association with galena, the latter generally predominating in the fissure veins, the former in local deposits derived from the enclosing strata. The former mode of occurrence has been described in the chapter on lead, and some of the descriptions which follow, being prin- cipally of lead-zinc deposits, must be considered to apply, in general, to lead. When blende is associated in minor quan- tities with lead, it can be extracted where economic methods are in use, but in our western silver-lead mines, blende is not found in sufficient quantities to be of much value. There- fore the Cordilleras have produced practically no zinc, although this metal may exist there as veins of blende. 244 ECONOMIC GEOLOGY OF THE UNITED STATES. which have escaped the notice of the prospectors, who would not be familiar with its appearance, the ore being non- metallic in lustre. In distribution, zinc differs widely from the last four metals, the chief source being the states of the Mississippi valley and one or two eastern states, notably New Jersey and Pennsylvania. Zinc in the United States. — No further description of the lead-zinc deposits of the Mississippi valley is called for, since the blende and galena are found together in the same stratum, often in intimate association. Nevertheless, especial attention is called to the description in the preceding section of this chapter, for comparison with the mode of occurrence in some of the foreign zinc mines. From this general region the chief supply of zinc comes from the Joplin district, in southwestern Missouri, and across the line in Kansas, where much progress has recently been made in the exploration of the deposits in the Keokuk group. Next to the mines of the Mississippi region the New Jersey zinc deposits are the most important in this country. This district includes two general mining areas situated close together, in Sussex County, one at Franklin Furnace, the other a few miles south of this at Ogdensburg., In both mines the ore is zincite, willemite, and franklinite, and the gangue calcite, included in nearly vertical beds of white limestone closely associated with, and for a long time sup- posed to be enclosed in, Archean gneisses. Not far distant from the mines there are igneous masses, and recent studies seem to show that the white crystalline limestones are not Archean, but Cambrian beds, metamorphosed by the intrusion of these igneous rocks, which are mainly granites. In the neighbourhood there are large areas of a blue dolomitic lime- LEAD AND ZINC. 245 stone of Cambrian age, which is not metamorphosed, and it is this which is believed, by those who have most recently- studied the region, to have furnished the zinc during a com- plete alteration to white crystalline limestone. In the blue limestone, blende is sometimes found cementing a breccia. The vein itself appears to be of true segregation origin, and the walls are not distinct, but the vein becomes poorer on either side, until only here and there a crystal or nodule of ore is found. Studies of these mines have convinced the author that segregation, as illustrated here, is a process, partly of replacement, partly of crowding the enclosing minerals aside to give room for those which are forming. Another important zinc mine is found in the Saucon valley, Pennsylvania, and this is also in the blue magnesian limestone, which has been very much fissured and crushed, the ore being deposited between the brecciated fragments. The ore in the upper parts of the mine is calamine, but it changes below to blende. From 1853 to 1876 this mine produced considerable zinc, but since then it has been of very little importance. In southwestern Virginia calamine occurs in crystalline limestone, and probably the ore here also changes to blende. Other zinc mines in the United States are of little importance. Foreign Zinc Mines. — Considerable zinc is found in Bel- gium and the Rhenish provinces of the German Empire. The ore in Belgium is chiefly calamine, although other ores also occur. It is found at Bleiberg, in small veins and irregu- lar masses, in a Carboniferous limestone crossed by a fissure vein which has been filled with brecciated fragments, partly cemented by ore, and then later reopened and again filled. Both blende and galena occur there. Near Aix la Chapelle 246 ECONOMIC GEOLOGY OP THE UNITED STATES. a bed of zinc occurs in Carboniferous dolomitic limestone, which it has partly replaced. The ore is calamine occurring in lake-like depressions in the strata. This region, which was exploited in the fifteenth century, has produced more than 1,500,000 tons of remarkably pure zinc ore. Near Cologne this metal is found, in the form of blende, with galena, in basin-like depressions. A very important zinc-producing region is in Silesia, in Germany, and extending into the neighbouring country of Poland. Here both calamine and galena occur in troughs, in a dolomite (Muschelkalk'), evidently the result of concentration from the dolomite. The calamine changes below to blende, and kernels of this mineral are found enclosed in calamine, showing plainly that the latter is derived from the former by weathering. This same bed of Muschelkalk produces zinc elsewhere in Germany, and blende is found also in the Black Forest, replacing fossils, and also in the various lead mines of the nation. The chief supply of this metal in Germany comes, however, from Silesia and the Rhenish provinces. The statements concerning the lead occurrence of Great Britain apply also to zinc, since this metal is practically coextensive with the lead. Austria-Hungary has zinc in very nearly the same modes of occurrence as Germany, dolomite being at times the country rock, while, in other places, lead-zinc ores are found in veins traversing meta- morphic, igneous, and sedimentary rocks. Important zinc deposits occur in Italy, chiefly on the island of Sardinia. Here also the ore is calamine and blende associated with galena, occurring in a dolomitic limestone. Other Euro- pean countries, notably Sweden, produce some zinc, but none of them are of particular importance. Several zinc- LEAD AND ZINC. 247 producing districts occur in Spain, the ores there also being calamine and blende. Outside of Europe and the United States very little zinc is produced ; but it seems hardly probable that this metal is confined to these two districts, and the fact that these are the two most explored and most accessible regions renders this still more improbable. There are no signs of exhaustion of our zinc ores ; but if they are exhausted, there need be little fear that their place will not be taken by new dis- coveries either in our western country, or in some other partly explored region. Origin of Zinc Deposits. — This metal, like many others, may be said to have a typical mode of occurrence, although it is true that there are variations from this. Ores of zinc, usually as minerals of secondary importance, occur in many of the deposits of other metals, particularly argentiferous galena. In such places the origin of the zinc is the same as that of the galena and other ores, whatever this may be. But when zinc predominates, or forms a considerable percentage of the ore, in the vast majority of important mines the associa- tion is with dolomitic limestone. It is not possible to state the exact meaning of this association. Dolomitic limestone is sometimes originally deposited as such, but at times it is the result of a secondary alteration of ordinary limestone. Admit that a limestone thus changing is zinc-bearing, and it is readily conceivable that, as one result of the alteration, the disseminated zinc may be segregated. Magnesian lime- stones, when originally deposited as such, are very fre- quently precipitated from solution in saline waters, usually dead seas. Such is the case with the Permian dolomites of Texas ; but in other dolomites the evidence points to accu- 248 ECONOMIC GKOLOGY OF THE UNITED STATES. mulation in open seas where precipitation has probahly not occurred. In these cases the magnesia may have been intro- duced by organisms which contained it in their tests or calcareous skeletons. Various hypotheses have been suggested to account for the mode of origin of the galena-blende deposits of the Mississippi valley, and these may with equal force be ex- tended to account for the zinc deposits elsewhere. There is a remarkably ujiiform association with dolomite, and from whatever source we may assume the original supply to have been derived, and these sources are probably various, subse- quent concentration, akin to the concretion of flint in chalk, has been brought about by the gathering together of the zinc from the dolomite, sometimes by metamorphism, as in New Jersey, sometimes by slow changes not strictly meta- morphic. Certain of the zinc deposits which occupy basins in the rock seem to have been precipitated in these positions originally, although it is possible that this is merely an appearance simulated by a deposit of secondary origin. These remarks apply with equal force to the associated galena. The striking feature of zinc, and of many lead deposits also, is the general association with sedimentary rocks and their accumulation without the intervention of the more potent vein-forming agencies. In this respect they differ from gold, silver, and copper, and more closely resem- ble iron. Uses of Zinc. — This metal, in the state of the oxide form- ing zinc-white, is used as a base for paint in the place of white lead. Formerly zinc was used for sheathing vessels, but very little is at present supplied for this purpose. For plumbing and roofing, zinc is in common use, and as a LEAD AND ZINC. 249 coating to iron this metal is extensively called for in galvanizing. One of the most important uses is in the manufacture of brass, which is ordinarily composed of from 66 to 73 parts of copper and 27 to 34 parts of zinc. The composition varies entirely according to the use for which it is intended, and, with the variation in proportion, the colour becomes more golden or whiter, according as the proportion of copper is increased or decreased. With an increase in. the proportion of zinc, the alloy becomes more fusible, harder, and more brittle. Brass was made long before zinc as a metal was dis- covered, and Aristotle says that the people by the Euxine Sea made their copper a beautiful whitish colour by mixing with it a white earth found there. Strabo also tells us that the Phrygians made brass in this way. Another alloy of zinc and copper in common use is white metal, in which zinc predominates. From this, buttons are frequently made. Imitation gold is also made by alloying zinc with a predominance of copper, varying from 77 to 85 per cent of the mass, and this is in common use as "gold- foil " for gilding. Zinc is also made use of in the construc- tion of electric batteries. This metal is much less important than those hitherto considered, with the exception of platinum, and less is produced in the world. Since 1875 the price of spelter ^ has gradually decreased from an average of 7 cents a pound to an average of 4.63 cents in 1892, and in December of that year the price was 4.40 cents a pound. Production of Zinc. — The available statistics for the pro- duction of zinc are not very satisfactory, for the reason 1 Spelter is the commercial name for zinc. 250 ECONOMIC GEOLOGY OF THE UNITED STATES. that it is frequently not smelted in the same state, or, at times, even in the same country, where it is produced. We have statistics for the production of spelter, but this shows little with reference to the distribution of the metal, which it is the purpose of these tables to illustrate. These statistics are introduced, however, as the best that can be obtained. The first table illustrates the spelter production in this country since 1882, but it will be noticed by com- parison with the second that this does not illustrate the actual distribution of the ore. PEODUCTION OF SPBLTEE IN THE UNITED STATES. Shoet Tons (2000 Lbs.). States. 1882. 1884. 1886. 1888. 1890. 1892. Illinois 18,201 17,594 21,077 22,445 26,279 30,800 Kansas 7,366 7,859 8,932 10,432 16,380 23,088 Missouri .... 2,500 5,230 5,870 13,465 18,530 16,161 Eastern and Southern "1 States .... J 5,698 7,861 6,763 9,561 11,153 13,751 Total .... 38,765 38,544 42,641 55,903 67,342 83,300 New Jersey and Pennsylvania furnish the greater part of the supply credited to the eastern and southern states. In 1873 only 7343 tons of spelter were produced in this country. LEAD AND ZINC. 251 PRODUCTION OF ZINC ORE IN THE UNITED STATES, 1889. Short Tons (2000 Lbs.). States. Shokt Tons. Value at Mines. 93,131 24,832 39,575 63,339 12,906 450 130 140 12,024,057 400,568 299,192 175,052 141,560 3,600 3,250 2,520 Wisconsin .... .... Kansas New Jersey and Pennsylvania . . Southern States Iowa Arkansas ... New Mexico Total . 234,503 .$3,049,799 In 1892 the production from the Missouri-Kansas mines ■was 155,000 tons, valued at 13,519,225, showing a marked increase in this industry. PRODUCTION OP METALLIC ZINC AND ZINC-WHITE IN THE UNITED STATES. Zinc-White. Metallic Zinc. Total Year. Metric Tons (2204 lbs.). Value. Metric Tons (2204 lbs.). Value. Value. 1880 1884 1888 1890 1891 1892 9,171 11,797 18,149 1763,738 910,000 1,600,000 1,600,000 1,600,000 1,200,000 21,088 34,976 50,729 57,789 72,834 75,589 §2,277,432 3,422,707 5,500,855 7,474,962 8,058,405 7,703,580 13,041,170 4,332,707 7,100,855 9,074,962 9,658,405 8,903,580 252 ECONOMIC GEOLOGY OP THE UNITED STATES. PRODUCTION OF SPELTER IN THE WORLD. Long Tons (2240 Lbs.). Districts. 1883. 1885. 1887. 1889. 1891. Rhine District and \ Belgium . . . . / Silesia United States . . . Great Britain . . . Spain Austria Poland 123,891 70,405 32,837 29,161 14,671 6,267 3,733 129,764 79,623 36,328 24,299 14,847 5,610 5,019 130,995 81,375 44,946 19,839 16,028 5,338 3,580 134,648 85,653 52,553 30,806 16,785 6,330 3,026 139,695 87,080 71,662 29,410 18,360 6,440 3,760 The total production of spelter in the world in 1891 was over 350,000 long tons. That the tables of spelter production possess very little value as illustrations of the distribution of the output, is shown by the fact that Italy has no place in the above table, although it is third in rank of importance as a zinc-producing country, and the ore of zinc is, with the . exception of sulphur, the most im- portant mineral production. The ore is entirely exported for reduction, and serves to swell the amount of spelter accred- ited to other countries, just as in the first table Illinois is the largest spelter-producer, although zinc is not mined in the state. CHAPTER XI. MERCURY AND MANGANESE. Mercury. California Mines. — Mercury, or quicksilver, is found in paying quantities in but one district of this country, andj here, as indeed throughout the world, the universal ore is the sulphide cinnabar, with which native mercury and some other ores are found in minor quantities. In this coun- try, which for a long time held second place as a mercury- producer, but three states have ever supplied any of this metal ; and of these, California is the only important one, the other two, Oregon and Utah, having had a small out> put for a short time only. Ores of mercury have been found in Nevada, New Mexico, and elsewhere ; but, although it is highly desirable to have new mines, none of them have proved important. It is noteworthy that a metal so important in gold mining should have been discovered in California at about the same time that gold was found there. In 1845 the occurrence of mercury was noticed, and when gold min- ing began, this metal was at hand in such abundance that California soon took second place in the quicksilver pro- duction of the world. The mercury of California occurs in a belt of metamorphic rocks, and in these a number of mines have been opened, the most famous being the New Almaden and the New Idria. These mines have decreased 253 254 ECONOMIC GEOLOGY OF THE UNITED STATES. their output of late years, but, as some others are increas- ing, the total output of the state in the last year or two has not decreased, although in fifteen years there has been a decrease to about one-third of the output at the beginning of this period. At New Almaden ^ cinnabar is found in two fissures which unite below, enclosing a wedge-shaped mass of rocks, chiefly slates. Running nearly parallel with this, and a short dis- tance away, is a dike of rhyolite, which is of recent age, and probably the cause of the quicksilver deposit. The cinnabar, which contains some metallic mercury, occurs in a gangue of dolomite, calcite, and quartz, containing also iron pyrite. There is apparently no substitution or replacement, but the ore has been deposited in cavities and has, at times, impreg- nated the porous rocks through which the fissure passes. Already the mine is below the 1800-foot level, and at this depth a temperature of 88° is encountered, which indicates that the volcanic heat is not yet entirely gone. The New Idria mine, of the same state, does not illustrate any new point, but the ore occurs there in sandstones. A third important mine of the same region is the Sulphur Bank, which was first opened as a sulphur mine and later developed for mercury. This is an extremely interesting mine, since the vein is of very recent date, and, indeed, is apparently not yet finished. A fissure, filled with brecciated fragments, crosses sandstone, shale, and a capping of augite andesite, and in this the cinnabar serves as a cement to the 1 A description of this mine will be found in the volume of the Eleventh Census upon Mineral Industries, pp. 202-245. Becker's Monograph XIII. U. S. Geol. Survey, 1888, entitled Geology of the Quicksilver Deposits of the Pacific Coast, contains a very complete description of these deposits. MERCURY AND MANGANESE. 255 breccia, at times impregnating the porous walls. Hot water still enters the vein, and it appears that the mineral deposition is still in progress, although the greater part of the work is done.^ The silica at present being deposited is still soft. Other mines are found in this same district, and some of them were opened in the early fifties. The old veins are practically exhausted and must apparently be abandoned soon, but new ones of promise have been recently opened. The following table shows the production of the five largest mines since 1850 : — PRODUCTION OF CALIFORNIA MINES. Flasks (76 •■ Lbs.). Mines. 1850. 1855. 1860. 1865. 1870. 1875. 1880. 1885. 1890. 1891. New Almaden T,723 29,142 7,061 4T,194 14,423 13,648 28,465 21,400 12,000 8,200 New Idria 2,0002 6,0002 9,888 8,482 3,209 1,144 977 792 Eedington 8,545 4,646 7,513 2,139 885 505 442 Sulphur Bank 6,872 10,706 1,296 1,608 8,429 Napa Consolidated . 4,416 8,606 1,875 4,454 Foreign Mercury Mines. — The most important quicksilver deposit in the world is in the Almaden mine of Spain, which has been worked since prehistoric times. Strabo speaks of it, and Pliny states that 10,000 pounds came from there to 1 Phillips' Ore Deposits, pp. 68, 73, and 569 ; Becker's Monograph (referred to above), and articles by Le Conte in the American Journal of Science as fol- lows : Vol. XXIV., 1882, pp. 2.3-33 ("The Phenomena of Metalliferous Vein Formation now in Progress at Sulphur Bank, California," Le Conte and Ris- ing); Vol. XXV., 1883, pp. 424-428 ("On Mineral Vein Formation now in Progress at Steamboat Springs," etc.) ; Vol. XXVI., 1883, pp. 1-19 (" Genesis of Metalliferous Veins "). 2 Estimated. 256 ECONOMIC GEOLOGY OF THE UNITED STATES. Rome, each year, it being worked by condemned criminals, who were probably slowly killed by mercurial poisoning, from which miners in almost all mercury mines suffer. Although worked for such a long period of time, the mine is not as deep as the New Almaden, for it has not gone far below 1000 feet. In the mine a temperature of 90° is encountered. The ore is cinnabar, with some native mercury, occurring in bunches and veins, in a quartz gangue containing also iron pyrite and galena. Whether it is a true fissure vein or an ore channel is not determined. There are three nearly parallel veins, sometimes twenty feet wide, separated by thin bands of slate from two to three feet in width, and in the lower levels the deposit is worked as a single vein. The country rock is Upper Silurian slates and limestones underlain by a mass of diorite, which is probably the cause of the deposit. The following table gives the output from this mine since 1850, the statistics from 1850 to 1870 inclusive being ap- proximate estimates : — PRODUCTION OF THE ALMADEN MINE. Flasks (76| Lbs.). 1850 ... 20,000 1860 24,000 1870 32,000 1880 41,640 1890 . 50,202 1891 47,993 The Idria mine, in Austria, is in Jura-Trias conglomerates, sandstones, and slates, which are locally impregnated with cinnabar. By far the greater part of the ore comes from bituminous slates, where it occurs in irregular pockets be- MBECUEY AND MANGANESE. 257 tween large areas of barren rock. Calcite, quartz, and pyrite also occur. The strata are tilted in places to a nearly vertical position, though not always at such a steep angle, and they are crossed by fissures. Since the mines grow richer as the depth increases, it is supposed that the source is from below, per- haps from some hidden mass of igneous rock. This mine has been steadily increasing its output, from 4100 flasks in 1850 to 15,000 flasks in 1891. Quicksilver comes also from Italy and from Russia. In the latter country there is a single mine in the province of Ekaterinoslav, which began to produce in 1887 ; but little is known of this mine, excepting that the ore is cinnabar. Other mercury mines have been worked in Russia in the past, and the discovery of new deposits is announced, but our information concerning them is very limited. A mercury mine is also situated in Servia, and from this source about a thousand flasks a year are produced. A cinnabar mine in the Palatinate, in Germany, was of importance from the fifteenth to the eighteenth century, but no ore is produced from there now. It was found impregnating slate strata which were crossed by intrusive melaphyrs. Outside of Europe and the United States, practically no quicksilver is produced, although there can be no doubt that veins exist. Some comes from Borneo ; and there is a mer- cury mine in Peru, the Huancavelica, which was opened in 1570. Here the ore occurs in slates and sandstones, and the way in which it impregnates the rock suggests that it was introduced in the form of a vapour. Of the Peruvian mines Bullman saysr^ "Ores of mercury are abundant, but the mines have been abandoned, or only worked spasmodically, 1 The Mineral Industry, Eothwell, 1892, p. 563. 258 ECONOMIC GEOLOGY OF THE UNITED STATES. for a number of years. The most celebrated of the mines is that of Huancavelica, which was discovered in 1570, and up to 1790 yielded, according to Castelnau, 104,045,200 pounds of metal, worth 167,629,380, upon a gross expenditure of 110,587,000. The discovery of this great mine was of the utmost importance, as it rendered possible the enormous out- put of the Cerro de Pasco and Cerro Potosi silver mines." Quicksilver is used in the extraction of this silver. In Mexico, mercury has been discovered in a number of places, but no large amounts have ever been produced. The ore is cinnabar, and occurs in limestones and slates, the Guadalcazar mines occurring in the former. Origin of Mercury. — • There is a marked uniformity in the ores of mercury, the sulphide being the almost universal ore unless it is decomposed to native mercury. A striking asso- ciation of quicksilver deposits with slates, sometimes lime- stones, is also noticed ; but this seems to be accidental rather than a case of cause and effect, for the association is not universal, nor is there any apparent reason for the associa- tion, unless, possibly, the organic matter in these strata aided in the precipitation. There are no reasons for believing that the mercury came from these rocks, but some of the sulphur may have been furnished by them. In a number of cases, the relation between the veins of mercury and neighbouring igneous rocks is such that one is forced to conclude that they are the cause of the deposits ; and in all cases the position of the ore is such that, even though no igneous rock appears, it is a reasonable inference to draw that such rocks exist at no great depths, having failed to reach the surface, as is very commonly the case with these lavas. Mercurial and sul- phurous vapours, accompanied, no doubt, by steam, have MERCTJET AND MANGANESE. 259 escaped from these igneous rocks by some passage-way, usu- ally a fissure, and upon becoming cooler these have been de- posited in the vein. Substances so easily turned to gas, when heat is applied, as the two elements sulphur and mercury, we can readily imagine to be made to adopt this mode of accumulation ; and it is interesting to note that the facts in the mines support this hypothesis. Becker, Le Conte, and others have shown that in the Sulphur Bank and other mercury mines, cinnabar is brought up in solution with alka- line sulphides and silica, and from this source deposited in the veins. Nevertheless there is good reason to still hold that the water was charged with these substances from gase- ous emanations from volcanic rock. Of primary importance in this connection is the peculiar distribution and the rarity of the metal. Mercury veins appear, therefore, to be in nearly all, if not in all, cases, contact deposits of the sublimation type, or indi- rectly deposited from a solution of dissolved mercury of this origin. It is conceivable, however, that, accompanying some volcanic eruption, mercurial vapours may become incorpor- ated in stratified rocks in a disseminated condition, and later be segregated. Their distribution is extremely irregular, and only a few localities may be expected to contain them ; namely, regions of recent volcanic activity. The reason why they do not occur more commonly in the neighbourhood of older igneous rocks is probably that the heat is too great for their formation. An igneous mass of granite, for instance, intruded into the strata at a depth of several thousand feet, does not become cooled for many thousand years. In the mean time the sul- phurous and mercurial vapours cannot condense in the neigh- 260 ECONOMIC GEOLOGY OF THE UNITED STATES. bourhood; but unless they form combinations with other ele- ments, there is a tendency for them to migrate from the parent mass, and become disseminated instead of accumulated. If a fissure ^ is at hand, their escape toward the surface would be facilitated, and the conditions for the formation of a vein would be present ; but if this is not the case, it is probable that the substances become disseminated. Still, it is con- ceivable that, under some circumstances, such deposits might be formed in the neighbourhood of the plutonic rocks ; but speaking generally, the regions of recent volcanic action are the seats of quicksilver veins. Uses of Mercury. — The most important use of quick- silver is in the extraction of gold and silver, by the pro- cess of amalgamation, as already described. Its power of forming amalgams with other metals makes it of use in the arts for the preparation of a substance to be used for sil- vering mirrors and for other purposes. The fact that it is liquid at ordinary temperatures makes it useful in the manu- facture of thermometers ; and this fact, added to its weight, renders it of especial value in the construction of mercurial barometers. In medicine this metal is used in various forms, chiefly as calomel, while cinnabar and other compounds of mercury are valuable in the manufacture of pigments. For this purpose, it was used by the American Indians and by other early races of people. The price of mercury, in San Francisco, has varied greatly since 1850. In 1850 it averaged 199.45 a flask; in 1855, 151.65; in 1874,1105.18; in 1883, 126.83 ; and in 1892, 138.80. 1 Available fissures are not liable to occur near intruded masses of igneous rocks ; for if they do, the lava will seek them and itself escape as an extru- sive rock. MEECITKY AND MANGANESE. 261 Production of Mercury. — The following tables show the distribution and variation in supply of mercury. The statis- tics for the United States are practically those of California. In the table showing the production in the world there are no statistics for Borneo, Servia, Russia, Mexico, and Peru ; but the total from these places is not great. PRODUCTION OF MERCURY IN THE UNITED STATES. Elasks (76J Lbs.). 1850 23,875 1855 31,941 1860 10,000 1865 53,000 1870 30,077 1875 50,250 1877 79,396 1880 59,926 1885 32,073 1890 22,926 1892 27,993 The most productive years in this country were between 1875 and 1881 inclusive ; but since then there has been a rapid decline, although, in 1892, owing to the opening of new mines, there was an increase in production, making the output greater than in any year since 1888. PRODUCTION OE MERCURY IN THE "WORLD. Flasks (76 J Les.). COUUTKIES. 1880. 1882. 1884. 1886. 1888. 1890. 1891. Spain 45,822 46,T16 48,098 51,199 51,872 50,202 47,993 United States . 59,926 52,782 81,913 29,981 83,260 22,926 22,886 Austria . 10,510 11,668 13,967 15,689 15,689 15,709 16,586 Italy 3,410 4,060 7,743 7,279 9,831 13,021 9,570 Total. 119,168 115,1T1 101,721 104,148 110,642 101,858 96,985 262 ECONOMIC GEOLOGY OP THE UNITED STATES. The steady decline of the United States, the general uniformity of production of Spain, and the gradual in- crease of both Austria and Italy are striking. Chiefly as the result of the decrease in output from the United States, the mercury supply of the world has suffered a decrease, which the increased production of other districts has failed to equalize. Should we need more mercury, there is every reason to believe that it could be readily supplied; but although the gold and silver industries caU every year for more quicksilver, it must be remembered that this demand is not as great as it was fifteen years ago, because the reducing works have on hand large sup- plies of mercury which have already been used and can be used again and again in gold and silver extraction. Manganese} General Statement. — The ores of this metal, of which there are a number,, are practically all oxides, such as pyrolusite, psilomelane, braunite, and wad. Other mineral combinations occur, and these are sometimes found with the above ores. As a metal, and in its mineralogical asso- ciations, manganese is very similar to iron, and this is true also of its geological occurrence and distribution. Like iron, manganese is widely distributed; but being a much less common metal, it is not as frequently accumulated into beds. However, when this is done, the ore, in the vast majority of cases, is bedded with stratified rocks 1 A very valuable and complete account of this metal, treated from the geological, chemical, and economic standpoints, will be found in the report on Manganese, by Dr. R. A. F. Penrose, Jr., Vol. I., Annual Eeport of the Geological Survey of Arkansas for 1890. MEKCCTRY AND MAifGANESE. 263 and is frequentlj^ associated with iron. In occuiTence it differs from iron in being less frequently formed by replacement; but its common position in the earth is the same as that of brown hematite and carbonate of iron; namely, either precipitated or concretionary. The marked similarity to iron has caused a frequent association of the two metals, and a great many of the brown hematites, and other ores of iron, are manganiferous. More or less iron is usually associated with the manganese and there is some- times enough manganese with iron to make the ore a manganiferous iron ore. There is every gradation between iron oxides and manganese oxides. Manganese-bearing zinc ores and manganiferous silver ores are also found. Although every state contains them, the actual ores of manganese, occurring in economic quantities in this coun- try, are limited. Since this metal is extensively used in the manufacture of steel, large supplies are mined with the iron and never separated. While this applies with full force to the ores containing small quantities of this metal, it is nearly equally applicable to the manganif- erous iron ores, which are exploited, ostensibly as iron mines, but are in reality chiefly valuable because of the contained manganese. Manganiferous silver ores at Lead- ville, Colorado, are mined for the silver, and the man- ganese-zinc ores of Franklin Furnace, New Jersey, are also worked for the zinc, but not for the manganese, al- though this is produced as a by-product. Aside from these sources, practically all of the home supply comes from three states, — Georgia, Virginia, and Arkansas. It will be noticed that this distribution coincides, in a general way, with the iron-smelting region ; and one may confidently believe that 264 ECONOMIC GEOLOGY OF THE UNITED STATES. if other sources are ever needed, they can easily be found. Indeed, even in the Appalachian belt there are manganese deposits that can be called upon for a supply at any time ; and no doubt the metal exists in parts of the far west. Manganese in the United States. — There is a manganese- bearing belt extending from Vermont to Alabama, skirting the old shore line of early Palaeozoic times. This metal is found at several points in Vermont, chiefly at South Wallingford and Brandon. At the former place the ore occurs as nodules, in a clay in Cambrian sandstone, while at Brandon it is found in Tertiary strata, probably derived from the disintegration of this same Cambrian stratum. The New Jersey manganiferous zinc ores are apparently in the same belt; and a deposit of very little value is found, in a similar position, in Lehigh County, Pennsylvania. On the western slope of the Blue Ridge, chiefly in Virginia and Georgia, the most important manganese deposits of this belt occur, although the other states have produced some. In Virginia there are a number of districts, but only one is of marked importance. This, the Crimora district, in the Shenandoah valley near Waynesborough, has produced about 140,000 tons of ore since it was first exploited in 1867. The ore is principally psilomelane and pyrolusite, in the form of nodules, of varying size, irregularly distributed throughout a bed of clay. Shafts and open-works are both used in the extraction of this and the other American manganese ores. From here southwards no important deposits are encoun- tered until the Cartersville district of Georgia is reached. In this region almost exactly the same mode of occurrence is observed. Since 1866 over 60,000 tons have come from Georgia, chiefly from this district. MEKCUEY AND MANGANESE. 265 Arkansas also has several manganese districts, but only one, the Batesville, in the northern part of the state, is important. Practically the same mode of occurrence is illustrated here, — a surface clay, the residual prod- uct of the disintegration and decay of Silurian limestones, through which the manganese was originally scattered in con- cretions, pockets, and sheets, in very much the same man- ner as the nodules and layers of concretionary flint and ironstone occur in chalk and limestones (Fig. 25). By this Fig. 25. — Diagram illustrating the origin of the manganese deposits of Arkan- sas, d, non-manganiferous limestone ; c, manganese-bearing limestone ; !), disintegrated limestone; a, residual clay with manganese concretions con- centrated. (Modified from Penrose.) decay the manganese has been concentrated, and the deposit is rendered valuable by reason of this as well as by the change in the nature of the enclosing rock from hard limestone to soft clay. The ore is irregularly distributed, and it is mined by open-works chiefly. Since 1850, 40,000 tons of ore have come from this deposit, and nearly all of this has been obtained since 1880. None of the other states are of marked importance, al- though Wisconsin and Michigan contain mines of manga- niferous iron carrying from 2 to 11 per cent of manganese. At Leadville, Colorado, manganiferous silver and manganese- bearing iron occur, but the latter is of value mainly as a flux 266 ECONOMIC GEOLOGY OP THE UNITED STATES. in silver-smelting and, although some of the manganese is saved, most of it is lost. One mine in California has in the past twenty-five years produced considerable manganese v^hich is chiefly used for local purposes. The ore occurs in the metamorphic Cretaceous rocks of the Coast Range, and, since 1867, about 10,000 tons of ore have been produced. Penrose describes^ an interesting maiiganese deposit, which is, however, of no economic importance, occurring at Gol- conda, in northern Nevada. The ore, which is an impure oxide, is in a lenticular bed in a breccia cemented by calca- reous tufa. Both the tufa and the manganese are evidently precipitated from lake waters in a basin from which the water has been evaporated. Many springs contain manga- nese, and since near this deposit there are hot springs charged with oxide of manganese, Penrose suggests that this may have been the source. Manganese spring waters entering the lake near this point furnished the water with an excess of the oxide of manganese, and this was precipitated after the manner of bog iron ore. Foreign Manganese Mines. — Canada annually produces a small amount of manganese, chiefly from New Brunswick and Nova Scotia, on the Bay of Fundy, where it occurs in Lower Carboniferous strata. At first the ore was obtained from clays and other products of disintegration of the strata ; but, this source being exhausted, the mines are now in the rock, where the manganese is distributed very irregularly, in bunches and seams parallel in general to the stratification, and probably of concretionary origin. In the eastern part of Cuba, several mines of manganese occur in clays, the ore being very rich pyrolusite and psilomelane, often containing ^ Journal of Geology, Vol. I., pp. 275-282. MEECURY AND MANGANESE. 267 as high as 56 per cent of manganese, and it is claimed that large beds of this ore exist in the several mines. The present output is shipped to this country. The only other manganese-producing country of the American continents is Chili, where vast deposits are said to exist ; but, owing to the difficulties of transportation, they are not fully developed. Moreover, there is no local demand for the ores, and they must be shipped abroad. No manganese was produced in Chili before 1881, and until 1885 very little was obtained. Of the three important districts only one, Carrizal, produces manganese at present, and this was not discovered until 1886. No geological description of the region is available, but it is known that the extensive deposits outcrop at the surface like beds or dikes. Whether these are true beds or veins cannot be stated, but the former seems more probable. Out- side of Europe, New Zealand and Australia are the only other notable manganese-producers. Europe is by far the most important continent in the produc- tion of manganese, and nearly every country produces some of this metal. Russia outranks all other countries in this respect, and there the ores are found chiefly in the Caucasus mountains. Little is known of these deposits, but Phillips states that the ore is pyrolusite in Miocene sandstone. In Great Britain manganese occurs with iron, both brown hema- tite and carbonate, and sometimes alone, as in Merionetshire. Here the ore is found in a volcanic ash, having been derived from the feldspar and accumulated in little veins and pockets in the mineralogical form of pyrolusite and psilomelane. It would be tedious to describe the occurrence in the other European countries, since there is a monotonous uniformity. France, Sweden, Portugal, Spain, Italy, Turkey, and other 268 ECONOMIC GEOLOGY OF THE UNITED STATES. countries all produce some. In most cases the ore is bedded and concretionary, and strata of all ages from the Cambrian to the Tertiary contain it. In the Harz Mountains, in Germany, this metal is obtained from small veins in a porphyry, in Italy from volcanic tufa, but usually the oc- currence is in the sedimentary rocks. Origin of Manganese. — The ore deposits of this metal may occur in almost any kind of rock, although limestone and clay strata are the most common associates. No par- ticular geological age can be said to be manganese-bearing, but, in this country, the most important source is the older Palaeozoic strata. Manganese, in one form or another, occurs in nearly all rocks, for it holds the fifteenth place in order of importance of rock-forming elements, and is one of the com- mon metals. It is more abundant in igneous than in other rocks, and this is undoubtedly the original source. Many minerals contain it in small quantities, and in many others it is an important element in the chemical composition. There are several score of minerals in which manganese forms an essential part, and some of them are quite common. These minerals exist in greater or less quantities in the metamor- phic and igneous rocks, and by the decay of these their prod- ucts find their way into the stratified rocks, either directly as sediment, or indirectly from solution in water. The pres- ence of manganese is frequently shown by- a brown or black stain, and the fern-like crystal form of one of its ores, known commonly as dendrites, is very common. Since the metal is very much like iron in chemical be- haviour, we find it occurring under the same general con- ditions. Water takes it into solution and precipitates it in the same manner that bog-iron ore is precipitated. It may MERCtJRY AND MANGANESE. 269 be gathered into regular layers, or it may be disseminated through the strata. If the latter is the case, it may, under favourable conditions, be gathered together at a later period, into beds and concretions of manganese in the same way that iron ores are gathered together to form ironstone concretions. Being less abundant and less valuable than iron, this ore cannot ordinarily be mined w^hen found in this condition ; and, indeed, the same is true of much of the iron found in the same mode of occurrence. For successful min- ing, the ordinary manganese must be concentrated still more ; and this has been done by nature, in many places, by the decay of the enclosing rocks and the removal of the soluble parts. Manganese ores, being less soluble than many of the minerals formed by this decay, remain behind with the residue in residual soil, and are naturally more concentrated by the removal of some of the enclosing minerals. Practi- cally all of the manganese mined in this country comes from this source, and in other countries considerable supplies are found in the same condition. Often, however, the final stage of concentration has been omitted, and the mines are in the rock itself ; but this is possible only where the ore is very pure, or abundant, or easily and cheaply exploited. Thus there are three stages in the formation of most man- ganese deposits, and to these, in many cases, a fourth is added. These are : first, derivation from the decay of crys- talline rocks (metamorphic and igneous) ; secondly, deposi- tion in the stratified rocks ; thirdly, concentration into nod- ules or concretions ; fourthly, a still further concentration by the decay of the enclosing rocks and the formation of a residual soil. In some cases the ore may be sufficiently con- centrated at the time of actual deposition, as in the Gol- 270 ECONOMIC GEOLOGY OP THE UNITED STATES. conda deposit of Nevada; and in others, as in the Harz Mountains, the ore may be derived and directly deposited in veins in the igneous rocks which furnish the manganese. These, however, may be considered exceptional deposits. Uses of Manganese. — Before the beginning of the Chris- tian era the ores of this metal were used as a colouring for glass, and even at present this is an important use of the oxides. Pure pyrolusite is used to colour glass and also pot- tery, producing the various shades of violet, purple, brown, and black. An excess of manganese produces the jet-black commonly seen in door-knobs, while a slight amount gives violet, and intermediate amounts purple and brown. Much also depends upon the degree of heat used in the process. The ores of manganese also act as decolourizers, and their introduction into ordinary glass corrects the green colour given by iron. Only pure ores are useful for these purposes, and the greater part of our supply is too impure to be of use in the industry of glass-making. Until recently the most important use of the manganese ores was in the manufacture of chlorine and bromine, the ore acting as a carrier of oxygen. For bleaching, in the manu- facture of disinfectants, as a drier in varnishes, in the print- ing of calico, and for other purposes, manganese is in common use ; but at present more than nine-tenths of the ore mined is used in the manufacture of iron and in alloys. In steel- making two forms of manganese-iron alloy are used, — Spie- geleisen, in which 25 per cent or less is manganese, and ferro-manganese, in which the amount exceeds 25 per cent. These terms are, however, used variably, and the percentage of the metals in the alloy varies greatly. The effects pro- duced on the iron are very important, but intricate. It pre- MEECUEY AND MANGANESE. 271 vents the formation of gas cavities during the solidification of the steel, restores carbon, carries off oxygen, and produces other valuable effects. The price of manganese varies so greatly with its richness and purity, and with the purpose for which it is adapted, that no figures of value can be given without entering into details. The value of the ore varies from eight to ten dollars a ton, being usually between nine and ten dollars. Production of Manganese. — The following tables illustrate the distribution of the manganese output of the world stated in tons of ore : — PRODUCTION OP MANGANESE ORE IN THE UNITED STATES. Long Tons (2240 Lbs.). Statbb. 1880. 1882. 1884. 1886. 1888. 1890. 1891. 1892. Arkansas 1T5 800 3,816 4,812 5,839 1,650 6,000 Virginia . 8,661 2,892 8,980 20,56T 17,646 12,699 16,248 5,000 Georgia . 1,800 1,000 6,041 5,568 749 8,575 2,000 Colorado 6,397 964 California 886 705 Vermont 1,000 none 49 none Total 5,761 4,582 10,180 80,198 29,198 25,684 23,416 17,000 Value . $86,415 $6T,980 $122,160 $277,036 $279,571 $219,050 $239,129 $170,000 Besides the above a few tons come annually from other states, but this does not materially affect the total. The marked decrease since 1886 in all the districts, excepting Arkansas, is a noteworthy feature of this table. The total for the United States shows a rapid increase, which in 1887 272 ECONOMIC GEOLOGY OF THE UNITED STATES. reached the highest point (34,524 tons), since which time it has strikingly decreased. In thirty years the manganese output of the United States has amounted to 300,000 tons. Since the annual consumption is about 50,000 tons, the coun- try produces much less than half the amount consumed. Cuba, Chili, and Eussia are the chief foreign sources of our manganese. In 1889 Michigan produced 81,341 tons of manganiferous iron, and Colorado 2075 tons, valued at about 13.25 a ton. Colorado produced 64,987 tons of manganiferous silver ores valued at f 3.50 ■ a ton ; and the New Jersey zinc ores pro- duced 43,648 tons of manganese residuum valued at $1.25 a ton, from which 14,124 tons of spiegeleisen were produced. PRODUCTION OF MANGANESE ORE IN THE WORLD. Metric and Other Tons. COXTNTKIES. 1881. 1883. 1885. 1887. 1889. 1890. 1891. Eussiai 11,224 17,029 60,458 58,135 77,937 182,346 190,0002 Chffis 4,041 47,521 28,683 47,986 34,462 United States i . . . 4,974 6,256 23,637 85,087 24,592 26,103 23,898 Cuba . . . 4,000 21,810 21,987 • Great Britain ^ . . 2,931 1,308 1,716 14,000 8,997 12,646 9,632 Sweden 1 .... 8,659 8,645 10,698 9,079 Turkey .... 8,000 Portugal , . 5,000 Italyi . . 1,802 4,434 2,208 2,147 2,429 Canada i 1,180 1,320 1,205 249 The above table is approximate only, since accurate statis- tics cannot be obtained. Marked fluctuations in the output 1 Metric tons (2204 lbs.). 8 Long tons (2240 lbs.). 2 Estimated rouglily. * Exported. MEECUKY AND MANGANESE. 273 are noticed, showing that the industry is more or less un- stable ; but the most striking feature of the table is the rapid increase in production of Russia and Chili. In 1888 the total production of the world was about 163,000 tons; in 1889, about 160,000 tons; and in 1891, approximately 300,000 tons, this increase being chiefly due to Russia and Chili. CHAPTER XII. TIN AND ALUMINUM. Tin} General Statement. — A single ore, the oxide cassiterite, is the source of this metal ; and it, more than any other equally common metal, may be said to have a typical mode of occurrence. It is found in place, in coarse granite, or in rocks immediately associated with such a granite, and excep- tions to this are extremely rare. Being heavy and non- destructible, tin oxide accumulates in placer deposits, exactly as does gold and platinum ; and nearly all of the actual tin mines in the world have been discovered by first finding stream-tin and then tracing the ore to its source. The greater part of the tin supply of the world is obtained from gravels, but there are also many mines in the rock. In distribution, this metal occurs throughout the world, usually wherever granite is found ; but paying tin deposits exist only where the ore is concentrated in river gravels or, under particularly favourable conditions, in the bed rock. Therefore tin mines are widely scattered, but comparatively rare. There are none in the United States which are at 1 A very complete description of tin mines and mining is found in Koth- well's Mineral Industry for 1892, pp. 439-462. A description of the occur- rence and metliods of obtaining tin in the Straits Settlements is found in the volume on Mineral Industries, Eleventh Census, pp. 257-264. The Cornwall and Devonshire mines are fully described in Phillips' Ore Deposits, pp. 110-154. This description of tin is mainly abstracted from these sources. 274 TIN AND ALTJMINtTM. 275 present producing ; but this industry is an exceptional one ; for, although none of the metal is produced, many per- sons are employed in mining for tin. Tin Mines of the ITnited States. — This metal has been found in nearly all the states of the Union where granite occurs. Thus cassiterite has been found in the New England and southern Atlantic coast states and in the Cordilleras, but ordinarily in such small quantities that even develop- ment is not deemed worth undertaking. Some shafts have been constructed, but so far without bringing any returns worth considering. Serious developments of tin mines have been made in Virginia, where for a number of years stream- tin was found sparingly in the gold-bearing gravels. On the western slope of the Blue Ridge, in the Shenandoah valley, tin was found in place, in 1880 ; and since then much work has been done in the development of this property, which promises weU. Here the cassiterite is found in small veins and in grains, and even nodules a foot or more in diameter, occurring in a coarse-grained granite. The ore also occurs here in quartz veins, associated with wolframite, beryl, and other minerals typical of tin veins. At about the same time that cassiterite was discovered in the Virginia granite, its presence was also noticed in North Carolina, where the ore is found in very nearly the same mode of occurrence as in the Black Hills. Cassiterite is also found here as stream-tin, but neither of these deposits has proved of value as yet. Alabama contains tin ore in stream gravels and also in a coarse gneiss. The most famous tin-bearing region in this country is that of the Black Hills, where, in 1883, cassiterite was found in place in a coarse-grained granite intruded into slates and 276 ECONOMIC GEOLOGY OF THE UNITED STATES. schists. Its occurrence was noticed many years before this in the auriferous gravels of that region. Here the ore occurs disseminated in the granite and in veins of pegmatite, which are composed of quartz and mica in coarse crystals. A large number of mining claims have been located in this district, chiefly in and near Harney's Peak, and several mines have been opened and extensively developed ; but up to the pres- ent time they have not sold any tin. Immense sums of money have been expended by companies with a large capi- tal, and recently reduction works have been built. These facts indicate confidence, on the part of the managers, that the tin deposits will soon begin to bring profitable returns; but, notwithstanding this, it is the opinion of many compe- tent American mining engineers that, with the existing con- ditions of inaccessibility, high price of materials and labour, these tin mines cannot be made to profitably compete with the more easily worked deposits in other parts of the world. If this is really true, and there seems good reason to be- lieve that it is, large sums of money have been extrava- gantly and foolishly wasted in development. The next few years will witness either a large output from these mines or a collapse of the enterprise. In California, tin has been known to exist, in some of the auriferous gravels, ever since their discovery; and since 1868 tin mining has been carried on intermittently near Riverside, on the San Jacinto land grant, but since September, 1892, this mine has been closed. It is practically the only tin mine in this country which has so far produced marketable tin. Prior to 1892, about 120 tons of this metal have been produced, and since then, to the time of suspension of opera- tions, about 140 tons were obtained. A striking resemblance ITS AND ALUMINUM. 277 is noticed between the mode of occurrence of the tin of this region and that of Cornwall, England ; for, in both cases, there is a granite mass cutting slates, and both of these rocks are traversed by quartz-porphyry dikes. All three of the rocks contain tin, but the most promising vein is in the granite. Associated with the ore are tourmaline, quartz, feldspar, and other minerals, and the tin is sometimes in veins, sometimes disseminated. Taking everything into consideration, this was considered, a few years ago, the most promising tin region in the country, but the fact that it has been closed, after a careful examination of its possibilities, indicates that it is not a profitable deposit. Indeed, it may be said that the United States does not at present show any distinct promise of producing tin. Lodes which might be worked in other countries are not uncommon, but the value of labour is so high that they cannot be developed, and so far the country has produced no "tin bonanzas." It is true that prospectors generally do not know tin ore from some of the iron ores, and there are, possibly, valuable deposits at present undis- covered. Foreign Tin Mines. — Cornwall, in England, is the most famous tin region of the world, and this metal has been produced from there for at least two thousand years. At first the cassiterite came from stream gravels, but now all the tin is obtained from mines. The principal sources are granite cutting slates, the slates themselves, and quartz- porphyry dikes which have been intruded into both of these. Associated with the tin are ores of copper, blende, and galena, as well as quartz, feldspar, mica, tourmaline, topaz, wolframite, etc., and the character, and even the kind, of ore varies from one rock to another. The veins are frequently 278 ECONOMIC GEOLOGY OP THE UNITED STATES. of the segregation type, crossing all rocks and sending out offshoots, often in such intricacy that a complete network of veins is formed. There is also a great variation in the width of these veins, for sometimes they decrease even to a mere line and then swell to a width of many feet. A peculiar mode of occurrence is noticed at St. Ives and else- where, where " carbonas " occur, these being large lenticular masses of granite impregnated with tin, and sloping away from the nearly vertical " parent vein." There seems to be a considerable variety in the occurrence of the tin; for at times the veins are apparently fissure veins, again segregation and often impregnation deposits. Next to Cornwall, Devonshire has been the most impor- tant tin-producing region of England, but at present this source appears to be exhausted. Here the occurrence is very similar to that at Cornwall, but no quartz-porphyry is present. In the eleventh and twelfth centuries Devonshire produced more tin than Cornwall ; but while the former has gradually decreased its output, Cornwall has shown a steady increase, from an average of about 300 tons a year in the thirteenth century, to over 9000 tons in 1891. During a period of 690 years, it is estimated that the two dis- tricts have together produced 1,128,000 tons of tin; and of this, not much more than 100,000 tons came from Devonshire. Elsewhere in Europe tin is not abundant, but it is mined in a number of countries. In France it is found in Brittany, where the geology very closely resembles that of Cornwall. The Erzgebifge region in Germany has tin in granites cut- ting crystalline schists, and in very nearly the same associa- tion as in Cornwall. This same tin-bearing belt extends TIN AND ALUMINUM. 279 into Bohemia, in Austria, where, at Schonfeld, tin was mined as long ago as the time when fire setting was used for min- ing in place of tools. In 1355 this was an important district. Cassiterite is found in granite in Finland ; and in Spain tin mines were worked by the Phoenicians in quartz lodes in slates and schists, but they are not now productive. During the reign of Agricola, Portugal produced stream-tin, and in this country tin is also found in the granite. By far the most important tin-producing district at the present time is that of the Straits Settlements. For at least four hundred years this metal has been exported from there, and it is possible that this was the source of the tin used in the manufacture of the early and prehistoric bronze. In the state of Perak, on the Malay Peninsula, tin has been obtained for at least a century. Granites, slates, and other rocks consti- tute the mountains of the region, and cassiterite is known to occur in the granite, although this source is not explored or worked. At present the tin produced comes entirely from a small area not exceeding twenty square miles, and from here two-thirds of the output of the Straits Settlements is obtained. Associated with the cassiterite in the gravels are water-worn fragments of granite and tourmaline, which show that here also the uniform geological and mineralogical association, noted above, is preserved, although it is said that tin has also been discovered in place in veins crossing a limestone. The methods of mining are extremely crude, the work being performed by Chinese and natives, but the Amer- ican process of hydraulic washing is about to be introduced. On the neighbouring islands of Banca and Billeton the occurrence of tin is the same as in Perak, since these are practically continuations of the same area. Here some 280 ECONOMIC GEOLOGY OP THE UNITED STATES. mining has been carried on in the bed rock. Tin is also found in the gravels of Sumatra and Burmah, and it is prob- able that other sources of this metal will be found in the gravels of other East India islands. If necessary, the output from these several districts could be greatly increased, and it is probable that when these superficial deposits are ex- hausted, as they must be before a great many years, a more permanent but less profitable supply will be found in the neighbouring bed rock. Australia is also an important source of this metal, the stream-tin having been noticed soon after the discovery of gold in both Victoria and New South Wales. Every coun- try of this continent has produced some tin, but the only important regions are in New South Wales and Queensland. The source of the ore is the Australian Cordilleras, where it exists, chiefly in granite, in geological association very simi- lar to that of Cornwall. At present, however, these sources are barely explored, the greater part of the supply being obtained from the gravels. The mode of occurrence and origin of the stream-tin is the same, in general, as that of the gold with which it is associated. Even the gravels which are buried beneath lava flows are tin-bearing. Vic- toria also produces some tin, and in Tasmania a rather unique occurrence exists, the ore being found there in a eurite-porphyry which traverses slates. Vast stores of this metal exist in Australia, both in unworked gravels and granites, and this region will undoubtedly long continue an important source of tin. In South America the only important tin district at pres- ent exploited is in Bolivia, where it has long been known to exist, although hitherto very little has been produced, ex- TIN AND ALUMINUM. 281 cepting as a by-product in silver mining in the Potosi dis- trict. Recently, by the construction of a railway, the tin of this section has become valuable, and the output will no doubt increase. The silver-tin deposits occur in a porphyritic diorite, intruded into sandstone, and also in a trachyte cut- ting slates. Mexico also produces tin, and in the state of Durango the cassiterite occurs in veins in porphyritic tra- chyte. For many years stream-tin has been produced in small quantities by natives, but the output is not important. Origin of Tin Ore. — The noticeable features concerning tin are the marked uniformity in character of the ore and the singularly uniform association with igneous rocks, par- ticularly with granite. Other igneous rocks, such as eurite, diorite, and trachyte porphyry, are stanniferous in some cases, but ordinarily the association is with granite. A study of the Cornwall mines shows that these deposits are not of con- tact origin, nor are they contemporaneous with the intrusion of the granite, as one might at first suppose, for they are found also in quartz porphyries which have been intruded into the granite since it solidified. One is, therefore, driven to the conclusion that these deposits have been derived by subsequent concentration, and their nearly constant association with granite points to this as the common source. In some cases the process of concentration is akin to that of segregation, but frequently the metal occurs in true veins. Notwithstanding these contradictory facts, it seems very probable that many of the tin deposits are actually of con- temporaneous origin with the granite. The position of the tin in the rock, the association with tourmaline, and other facts, point to this conclusion. Indeed, it is not improbable that some of the coarse granitic or pegmatite veins are them- 282 ECONOMIC GEOLOGY OE THE UNITED STATES. selves actual intrusions and the source of the tin. The genesis of the ore has not been determined, in spite of the apparent simplicity of occurrence and the great age of the mines. Ordinarily the ore is too disseminated for profitable mining, and consequently a second stage is generally neces- sary ; namely, natural concentration in river gravels, which are the source of by far the greater part of the world's supply of tin. Uses of Tin. — The manufacture of bronze and of tin plate calls for the greater part of the tin supply, although some is used in plumbing and for some minor purposes. Bronze has already been described under copper. Britannia metal, usually composed of from 82 to 90 parts of tin alloyed with antimony and minor quantities of copper and sometimes zinc, is used for various purposes in the manu- facture of cheap utensils, etc. The manufacture of tin plate, which is so useful in tin ware and tin cans, consists simply in coating iron with tin to exclude the air and pre- vent the iron from rusting. In the United States, and in all European countries excepting Great Britain, the tin con- sumed is almost entirely imported. This and platinum are the only important metals which we find it necessary to import extensively. In 1892 tin sold at 20 cents a pound; but since 1885 the price has fluctuated from 16| to 39.95 cents a pound, with an average price of a little over 20 cents. These fluctuations are due not to variations in supply, but to the operations of the syndicates which control the supply. The tin and tin plate imported into this country in 1891 were valued at $33,991,668, there having been a steady increase since 1870, when the imports amounted to only TIN AND ALUMINUM. 283 $9,671,759. Of the total imports for 1891, 125,900,305 were tin plate and sheet tin. Production of Tin. — The following table shows the out- put of tin from the leading districts in the world : — PRODUCTION OF TIN IN THE WORLD. Short Tons (2000 Lbs.). DiSTKICTS. 1880. 1885. 1890. 1891. Straits Settlements . . Great Britain .... Australia 20,226 ■ 8,918 9,177 25,280 . 9,331 9,088 38,019 9,000 6,415 42,560 9,354 5,991 Total 38,321 43,699 53,434 67,905 Besides these regions, in 1891 about 1550 tons of tin were produced in Bolivia, not more than 50 tons in Mexico, 720 tons of ore in Austria, 75 tons of tin ore in Germany, and 57 tons in the United States. In 1892 the United States had an output of 65 tons, valued at |29,827. Aluminum.''- Occurrence of Aluminum. — No metal has, in the last few years, attracted more attention than aluminum, which has had such a remarkable development that we are hardly ^ A good account of aluminum, although at present rather old in some respects, owing to the rapid progress in production of the metal, will be found in Aluminum, its Properties, Metallurgy, and Alloys, Richards, 1890. Another account is found in the Eleventh Census volume on Mineral Industries, pp. 277-284 ; Mineral Resources of the United States, Day (U. S. Geol. Survey), 1891, pp. 147-163; and Rothwell's Mineral Industry, etc., 1892, pp. 11-18. 284 ECONOMIC GEOLOGY OE THE UNITED STATES. able to state its present position or predict its probable future. Until a few years ago, it was only a chemical curiosity comparable with many of the rare metals; but now it is already a common metal, pushing its way into the arts in competition with the older and well-established metals. Before 1827 aluminum was unknown, while, prior to 1857, it was a decided curiosity, and it remained of no practical importance until a few years ago, when cheap processes for its reduction were successfully introduced. Aluminum is the most abundant metal and the third most common element in the earth's crust. Hundreds of min- erals, particularly the complex silicates of alumina, contain this metal in essential combinations, and it is present also, in smaller quantities, in other minerals. In ordinary clay, which is hydrous silicate of alumina, there is an inexhausti- ble source of this metal; but the mineralogical association is too refractory for profitable separation with the present methods. The ores which can be made to give up their aluminum easily are very few. Of these, corumdum the oxide, is too valuable for abrasive purposes to be used as a source of the metal ; diaspore and gibbsite the hydrous oxides, are not found in sufficient abundance; and alumnite the sulphate, although found in some places in the west, par- ticularly in New Mexico, does not serve as an ore, because of the competition of more abundant and available minerals. Until recently the chief source of the metal was cryolite, the fluoride of sodium and aluminum (AlgFg, 6 NaF), which occurs in large quantities in Greenland, from which region it has been brought to this country, for a number of years, to be used in the extraction of aluminum. Now bauxite TIN AND ALUMINUM. 285 (AljOgHg) is the chief source of this metal, and it is so new for this purpose, and has become so important, that a detailed description is introduced. '- '^- -^ ^ P •• ' -■ • '- Bauxite is, in reality, a limonite in which a part of the iron has been replaced by aluminum; and the true bauxite contains from 50 to 70 per cent of alumina. It was first found in the village of Baux in southern France, and was, for a time, worked as a source of iron ; but the ore proved of little value for this purpose. In mode of occurrence it closely resembles limonite, being found both in nodules and in an earthy form. The colour of the pure mineral is white, however, and the mineral is both soft and granular. Bauxite, at the French locality, occurs in limestone, through which it is scattered in beds, nodules, and grains, and it is believed that it was deposited by precipitation in lakes, simi- lar to the mode of formation of lacustrine limonite, and later concentrated by concretionary action. Other deposits in France, Italy, Austria, and Ireland confirm this view, but in some places, particularly in Germany, the mineral is evidently derived from the decomposition of basalt. These facts point to two probable modes of origin for the Euro- pean bauxite. In America this mineral is found in Alabama, Georgia, and Arkansas; and when explorations have been carried into other regions, particularly the volcanic and lacustrine regions of the Cordilleras, there seems to be no reason to doubt that extensive deposits will be found. Mining for bauxite was begun in Alabama late in 1891, and the first shipments were made in 1892. The ore is associated with limonites and kaolins, resting on Lower Silurian dolomitic limestone of the Knox series ; and in Georgia the occur- 286 ECONOMIC GEOLOGY OF THE UNITED STATES. rence is exactly the same, the ore in both cases being scattered through clay and near the manganese deposits. This mineral may have been concentrated from the decay of the limestone, but Dr. Spencer, the state geologist of Georgia, considers it a precipitated deposit formed in lagoons, the mineral having been derived from the solu- tion of portions of decomposed crystalline rocks which exist about twenty miles east of there. Recently Dr. Bra}|ner, state geologist of Arkansas, has announced the discovery of bauxite in large quantities in the Tertiary of Arkansas, where it is found near syenite masses, with which it seems to be associated in point of origin. History and Metallurgy of Aluminum. — In 1807 Sir Hum- phry Davy first attempted to obtain aluminum from its oxide ; but he was not successful. It was not until 1827 that Wholer was successful in an attempt to separate alumi- num by means of potassium, and as a result he obtained a fine gray powder. The same chemist obtained the metal in globules in 1845 ; and in 1854-1855 Deville, a Frenchman, improved upon this method, and invented a process for the extraction of sodium at a greatly reduced price (from 2000 francs to 10 francs per kilogramme). By substituting this metal for potassium, the beginning of the industry of alumi- num reduction was made, and for thirty years this Deville process was used. Deville also introduced the use of elec- tricity in the reduction of this metal, but the high cost of producing this prevented him from anticipating the present electrolytic process. Since 1886 many improvements have been made in the process of aluminum extraction, but none have been more important than the introduction of electricity and the reduction in the cost of sodium by a new process TIN AND ALUMINUM. 287 invented by an American, Castner. A number of patents have been issued for electric processes of reduction, and the price of the metal has steadily fallen. If this continues, aluminum must soon enter the market as a -formidable competitor of some of the common metals. The remark- able progress of the industry can be no better shown than by the following table, which illustrates the fall in price : — COST OF ALUMINUM PER POUND. 1856, Spring $90.90 1856, August . 27.27 1886 12.00 1889 2.00 1891 90-.75 1892 . . 50 It is not within the scope of this treatise to discuss metal- lurgical processes, but it will be of interest to state briefly the process by which aluminum is extracted from the oxide in the works at Pittsburg, Pennsylvania.^ The principle is that in the presence of a melted fluoride, alumina is decom- posed by the electric current, and metallic aluminum lib- erated. The ore is fused in a flux of fluoride of aluminum and sodium, and a powerful electric current is applied, which liberates the aluminum, while the oxygen forms carbon dioxide with a series of carbon blocks. The fluorides act as vehicles for the alumina. From time to time the metal, which sinks to the bottom, is drawn off, and more ore is added, so that the process of reduction is practically a con- tinuous one. ' Extracted from a statement in the Mineral Resources of the United States, Day (U. S. Geol. Survey), 1891, pp. 154, 155. 288 ECONOMIC GEOLOGY OP THE UNITED STATES. The Uses of Aluminum. — This metal has been heralded as a competitor of iron, copper, and nearly all the common metals, but it seems highly improbable that it will ever seriously compete with most of these. It has properties which fit it for especial uses, for which other metals are poorly adapted. Aluminum is beautiful white in colour, and is not sensibly affected by the atmosphere, which makes it in this respect superior to silver. In malleability and ductility it resembles gold and silver, and can therefore be hammered into sheets and drawn into wire. Without a great reduction in price, it cannot be made to replace iron and copper wire ; and the fact that its power of conducting electricity is less than that of copper, makes it probable that it will not replace this metal in electricity. It has been stated that aluminum will rival steel, but this is unfounded, because its tensile strength is only about that of cast iron. Therefore, for pur- poses which require a high degree of tensile strength, alumi- num cannot be used without greatly increasing the bulk ; and, since it is unlikely that the price will decrease below that of steel, these uses of this metal will probably never be made. The strongest point in favour of aluminum, aside from its freedom from tarnish and its beautiful white colour, is its extreme lightness. These various properties adapt this metal to certain uses, for which it will perhaps replace some of the brass, copper, tin, nickel, and the white alloys. Still, the position of aluminum must be considered doubtful, although nearly every one admits that it has a bright future. At present the chief uses of the metal are toys, fancy articles, and ornamental work in machinery. An almost infinite number of such uses are now made of the metal, among which may be mentioned canteens, sword scabbards. TIN AND ALUMINUM. 289 surveying-instruments, race boats, and other purposes where lightness is desired. For plumbing it has not yet come into use, because of the difficulty of soldering. Alumi- num wire promises to be valuable for some purposes, since it can be drawn into fine threads and spun, and does not tarnish. The alloys of this metal have already assumed importance. A small amount added to steel increases its value in several respects, but primarily by preventing air-holes in the castings. There is an increasing demand for aluminum bronze, and for different purposes this alloy is made of different proportions of the component metals. With 10 per cent of aluminum, copper is given remarkable strength, which fits it for pur- poses where great tensile strength is required. Copper con- taining about 5 per cent of aluminum is capable of being worked like steel, and there is reason to believe that this may become important. Every year scores of patents are granted for different kinds of aluminum alloys, and already there are many hundred such patents. In a very few years these will be tested and their relative importance determined. Taking everj^thing into consideration, it may be safely predicted, that, if the price of aluminum can be reduced to ten or twenty cents a pound, which in the light of the past history seems not improbable, innumerable uses, probably chiefly in the alloys, will be found for this metal. It may take the place of tin, which the world can well spare, since it is liable to become exhausted in time, and it may even interfere with the value of zinc, particularly with the use of zinc in the manufacture of brass. Even some of the uses of iron and copper may be replaced by this metal, but there need be no fear that it will seriously interfere with the 290 ECONOJvnc geology of the itkitbd states. demand for the important metals, unless its cheapness becomes as marked as its abundance in the earth. Its rery cheapness will serve to prevent its extensive use in place of silver, and, while it may replace nickel for purposes of plat- ing, this metal is making for itself a demand in other direc- tions for which aluminum can scarcely be made to serve. By the introduction of copper-aluminum alloys, both metals will probably have their importance increased. This metal will undoubtedly assume its proper position in the next twenty-five years ; and, without accepting the rather absurd claims made by enthusiasts, it seems certain that this will be an important and prominent position among metals. Production of Aluminum. — The extremely rapid growth of the aluminum industry in this country is shown in the following table : — PEODUCTION OF ALUMINUM IN THE UNITED STATES. Pounds. 1882 none 1883 83 1884 150 1885 283 1886 8000 1887 18,000 1888 19,000 1889 47,468 1890 61,281 1891 168,075 1892 294,813 The value of the aluminum produced in the United States in 1892 was |191,303. In 1890 the total amount of aluminum alloys used in this country was 171,759 pounds, while Ger- TIN AKD ALUMINUM. 291 many, in 1892, used 616,000 pounds of aluminum bronze. Switzerland produced, in 1892, 629,420 pounds of aluminum ; France, 132,000 pounds; and other European nations were also heavy producers ; but, since the industry is so recent, statistics are not very full nor valuable on this subject. The ore bauxite, from which this was obtained, came in America chiefly from Alabama, which, in 1891, produced 3600 tons, and in 1892, 7200 tons, and from Georgia, which produced 3300 tons in 1891. In the latter year we imported 17,936,504 pounds. Baux, in France, produced 20,000 tons of bauxite, in 1888, much of which was exported. There are no statistics available for the production of foreign bauxite. CHAPTER XIII. MISCELLANEOUS ORES AND GENERAL REVIEW OF THE METALS. Nickel and Cobalt. Mines in the United States. — These two metals occur associated, and much of the cobalt is produced as a by- product in the separation of nickel from the ore. The ores are niccoliferous pyrrhotite, millerite (the sulphide), nic- colite (the arsenide), annabergite (the arseniate), and, in New Caledonia and also in other places, garnierite a hydrous silicate of magnesia and nickel, which is a brittle, apple-green mineral. In this country nickel has been found in the meta- morphic rocks of Massachusetts and Connecticut ; but none is produced from these states at present, and the same is true of a deposit of garnierite which occurs in serpentine in North Carolina. A small percentage of nickel and cobalt is saved as a by-product in the smelting of the lead produced at the mine La Motte in Missouri. Colorado has a non- productive nickel-cobalt arsenide and sulphide mine; and, iu Nevada, the same ores are found at Lovelock's station, where a quartz vein, bearing these metals, occurs in an iron- bearing band. Although the mines on this vein have been developed, very little ore is produced at present. There are mines of pyrrhotite in Oregon, and also of garnierite in ser- pentine in the same state. None of these mines are at present of importance. 292 MISCBLLANEO0S OKES. 293 Practically all of the nickel and cobalt of the country comes from Lancaster Gap in Pennsylvania, which, until a few years ago, was one of the most important mines of these metals in the world. From early in the last century until 1852, this mine was exploited for copper, but since then its output has been chiefly nickel and cobalt. The ore is niccoliferous pyrrhotite and chalcopyrite, carrying from one to three per cent of nickel and some cobalt. The vein is apparently a fissure, or possibly a segregation vein, at the contact between mica schist and a wedge or lenticular mass of amphibolite. This deposit is fast becoming exhausted, and, unless new deposits are discovered, the district will soon become non-productive. Foreign Mines. — In Europe the most important nickel- cobalt-producing countries are Norway and Sweden, where niccoliferous pyrrhotite occurs in several places in the metamorphic rocks. Although this region at present ranks third in the world, and has been a producer of cobalt and nickel for many years, it is still of little importance. Austria- Hungary, Prussia, and Great Britain all produce small quan- tities of these ores, chiefly as by-products in mines of other metals, such as those in the Freiberg district, etc. The most important mines of nickel and cobalt in the world are in New Caledonia, where the ores were discovered in 1867, although not worked until 1874. In many parts of the colony, garnierite occurs in serpentine, filling cavities and little veins in a decomposed clay consisting of chrome iron and cobalt-manganese iron. This appears to be a product, not of metamorphism, but of later accumulation. Next in importance to this region is that of Sudbury in Ontario, Canada, which has increased its output at a remarkable rate in 294 BCONOMIC GEOLOGY OP THE UNITED STATES. the past few years. The ore is niccoliferous pyrrhotite and chalcopyrite, occurring in Hiironian gneisses ; and, as in the case of the Pennsylvania mine, which it closely resembles, it was at first worked for copper. Very little cobalt occurs here. Since all conditions for profitable extraction exist in this mine, it promises to control the nickel supply of the world. Cobalt is obtained chiefly as a by-product in the produc- tion of nickel, but in some places cobalt ores occur singly. The manganese-cobalt-bearing clay, associated with the New Caledonia nickel, is an instance of this, as is also a cobalt glance found in Chili. Origin of ITickel and Cobalt. — All of the important depos- its of these ores occur in metamorphic rocks, — the sulphides and arsenides in gneisses and schists, the magnesian silicate garnierite, in serpentine. This latter association is noticed in New Caledonia, North Carolina, Oregon, and elsewhere. Whether they are a product of metamorphism, — that is, segregation deposits of metamorphic origin, — or whether they have been derived by a subsequent process of concen- tration cannot be definitely stated ; but the constant associa- tion with metamorphic rocks suggests the former as at least a general, if not a universal, explanation. Uses of nickel and Cobalt. — Until within a year or two nickel was so unimportant that the opening of a large mine succeeded in closing the smaller ones ; but from this time on, the metal promises to grow in importance. There is a certain demand for this metal in the manufacture of cheap jewelry, particularly watches, for German silver, for coinage, and for purposes of plating. The latter use has been steadily in- creasing, and the rapid introduction of bicycles has been largely responsible for this. But recently the invention of MISCELLANEOUS ORES. 295 nickel-steel alloy has created a new and very important use for this metal. An addition of a small percentage (about 4 per cent) of nickel to steel gives to it a greatly increased toughness and tensile strength. This steel is now being used for armour plates, and will probably be introduced into the manufacture of propeller shafts and other parts of machinery and engines, as well as for gun and cannon barrels. A nickel-copper alloy (20 per cent nickel and 80 per cent copper) is being used as a casing for the bullets of the small- bore guns in use among the European armies. German silver, a general name given to a variety of compounds, is an alloy of nickel, copper, and zinc. Altogether the future of this metal is very bright, and there seems little doubt that some of the smaller and un- developed mines of this country will soon begin to produce at a profit. During 1892 nickel varied in price from 50 to 60 cents a pound. Cobalt is used, in the form of the oxide, in the manu- facture of a pigment, the intense and permanent cobalt blue which is used in the manufacture of paints, coloured porcelain, etc. There are also some minor uses, chiefly in chemistry. Production of Nickel and Cobalt. — The following statistics illustrate the production and distribution of these metals in this country and in the world : — PRODUCTION OF NICKEL IN THE UNITED STATES. Pounds. 1876 201,367 1880 233,893 1885 . 277,904 1890 200,332 1891 120,848 1892 ... .... 96,152 296 ECONOMIC GEOLOGY OP THE UNITED STATES. The falling-off in production in the past few years is due to the exhaustion of the Lancaster Gap mine and the compe- tition of the Canadian nickel. In 1891 the United States imported 345,286 pounds of this metal. The value of the output in 1892 was $57,691. PKODUCTION OF NICKEL IN THE WORLD. POHNDS. Countries. 1889. 1890. 1891. New Caledonia Canada Norway and Sweden .... United States 3,045,641 682,773 240,222 217,633 3,500,613 1,435,742 162,742 200,332 5,399,800 4,626,627 160,000 120,848 In addition to the above, Germany, Great Britain, Hun- gary, and some other nations produced unimportant quan- tities. PRODUCTION OF COBALT OXIDE IN THE UNITED STATES. POONDS. 1870 3,854 1880 7,251 1891 7,200 1892 8,600 At present, about 200 tons of cobalt oxide are consumed in the world. In 1888 Chili exported 25 tons of cobalt ores (215 tons in 1887), and Prussia produced 33 tons. New Caledonia and other countries also produced cobalt; but there are no exact statistics, although New Caledonia ex- ports from 2500 to 4000 tons of cobalt ore a year. MISCELLANEOUS ORES. 297 Antimony. This metal occurs in a number of minerals, but the only- important source is the sulphide stibnite. The usual mode of occurrence is in quartz veins, either of segregation origin or true fissure veins, but there seems to be no general asso- ciation of country rock, although slates are often the enclos- ing strata. In this country antimony has been found in a number of states, but only one, Nevada, is an important pro- ducer. Arkansas contains stibnite deposits in the south- western part of the state, where it occurs in quartz veins parallel to the bedding. In Kern County, California, this ore is also found in quartz veins, but none is produced from there. Antimony ore exists in Nova Scotia and New Bruns- wick, Australia, Borneo, Japan, which is the chief source, and in nearly all the European countries, principally in Portugal, Spain, Austria-Hungary, Italy, and France. In all of these mines there is a marked uniformity of occurrence, although in some of them other ores of antimony are also found ; and some, notably those of Australia, are auriferous. Antimony is of chief value for the alloys into which it enters ; for, although brittle itself, it imparts a peculiar hard- ness and toughness to some metals, notably lead. Of these alloys the most important is type metal, which is a mixture of lead and antimony. Britannia metal, pewter, and Babbitt metal (copper, tin, and antimony), all contain antimony, and the metal also enters into certain chemical compounds and substances used for medicine. It is also used in vulcanizing rubber. Although valuable in an alloy of lead, antimony makes gold and silver brittle, and even as small an amount as one-tenth of one per cent injures copper very seriously. 298 ECONOMIC GEOLOGY OF THE UNITED STATES. The price of antimony varies greatly, since the supplies are local and widely distributed. In 1891 the price fell from 19 to 12 cents a pound on account of rumours of an increased supply from Japan. Since these rumours were unfounded, the price rose to 16.25 cents in December, but it then fell and at several times during the year 1892 sold for less than 12 cents a pound. The following statistics are the only ones accessible. We have no statistics for the production of antimony from Borneo, Portugal, and France. PRODUCTION OF ANTIMONY IN THE XHSTITED STATES. Pounds. 1880 . 100,000 1885 100,000 1890 . 257,768 1891 910,000 1892 956,000 The United States in 1891 imported antimony to the amount of 1313,909, and the value of the metal produced by the country was approximately $45,000 at San Francisco. PRODUCTION OF ANTIMONY ORE IN THE WORLD, 1891. Metric Tons (2204 Lbs.). Japan 32001 United States 1000 Italy 782 Austria-Hungary 557 Spain 5472 Canada in 1886 produced 603 tons; but since 1888 the output has rapidly decreased, and in 1891 only 9 tons were furnished. Italy in 1885 had an output of 2887 tons. The 1 Estimated (in 1890, 3173 tons). 2 Exported. MISCELLANEOTJS OEES. 299 total production of antimony in the world was probably not far from 10,000 tons in 1891. Chromium. Chromium is not used in the metallic state, but is chiefly valuable for its chemical compounds, particularly the various pigments, — chrome yellow and chrome green, and bichro- mate of potash, which is used in calico-printing. A small amount of the chromium supply is used in the manufac- ture of chrome steel, which is remarkable for its extreme hardness, and is used for burglar-proof safes, hard-edged tools, etc. The mineral is invariably chromite or chrome iron ore, a combination of ferric and chromic oxides in varying propor- tions, and often containing other substances as impurities. This mineral is one of the products of the alteration of min- erals and rocks to serpentine, and it occurs uniformly in association with serpentine. In America, chromite has been found in varying quantities throughout the belt of metamor- phic rocks from Maine southwardis, wherever serpentine is found. Formerly mines were located in Maryland, and later in Pennsylvania, and, as a result of this, Baltimore became the centre of the chromium industry in this country, a posi- tion which it still holds in spite of the fact that the ores in this region are exhausted. At present the only important sources of chromite in the United States are in California, where it occurs in abundance. But, owing to the difficulties of transportation and the distance from the market, these deposits are exploited in a very indifferent manner, and there is very little profit in the attempt to compete in the eastern market with the Asiatic and European chromite. 300 ECONOMIC GEOLOGY OF THE UNITED STATES. In the Urals, chrome iron ore is found in a number of places, and it is obtained also from Greece and Austria- Hungary ; but by far the most important source is in Asia Minor, near Brusa, fifty-seven miles east of Constantinople, where it occurs in pockets and bunches in serpentine. The greater part of our supply of this ore comes from there. In 1892 the chrome ore produced in this country amounted to about 3000 long tons, valued at 130,000, while the ore imported exceeded 5000 long tons, and the imports of chro- mate and bichromate of potash amounted to over 1,000,000 pounds. We have abundant supplies of this ore, if we ever need to draw upon them, but the demand is limited and the foreign ores are much more favourably situated for exploita- tion and transportation. Iron Pyrite. Although an ore, this mineral is used as a source, not of the metal, but the non-metallic mineralizer, sulphur. This ore is sometimes a source of copper and also of gold, as has already been stated; but iron pyrite proper is of value only for its sulphur, and for this reason it is used in the manufacture of- sulphuric acid. The marvellous increase in the demand for this acid, chiefly for the manu- facture of kerosene oil and superphosphates, calls for increas- ing supplies of pyrite. In 1870, 70,000 tons of sulphuric acid were manufactured in the United States; in 1880, 285,000 tons; and in 1892, nearly 580,000 tons. At the same time the amount of iron pyrite mined has increased from 2000 Jong tons in 1880 to 106,250 tons in 1892. The imports of pyrite in 1892 amounted to 210,000 long tons. MISCELLANEOUS ORES. 301 The iron pyrite mines of the United States are located chiefly in metamorphie rocks, slates and schists princi- pally, where the mineral occurs bedded, segregated, and in true veins. An extensive pyrite-bearing belt extends through Maryland, Virginia, and the Carolinas, but at present the principal source of the mineral in this belt is Virginia. Massachusetts has an output of 40,000 tons a year from the Davis mine in Franklin County. In the other New England states pyrite is common, but not much is produced. Indeed, surprisingly little attention has been paid in this country to this common but, when properly treated, often very valuable ore. Much of our supply of pyrite is foreign, coming chiefly from Canada, Newfound- land, and Spain. The occurrence there is not unlike that of the United States, and some of the ores are valuable also for their copper contents. The following table shows the pyrite production of some of the leading countries of the world : — PRODUCTION OF PYRITE IN THE WORLD, 1891. Metric Tons (2204 Lbs.). Spain 283,7241 Germany 128,288 United States 111,105 Canada 59,312 Hungary 50,000 ^ Italy 19,868 Great Britain 15,7163 The output of pyrite from the United States in 1892 (107,985 metric tons) was valued at $357,000. 1 Exported. ^ Estimated. 3 In 1866 Great Britain produced 187,622 tons. 302 ECONOMIC GEOLOGY OF THE UNITED STATES. Greneral Review of Metals. Reviewing briefly, it may be said that silver and silver- bearing lead ores are found in a wide variety of associations, chiefly, however, in true veins, and in these, associated very commonly with other ores such as copper, zinc, tin, and gold. The ores of lead are numerous, but this metal is found almost invariably as the sulphide, or some mineral derived from the alteration of this. Aside from the argen- tiferous galena, lead is found abundantly in non-argentif- erous galena, in association with zinc blende, or some mineral derived from the alteration, of these; and in such association the mode of occurrence is almost uniformly in dolomitic limestone. Copper is also found in many diverse positions in the earth and in numerous mineralogical asso- ciations ; but the two chief sources of the metal are native copper in one district and the sulphide in many districts. The latter ore frequently bears gold and silver, and it is not uncommon to find it associated with other ores as, for instance, in the famous English and German mines. One striking feature connected with copper ores is their almost universal association with igneous rocks, which appear to be their source, sometimes by the formation of contact accumu- lations, but more commonly by subsequent aggregation. Iron has numerous modes of occurrence, dependent upon a variety of circumstances, not the least important of which is the character of the ore itself. Brown hematite is typi- cally precipitated; red hematite is sometimes altered limo- nite, sometimes a replacement deposit. The carbonate is prevailingly concretionary in occurrence, and magnetite is frequently accumulated by segregation during metamor- MISCELLANEOUS ORES. 303 phism. Nearly all of these deposits of iron are either bedded or have the appearance of being bedded, as the result of the peculiarity of their secondary accumulation by segregation or replacement. Manganese resembles iron in its mode of occurrence, particularly the brown hematite and carbonate, and the same is true of the ore of alumi- num, bauxite. Nickel and cobalt prevailingly occur in metamorphic rocks, chromium typically and almost uni- versally occurs in serpentine, and iron pyrite is also found in metamorphic rocks, chiefly iron-bearing slates and schists. Few metals have more typical modes of occurrence than gold, which occurs in superficial deposits derived from the disintegration of gold-bearing veins, themselves almost equally typical in the fact that they are quartz veins, bearing iron pyrite, and apparently usually of segregation origin. Gold ore is practically all native ; and in this there is a close resemblance to platinum, as there is also in the fact that both occur very commonly in stream gravels. This is the universal source of platinum, but this metal is also found in serpentine rocks, although since little is known concerning the source of platinum, this cannot be definitely stated to be the typical occurrence in the rock. Like gold and platinum, much of the tin that is mined comes from stream gravels, where it accu- mulates for the same reason that the other two metals do ; namely, its high specific gravity and practical inde- structibility. In the rock, tin is all but universally found in or near coarse granites, although some tin deposits occur in other igneous rocks. Finally, mercury is nearly always associated with igneous rocks of recent origin, and it is apparently a contact deposit, in part the result of 304 ECONOMIC GEOLOGY OF THE UNITED STATES. sublimation. Both tin and mercury occur in typical ores, the first as an oxide, and the latter as a sulphide, and other occurrences may be considered rare. These generalizations must not be understood to be of uni- form application. There are exceptions to nearly all these statements; but they are made as general remarks which have an application in the majority of cases. The examples on the preceding pages illustrate the principles here enun- ciated, and a more widespread study of ore deposits verifies them even more strikingly. Under the conditions above named, the various ores are usually found ; and consequently we may properly conclude that, under similar circumstances, other similar mineral deposits will generally be found; but while we may look to these modes of occurrence for the major part of our ore deposits, we need not be surprised to find wide variations from these types, and the reason for this is to be found in the widespread distribution of ore, in disseminated form, through the earth's crust, as well as the great variety of changes which the crust has undergone. The United States may be considered the great metal- producing country of the world. In the case of a very few metals, principally platinum and tin, we are practically non- producers, but in the others we hold a high rank. Our country stands first in the production of iron, gold, silver, and copper, the four most important metals ; second in the production of lead, zinc, and mercury, which are probably the next most important ; either third or fourth in the pro- duction of manganese and pyrite ; and it holds a minor rank in the production of nickel, cobalt, antimony, and chromium, which are distinctly minor metals. The following table shows the value of the metalliferous output of the country MISCELLANEOUS ORES. 305 for 1892. The total metal production of the United States for 1892, exclusive of the ores mentioned in the table, was valued at 1318,638,596, while in 1880 the value was only 1201,283,094. PEODUCTION OF METALS AND METALLIC ORES IN THE UNITED STATES, 1892. Pig iron $136,806,915 SOver 83,909,210 Copper 37,850,000 Gold 33,000,000 Lead 17,917,000 Zinc 7,703,580 Mercury 1,119,720 Pyrite 357,000 Manganese ore 170,000 Nickel 57,691 Antimony 51,600 Chrome-iron ore 30,000 Tin 29,827 Cobalt oxide 6,450 Platinum 1,750 The distribution of these products in the country is very marked. In only three states, Montana, Colorado, and Cali- fornia, are four of these metals found in sufficient abundance to give the state a rank among the first five ; and if chromium be excluded, California must be omitted. Montana is the most important state, Colorado second, Michigan third, and California fourth. The following table shows the dis- tribution of the metals, in the first five important states, when there are as many. It will be noticed that but eighteen states are included in such a table ; and if man- ganese is not included, the number is reduced to fifteen. If 306 ECONOMIC GEOLOGY OP THE UNITED STATES. iron, manganese, and nickel are excluded, all of these states, with the exception of Michigan, Wisconsin, Missouri, and Kansas, are in the Cordilleras ; and the last two of these states are important only for lead and zinc. Thus the dis- tribution of these metals, in abundance, is extremely local. While nearly all of the metals are found in the states and territories of the far west, iron and manganese occur in the east, and zinc principally in the central states. There- fore, the fact that the United States is pre-eminently the country of metals is due chiefly to the peculiarities of the geology in the Cordilleras. In the following table the relative rank of the states, in the production of a given metal or ore, is indicated by numerals above the estimated value of the mineral product. For iron the value of the ore at the place of productioir is given, instead of the value of the pig-iron production, which is much greater and differently distributed, this being not necessarily near the mines which produced the ore. The value of the iron production gives a different rank to the states from that which is given by amount of output, since different ores are of different values. This will be seen by comparison with the tables in the chapter on iron. The actual output of lead, zinc, and some of the minor metals is not well shown in the table; but this will sufifice to illus- trate the general distribution, which is the object sought in the preparation of the table. MISCELLANEOUS OEES. 307 i 1 1 1- 1 ED 1 i 1 a o i a. V s o ? d t ^ 1 1 1 O P 00 m ^ S:^ W 00 05 3^ K >■ J^H ^aSw >• CO o ^ ^ K ^ "^ S «, ?- W H-* o tr" • t> 1? 3 l-t B CO " ►-1 o IS S i-» ; J=> K «0 ° s ■ Part III. NON-METALLIC MINERAL PRODUCTS. CHAPTER XIV. COAL. General Statement. — There is practically every gradation from peat to graphite. Many of the brown coals of Texas, and other parts of the west, contain woody fibres, only slightly altered from their original condition, and very closely resembling peat in many characteristics. These grade, sometimes in the same bed, to bituminous coal, which is soft and lustrous ; and this in turn may grade into semi- bituminous, a much harder, more compact, and purer coal. In New Mexico, where porphyry dikes have crossed a coal bed, bituminous coal is altered to anthracite ; and in Rhode Island, where coal beds have been subjected to marked regional metamorphism, graphite and graphitic anthracite have been produced. A final stage in the alteration would be the formation of a bed of graphite ; but we know of no such bed that can be directly traced to this origin, although some of the Rhode Island graphitic anthracites very closely approach this condition. Briefly, therefore, coal may be said to be altered vegetable accumulations, the degree of alteration producing different grades of coal, even up to anthracite. The alteration indi- cated by these changes consists partly in compacting the bed, but chiefly in driving off the volatile substances and water and concentrating the carbon. By this process, the percentage of carbon is increased, from as low as 5 per cent to 88 per cent, 311 312 ECONOMIC GEOLOGY OP THE UNITED STATES. and even more. The changes which result during this altera- tion are indicated in the following table of analyses : — ANALYSES OF PEAT, LIGNITE, A ND COALS Peat. Lignite. BiTUMiNons Coal. Aktheacite. Dismal Swamp. Athens, Texas. Atascosa County, Texas. Leon County, Texas. Waldrip, Texas. Penn- syl- vania. Penn- syl- vania. Penn- syl- vania. Penn- syl- vania. Moisture 78.89 9.10 1/ 13.285 14.670 4.55 / 0.9 1.8 2.74 1/ 2.93 Volatile matter . 18.84 42.20 59.865 87.320 88.50 25.63 20.87 4.26 4.29 Fixed carbon . 6.49 7.37 18.525 41.070 44.80 51.80 67.20 81.51 88.18 Ash. .78 41.82 8.325 6.690 12.14 17.77 8.80 10.87 4.04 Sulphur . 0.62 2.360 0.250 7.96 4.4 1.83 0.62 0.55 Coal is widely distributed throughout the world, and even in many countries where it is not mined it exists in great quantities. Europe and the United States produce practi- cally all the coal of the world ; and, in Europe, by far the greater part of the supply is found in Great Britain, Ger- many, France, Austria-Hungary, and Belgium. Our own country has a number of important areas.^ Probably there are not far from 300,000 square miles of coal-bearing strata in this country ; but by no means is this all available coal, since over large areas it is either too thin or too impure for profitable extraction. The actual coal-produdng area, either at present worked or available for the future, is not over 50,000 square miles, and of this only a small part is now being worked. ■■ Detailed descriptions of the coal areas of the United States will be found in the Eleventh Census volume on Mineral Industries, pp. 343-422, and in The Mineral Besources, Day (U. S. Geol. Survey), particularly the volume for 1891, pp. 177-402. COAL. 818 In the Eleventh Census report the coal-bearing strata of the country are divided into seven areas, as follows : (1) the New England basin, including a small section in Rhode Island and southern Massachusetts, having an area of about 500 square miles ; (2) the Appalachian district, at present the most important, with an area of 65,000 square miles, and extending from Pennsylvania to Alabama ; (8) the Northern area, of about 7000 square miles, in Michigan ; (4) the Cen- tral area, 48,000 square miles in extent, embraced in the three states, Illinois, Indiana, and western Kentucky; (5) the Western area, a poorly defined region, covering more than 98,000 square miles, and divisible into many minor dis- tricts, extending more or less brokenly from Iowa to the Rio Grande ; (6) the Rocky Mountain area, of indefinite extent, with scattered basins known to exist in nearly all the states and territories of the Rocky Mountain belt; and (7) the Pacific Coast district, the area of which is also unknown, but in which are included the three states of Washington, Oregon, and California. An eightli area might well be added, to include the Alaskan coal fields, which will soon be developed. Coal, unlike the great majority of metalliferous deposits, is an actually bedded stratum, formed, as a part of the sediment- ary series, in a manner wliich is more fully referred to in the following pages. Before the development of our western country, coal, properly speaking, and excluding the lignites, was supposed to be the product of a single age, the Car- boniferous, and fuels of later origin were believed to be of very local nature and lignitic structure. But the opening of the coal mines in the Rocky Mountains has shown the fal- lacy of this belief, for here we find beds of all ages, since the Carboniferous, and in all stages of alteration, even to 314 ECONOMIC GEOLOGY OP THE UNITED STATES. anthracite. The Cretaceous and Tertiary ages are, in this district, the most favoured with coal beds ; but this is doubt- less due, in large measure, to the fact that the rocks of these ages are much better developed than any of an age subsequent to the Carboniferous. With the exception of thin seams in the Lower Carboniferous and Devonian strata, there are no coal beds in rocks lower than the Coal Measures. New England Coal Basin. — This region is of interest, not for the amount produced, but for the peculiar nature of the coal. Although never a heavy producer, this region has been worked, more or less continuously, for a long period. Unlike the greater part of our coal, the beds of this district are highly tilted, and some of the mines have extended to a considerable depth. A few thousand tons are annually produced, but this burns with such difficulty that it is of use only where there is a strong draft, as in a blast furnace ; but this difficulty is partly compensated for by the length of time which it burns and the large amount of heat furnished. A very peculiar industry for a coal region has been recently begun upon the basis of the graphitic nature of these anthracites. This is the manu- facture of pipe-coverings, stove-facings, stove-blacking, and paints, which shows the peculiar condition of the coal beds. The graphitic nature of the anthracite is due to the metamorphism of the coal-bearing beds, by mountain-building forces, which have, by folding and faulting, resulted ia altering the nature of the enclosing rocks, in some cases to well-defined schists. A considerable thickness resulting from folding is noticed in some of the beds of coal, that at Portsmouth being from three to ten feet thick ; and it is not impossible that, in some of the less metamorphosed COAL. 315 parts of this area, valuable coal beds exist beneath the drift coating. This area may be considered a part of the coal-beariag series of Nova Scotia, the age being the same, and the conditions of formation similar, but the metamor- phism being much less in the latter district. Appalachian Coal District. — In this area are included the coal fields of Pennsylvania, Ohio, Maryland, Virginia, West Virginia, eastern Kentucky, Tennessee, Georgia, and Alabama ; and the Coal Measures are practically continuous from northern Pennsylvania to western Alabama. The coal beds follow the folds of the Appalachians and extend into the level plateau country at the western base of the moun- tains. While this coal is confined to a single age, the Upper Carboniferous, it is not a continuous layer, but a series of lenticular beds at different horizons in the Coal Meas- ures, varying in extent and in thickness, sometimes gradu- ally, sometimes abruptly, from a fraction of an inch to several feet. A thin seam may thus become thicker, in a given direction, and then again lose thickness ; and, in the shaft sunk to a coal bed, numerous seams of coal, of varying thickness, may be encountered. This coal was first discovered in Virginia in 1701, in Ohio in 1755, and in western Pennsylvania in 1759. The first coal mines regularly opened in the country were near Richmond, Virginia, in 1750. There are two kinds of coal in this district, the bituminous (including semi-bituminous) and the anthra- cite, both of which occur in the same series of rocks, the Coal Measures of the Carboniferous, but in different parts of the district. The anthracite fields, which produce practically all of this kind of coal in the country, are confined to the eastern 316 KCONOMIC GEOLOGY OF THE UNITED STATES. part of Pennsylvania, where there are three general regions, the Wyoming, Lehigh, and Schuylkill, which are properly divisible into five well-defined fields or basins. Coal was first discovered here in 1790, and the first shipments were made in 1800 ; but not until 1825 was the region made to produce extensively, since the difiiculty of burning the coal prevented consumers from attempting to use it. The reason for the occurrence of anthracite in this part of Pennsylvania, and its absence elsewhere in the district, is that the coal basins here have been subjected to a cer- tain amount of metamorphism by the folding which has produced the Appalachians. This folding is far less than that to which the Rhode Island-Massachusetts basin was subjected, but was sufficient to drive off much of the water and volatile matter and produce anthracite. It is probable that considerable quantities of this coal have been removed by the extensive denudation to which the Appalachians have been subjected since their formation. The following table is of interest, since it shows the increase in production of anthracite, in these fields, from the very first. Between 1820 and 1891 inclusive, the out- put of this region has amounted to 779,639,326 long tons, and the Wyoming district is the most important of the three. PRODUCTION OF ANTHRACITE IN PENNSYLVANIA. Long Tons (2240 Lbs.)- 1820 365 1830 174,734 1840 864,379 1850 3,358,889 1860 8,513,123 1870 16,182,191 1880 23,437,242 1890 36,615,459 1891 • 40,448,336 COAL. 317 The bituminous field of the Appalachian area is far more important, in point of output, than any of the other regions ; and in this Pennsylvania is the greatest producer. This does not necessarily mean that there is a greater supply of coal here than elsewhere, but that there is a better market and consequently a greater development of the possibilities. The iron industry is largely responsible for this. Where coal is not found iron cannot be profitably mined, excepting under conditions of exceptional facilities for exploitation and trans- portation, which admit of the shipment of the ore to smelters near the coal supply. Both coal and iron occur in this belt ; and in development the two industries have progressed together, so that, at present, both iron smelting and coal mining are carried on, in this district, on a very extensive scale. So fixed is the industry of iron smelting here, that, even though the iron supply may decline, as it has and will continue to do, it will probably continue to increase and be fed with iron from outside, while the industry of coal mining will increase. There are other factors to be considered also, chiefly the fact that this region was the first to be developed industrially, and that it is favourably situated for transporta- tion of coal and articles manufactured by the aid of coal. In no state is the value of iron mining to coal production better shown than in Alabama, where, in 1870, the output of coal was only 13,000 short tons ; in 1880, 380,000 tons ; in 1887, about 2,000,000 tons ; and in 1891, 4,759,781 tons. A comparison with the statistics of iron will show the relation of the two products. "West Virginia has also had a remarkable increase, from 1,568,000 short tons in 1880, to 9,220,665 tons in 1891. Nearly all of the other states of the Appalachian district show a marked increase in coal output, and this 318 ECONOMIC GEOLOGY OE THE UNITED STATES. is largely attributable to the increase in the output of iron manufactures. Central, Western, and Northern Coal Areas. — There is very little to be said about these areas. The Northern basin is of very slight importance, and in the past ten years it has decreased its output. Of the other two districts, the Central has a much larger output, and the states of both districts have steadily increased their production. The coal beds are in practically horizontal strata of the Coal Measures, and coal mining is, therefore, not usually difficult or expensive. Both the age and the conditions of accumulation, and, therefore, the modes of occurrence, are the same here as in the Appa- lachian district. It is doubtful if the division between the Western and Central areas is well founded, since the dividing line is the Mississippi, and the cause for the division is merely that this river has removed the Coal Measures from its valley. Mis- souri and Illinois belong to practically one geological area, and the division is highly artificial. It would be much bet- ter to have for the fifth division the Texas and other post- Carboniferous coals of the trans-Mississippi region. In the more western parts of the area, and in various por- tions of Texas, there are Cretaceous and Tertiary deposits of coal and lignite, some of which are mined for local purposes, but most of which are at present of no economic value. They form a reserve supply which can be drawn upon in the future; and some believe, in the very near future. The Texas field illustrates this occurrence, for, aside from a rather small and not very important area of true Carbonifer- ous coal, there are extensive deposits of both Cretaceous and Tertiary fuel in this state. On the Rio Grande, at several COAL. 319 points, both lignite and bituminous coal, of Cretaceous age, occur; and, in eastern Texas, there are very thick beds of Tertiary lignite in the coastal deposits. These are easily mined, but, on account of their position, their impure nature, and friable structure, they do not seem to promise to be of immediate importance.^ Rocky Mountain, Pacific Coast, and Alaskan Coal Areas. — - In these districts, coal, in the form of lignite, bituminous coal, and even anthracite, is found in several areas, and in strata of several geological ages, chiefly Tertiary and Creta- ceous, and more rarely Carboniferous. Some of these states have increased their output in the last decade at a remarka- ble rate, and this section maybe considered the coal reserve of the country, for even the larger producers have by no means developed their coal fields to even one-half their capacity. The area and extent of these coal fields cannot be stated, but we know that there are immense supplies. Very little anthracite is found, and this is surprising when the changes through which these rocks have passed are considered. A bed of anthracite, about six feet thick, is found in Colorado, and another exists in New Mexico ; in both places the meta- morphism being that of contact with intrusive igneous rocks. This coal appears to be of as good quality as that of Pennsyl- vania. The bituminous coal of Colorado, 'although of Creta- ceous age, is also of excellent quality, and it occurs in thick and extensive beds. There is excellent prospect for the future of this state as a coal-producer, and the same is true of other states in this belt ; but the lack of market, and the 1 These coals and the methods by which they may be utilized are described by E. T. Dumble in a Report on the Broion Coal and Lignite of Texas, pub- lished by the Texas Geological Survey. 320 ECONOMIC GEOLOGY OF THE UNITED STATES. difficulty of convincing eastern people that this fuel is hetter than lignite, have interfered with the more rapid develop- ment of the fields. On the Pacific Coast the most important state as a coal- producer is Washington, wheve lignites, bituminous and anthracite coals are found, the different kinds being the result of different degrees of metamorphism caused locally by the intrusion of igneous rocks. With the development of the west these Cretaceous coals will be more and more valuable, and already the output has become important, having in- creased, since 1885, from 380,250 to 1,056,249 ghort tons. In Alaska, coal has long been known to exist, and there is promise of immediate development. The Russians knew of the existence of coal before they sold the territory to the United States, but the industrial and climatic conditions have interfered with its development. There are extensive and thick seams which can be easily worked. Of foreign deposits, nothing need be said, since no new fea- tures are illustrated. Coal is extremely widespread and abun- dant in all explored continents ; and, even with the present rapid production, there need be no fear of an exhaustion of the supply for many centuries to come. Not only are there great reserves in our western territory, but in the continents other than this and Europe, coal, though not produced in great quantities, is by no means scarce. It has been formed ever since the Carboniferous, whenever the conditions were favour- able, and this has been by no means an uncommon geologi- cal condition. There is good reason to believe that the demand will cease before the supply is exhausted. The following table shows the distribution of coal in the several areas of the country : — COAIi. 321 PRODUCTION OF THE COAL AREAS OF THE UNITED STATES. Short Tons (2000 Lbs.). Total Abeab. 1880. 1887. 1890. 1891. 1870-1892 inclusive. f Bituminous, Appalachian ■{ i Anthracite, 29,834,632 55,193,034 73,008,102 77,934,563 983,909,805 28,640,819 39,606,255 46,468,641 50,665,481 561,627,2691 Central .... 8,150,195 14,478,883 20,098,533 20,827,823 254,821,177 Western 8,212,787 10,193,034 10,470,489 11,023,817 138,470,000 Eocky i Bituminous . Mountain \ Anthracite . 1,067,314 3,646,280 6,160,782 7,185,707 58,848,504 86,000 56,0002 60,0002 Pacific Coast . , 425,170 854,308 1,435,914 1,201,376 12,313,040 Northern . 100,800 71,461 74,977 80,073 1,455,289 New England Anthracite, 6,176 6,000 500 Total 71,487,883 124,015,255 167,788,666 168,566,669 1,956,444,684 The total value of coal produced by the United States between 1870 and 1892 inclusive was 12,237,258,218. Origin of Coal. — That coal is derived from vegetation is proved by a number of indisputable facts. In the first place, its carbonaceous nature is strongly suggestive of this origin, and, in the less altered coals, the vegetable origin is proved by the actual presence of plant fibres, seeds, etc. Even where, with the naked eye, stems of plants and impressions of ferns cannot be seen, unless the coal is too greatly meta- morphosed a microscopic study shows the presence of woody fibre and plant remains of one kind and another. Indeed, actual tree trunks are quite perfectly preserved, and, in some cases, although the strata have been tilted and dis- turbed, these trees rise through the coal beds, at right angles to the stratification, with their roots extending into the clay 1 Includes Rocky Mountain anthracite. " Estimated. 322 ECONOMIC GEOLOGY OF THE UNITED STATES. beneath the coal. Such a condition has been observed in the Nova Scotia coal fields and elsewhere. The tree trunks stand where they grew, just as some trunks of trees stand at present in bogs, either partly or completely buried. These facts prove the point that vegetation is the origin of coal, but in just what manner these accumulations were made is not quite so clear. The accumulation of peat bogs is familiar to all who have dwelt in northern lands. A pond is partly filled with sediment, it then becomes transformed to a morass, and eventually to a swamp, by the growth and decay of vegetation, first reeds, then moss, and finally bushes and trees. Year after year additions are made to the vegetable accumulations, until, finally, a bed of peat is formed ; and in the typical peat bed, one of the most important of the bog- forming plants is a moss belonging to the genus Sphagnum. This vegetation, dying upon the surface, would not accumu- late, for, as is well known, organic remains quickly decay in the air ; but beneath water this destruction is arrested and the vegetation even preserved by the various organic acids pro- duced by a partial decay. Thus, it is not uncommon to find tree trunks in swamps, at a depth of several feet beneath the surface, so perfectly preserved that the marks of beaver teeth can be seen, although these were made perhaps several cen- turies or even a thousand years ago, when the swamp was inhabited by beaver. One might at first assume that, since there is every grada- tion between peat and coal, the original condition of coal was actually peat, and this has given rise to the Peat Bog Theory^ for the origin of coal. This may have been the origin of 1 On the Vegetable Origin of Coal, Lesquereux, Annual Report, Pennsyl- vania Geological Survey, 1885, pp. 95-124. COAL. 323 some' coal beds, particularly those of the western Tertiary- strata, which were deposited in inland seas and lakes. With many of the Carboniferous coal beds, and also some of those more recently formed, another mode of origin must be sought. By a study of the coal beds it is found, that, both beneath and above, there are clays, limestones, and sandstones of marine origin and containing marine fossils. The coal is therefore directly associated, in point of origin, with the sea. Indeed, there are rapid and striking alternations from coal to sedimentary beds, then to coal, and so on, often for scores of feet Tcrtically. Sometimes the coal beds are thin seams, mere films of carbonaceous matter, but at other times they assume a thickness of a number of feet. Although both overlain and underlain by marine sediments, the coal plants themselves are not marine, but of types which, so far as we know, are at present exclusively dwellers on the land. Therefore we must find an explanation which will account for the accumulation of land plants either in or very close to the sea. Moreover, conditions for the preservation of the plant tissue must be present, and these conditions are evi- dently the presence of bodies of water, either salt or fresh. Two possible explanations suggest themselves : one, that the coal plants have been washed into the sea ; the other, that they grew on or near the shore line and fell into shallow bodies of water. The first of these, which may be called the Ustuari/ Theory, is that rivers carried vegetation down with them, and caused it to accumulate in estuaries and bays at the mouths of the rivers. There seems to be very little reason to doubt that this, like the peat bog theory just de- scribed, is an actual cause for some such deposits. In the delta of the Mississippi, vegetable accumulations are en- 324 ECONOMIC GEOLOGY OF THE UNITED STATES. countered in borings, and these are the result of the strand- ing and accumulation of rafts of timber which have been floating down the river for centuries. Even at present, al- though much of the forest of the valley has been removed, portions of the bank are undermined during the floods of the river, and the trees and bushes which grew upon them are floated off toward the sea. But, while this may be admitted as a possible, indeed as an actual cause, it cannot be extended to include all or even a large number of the coal beds. There are numerous fatal objections to the universal appli- cation of this theory. In the first place, a river transport- ing logs carries sediment also, and beds so formed will be much more impure than coal beds usually are; secondly, such deposits must be local and of a more limited area than many of our coal basins ; thirdly, under such conditions the plant fragments must be water-worn and broken, and we could hardly expect to have preserved in abundance, as we really do, even the most delicate parts of very fragile ferns ; and, finally, it is not probable that in such deposits tree trunks would grow and be preserved in place as they are in some coal strata. In support of this theory it may be urged that the coal occurs in basins, or linear areas, which might well be estu- aries ; but this is also exactly what is demanded by the third theory, which may be called the Seacoast Swamp Theory. Aside from the objections urged above, against the estuary theory, none of which apply to this one, it is a notable fact that beneath coal beds there is commonly a clay stratum, called fire clay, which owes its peculiar properties to the absence of certain soluble salts needed by vegetation; and this suggests strongly that the soils have been robbed of COAL. 325 these elements by plants, and most probably by the plants that have been accumulated in the overlying coal beds. If we assume the existence, during the coal period, of coastal swamps and lagoons, such as exist at present on many coasts, and are well illustrated by the marshes about Newark and Jer- sey City in New Jersey, all of the facts connected with most coal beds are easily explained. There are in the coal basins even channels similar to salt marsh channels or coastal rivers. It is also a fair assumption to make, that much of the coal- forming vegetation could grow in such places. At present, only a very few plants can live in salt water, or in places invaded by salt water; but, if one thing has been more plainly taught by geology than any other, it is that animals and plants have changed, not only in form and development, but in habits ; and, since it is not improbable that land vege- tation came originally from oceanic types, the change in habit here suggested is certainly possible, and we may even say, probable. On the eastern coast of the United States there are a number of phenserogams living, not only on salt marshes, but one, the eel grass, growing and flowering en- tirely submerged in salt water; and, on the Florida coast, the mangrove tree grows with its roots in salt water. No especial incredulity need, therefore, be felt in considering the possibility of a more widespread adoption of this habit by the Carboniferous vegetation, which differed so markedly from the present types of plant life. It is not, however, abso- lutely necessary to assume this condition, for it is possible that there existed along the shore line extensive swamps which were either fresh or only slightly saline. A study of coal deposits indicates not a single, but several explanations for their origin. Some were formed as peat 326 ECONOMIC GEOLOGY OF THE UNITED STATES. bogs ; some, particularly those of the western Tertiary and Cretaceous areas, were formed upon the margins of lakes and inland seas ; not a few were, no doubt, accumulated in sea- shore estuaries ; and probably most of the Carboniferous coal beds were formed along coast lines in shallow lagoons, or seacoast swamps, either fresh or saline, and probably both. Attention may be called, in this connection, to the fact that the geological conditions in this country favoured the latter mode of accumulation in the three important coal-bearing ages. During the close of the Carboniferous period a great sea was beginning to be transformed to land, as the fore- shadowing of the development of the Appalachian Mountains and the central plateau. Skirting the old, pre-Palseozoic mountain area of the seacoast states, there stretched west- ward a region of shallow water and low, swampy land, upon which the coal vegetation grew. In the Central area, and in parts of the Cordilleras, the same conditions prevailed; but, in the latter region, these were better developed in Cretaceous and Tertiary times ; and here, by the mountain growth, large inland seas and lakes were produced, in which coal beds were accumulated. Conditions existing in Carboniferous Times. — A number of interesting questions arise concerning the conditions exist- ing in the Carboniferous period. Why do we find such rapid alternations of coal beds with marine sediments? It has been held that this is due to rapid alternations in sea-level, or, rather, land position ; that the land rose and fell, now being occupied by swamp plants, again submerged by the ocean, and this followed by other similar alternations of level and condition. This may be true ; but so many alternations are called for, none of them producing high land, that some COAL. 327 simpler explanation may be sought. These phenomena may- be accounted for by assuming a swampy land area, not un- like the coastal plains of Texas, gradually sinking, but with occasional halts, or periods of less rapid sinking. When land existed, plants grew ; but, if the submergence were more rapid than the building up, water prevailed until the rate of sinking was less rapid than the rate of filling. Whea such a period of slow submergence, or perhaps even absence of submergence, prevailed, sediment filled the bays, vegetation grew upon their margins, lagoons were built behind bars, and salt marshes were formed, just as they are at present, under the same conditions. In this manner the apparent elevations may have resulted from fill- ing rather than actual rising of the land. So, by a gradual submergence, a mere variation in rate will bring about all the conditions of alternation ordinarily noticed in coal beds. This does not deny the possibility of elevations also, for these would cause the alternations even more rapidly ; but it does call in question the necessity of a theory which requires a large number and great variety of elevations and submergences, since this necessitates an instability of the land rarely witnessed anywhere outside of local volcanic areas, and our immense coal fields were not formed in such places. Another question that may be asked is, what were the climatic conditions in the Carboniferous period? It has been very commonly assumed that the climate was moist, tropical in heat, and the atmosphere laden with carbonic acid gas for plant food. The large size, and apparent lux- uriance of the vegetation, resembling our present tropical flora, have been appealed to in support of this. That the climatic conditions were different from the present, even as 328 ECONOMIC GEOLOGY OF THE UNITED STATES. late as the Tertiary period, is proved by a study of the Arctic regions, where not only animal and plant fossils, but even coal beds, are found in the rocks now situated in a region of perpetual snow. The value of the evidence in favour of these, from our present standpoint, abnormal conditions, has, it seems to the author, been unduly mag- nified. The evidence of luxuriant Carboniferous vegetation does not appear of so much importance when one has seen the giant trees of California and the primaeval forests of Canada. A good soil and a moist, and not too cold climate, will produce striking results in vegetation. It is doubtful if any trees in the Carboniferous period exceeded in size the giant Sequoia of California. Moreover, fossils of animals show us plainly enough that types which are now small throughout the world were once gigantic in size ; and the same may be equally true of plants. A new field and a newly acquired habit give to both animals and plants great powers of remarkable development. Before the Carbonif- erous period practically no land plants existed, and the soil was not, therefore, robbed of its plant food. Moreover, the Carboniferous land was made of a virgin soil just elevated above sea-level. Under such conditions, with a temperate climate, a luxuriant vegetation might easily be developed. It seems that we must grant moistness to the atmosphere, and the presence of oceans, where now is land, transforming the old mountain areas of the east into islands, makes such an assumption entirely within reason. When one reads the accounts of Eussell ^ describing the luxuriant, almost trop- 1 An expedition to Mount St. Elias, Alaska, National Geographic Maga- zine, III, 1891, pp. 53-204 ; American Journal of Science, XLIII, 1892, p. 178 ; Journal of Geology, I, 1893, p. 233. COAL. 329 ically luxuriant, forest at present actually growing on a moraine which rests on a living body of ice, near the terminus of the great Malaspina glacier of Alaska, he is ready to believe that no great revolution of climate is necessary to carry the vegetation of the Carboniferous period as far within the Arctic circle as man himself has penetrated. Transform the highlands of the Arctic to low- lands, and much of the ice will disappear ; then add to this a slight increase in the mean annual temperature, and vege- tation would find a home there. Peary, Lockwood, and others, state that the land lying north of Greenland is free from snow in summer, notwithstanding the presence of the great Greenland glacier to the south and of a frozen ocean all about. This is due in large measure to the fact that the land is low ; and if the mountains and highlands of Green- land were lowered to near sea-level, the climatic conditions of the Arctic would be greatly changed. Climate is strikingly dependent upon geography. The object in presenting these considerations is not to deny the possibility, nor even to question the probability, of a marked change in climatic conditions in the northern hemisphere during Carboniferous times, but to point out the fallacy of the statement so frequently made, that trop- ical conditions extended to the poles. Possibly this was the case, but probably it was not, and, in any event, the argu- ment upon which these statements are chiefly based, the resemblance of the coal flora to our present tropical flora, is not of much value after the lapse of time and the striking changes which have taken place in form and habit of fauna and flora since the Carboniferous period. The question is sometimes asked, why are coal beds not 330 ECONOMIC GEOLOGY OP THE UNITED STATES. present in periods earlier than the Carboniferous? and the answer is, simply, that land vegetation had not been evolved in great luxuriance in earlier periods. A current statement, frequently found in text-books, is, that the reason for this was the too great abundance of carbonic acid gas in the atmosphere. According to this assumption, the early land vegetation laboriously extracted this carbonic dioxide, until just the proper percentage remained for the luxuriant Car- boniferous vegetation, but too much for air-breathing ani- mals, which came after the atmosphere had been cleared of the deleterious gas by the Carboniferous plants, — having the way prepared for them, as it were. Aside from the logic of animal and plant succession, which is as above stated, and which is readily explained in another way, — namely, normal evolution, — it is difficult to see upon what basis this assumption of an excess of carbonic acid gas in the atmosphere is based. To be sure, carbon taken from the air is sealed in the rocks in the form of both animal and plant remains ; but, on the other hand, it is being liberated by the decay of rocks ; and it is very doubtful if the supply of this gas in the atmosphere is sensibly different to-day from what it was in the beginning of the Carboniferous. If we should grant the assumption, for the sake of argu- ment, it would seem that a gradual decrease in amount and luxuriance of vegetation would necessarily follow upon the exhaustion of the carbonic dioxide ; but, on the con- trary, vegetation has increased in height of development and has certainly not lost in luxuriance. Ever since the Carboniferous the land areas of all the world have been clothed with vegetation, and so they are to-day. Moreover, COAL. 331 if geological interpretations have been correctly made, there is more land at present than ever before, and this land has been continuously increasing in amount since the Car- boniferous. The simple fact is, that the greater part of the carbon taken from the air is given back again when the plant or animal dies, and the place of that stored away in the rocks is fully filled by supplies furnished by rock decay. Uses of Coal. — It would be difficult to make a compari- son between the value of coal and iron, since both are so important and intimately related. Probably, however, iron must be considered of more value, since there are so many possible uses for it, and no available substitute, whereas coal is not an actual necessity, although in the present state of industry it seems to be. The importance of the coal industry is shown by the fact that in 1892 coal valued at not far from §200,000,000 at the mines was produced in this country, and in 1891, 205,000 persons were employed, directly or indirectly, in the production of coal. Of bituminous and anthracite coal, the country produced 171,769,355 short tons in 1892, 49,735,744 tons of this being anthracite, and the balance bituminous (including all varieties of coal excepting anthracite). Our exports in 1892 amounted to nearly 2,500,000 tons, and our imports to a little over 1,000,000 tons. The consumption of coal in the country per capita amounted to 6234 pounds. Undoubtedly the most important single use of coal is as fuel for heating and cooking purposes; but as fuel in the manufacture of materials requiring heat, immense quan- tities are called for as well as in the production of energy in the form of steam. Our locomotives and engines for 332 ECONOMIC GEOLOGY OP THE UNITED STATES. manufactories and for steamships are consuming coal at a remarkable rate whicli is every day increasing; and the rapid expansion of electric transportation in small towns and suburban districts is also increasing the demand for this fuel. One of the most remarkable advances in the use of coal is that made in the manufacture of pig iron and steel. Bituminous coal, transformed to coke by driving off the volatile substances in ovens, is rapidly supplanting anthra- cite and charcoal. Whereas in 1880 only 5,287,741 short tons of coal were used for this purpose, in 1891, 16,844,540 tons were consumed, producing 10,852,688 tons of coke valued at $20,393,216. A relative decrease must have been caused in the consumption of coal for coal gas by the introduction of electric lights ; but the falling off in this respect is more than compensated for by the increased demand for coal in the production of electricity. It is an interesting question what the future of coal will be. Some predict that the supply will fail us, and these favour more economical methods of production and use; but, while this maj' be true of localities, and even of some countries, there seems to be no need to fear it in this country, nor in the world, for such a length of time that we need hardly trouble ourselves with the question. The tendency of the present seems to be rather toward a decrease in demand than a decrease in supply. This has not as yet made itself distinctly apparent, nor is it an absolute cer- tainty; but when we learn to economically win our elec- tricity from the wasted forces of nature, the waterfalls, or, as some predict, from heat direct, and then learn to store it for transportation, and to convert it from electrical energy to heat energy, there will come a time when coal COAL. 333 will be found of much less value than at present. This is now little more than a dream, but wonderful things are being done with electricity, and electricians assure us that we have hardly begun. Production of Coal. — In the production of the metallic minerals the far west was found to be of prime importance, but in the non-metallic products of the earth that section of the country assumes a much lower rank. The reason for this is that alreadj"- given for the absence of an impor- tant iron output in the west, — less a lack of supply than an absence of market, or, in other words, a smaller degree of industrial progress. The following tables of coal output illustrate this distribution and other features connected with the production of coal at home and abroad: — PEODUCTION OF COAL IN THE UNITED STATES. Short Tons (2000 Lbs.). States. 1870. 1875. 1880. 1885. 1890. 1893. Pennsylvania ] (Anthracite) 1 16,650,276 28,120,780 26,249,711 88,836,973 46,468,640 49,735,744 Pennsylvania 1 (Bituminous) ) 7,798,617 11,760,000 21,280,000 26,000,000 42,302,173 41,424,984 Illinois . . . 2,624,163 3,920,000 4,480,000 11,884,469 15,274,727 17,949,989 Ohio . . 2,527,2S1 5,447,970 7,840,000 8,754,120 13,203,522 14,560,000 West Virginia . 618,878 1,120,000 1,404,008 8,869,061 6,002,800 8,710,878 Alabama . . 10,999 67,200 380,000 2,492,000 4,090,409 5,275,000 Maryland 1,819,824 2,623,905 2,692,497 2,883,837 3,857,813 4,036,288 Iowa . , 263,487 1,120,000 1,792,000 4,012,675 4,021,789 3,820,000 Colorado 4,600 98,638 375,000 1,898,796 8,075,781 3,771,234 Indiana . 487,870 896,000 1,680,000 2,378,000 8,305,787 8,309,700 Kentucky 150,682 560,000 1,120,000 1,904,000 2,488,144 8,020,050 Missouri 621,930 840,000 1,680,000 8,080,000 2,437,899 8,017,286 Total for the 1 United States, f 83,003,815 58,121,029 73,647,997 112,609,811 156,073,611 171,769,865 334 ECONOMIC GEOLOGY OF THE UNITED STATES. Besides these states, four others, Kansas, Tennessee, Indian Territory, and Washington, produce between 1,000,000 and 3,000,000 tons annually, and the first two more than 2,000,000 tons. A noteworthy feature of this table is the rapid in- crease in the coal output of all the states, but especially of Alabama and Colorado. It is also a striking fact that the three leading coal-producing states in 1870 maintained their position in 1892. These three states, Pennsylvania, Illinois, and Ohio, together produced, in 1892, 128,670,000 tons out of the total 171,769,000 tons produced by the country. Pennsylvania supplied considerably more than one-half the total of the United States, but the percent- age of Pennsylvania's output to that of the .rest of the country has decreased considerably since 1870, owing to the rapid increase in output in other parts of the country. In twenty-three years the United States has increased its coal output to more than five times the amount at the beginning of that period, or at the average rate of more than 6,000,000 tons a year. The average cost of bituminous coal at the mines in Pennsylvania in 1891 was $1.00 a ton, and of anthracite coal 11.79 a ton. Therefore the value of the total output of 168,566,669 short tons was $191,133,135. This of course does not at all represent the retail price, after shipping and passing through the hands of dealers, for this price varies greatly according to a variety of conditions, chiefly the distance from the mine and the manipulations of coal combinations. COAL. 335 PRODUCTION OF COAL IN THE WOBLD.i Metric Tons (2204 Lbs.)- Countries. 1865. 1870. 1875. 1880. 1885. 1891. Great Britain, 99,769,613 112,241,531 185,491,837 149,378,744 161,968,786 188,519,767 United States, 24,790,400 29,948,602 48,204,201 66,881,213 102,186,761 163,851,182 Germany 28,327,800 34,830,600 48,682,400 59,118,086 73,675,515 94,252,278 Austria- Hun- ) gary . . ' 2,028,089 8,855,946 13,062,738 14,800,000 20,485,463 27,000,000 France . 11,840,000 13,300,000 16,956,840 19,361,564 19,510,530 26,199,745 Belgium . . 11,840,603 13,697,110 16,011,831 16,886,698 17,437,608 19,865,845 Russia . . . 331,000 696,209 1,171,736 3,266,844 4,278,476 7,000,0002 Spain . . . 450,000 661,932 610,000 847,128 945,904 1,286,000 All Other ) Countries ' . 2,712,495 4,041,111 6,258,917 9,079,774 12,389,072 17,126,738 Total fori World . I 182,080,000 217,823,000 285,300,000 839,870,000 412,818,000 535,101,000 The rapid increase in output of nearly all the countries is a striking feature of this table ; but this is particularly notice- able in the case of the United States, Austria-Hungary, and Eussia, and the group of unspecified countries. Spain, France, and Belgium have shown a smaller rate of increase ; and the two latter countries have fallen in rank, although they have increased their output. The marvellous increase in the coal production of the United States is especially note- worthy ; and it will not be surprising if, in the next decade, 1 This extremely valuable table is extracted from a more complete one in Rothwell's Mineral Industry (p. 84), which has served as the source of many of our statistics. Any student interested in the statistics of mineral production will find this subject admirably and fully presented in that treatise. 2 Probably the output of Russia for 1891 was nearer 8,000,000. 336 ECONOMIC GEOLOGY OP THE UNITED STATES. this country assumes first place among the coal-producing nations, which it can easily do, if the demand increases suffi- ciently, since our possibilities are certainly exceeded by no other country in the world. Over three-fifths of the coal of the world is obtained in the United States and Great Britain. In the last twenty-seven years the average rate of increase in the coal output of the world has been about 13,000,000 tons a year. CHAPTER XV. PETEOLEUM, NATURAL GAS, AND ASPHALTUM.^ Petroleum. General Statement. — Petroleum, natural gas, and salt water frequently occur, more or less intimately associated, in strati- fied rocks. While sandstones and conglomerates are the chief sources of these substances, they are by no means confined to these rocks; but in some places are found in shales, in others, in limestones. The geological age of the petroleum-bearing strata is also variable. In the eastern states this substance occurs chiefly in the Silurian and Devo- nian sandstones and conglomerates, but some is also found in the Carboniferous strata. Practically no oil occurs in strata earlier than the Silurian. By far the most important single source of oil, at present, is the Trenton limestone horizon of the Silurian, in which the Ohio and Indiana fields are situated. Shales of the Laramie stage of the Cretaceous bear oil in Colorado; and in California the age of the oil- 1 The statistics and distribution of these substances in the United States are fully treated in the Eleventh Census volume on Mineral Industries, pp. 425-591 ; in Rothwell's Mineral Industry ; and the various volumes of The Mineral Resources of the United States, Day (U. S. Geol. Survey). The geology of the subject is discussed by Orton in the Eighth Ann. Rept. U. S. Geol. Survey, 1889, pp. 475-662. There is also an important discussion of the subject in the Tenth Census, Vol. X., pp. 1-319. "Various reports of the State Surveys of Ohio and Pennsylvania also contain discussions on petro- leum. A complete bibliography of the sutject will be found in Carll's re- port, Annual Report for 1886, Part II., pp. 830-895. 337 338 KCONOMIC GEOLOGY OF THE UNITED STATES. bearing strata is Tertiary. Thus, although in the early his- tory of the petroleum industry the Palaeozoic was believed to be the only source of oil, it is now found to range through all ages from Lower Silurian to Tertiary. From the very earliest times in the history of this country, the existence of petroleum has been known, by reason of its seepage at the surface, in oil springs ; but before the dis- covery of oil in a well at Titusville, Pennsylvania, in 1859, no petroleum was produced. Immediately after this discov- ery, explorations were begun elsewhere in Pennsylvania ; and these have been extended, practically all over the country, with the result of finding oil in the majority of the states, although the profitable production is confined to a few dis- tricts. Many remarkable developments have been made, par- ticularly those in 1885, when the importance of the Trenton limestone was first recognized. There are undoubtedly other fields yet to be discovered ; for even in as thoroughly explored a state as Pennsylvania, new fields of great impor- tance were discovered only a few years ago. Distribution of Petroleum. — Petroleum occurs, in rather lim- ited areas, in various parts of the United States. The well- known oil regions, which produce the greater part of the supply of the country, are the western Pennsylvania-New York field, two fields in Ohio, the West Virginia field, one in Colorado, and one in California. Although a few other states produce some oil, none of these are of immediate promise ; but the past history of the petroleum industry is such that it is not safe to make predictions with reference to the possible future of these districts. Outside of the United States, the principal oil fields are in the Caspian region, Canada, Japan, and New Zealand; but the United PBTBOLBUM, NATUKAL GAS, AND ASi'HALTUM. 339 States and Russia are far more important than all the others. Little need be said with reference to the distribution of petroleum, aside from the above general remarks and the statistics in the latter part of this section. Until 1875 all the petroleum of the country came from the Pennsylvania- New York field, which is continuous, and must therefore be considered as one field. Various oil-bearing sands of Devo- nian age are found there, in irregular areas, and since 1859 they have been productive. Even as late as 1891, important developments were made, in this district, by the discovery of an oil pool called the McDonald field, which, in the latter part of 1891, had a production of 84,000 barrels a day ; but this has decreased, and at the close of 1892 the daily flow was about 18,000 barrels. In the last six months of 1891, it is estimated that 6,000,000 barrels of petroleum were pro- duced from this field. Most of the old wells have dimin- ished their flow, and many of them are now non-productive. New supplies will probably continue to be found in this field at intervals ; but eventually this will cease to be the case, and the old ones will probably give out. This seems to be the future of the petroleum industry, and already there are signs of its approach. During 1892, West Virginia increased its output by sup- plies from newly discovered fields in the same general belt as that of Pennsylvania. Since 1885, Ohio has assumed marked importance in this industry by the discovery of oil in large pools in various parts of the Trenton limestone. In Colorado there is a small area, called the Florence field, which has produced, and still continues to produce, consid- erable oil from a bituminous shale in the upper strata of the 340 ECONOMIC GEOLOGY OP THE UNITED STATES. Cretaceous. The California oil comes from sands bedded with shales of Tertiary age. These oils are quite remarkable from the fact that they occur in highly tilted strata, instead of in nearly horizontal rocks, as is usually the case. In Russia, oil occurs in the region of the Caspian, in Canada in the province of Quebec, and oil is also found in Japan, in Peru, New Zealand, and in small quantities in several Euro- pean countries. Origin of Petroleum.^ — There are great variations in the character of petroleum, not only in different districts, but even in the same field._ Some are dark and heavy, others are comparatively light and clear, the former being better lubricating oils, the latter serving as a basis for the produc- tion of illuminating oils. In some, the solid basis is paraf- fin, but those of California have asphaltum for a basis. There is a resemblance between natural oils and certain oils pro- duced from the distillation of animal remains such as men- haden oil, and between natural gas and gases produced artificially from coal, and from the decay of organic remains. Indeed, natural gas is principally composed of marsh gas. This has led to the theory that these substances are the result of natural distillation of organic remains in the rocks, and this theory is quite generally accepted by Amer- ican students of the subject. It may be stated that theories have been offered to account for petroleum and natural gas by chemical reactions between inorganic substances; but, although offered by eminent chemists, the theory has little to recomroeftd it aside from the fact that changes such as are suggested would produce petroleum. The 1 This subject is discussed by J. P. Carll in Eeport III., Pennsylvania Geol. Survey, pp. 270-284. PETKOLBUM, NATUEAL GAS, AND ASPHALTUM. 341 geology of the oil fields excludes these theories. By the decay of vegetation hydrocarbons of gaseous, liquid, and solid nature result, and by a concentration of the solid and liquid products, through the loss of the gaseous hydrocar- bons, petroleum is produced, and by a still further process of concentration solid paraffins or asphalts are formed. A chemical analysis of natural oils and gases would show a close resemblance to those artificially produced, but the chemistry of the hydrocarbons is so complex that little can be given in this connection. Naphtha, benzine, illuminating oils, etc., compose it. While we must believe that these substances are derived from the decomposition of organic matter, there is an oppor- tunity for a variety of explanations of the process by which this was brought about. Some have held that vegetable matter has produced the hydrocarbons, and others, that the source is from animal fossils ; probably each and a combina- tion of the two are correct for different fields. A study of the stratified rocks shows that certain shales and limestones are highly bituminous and that some are foetid from the odour of decayed animal remains. There are abundant rea- sons for the belief that petroleum has resulted from the slow destruction of organic remains, both animal and vegetable, during the changes through which the rocks have passed. It has been suggested that the source of the hydrocarbons is the coal, these having been driven off, with comparative rapidity, by a process of destructive distillation analogous to the production of artificial oils and gases. Unfortunately for this theory the greatest supply of these substances comes from rocks below the horizon of the coal, and moreover the larger oil fields are in horizontal rocks which have undergone 342 ECONOMIC GEOLOGY OP THE UNITED STATES. very little metamorphism. Therefore, while it must be ad- mitted that this is a possible source, it is not the source of the bulk of our petroleum. Destructive distillation may- account for the oil in the tilted rocks of California, and for the Colorado oils, but it cannot be accepted for the fields of the east. The distribution of oil and gas through the rocks presents many interesting features. At first they were supposed to be confined to the rocks beneath the valleys, the theory of the well-drillers being, that in some way the surface topog- raphy influenced the distribution of the petroleum; but there is of course no such association. A thorough study of the oil fields thus far explored shows that, while this substance may occur in any stratified rocks, of almost any geological age since the Cambrian, the petroleum in a single area is confined to. a definite bed, whose depth from the surface and probable extent can be predicted with considerable accuracy. Taking our eastern fields as a basis, since they are so much better explored and understood, it is found that, in a single produc- ing field, the oil occurs in more or less restricted areas or " pools," and that the pools in the Pennsylvania-New York district are more or less linear in extent, with their longer axes in general parallelism with the axes of the Appalachian folds. In distribution and behaviour the oil has a certain resem- blance to underground water. This resemblance is noticed in the tendency of these substances to accumulate in porous strata bounded, above and below, by more impervious layers. Where these strata outcrop, oil sometimes oozes out at the surface, like a spring of water. When a well is drilled into an oil-bearing stratum, the petroleum rises to the sur- PETROLEUM, NATURAL GAS, AND ASPHALTUM. 343 face, after the manner of an artesian well, and at times, single wells produce many thousands of barrels in a day. The resemblance ceases here, and we find that there are certain marked differences. A supply of underground water is perennial, and, year after year, an artesian well will continue to flow with unabated volume because the surface rains soak into the earth and take the place of the water which escapes. But the supply of oil is the accumulation of ages, and, when once the stratum is exhausted of its store, no more will come, excepting, perhaps, after a long period of time, when fresh supplies have been formed. Moreover, while the force of ejection of the oil is, in part no doubt, hydrostatic, as in the case of artesian wells, yet there seems abundant reason to believe that this force is in no small degree due to the expansion of contained It might, perhaps, be expected that oil would accumulate more rapidly in mountainous regions where distillation of a destructive nature is in operation, such as that which drives off the volatile substances from coal to produce an- thracite. But probably this very force of metamorphism aids also in the distribution of these substances, chiefly by producing joints and fissures through which they can escape, imitating, in a natural way, the artificial process of tappings an oil pool by a drilled well. For the forma- tion of oil accumulations the strata must usually remain practically undisturbed. Under these conditions the so- called pools are formed, this name being given because the oil is distributed unequally, as if in pools. When such an area is reached by a drilled well, gas sometimes escapes, then oil, and finally salt water; but at times this 344 ECONOMIC GEOLOGY OF THE UNITED STATES. order is reversed, or in some cases oil first flows, or all three may come at once, or only one of the three substances may come, from a single well, throughout its history. There are probably various explanations for these phenom- ena, and several theories have been advanced to account for them. If the three substances are accumulated in a stratum, it is natural to expect that they will be stratified according to their specific gravity, the gas at the top and the salt water at the bottom. One of the old theories to account for the accumulation of these substances into pools or limited areas and for their irregularity of escape, is the Cavern Theory. This assumes that the gas, oil, and salt water have accumulated in subterranean caverns, of irreg- ular form, and that they occur in layers, the gas at the top, then oil, and finally salt water at the bottom. If the arch of the cavern be pierced by the well, the order of flow will be gas, then oil, and finally salt water; but if one end be encountered, near the lower levels of the cavern, salt water will first escape, while oil will come first if a point a little higher up on the sloping side of the cavern be encountered. There is very little reason to believe that this theory is applicable, and good reasons for doubting its value, for it is highly improbable that such caverns exist, particularly in a bed of sandstone or conglomerate, where caverns would be difficult of formation. Moreover, the well-borings show no signs of large cavities. Recently the Anticlinal Theory'^ has been brought into prominence by the rapid development of the oil fields of 1 1. C. White, The Mannington Oilfield and the Histoi-y of its Develop- ment, Bull. Geol. Soc. Am., Vol. 3, 1892, pp. 187-216. PKTKOLEUM, NATURAL GAS, AND ASPHALTUM. 345 West Virginia, which have been opened, in part, upon the basis of predictions made in accordance with this theory. It is, briefly, that beyond the main folds of the Appalachians the strata, on the bordering plateau at the western base of these mountains, were thrown into a series of waves or folds of slight elevation, and that the oil, furnished by the decom- position of organic remains, tending to accumulate in the porous strata, found it possible to accumulate in the highest parts of these strata ; namely, in the crests of the low anti- clines, while the intervening troughs or synclines were left barren, or nearly so. Gas would rise to the extreme crest, while oil and salt water would be found on the outside at a slightly lower level. This theory accounts for the general parallelism of the fields to the axes of the Appalachian folds, for their limited extent and distribution, and, indeed, for all the general features exhibited. There can be little doubt that the anticlinal theory is proved, so far as the West Virginia fields are concerned, and also that it accounts for some of the fields in Pennsylvania ; but there is good ground for doubting whether it can be extended to all of these fields. Some of the oil pools appear to be due to original irregularities of the oil-bearing stratum. These strata are of marine origin, and it is a familiar fact to be observed in all sediments from water, whether on the seashore, lake shore, or river banks, that they vary in char- acter from place to place. Thus, on a beach the material is pebbly in one place and sandy in another, and the same stratum may be sandy near shore and clayey off shore. Moreover, the sediments deposited opposite the mouths of rivers differ from those formed in the intervening areas. Therefore a horizon, such as one of the oil-bearing sands, 346 ECONOMIC GEOLOGY OF THE UNITED STATES. may vary markedly in even a small area. Perhaps the texture varies, or possibly more iron or lime were furnished in one place than in another, and this would allow some parts of the bed to become firmly and compactly cemented, while other portions remained loose and pervious. The stratum, below or above, which furnished the oil may have varied in its ability to supply the petroleum, and in one or all of these ways there may very well have been a marked variation in either the supply or the concentration of the gas or the oil, thus causing an accumulation into limited areas, pools, or pockets, and this theory may be called the Pocket Theory. The essential features of an oil pool are a source of supply and a porous stratum bounded above and below by more impervious strata. The source is some neighbouring layer rich in organic remains, and the porous stratum acts as a res- ervoir. The exact mode of accumulation may vary, the organic material being changed to oil and gas by a process of slow distillation, and gathered into the reservoir, which may be a porous pocket in an irregularly porous stratum, or else in the crests of low anticlines. This has been written with especial reference to the Appalachian oil fields; but, while the general remarks hold for some other fields, they cannot be extended to those of California. There, however, as probably also in all other oil fields, the source of supply is organic remains, although the exact mode of accumulation is different. Uses of Petroleum. — The remarkable growth of the kero- sene oil trade, as the result of the discovery of our large stores of petroleum, is a matter of history with which we are all familiar. In 1892, 54,291,980 barrels (of 42 gallons) of PETKOLETJM, NAT0EAL GAS, AND ASPHALTUM. 347 crude petroleum were produced in this country, and of this, 36,545,634 barrels were used in the manufacture of illumi- nating oil, while 17,676,212 barrels were used as fuel oil, and 70,134 barrels for lubricating purposes. Wonderfully expensive methods of piping are employed for the transpor- tation of this oil to distant points and also for its reduction ; but because of the great scale upon which these operations are conducted, these methods are economical. This has created an industry in which the United States holds almost a unique position. Not only is our home demand fully sup- plied, but the products of the petroleum industry find their way into nearly all the markets of the world. In 1891, 531,445,099 gallons of illuminating oils, valued at $34,879,759, were exported from this country, and over $11,000,000 worth of other products made from petroleum were also exported. Aside from the production of illuminating and lubricating oils, the product of some districts is used chiefly for local fuel. During the reduction of petroleum to illuminating oils, naphtha, benzine, and gasoline are formed ; and a solid residuum of the paraffin series, used in the manufacture of vaseline and other similar materials, is also produced. All of these substances are manufactured for export as well as for the home market. Petroleum must be classed with coal and iron as one of the most important mineral products of the country and one which has added largely not only to our industrial progress, but also to the comforts of living. Production of Petroleum. — Statistics for the production of petroleum in foreign countries are difficult to obtain, but the following tables show the distribution of the output in this country, and, in a very general and incomplete manner, in the foreign nations : — 348 ECONOMIC GEOLOGY OF THE UNITED STATES. PRODUCTION OF PETROLEUM IN THE UNITED STATES. Bakeels (42 Gallons). States. 1860. 1870. 1876. 1880. 1885. 1888. 1890. 1898. Pennsylvania ) and New York ' 500,000 5,260,745 8,968,906 26,027,631 20,776,041 16,488,668 28,458,208 32,080,000 Ohio 31,763 38,940 650,000 10,010,868 16,124,656 20,000,000 West Virginia . 120,000 179,000 91,000 119,448 492,678 1,000,000 Colorado . 297,612 368,842 700,000 California 12,000 40,562 825,000 690,833 307,360 485,000 Indiana 63,496 70,000 Total for the) United States i 500,000 5,260,745 9,132,669 26,286,123 21,847,206 27,612,025 45,822,672 54,344,500 In 1859, which was the first year of petroleum production, 2000 barrels were produced, and, from this time till the close of 1862, it is believed that fully 10,000,000 barrels of oil ran to waste in the Pennsylvania field, because there was no market for it. From 1859 to 1882, the output of Pennsyl- vania increased rapidly, the production in the latter year amounting to 30,053,500 barrels. There was then a period of exhaustion of old wells and a failure to open extensive new fields, which culminated in the very low production of 1888. Since then the discovery of new pools has caused a marked increase in the output, until, in 1891, the highest output ever reached, over 34,000,000 barrels, is recorded. Very nearly the same variations appear in the table of total output, since, until 1887, the production of the country was practically that of the Pennsylvania-New York field. The remarkable increase of output since 1887 is attributable, in large measure, to the development of the Ohio fields and the discovery of the new pools in Pennsylvania, although PETROLEUM, NATURAL GAS, AND ASPHALTUM. 349 the other oil-producing states have helped this increase slightly. At the close of 1891 the United States had produced, since the opening of the first well, 508,447,362 barrels of crude petroleum, of which 429,755,990 barrels, or 84.5 per cent of the total, came from the Pennsylvania-New York fields, and 64,377,499 barrels, or 12.7 per cent, from Ohio, these three states together having produced 97.2 per cent of the output of the country. In 1891, the Pennsylvania-New York field supplied 60.8 per cent ; Ohio, 32.7 per cent ; and West Vir- ginia, 4.4 per cent, of the total output of the country. PRODUCTION OF PETROLEUM IN THE WORLD. Metkic Tons (2204 Lbs.). Countries. 1889. 1890. 1891. United States . . . Russia Germany Peru Canada! Italy Japan 1 4,925,647 3,306,814 9,519 2,151 639,991 177 6,418,765 3,974,531 15,226 2,324 765,029 417 48,027 7,595,702 4,000,0002 15,315 755,298 1,155 The value of the crude petroleum produced in the United States in 1892 was 130,229,128. Natural Gas. General Statement. — In general, the description of petro- leum applies to natural gas. It belongs to the group of 1 Barrels. ^ Estimated. 350 ECONOMIC GEOLOGY OF THE UNITED STATES. hydrocarbons and is a member of the paraffin series. Marsh gas constitutes from 50 to 90 per cent of the Pennsylvania gas, and with this there is nitrogen, carbonic dioxide, and some other gases. The following analyses will give an idea of the chemical composition of some of the natural gases : — ANALYSES OF NATURAL GAS. FiNDLAT, Ohio. fostobia, Ohio. Saint Maky'8, Ohio. Stockton,! Califoenia. Pennsylvania. Hydrogen ... 1.64 1.89 1.T4 0.06 Very Uttle. Marsh gas . 93,35 92.84 98.85 88.00 Parafltas, 84.26-97.7. defiant gas , . . 0.35 0.20 0.20 Carbonic dioxide . . . 0.41 0.55 0.44 0.05 Less than 1 per cent. Carbonic acid 0.25 0.20 0.23 Oxygen . 0.39 0.35 0.35 0.06 Trace Nitrogen . 3.41 8.82 2.98 2-16. Sulphuretted hydrogen, 0.20 0.15 0.21 Trace. The geological distribution of natural gas very closely re- sembles that of petroleum, it being widely distributed through the strata from the early Palaeozoic to the present. Marsh gas, which is very similar to this, is being formed at present in swamps by the decay of vegetation. In Pennsylvania the natural gas is found chiefly in the Upper Carboniferous, in Ohio in the Trenton limestone, and more rarely and less abundantly in local reservoirs in the drift. As in the case of petroleum, a porous rock, vnth impervious enclosing strata, is the common reservoir, and the reason for this is the same in both cases. There is also a frequent association of gas with low anticlinal crests ; and, while it is frequently found 1 Incomplete. PETEOLEUM, NATURAL GAS, AND ASPHALTUM. 351 free from association with petroleum, this association is not uncommon. Natural gas has been found in nearly all the states and territories, but the most important sources are western Pennsylvania and New York, northwestern Ohio, and eastern central Indiana. The origin of this gas is the same as that of petroleum, the one being a gaseous, the other a liquid, representative of the paraffin series of which paraffin wax is the best known illustration of the solid form. Natural gas was known to exist in the very earliest days of the exploration of western New York, where it escaped from crevices in the rock. In 1821 a well was drilled at Fredonia, Chautauqua County, New York, and gas for light- ing purposes was obtained. Other wells were found later, in the same region, and in 1841 natural gas, which had long been known to exist in Virginia, was introduced into the manufacture of salt for purposes of evaporation. Gas was also found to exist in association with the salt in salt wells, but the most important development of the gas fields has come since the discovery of petroleum in 1859. The ex- tensive drilling for oil, which has been carried on all over the Union, has succeeded in developing gas fields, not only in association with petroleum, but also in regions where this substance is not found. Since 1880 gas has become an important factor in and near the oil fields. Aside from the sources of this substance above mentioned (Pennsylvania, Indiana, Ohio, and New York), soma is also produced in Kentucky, West Virginia, California, and, in still smaller quantities, in other states. Outside of the first four states there are very few uses for natural gas, and the indus- try of its production is therefore not as well developed as the quantity of this substance would seem to warrant. The 352 ECONOMIC GEOLOGY OP THE UNITED STATES. Ohio field has been found to extend into Ontario, and consid- erable is produced in this province. In China, also, wells have been bored, and large stores found, and natural gas has been discovered in other places ; but there is more of this substaftce in the United States than in any other country in the woild. When gas is first found, it issues from the wells with tre- mendous force, under the pressure of the strata and of its own compression. Four wells in the Findlay gas region each pro- duced over 1,000,000 cubic feet per day, and one, the Karg well, produced, at first, over 12,000,000 cubic feet per day. Some wells have had a pressure of 800 pounds to the square inch, and many have a pressure of from 400 to 500 pounds. The Findlay wells, when first found, in 1885, had a pressure of 450 pounds to the square inch, in 1886, 400 pounds, in 1889, 250 pounds, and in 1890 as low as 170 pounds to the square inch. These figures show that the gas wells are by no means permanent. Since 1888 the pressure, and conse- quently the output, of the great wells has been decreas- ing, and some which at first seemed inexhaustible are rapidly approaching the end of their productive days. The companies producing gas have recognized the probable fate of the industry, and are applying much more economical methods of using and distributing it. Already the natural pressure has been supplemented in some wells, by pumping, and, where this has been introduced, it will continue the gas supply a little longer ; but, in general, it is a last resort em- ployed in a nearly exhausted well. This failure of supply is exactly what was predicted by those whose studies of the gas and oil fields forced them to the conclusion that these substances were simply stored in the rocks, and not continu- ously supplied, as some well-owners believed. PETROLEUM, NATUKAL GAS, AND ASPHALTUM. 353 Uses of Natural Gas. — "When first found, the natural gas was of very little use, and immense quantities were allowed to escape. Its value soon became recognized, however, and efforts were made to introduce it for fuel and for illuminat- ing purposes. This is still practically the only use of gas, although it is also used in the preparation of lampblack for the manufacture of the carbon-points for electric arc lamps. Aside from the latter use natural gas is of im- portance only locally, and this is the first substance dis- cussed of which this is true. It cannot be exported, nor can it be conducted to any great distance from the wells. As a fuel, natural gas is used for heating and cooking, in the manufacture of iron and steel, for glass manufactur- ing, and, indeed, for scores of purposes where cheap fuel is needed. Gas has been so successfully introduced for these purposes, in the region near its source, that espe- cially prepared burners are introduced, and very little waste is now experienced; but, with the approaching exhaustion of the wells, serious problems are about to be presented; and, indeed, already some of the companies are refusing to supply large manufactories with this fuel. Probably new fields will be discovered, but it is hardly likely that in the old regions many important new ones will be found. Little by little the industry must fail; for, unlike most industries, this is dependent entirely upon local and com- paratively limited supplies ; and, while an iron foundry, by the transportation of iron from other fields, might survive the exhaustion of neighbouring iron mines, this is not possible in the gas industry. The following table shows the various uses for which gas was employed in 1889 : — 354 ECONOMIC GEOLOGY OF THE UNITED STATES. CONSUMPTION OF NATURAL GAS IN THE UNITED STATES, 1889. Cubic Feet. Various industrial establishments : brick and pot- tery burning, electric plants, machine shops, foundries, etc., 2360 establishments in all . . 236,900,000 Iron and steel mills 171,500,000 Heating and cooking 62,500,000 Drilling and operating oil and gas wells .... 30,000,000 Miscellaneous uses 25,000,000 Glassworks 18,750,000 Pumping oil 7^500,000 Total 552,150,000 Production of Natural Gas. — There is very little basis for an exact estimate of the production of this substance, since so much is wasted, and so many different ways are made use of, by the various companies, for measuring their production. The current method of estimating the natural gas output is to state the value of the coal which it has displaced ; but this sometimes underestimates and sometimes overestimates the value of the production. The following tables are based upon this method of estimate, combined with the known amount received by some of the companies : — PRODUCTION OF NATURAL GAS IN THE UNITED STATES. Stattes. 1885. 1887. 1888. 1889. 1891. Pennsylvania $4,500,000 $13,749,500 $19,282,375 $11,593,989 $7,834,016 Indiana . . 600,000 1,320,000 2,075,702 3,942,500 OMo . . 100,000 1,000,000 1,500,000 5,215,669 3,076,325 New York 196,000 883,000 332,500 530,026 280,000 Kentucky 2,580 83,993 West Virginia 40,000 120,000 120,000 12,000 35,000 PETEOLEUM, NATURAL GAS, AND ASPHALTUM. 355 In 1889, Pennsylvania produced over one-half of the supply of the country, Indiana about one-fourth, and Ohio nearly one- fifth ; or the three states together about nineteen-twentieths of the supply of the country. The rapid increase in Pennsyl- vania's output, which reached a maximum of over $19,000,000 in 1888, followed by a rapid decline, is a noteworthy feature of the table. Ohio has also rapidly increased its output, and this has been followed by a decline, while the Indiana output has gradually increased. NATURAL GAS PRODUCTION OF THE UNITED STATES. 1882 $215,000 1883 475,000 1884 1,460,000 1885 . 4,857,200 1886 10,012,000 1887 15,817,500 1888 22,629,875 1889 21,097,099 1890 18,742,725 1891 . . . 15,500,084 1892 . 13,000,000 Before 1882 much gas was produced, but it was practically all wasted. The wonderful increase from 1882 to 1888 and then the continuous and rapid decrease to the present time are very striking features of the table, and these variations are primarily due to Pennsylvania. The value of the natural gas produced in Canada, in 1892, was fl60,000. Asphaltum. Certain semi-solid bitumens, varying slightly in character, and to which different mineralogical names ^ are given, are 1 The names of the various varieties are albertite, asphaltum, hrea, elaterite, gilsonite, grahamite, lithocarhon, maltha, uintite, and wurtzilite. 356 ECONOMIC GEOLOGY OP THE UNITED STATES. included under the general term of asphaltum. In this country, as in many others, bituminous shales and limestones with very small percentages of bitumen are not uncommon and some of them are sufficiently bituminous to be employed directly, in place of prepared asphalt,^ while others are used as a source of asphalt. Bituminous sandstone is quarried extensively in Kentucky and California, while in Utah a bituminous limestone is used for a source of asphalt; and in this territory there is also found a variety known as gil- sonite. Recently an extensive deposit, which is called htho- carbon, has been discovered in western Texas, but as yet there has been no output. Other deposits are known to exist elsewhere in this country, but at present they are of little importance. The chief supply of the asphalt used in the United States comes from the island of Trin- idad, where the famous pitch lake occurs; but other re- gions, notably Sicily, also produce asphaltum. The origin of this substance is, in some places at least, from organic remains, by a slow process of distillation similar to that which produces petroleum. In the bituminous lime- stones and shales, bitumen, instead of petroleum, has resulted by the concentration of the solid parts and the dissipation of the volatile portions. This has resulted, in the sedimentary strata, from slow distillation ; but, in the neighbourhood of igneous rocks, it may have been caused by destructive dis- tillation. The resemblance between this mineral and petro- leum is shown by the fact that in the California petroleum the solid base is. a form of asphaltum. It has been suggested that the stages of change are first the transformation of 1 The term asphaltum is given to the unfinished product, and asphall is the commercial name for the finished product used in street-paving. PETKOLEUM, NATUEAL GAS, AND ASPHALTUM. 357 organic remains to oil, then to asphaltum, next to jet, and, finally, under suiScient metamorphism of the proper nature, to diamond. While this is purely hypothetical, it is not improbable. The chemical composition is closely like that of parts of some petroleums, and the California petroleum has asphaltum for a base. Products closely resembling asphaltum can be produced artificially. This substance is employed, in the form of asphalt, for paving streets, and this is by far its most important use ; but it is also made use of as a varnish for coating piles and wharf timbers. PEODUCTION OF ASPHALTUM EST THE UNITED STATES. Year. Short Tons. Value. 1880 444 $4,440 1885 .3,000 10,500 1890 40,841 190,416 1892 54,985 291,250 Owing to the cost of transportation, the greater part of the asphaltum produced in the United States cannot com- pete with that shipped from Trinidad and elsewhere, and our supply is consequently used chiefly near the point of production. In 1892, while we produced 54,985 tons, our imports amounted to 109,582 tons, the greater part of which came from Trinidad. Ozokerite. A mineral belonging to this series is mineral wax or ozokerite (ozocerite), which occurs in Galicia, in Austria- Hungary, but which has also been found near Thistle in Utah. It is a yellow mineral, grading to a dark brown. 358 ECONOMIC GEOLOGY OF THE UNITED STATES. sometimes greenish, and varies in hardness from very soft to the hardness of gypsum. It may be considered an altered form of a petroleum, robbed of its volatile substance, and more nearly resembling that of Pennsylvania than that of California. It is chiefly a solid paraffin with some ben- zine, naphtha, etc. The uses of this mineral are, as a substitute for beeswax, in the manufacture of candles, for purposes in which vaseline is employed, and as an insulator in electricity. Before 1888, when ozokerite was discovered in Utah, Galicia was the source of this mineral, which was first obtained there in 1862. Our product, in 1892, was 130,000 pounds, valued at $7800, while we imported 1,250,000 pounds. The industry of mineral wax produc- tion is slowly increasing. CHAPTER XVI. BUILDING-STONES AND CEMENTS. Building-Stones} General Statement. — The non-metallic structural materials may be divided into four groups, — building-stones, ornamental stones, natural and artificial cements, and clays. All but the last of these are included in this chapter, the clays being omitted here, since a very important use for these substances is the manufacture of pottery and ornamental vrare. Gypsum, which is also used for structural purposes, is omitted here, but is considered under fertilizers, since this is one of the most important uses of the mineral. Under building-stones is included the limestone burned and used for fertilizing pur- poses, and that, also, which is burned for lime to be used in plaster. For the term luilding-stones a more comprehen- sive word might be substituted, since under this heading is included, not only the stones used for building, but those also quarried for other structural purposes, such as pave- ments, fences, bridges, monuments, etc. ; but, although this is perhaps a poorly chosen term, it is employed here because it is in common use in the statistical works. Practically, none of these products are of value for expor- ^ The general subject of building- stones is treated by Merrill in his Stones for Building and Decoration, New York, 1891 ; and, in this connection, Burnham's Limestone and 3Iarhle will be found of value. The Tenth Cen- sus volume on Building-stone is also of value. 359 360 ECONOMIC GEOLOGY OF THE UNITED STATES. tation, but nearly every country, and, in our own country, nearly every section, produces its own supply. Thus, in regions of granitic rocks, granites are commonly used, while in sandstone regions, buildings and other structures are more commonly made of this stone than of any others. Only the very finest quality of stone is capable of profitable trans- portation, and hence we neither export nor import any but the best, usually ornamental stone. Where particular kinds and colours of marble are desired for interior decoration, or certain granites or marbles are needed for monuments, these are imported in some cases ; but the amount of these im- portations is very small, being greater for marble than for any other stone. Even within the country there is a very small amount of distant transportation. Certain colours of stone, needed for trimming, may be carried long distances where a particularly beautiful building is to be constructed ; and where cheap transportation by water is possible, even paving-blocks may be carried several hundred miles; but, notwithstanding these exceptions, the industry of building- stone production is essentially a local one. If statistics were obtainable of the distribution of the stone product which ' is actually sold, this would be found to be very marked, but not nearly so striking as it really is, since large quanti- ties of stone used for structural purposes are never put upon the market, but are quarried by the consumers. For this very reason the statistics of building-stone production, as given below, are far below the actual value of the industry. Granite. — -Under the term granite, as used in the trade, is included a great variety of igneous and metamorphic rocks, among which are the true granites ; and these, it is true, form the greater part of the so-called granites. Normal BUILDING-STONES AND CEMENTS. 361 granite, using the term in its strict scientific sense, is an igneous rock intruded at considerable depth into the earth, hence a plutonic rock, having a coarsely crystalline structure and being made up of a granular, interlocking series of quartz, orthoclase, feldspar, and grains of either hornblende or mica' (usually biotite), sometimes both. Other minerals are present, usually in minor quantities, and as accessories. The coarseness of texture varies greatly from an extremely fine grain to a very coarse rock ; and, indeed, some granites are entirely too coarse for use. The colour is also extremely variable, some being almost white, others a very dark green, some blue, and some red. These colours depend in cer- tain cases on the proportion ' of the constituent minerals, but most commonly upon a pigment contained in the feld- spars. Even in the same rock some of the feldspars are red, while others are white, and just what these pigments are is not always easy of determination. It is sometimes minute grains of iron and often a series of microscopic inclusions of some coloured mineral. Different kinds of granite are used for different purposes. For monuments and ornamental work there is an especial de- mand for coloured granite, generally of fine grain, which fits it for polishing ; but in many of the uses for which granite is employed the colour is of minor importance, durability, hard- ness, and cheapness (the latter depending upon the ease of working it) being of prime importance. This stone occurs in large masses almost entirely in the older rocks, and very com- monly in the metamorphio series. This is one reason why New England is of so much importance in the production of granite; but it is also necessary that the rock shall be so situated that it can be easily quarried and transported at a 362 ECONOMIC GEOLOGY OF THE UNITED STATES. slight cost to a good and permanent market. Thus it is that so many quarries are situated on or near the seashore where water transportation is possible. Another important feature in granite is to have its texture and colour moderately uniform, and many very beautiful stones are rendered of little value, for most purposes, by reason of frequent inclusions or bunches of darker coloured minerals, which give to the rock a blotched surface. These bunches are, in some cases, actual inclusions of some other rock torn off from the country rock, when the granite was forced in a molten condition through the strata into its pres- ent position. These are partly melted and merged into the granite, but the centre is frequently very little changed and forms a marked contrast to the stone. Even more common than these are the dark bunches known as basic secretions, which are accumulations of the darker minerals of the rock into bunches by a process analogous to concretion, which operates while the rock is cooling from the igneous condi- tion. Thus, hornblende, biotite, magnetite, and other basic minerals, gather together into bunches which are frequently so abundant that it is impossible to obtain a slab which is free from them. In some granites, particularly the colpured and darker kinds, these are very abundant, while in the lighter granites they are often nearly absent; and even in the same quarry there is considerable variation in the abun- dance of these patches. Granite is an extremely hard and durable rock. The quartz which it contains, although brittle, and thus affect- ing its crushing strength, is practically indestructible, and feldspar normally weathei-s slowly and does not seriously injure the rock. It is also nearly as hard as quartz and BUILDING-STONES AND CEMENTS. 363 somewhat less brittle. The weakest parts of the stone are the basic minerals, chiefly the biotite, hornblende, and mag- netite, which are generally in less abundance than either the quartz or feldspar. Under the influence of the weather these begin to decay to other minerals, of which the oxides of iron are the most prominent. It is this which causes the red stain or rust upon joint planes, sometimes extending into the rock for a distance of several inches. Quarrymen call this the " sap," as if it were rising from the granite and passing out, while in reality it begins at the surface of the joints and slowly extends inward as fast as the percolating water can effect the necessary changes in the minerals. At first this does not materially weaken the rock, although it soon com- bines with other changes, particularly the kaolinization of the feldspar, and causes the granite to crumble. For a long time this "sap" stain was believed to ruin the stone, but recently it has been introduced into buildings; and, when the main part of the structure is composed of this rusted rock, trimmed with a lighter coloured stone, a very beauti- ful building is constructed. Instead of being thrown away, as it has been in the past, this rusted granite, because it is comparatively scarce, promises soon to become one of the most valuable products of the granite quarry. This rock is so hard that but for the presence of planes of mechanical weakness it could not be utilized for many purposes for which it is now so valuable. These planes are of two kinds, — joint planes and microscopic planes (rift), along which the rock tends to split. There are ordinarily four sets of joint planes in a granite quarry (Plate II.). One of these is a nearly horizontal jointing, which some- times assumes an angle of 15° or 20°, and is the result of 364 ECONOMIC GEOLOGY OF THE UNITED STATES. the contraction of tlie rock during cooling. By this set of joints the granite is traversed at various intervals, the divisional planes forming dome-shaped blocks with a radius of many yards, sometimes of several hundred feet. In some quarries the joints of cooling are so numerous that large blocks cannot be extracted ; but in others, where the horizontal joints are several yards apart, it is possible to obtain immense blocks of the granite. The other three sets are nearly vertical, two of them meeting at an angle approaching a right angle, while the third cuts diagonally the rhomboidal blocks thus formed. These are joint planes, partly of contraction, partly of mechanical origin, the re- sult of folding and crushing of the granite during sub- sequent movements of the rocks. As in the case of the nearly horizontal joints, there is great variety in the num- ber of the planes of breakage, and while sometimes they are twenty, thirty, or even as much as fifty feet apart, in other places they cut the rock in such numbers that it breaks into small pieces, a veritable fault breccia, which ruins the granite for economic purposes. These joint planes are of great importance in quarrying, since they form bounding planes, beyond which the charge of powder used in blasting will not break the rock. A series of smooth, naturally-formed working faces are thus furnished, and the work of quarrying greatly facilitated. Near the surface the joint planes furnish channels for the passage of underground water ; and it is for this reason that their faces, and the granite for some distance in from these, are discoloured by iron rust ; but as the depth of the quarry increases, the joint planes become less numerous. This shows that the joints are, in some cases at least, merely BUILDING-STONES AND CEMENTS. 365 microscopic planes of splitting developed by percolating water. The green seams which are present in many quar- ries illustrate this still better. These are joints, along which some chloritic minerals have accumulated, and which are called blind seams by the quarrymen when the chloritic minerals are absent or not present in sufficient abundance to be indicated on the surface of the freshly quarried rock. Even after the block has been blasted from the quarry, these seams may not be visible, and sometimes, during the final shaping of the stone, it splits along one of these invisible planes, and causes the loss of all the labour employed. This is not a very common occurrence, but it is interest- ing for the purpose of showing what joint planes prob- ably are. Even more important than the joints are the microscopic planes of weakness known by quarrymen as " rift." ^ Exam- ined with the microscope, these are shown to be microscopic breaks and tiny faults crossing all the minerals, but usually not with sufficient development to injure the strength of the rock. In well-rifted granites these planes of breakage can be seen with the naked eye; but at times they are shown only when the rock is split, by a tendency to a smooth fracture in certain dii'ections. There are three sets of smooth-fracture planes in some quarries, the most pro- nounced vertical plane being called the " rift " ; the second, the "cut-off"; and the third, a horizontal plane, the "lift." One of the first things to be determined in opening a quarry 1 The remarks upon rift are based upon a study of the granite in the quarries at Cape Ann, Massachusetts. So far as is luio-vm, studies of this phenomenon similar to those made by the author have not been carried on elsewhere, although rift is common in granite, 366 ECONOMIC GEOLOGY OP THE UNITED STATES. is the direction of these planes, and in drilling holes for splitting the rock these directions are followed. The rift furnishes the direction for the greatest length of the block the cut-off for the least important end, and the lift for cleaving the block upon the third side. "When these planes are well developed, large blocks twenty or twenty-five feet square, and even more, are readily split from the quarry, with such smooth faces that very little dressing is needed to prepare the rock for polishing. In no class of work is this tendency of splitting so needful as in the preparation of paving-blocks, the cheapness of which depends upon the facility of breaking in three directions. Aside from granite proper, many other igneous and some metamorphic rocks are used as granite, and called by this name in the market. One of these is gneiss, a metamorphic rook, which, in some cases, so closely resembles a granite that only a careful study serves to distinguish it. This rock, however, frequently has a lower crushing power than granite, because of the presence of the gneissic structure, which is a direc- tion of weakness, often very marked. One of the principal objections to gneiss is the lack of uniformity of texture and colour, which, excepting in unusual cases, is not so good as in ordinary granites. Much gneiss, however, which is quar- ried and sold as granite is a really good stone which cannot be distinguished from a good granite by the ordinary char- acters of economic importance. Very nearly every igneous rock is quarried and sold as granite,^ and some of them are not seriously inferior to true granite. Syenites, in which there is no quartz, are not as strong chemically, as true 1 Upon pages 598, 599, Eleventli Census volume on Mineral Industries, will be found, tabulated, the various varieties of rook sold as granite. BUILDING-STONES AND CEMENTS. 367 granites; but they are of better quality than many of the igneous rocks. The basic rocks, such as diabase and diorite, contain minerals which decay so readily that they are gen- erally unfit for exposed work. By far the greater part of the rock quarried and sold as granite is normal granite; but since so much that is not of this species is sold under this name, one should, before using any other kind, carefully study the character of the rock, provided a use is to be made of it which requires durability and strength. Granite is employed for a variety of purposes ; and its value varies greatly, according to the use to which it is to be put and the location of the quarry. In 1889 the total value of the granite produced in the United States was as follows : — VALUE OF THE GRANITE PRODUCED IN THE UNITED STATES, 1889. Building purposes $6,166,034 Street work 4,456,891 Cemetery, monumental, and decorative purposes, 2,371,911 Bridge, dam, and railroad work 1,238,401 Miscellaneous uses 230,858 Total value $14,464,095 This represents a total of 62,287,156 cubic feet of granite actually sold, but makes no allowance for a not inconsider- able amount quarried and used by private individuals and corporations, but not placed upon the market. Large quan- tities of granite are wasted in the course of quarrying and dressing operations. 368 ECONOMIC GEOLOGY OP THE TTNITED STATES. PRODUCTION OP GEANITE IN THE UNITED STATES. States. 1880. 1889. 1891. Massachusetts Maine California Connecticut Georgia ......... New Hampsliire Rhode Island Vermont Pennsylvania $1,329,315 1,175,286 172,450 407,225 64,480 308,066 628,000 59,675 211,454 12,503,503 2,225,839 1,329,018 1,061,202 752,481 727,531 931,216 581,870 623,252 $2,600,000 2,200,000 1,300,000 1,167,000 790,000 750,000 750,000 700,000 575,000 Total for the United States . $5,188,998 $14,464,095 $13,867,000 In 1891 nine states, Maryland, Wisconsin, Colorado, Mis- souri, New Jersey, Virginia, New York, Delaware, and South Dakota, named in the order of their importance, produced more than $100,000, and less than |500,000, worth of gran- ite. It will be noticed that all the New England states are included in the first eight granite-producing states of the Union, this being the first economic product in which any one of them has held a high rank. During the year 1891, 18,167,000 of the total output of the country came from these states. Nearly the entire supply came from the east- ern states, and the greater part of this from the states of the extreme east. The rapid development of the granite indus- try is shown in the table, but in the last year a considerable decline is noticed. Particularly striking is the development of the industry in Georgia, Vermont, California, and Con- necticut. BUILDING-STONES AND CEMENTS. 369 Sandstone. — Sandstone, being a sedimentary rock, will naturally be found where sedimentary strata abound ; and in our country these conditions are most markedly developed in the central states. None is found in the metamorphic region, excepting in isolated basins, where later rocks have accumulated, as in Connecticut. Very little is produced in the Cordilleras, but less because of its absence than by rea- son of the difficulty of iinding a market for it. The geological age is very variable, and sandstones are found in all sedimentary strata from the Cambrian to the Tertiary ; but the greater part of our supply comes from the Palaozoic in the central states and the Triassic in Penn- sylvania (in part). New Jersey, and Connecticut. The rock is composed of grains of sand, usually of quartz sand, with some feldspar, mica, etc., cemented, sometimes by silica, but more commonly by iron or by carbonate of lime. It is, therefore, a very good building-stone, provided the grains are firmly cemented. Usually the crushing power is not great ; but owing to the abundance of quartz, the chemi- cal durability is very marked. If the cement is silica, the rock is as durable as any common rock can be ; but such sandstones, or quartzites, are not commonly used, because of the difficulty of quarrying and dressing so hard a rock. With a firm lime or iron cement the stone is sufficiently durable for ordinary purposes ; but even in such cases, and much more markedly when the cement is not firm, water dissolves the cement, and forms crevices, which heat and frost expand, causing the grains of sand to fall apart and the stone to crumble. The effect of weathering is very well shown in many old buildings made of sandstone ; but there are such buildings, many centuries old, which are sufficiently well 370 ECONOMIC GEOLOGY OP THE UNITED STATES. preserved for use at present. It is not as durable as good granite, but is one of the best building-stones. In the texture there is great variability, though this is not as marked as in granite ; for, when the grain is coarse, the rock is a conglomerate, and, ordinarily, this stone is not suited for building purposes. From this extreme, sandstones grade to a very fine-grained rock; and some of these are almost clay rocks, being, properly speaking, argillaceous sandstones. The colour is also variable : blue or green, in shades of varying intensity, as well as red, pink, brown, and white being the most common; but in the sandstones there is an almost infinite variety of colouring. According to the localities from which the stone is obtained, and fre- quently to the colour or texture, various commercial names are employed, such as blue or buff Amherst (Ohio) sand- stone ; Portland (Connecticut) brownstone ; freestone, a name given to sandstones which may split easily or freely in various directions ; Berea (Ohio) grit, etc. The method of quarrying sandstone varies greatly, accord- ing to the locality and character of the stone; but, in aU cases, the fact that it is a sedimentary rock aids the quarry- ing, by giving one direction of easy splitting parallel to the bedding. Where the strata are thick bedded, that is, with the parting planes of stratification far apart, it is often pos- sible to obtain large blocks ; but in this case the quarrying operations are more difficult, and blasting is resorted to for the purpose of breaking the rock across the bedding. In thin-bedded sandstones channelling-machines are employed to cut from layer to layer, and, in some of the Connecticut brownstone quarries, the rock is grooved with pickaxes, and then split by driving wedges at intervals in the grooves ; but BTJILDING-STONBS AND CEMENTS. 371 this is possible only when the rock is soft. In all quarrying operations vertical joint planes are of great service, and this is true of sandstones as well as of other rocks. (/^These joints prevail throughout all strata, although they are sometimes absent. \ The value of sandstone varies greatly vrith the colour, texture, and the demand for particular kinds. During the census year 1889, 71,571,054 cubic feet of sandstone were quarried and sold for the following purposes: — VALUE OF THE SANDSTONE PRODUCED IN THE UNITED STATES, 1889. Building purposes $7,121,942 Street work 1,832,822 Bridge, dam, and railroad work . . . 1,021,920 Atrasive purposes 580,229 Miscellaneous 259,144 Total for all purposes $10,816,057 PRODUCTION OP SANDSTONE IN THE UNITED STATES. States. 1880. 1889. 1891. Ohio Colorado Connecticut Pennsylvania New York $1,871,924 9,000 680,200 627,943 724,556 $3,046,656 1,224,098 920,061 1,609,159 702,419 $3,200,000 750,000 750,000 750,000 500,000 Total for the United States . $4,780,391 $10,816,057 $8,700,000 The bluestone industry is included in the statistics for 1880 and 1891. A marked increase is noticed in the produc- 372 ECONOMIC GEOLOGY OP THE UNITED STATES. tion of the country and of some of the states, notably Colorado and Ohio, between 1880 and 1889, and a marked decline, from 1889 to 1891, in the production of all the states, excepting Ohio, which is pre-eminently the sandstone- producing state of the Union. Seven states, Wisconsin, Massachusetts, New Jersey, Minnesota, Michigan, California, and Missouri, named in the order of their importance, pro- duced between |100,000 and |500,000 worth of sandstone in 1891. Bluestone. — A very fine-grained variety of shaly sand- stone, usually of a bluish colour, and consisting of particles of silica and some argillaceous matter, cemented by silica, is included under this heading. Ordinarily in statistical studies this rock is included under the sandstones ; but in the Eleventh Census report it is given a separate considera- tion, because the rock differs from sandstone both in char- acter and use. The stone, which is intermediate between a shale and a sandstone, might, with propriety, be called a siliceous shale. Its colour is usually a dark blue, but some- times it is light blue, sometimes green, and, in some cases, even brown. The value of the stone depends upon its fine texture and hardness, in part, but chiefly upon its thin- bedded nature, which allows it to be obtained in thin slabs suitable for flagging. This is its principal use, although it is being introduced for other purposes where thin slabs are needed. In the bluestone flags there are frequently pre- served most excellent ripple marks, which prove that when it was formed, shore-line conditions prevailed at the point of deposition. New York is the principal bluestone-producing state, and it is found there in several counties, chiefly in the central BUILDING-STONES AND CEMENTS. 373 part of tlie state. Both Pennsylvania and New Jersey also produce flagstones of this type. The following table shows the value of the industry, but does not give returns from a large number of small quarries, which produce small quan- tities of flagging for local purposes. Many of these quarries are opened by farmers, and worked at intervals when farm- ing work is not pressing. PRODUCTION OF BLUESTONE IN 1889. New York .... ... $1,303,321 Pennsylvania .... . 377,735 New Jersey . 8,550 Total $1,689,606 Slate. — This rock is formed by the alteration of clay strata, of sedimentary origin, and the slaty cleavage is a new structure imposed by pressure and metamorphism, which have sometimes operated even to the extent of destroying the original bedding. The new structure, which is called slaty cleavage, is developed at right angles to the direction of the pressure, and consists in the formation of new minerals, chiefly hydrous and other micas, which give to it the shiny surface of the slate faces and the ease of splitting in a given direction, parallel to the faces of the mica plates, and dependent upon the general parallelism of these plates. It is an intermediate stage between clay rocks (such as shales) and mica schist. The sedimentary origin of the rock is sometimes shown by the presence of bedding planes, usually at an angle with the cleavage, and more rarely by the presence of distorted fossils. In colour the slate is usually slate-blue; but there are green, brown, purple, and red 374 ECONOMIC GEOLOGY OP THE UNITED STATES. slates. These shades depend upon the prevailing colour of the component minerals or upon some stain or pigment, the red and brown being due to iron, the purple to manga- niferous minerals, the green to chlorite, and the blue to a combination of chlorite, carbonaceous matter, and other substances. Slates may be of any age where metamorphism has altered clay rocks to the stage of slates. They are almost uni- versally absent from the Archean, because, if clay rocks ever existed there, they have passed the slate stage of meta- morphism and become mica schists. These rocks are usually absent from the strata of post-Palseozoic age, for the reason that rocks of this age have not usually been exposed to extensive metamorphism. Still, in California the strata of the Sierra Nevada consist in part of slates of Cretaceous age, and there are more recent slates elsewhere. The Palseozoic age, and of this the earliest members, is the most important slate-bearing series both in this country and elsewhere. This rock is widely distributed, but the most important states are situated in the Appalachian and New England regions, where there is a belt of Cambrian and Silurian age, extend- ing from Vermont to Georgia. The value of slate depends upon the presence of the remarkable cleavage which admits of its being split readily in a single direction so that thin sheets of moderate size can be obtained. In quarrying slate, joint planes are of great importance ; but when they are too numerous, the rock splits into such small blocks that slate for tiling cannot be ex- tracted. While this rock is extremely common, good roof- ing-slate is comparatively rare, because either the texture is not uniform, or the colour not suitable, or the cleavage not BUILDING-STONES AND CEMENTS. 375 properly developed, or joint planes too numerous. Many slates, called argillites, have not had the slaty cleavage developed to a marked degree, either because of the original texture, or the fact that metamorphism has not been suiS- ciently powerful. On the other hand, some slates have such a shaly structure that the flakes are too thin for use ; others have several cleavages, which cause the rocks to split with an irregular surface ; and in some the bedding is not suffi- ciently destroyed to prevent its furnishing a second plane of cleavage. A good roofing-slate must be massive and strong, with only one cleavage, which must be well devel- oped; and it should have a uniform texture, a permanent colour, and should not be too brittle for cutting into regular forms. While the greater part of the slate is dark blue, the light blue, green, red, and other colours are used for figures, margins, and, in general, for relieving the monotony of a single colour in roofing. By far the greater part of the supply is used for roof- ing, but some is also consumed in the manufacture of slates for school purposes, for strips, flagging, sills, mantels, wash- bowls, and many minor purposes, where an easily worked rock of uniform texture and colour is desired. Marbleized stone, which is being introduced for interior work, in imita- tion of banded and coloured marble, is made by a process of graining with colours upon slate tablets and slabs. Some of this work is very beautiful, but the fact that it is an imita- tion, and not permanent, is liable to prevent its general in- troduction. The rapidly increasing use of metal for roofing is interfering with the consumption of slate for this purpose, particularly in the east. In 1891 the total consumption of slate was valued at 13,825,746, of which 13,125,410 worth 376 ECONOMIC GEOLOGY OP THE UNITED STATES. was used for roofing purposes, this amount representing 893,312 squares of slate. PEODUCTION OF SLATE IN THE UNITED STATES. States. 1880. 1889. 1891. Pennsylvania $863,877 $2,011,726 $2,141,905 Vermont 352,608 842,013 955,617 Maine 83,800 219,500 250,000 New York 95,500 126,603 176,000 Virginia 51,000 113,079 127,819 Maryland 56,700 110,008 125,425 Total for the United States . $1,529,985 $3,482,513 $3,825,746 Limestone. — Deposits of carbonate of lime are sometimes precipitated from solution, but most frequently they are the accumulations of animal remains, generally of coralline animals. By these agencies vast stores of limestone have been built in all geological ages, and consequently every part of the country produces this stone. In Florida, and in many oceanic islands and coral reefs, accumulations of recent shells and coral fragments have been loosely cemented, forming a coquina which is used locally for building purposes. This coquina differs in no essential particular from true limestone, excepting in the degree of consolidation ; and since it is being formed under our very eyes, it serves as an excellent illustration of the ease with which rocks may be consolidated when there is present an abundant supply of a very soluble mineral, such as calcite, which is the cementing material of limestone. BUILDING-STONES AND CEMENTS. 377 In colour limestone varies markedly, from black to pure white, with abundant blues, browns, and grays. The text- ure varies from a very fine grained compact rock to a semi- crystalline, and even a very coarsely crystalline marble com- posed of calcite crystals. It may be nearly pure carbonate of lime, or a nearly pure magnesian carbonate or dolomite ; it may be a black carbonaceous or bituminous limestone; or it may pass by gradations from an argillaceous limestone to a limy shale; and between these various kinds there is every gradation. Under the term limestone should properly be included only those rocks which are composed chiefly of carbonate of lime ; but commercially, siliceous, argillaceous, and mag- nesian limestones are all included under limestone. More- over, there is a peculiar complication resulting from the attempt to separate marble from limestone. When a lime- stone has been metamorphosed, the carbonate of lime becomes altered to crystalline calcite, and the impurities gather together either in bands of different colours or in bunches of various minerals. This results in the formation of true marble, which should very properly be separated commercially from ordinary limestone, since it is metamor- phosed and crystalline, and, being capable of a high polish, serves for purposes for which ordinary limestone cannot be used. But under the term marble, in its commercial sense, is included many non-crystalline limestones, which, by polishing, show either banding or some desired colour, such as black. Consequently marble in its commercial significance is made to include stone which is not true marble. Nor is the term limestone any more exact, since, not only does it include many very impure limestones, but 378 ECONOMIC GEOLOGY OF THE UNITED STATES. also true marble, when this is not situated in positions favourable for quarrying, or has not a sufficiently fine text- ure, or cannot be obtained in sufficient quantities, or in large blocks. Commercial limestone may be said to be any rock contain- ing a sufficient quantity of carbonate of lime to pay for burn- ing ; and commercial marble may be defined as any limestone, crystalline or non-crystalline, which is susceptible of a polish, and has a colour and texture suitable for ornamental work, and a position favourable for economic extraction. The terms are therefore far from scientific. Properly speaking, marble is metamorphosed and either partly or completely altered limestone, usually semi or wholly crystalline. But since there is every gradation from one form to the other, it is difficult to always distinguish them, as, indeed, it is in the case of all sedimentary rocks, for there is every gradation from conglomerate to sandstone, from sandstone to shale, from shale to limestone, and from limestone to marble. In 1889 the total supply of limestone produced in the country was used for the following purposes: — USES OF LIMESTONE IN 1889. Lime $8,217,015 Building 5,405,671 Street work 2,383,456 Flux . . 1,569,312 Bridge, dam, and railroad work . 1,289,622 Miscellaneous 230,103 Total $19,095,179 For some of these purposes it is not necessary that the rock should have particular qualities, but for others it should BUILDrNG-STONBS AND CEMENTS. 379 be comparatively pure. This table does not fully repre- sent the value of the industry, particularly that part of it which is represented in the manufacture of lime, and that used as a flux. Full returns have not been obtained from many blast furnaces which quarry their own flux, and there are, in operation upon farms, large numbers of lime-kilns for burning limestone to be used either as a fertilizer or a plaster. These two industries should have their total increased; and probably the total value of the limestone quarried and used for all purposes is over $21,000,000. PEODUCTION OF LIMESTONE IN THE UNITED STATES. States. 1880. 1889. 1891. Indiana Pennsylvania Illinois Missouri Ohio $593,375 240,934 1,320,742 421,211 669,723 207,000 189,320 201,593 $1,889,336 2,655,477 2,190,607 1,859,960 1,514,934 1,523,499 1,708,830 813,963 613,247 $2,100,000 2,100,000 2,030,000 1,400,000 1,250,000 1,200,000 1,200,000 675,000 600,000 New York Wisconsin Minnesota Total for the United States . $6,856,681 $19,095,179 $15,792,000 The combined value of the marble and limestone indus- tries in 1880 amounted to only 16,856,681, while in 1889 it exceeded 125,500,000, showing a striking increase in ten years. Thirteen states, California, Iowa, Alabama, Kansas, Kentucky, Nebraska, Texas, Vermont, Virginia, Maryland, 380 ECONOMIC GEOLOGY OP THE UNITED STATES. Connecticut, Massachusetts, and New Jersey, named in the order of their importance, each produced over flOO,000 and less than $500,000 worth of limestone. Almost one- half of the limestone of Indiana and Illinois is used in building, nearly all of the output of Pennsylvania is used for lime and flux, and all of the output of Maine is manufactured into lime. The following table shows the rank of the various states in the several industries : — USES OF LIMESTONE BY STATES, 1889.1 TJSES. Penn- sylvania. Illinois. Indiana. Mis- souri. New York. Ohio. Maine. Lime $1,195,955 VIII. 1866,245 $340,815 VII. $465,390 III. $837,618 $581,325 $1,528,499 Building . VIII. 288,481 1,084;656 994,318 IIL 542,871 rv. 444,291 407,388 Street work IX. 72,512 505,576 III. 816,722 6701851 rv. 197,091 183,'2S5 Flux. 949,083 166,507 XXIII. 1,056 XVI. 5,691 vn. 82,750 III. 105,968 Bridges, dams, etc.. IV. 155,658 I. 233,710 III. 169,720 II. 175,786 124,518 Marble. — • Vermont is the principal marble-producing state of the country, the most important quarries being situated near Rutland, where there are extensive beds of a well-crystallized white and blue banded, and a clouded blue marble associated with a pure white crystalline marble. In the West Rutland quarries the strata dip to the west from a gentle slope to a dip of nearly 80° ; and, in these beds, quarries have been opened to a depth of over three 1 The numerals refer to the relative rank of the various states in the dif- ferent branches of the limestone industry. BTJILDING-STONES AND CEMENTS. 381 hundred feet. This belt of limestone extends, with greater or less continuity, to Long Island Sound, but, in the greater part of it, the marble is not suitable for ornamental pur- poses ; and, where quarried, is used chiefly as a source for lime. The so-called marble of Tennessee is not in reality a marble, but is a partly metamorphosed limestone in which the abundant fossils still show plainly, and hy their differ- ence of colour and their form, give to much of it its particular value. There is a considerable variety of colour, from light pink to chocolate brown, and often mixtures of these colours. In New York a coarsely crystalline, mottled, and banded blue, greenish, and white marble is found in St. Lawrence County ; and in Westchester County a mottled dolomitic marble is quarried. A dull brown limestone, containing fossils, is obtained in Greene County, and a black limestone occurs at Glens Falls, in Warren County, New York. Georgia, Maryland, California, Penn- sylvania, and Virginia are also marble-producers, and in some other states this stone has been found. It may be safely predicted that the best marbles of the country have not yet been exploited ; for, in the Cordilleras, there are exten- sive deposits of beautiful and variously coloured marbles, which will some day rival the best Italian products. As in the case of nearly all building-stones this region, be- cause of its inaccessibility, has not been developed ; but even at present it would be possible to put upon the market some of these beautiful stones. In the Eleventh Census report both serpentine and onyx are included under marble, and we have no recent statistics of the production of these ornamental stones. Onyx is 382 ECONOMIC GEOLOGY OP THE TJNITBD STATES. found in this country only in the western part. There is a deposit of this stone in San Luis Obispo County, Cali- fornia, but, although it resembles the Mexican onyx, and is very beautiful, it has not as yet assumed marked importance, because of its inaccessibility. At present onyx is quarried in Arizona, about thirty miles east of Prescott. It outcrops here in a bluff, and is stratified with a breccia, being, apparently, a precipitation from lime-bearing waters which have received their carbonate of lime by percolation through the neighbouring igneous rocks. This onyx compares favour- ably with that of Mexico, but, although some is sold, our chief supply of this stone still comes from the latter country. Serpentine is known to exist in various parts of the belt of metamorphic rocks, from New England to Georgia, and also in the Cordilleran metamorphics ; but it rarely occurs in sufficient abundance and of the proper colour to be of economic value. There are, however, serpentine quarries in Maryland, from which a stone varying in colour from pale to dark green is produced. Serpentine is a product of metamorphism and alteration from certain rocks and minerals, notably from olivine and olivine-bearing rocks. Over 80 per cent of the marble consumed in this country is produced at home, but considerable ornamental stone for interior decoration is imported, principally from Carrara in Italy, from which place we obtain three-fourths of our imports of this stone. Marble is used almost entirely for interior decoration, for ornamental work, monuments, grave- stones, and some of the more costly buildings. It is not nearly so commonly used for building purposes as the other stones. BUILDING-STONES AND CEMENTS. 383 PRODUCTION OF MARBLE IN THE UNITED STATES. States. 1880. 1889. 1891. Vermont #1,340,000 $2,169,560 $2,200,000 Tennessee 173,600 419,467 400,000 New York 224,500 354,197 390,000 Georgia 196,250 275,000 California 87,030 100,000 Maryland 65,000 139,816 100,000 Pennsylvania .... 45,000 Total for the United States. . $2,033,595 $3,488,170 $3,610,000 Summary of Building-Stone Production.^ — The ten lead- ing stone-producing states in 1889 were Pennsylvania, Ohio, New York, Maine, Vermont, Massachusetts, Missouri, Illi- nois, California, and Connecticut, all^ofwhich produced more than $2,000,000 worth of stone^in the last census year. Five other states, Indiana, Colorado, Wisconsin, New Jersey, and Minnesota, produced over $1,000,000 worth of stone in 1889. Forty-four states and territories produced 153,085,620 worth of stone for building and other purposes. Of this total, Pennsylvania supplied 18.8 per cent, or 17,319,199 worth of stone. All commercial varieties are found there, but the chief products are limestone, slate, and sandstone. Ohio, which ranks as the second most important 1 Tor a more complete statement of the economic importance of the stone industry in the various states of the United States, reference may be made to the Eleventh Census volume on Mineral Industries, pp. 595-666, and the Mineral Besources of the United States, Day (U. S. Geol. Survey) 1889- 1890, pp. 373-440. An excellent book upon the general subject of building- stones is Merrill's Stones for Building and Decoration, New York, 1891. 384 ECONOMIC GEOLOGY OF THE UNITED STATES. stone-producing state, supplies almost exclusively sand- stone and limestone, in the former of which it holds first rank. All varieties of stone are obtained in the third state, New- York, but the most important are limestone and bluestone. Maine owes its rank to the numerous granite quarries, and to the industry of lime production, for which purpose the entire output of limestone is employed. In Vermont the most important stone is marble, but slate is also quarried extensively, and in this industry Vermont holds second place, while in the production of marble it has an output nearly twice as great as all the other states combined. The granite industry, in which Massachusetts holds first rank, is the only important stone industry of the state, although small quantities of sandstone and limestone are also obtained. Missouri produces principally limestone and some granite, Illinois practically nothing but limestone, California supplies stone of several varieties for local and Pacific Coast con- sumers chiefly, and Connecticut is a producer of granite and sandstone. Indiana leads in the production of lime- stone, and this makes the greater part of its stone output ; Colorado produces principally sandstone ; Wisconsin chiefly limestone ; New Jersey, sandstone, slate, granite, and lime- stone ; and Minnesota, limestone and sandstone. It will be noticed that the metamorphic rocks, slates, and marbles, and the granites, occur almost exclusively in the belt of metamorphic rocks extending from Canada to Georgia and in the area of metamorphics about Lake Supe- rior. Other metamorphic areas, particularly in the Cordil- leras, contain stores of these stones, but they will not be extensively quarried, except for local purposes, for the reason BUILDING-STONES AND CEMENTS. 885 that they cannot compete with the eastern stone found near the market. The sedimentary rocks, limestones, bluestones, and sand- stones, are obtained principally from the Central States, where the strata are all of Palaeozoic age and nearly hor- izontal. Being horizontal, they are not too much altered or broken, and yet, on account of their great age, they are sufficiently cemented and indurated for building purposes. Not a small percentage of these stones comes from the strata of the same age, which are folded into the Appa- lachians; and by far the greater part of the Cordilleras are made up of similar sedimentary rocks, which, for the same reason that applies to the metamorphic and igneous building-stones, are not of value except for local purposes. There is no need of importing any kind of building-stone, and, if called upon, we could quarry enough of nearly all kinds of stone to supply the needs of the world. No other nation has an output of building-stone so varied and so great as that of the United States, and no other nation has such immense stores which are of good quality, but of no immediate value because of the absence of a market. As has been said above, a building-stone to be of value in this country must be either of exceptional quality or accessible to a good market. The following table shows the output of all kinds of stone from the fifteen most important states, each of which pro- duces over $1,000,000 worth a year. In 1889 the production of these states was within 110,000,000 of the total for the country. 386 ECONOMIC GEOLOGY OF THE UNITED STATES. PRODUCTION OP STONE JS THE UNITED STATES, 1889. Pennsylvania $7,319,199 Ohio 4,561,590 New York 4,418,143 Maine 3,968,838 Vermont 3,789,709 Massachusetts 3,307,578 Missouri 2,516,159 Dlinois 2,208,503 California 2,126,515 Connecticut 2,112,960 Indiana 1,933,319 Colorado 1,676,862 Wisconsin 1,264,016 New Jersey 1,172,119 Minnesota 1,102,008 Total for the United States . . . $53,035,620 BUILDING-STONE PRODUCTION OF THE UNITED STATES. Kinds. 1880. 1889. 1891. Limestone $6,856,681 $19,095,179 $15,762,000 Granite 5,188,998 14,464,095 13,867,000 Sandstone 4,780,391 10,816,057 8,700,000 Slate 1,529,985 2,033,595 3,482,513 3,488,170 1,689,606 3,825,746 3,610,000 Marble Bluestone . . . ... Total huilding-stones and lime $18,356,055 $53,035,620 $47,294,746 BXnLDING-STONES AND CEMENTS. 387 Natural and Artificial Cements?- By mixing burned limestone or lime with sand and water, a plaster is produced, which, upon drying, hardens to form a cement, the ordinary material used for plaster ; and the importance of this industry may be inferred from the fact that, in 1892, 70,000,000 barrels (200 lbs. each), valued at $38,500,000, were produced in this country. Cements which have the power of setting and hardening under water are commonly called hydraulic and Portland cements. These are either a natural or artificial mixture of carbonate of lime and clay heated to a high temperature and then ground to a powder. Argillaceous limestones sometimes contain the proper pro- portion of clay and carbonate of lime for the formation of hydraulic cement; but more commonly the per cent of these materials is not exactly correct, and then either a poor cement or a valueless product results. Properly speaking, hydraulic cement is made from natural hydraulic limestones, burned at a moderate temperature, while Portland cement is made from a mixture of chalk, or marl, and clay burned at a high heat. In this country hydraulic cement is made chiefly in New York state, from a shaly limestone, which occurs at the top of the Salina group, and extends through several counties. The industry is principally concentrated in Ulster County. Portland cement, which sets more slowly, but produces a much harder and stronger cement, is manufactured in England, Germany, and France on a very large scale; but 1 This industry depends so largely upon the method of manufacture, that little is necessary here, excepting to point out the source of the materials used. Valuable accounts of the cement industry will he found in The Mineral Besouroes of the United States, Day (U. S. Geol. Survey), 1891, pp. 529-538, and in Rothwell's Mineral Industry, 1892, pp. 49-56. 388 ECONOMIC GEOLOGY OF THE UNITED STATES. in this country very little is produced, although calcareous marls and chalks suitable for its manufacture are found in numerous places, and the industry promises to grow rapidly. Great care is needed in obtaining the proper proportion of clay and carbonate of lime, and also in mixing these together. The following analyses will give an idea of the chemical character of the cement-rocks and cement : — ANALYSIS OF HYDRAULIC CEMENT ROCK, ROSENDALE, ULSTER COUNTY, NEW YORK. Carbonate of lime 45.91 Carbonate of magnesia 26.14 Silica and insoluble 15.37 Sesquioxide of iron, and alumina .... 11.38 Water and undetermined compounds . . 1.20 There is, however, great variability in composition, but the above is a fair average analysis. ANALYSES OF PORTLAND CEMENT MIXTURES. COPLAT (Pa.) Natural Rock and Limestone. , "Warner's (N.T.) Clay and Marl. Yankton (South Dakota) Clay AND Limestone. Argillaceous Limestone. Limestone. Clay. Marl. aay. Limestone. Lime 87.60 50.15 11.25 51.55 6.28 51.00 Silica , . . 18.84 4.46 44.74 1.06 61.53 4.14 Alumina . . . 4.08 1.00 18.70 .64 20.74 1.81 Sesquioxide of iron 8.41 .48 4.25 .85 4.01 2.72 Magnesia . . . 1.39 .87 1.29 .91 1.72 Trace Alkalies . . .19 Trace 1.20 2.29 Trace Carbonic acid . . 81.05 40.40 7.50 40.70 3.09 39.99 Sulphuric acid . 2.78 2.07 Sulphur ... .73 .15 1.26 .60 Water. . . 9.25 Organic and undetermined, 8.21 2.49 2.86 .08 Total . . 100.00 100.00 100.96 100.14 100.00 100.16 BUILDING-STONES AND CEMENTS. 389 There is, therefore, a marked variability in the kind and composition of the rock used in the manufacture of these artificial cements. A greater uniformity is obtained in the products, but even here there is some variety. ANALYSES OF NATURAL AND PORTLAND CEMENTS. Hydkaouc. Portland. Rosendale, Ulster Co., N.Y. Akron, N.Y. Coplay, Pa. Onondaga Co., N.Y. Silica 22.75 16.70 37.60 16.65 5.00 1.30 29.64 6.42 54.77 9.17 20.64 6.93 5.41 62.79 1.72 .27 .99 1.14 22.10 6.84 2.10 63.00 97 Alumina . . Sesquioxide of iron Lime ... Magnesia ■ Alkalies .... 4 00 Carbonic acid . Undetermined .90 .09 PRODUCTION OF CEMENT EST THE UNITED STATES. Htdkaulic. Portland. Total Barrels. Value. Barrels. Value. Value. 1882 . . . 1885 .... 1892 .... 3,165,000 4,000,000 8,132,593 13,481,500 3,200,000 5,549,163 85,000 150,000 525,360 $191,250 292,500 1,036,935 13,672,750 3,492,500 6,586,098 In 1891 the total value of the hydraulic cement output was 5,613,522, of which New York produced $3,046,279, Indiana- 390 ECONOMIC GEOLOGY OF THE UNITED STATES. Kentucky |983,456, and Pennsylvania 1536,600. Of the total of 11,067,429 worth of Portland cement produced in this country in 1891, Pennsylvania supplied $532,850, and New York $290,250. Our imports of cement in 1892 amounted to $3,378,824, this being principally Portland cement. CHAPTER XVII. SOILS, CLAYS, PERTILIZBKS, ARTESIAN WELLS, AND MINERAL WATERS. Soils.T- The subject of soils cannot be treated here in more than a very general and cursory manner, and the chemical con- sideration must be entirely omitted. In general, soils may be classified into two groups, — indigenous and transported. The first group includes those which have been formed approximately at the point Avhere they rest, the second those which have been borne from some outside source. Of these there are several kinds. Residual soils may be classed as indigenous, and they result from the decay and disintegration of the rock which underlies them. A rock, even the hardest and most dura- ble, is susceptible to changes in structure or even in chem- ical composition under the ordinary influences of weather. The building of sandstone, limestone, or granite shows the effect of weathering by a crumbling which results from long-continued exposure. The rain dissolves soluble por- tions and forms crevices into which water may enter, and this, if frozen, prys open the crevices and aids in the disin- tegration. Sudden changes of temperature from warm to 1 Professor N. S. Shaler has prepared an admirable treatise upon soils, which is published in the Twelfth Annual Report of the U. S. Geol. Survey, pp. 213-345. 391 392 ECONOMIC GEOLOGY OF THE UNITED STATES. cold, or from cold to warm, cause contraction or expansion, which aids the fragments in breaking. Lichens clinging to the wall send root-like threads into the crevices, and these, upon the growth of the plant, tend to wedge fragments from the rocks. It is exactly this process which causes the formation of residual soils. The rock disintegrates, percolating water permeates the resulting material, and, dissolving the soluble minerals, carries them away in solution. The work which lichens at first did on a small scale, is continued on a larger scale by the prying action of the roots of larger plants and trees. The ants, the rodents, the earthworms, and the many creatures which live in the soil aid in the work. As a result of these various agents, rock crumbles and tends to become ever finer in texture, while at the same time the soluble salts are removed. There is a tendency, therefore, to concentrate the insoluble particles and thus form a residue, — the normal residual soil. By the decay of rocks, the soil at first maintains certain characteristics of the parent rock, and a limestone soil there- fore differs from a granite soil. In other words, certain of the soluble salts are not removed, and these give to the resulting product a character indicative of its origin. Ulti- mately, however, all of the soluble salts would be removed, and the resulting soil would not vary essentially from one rock to another. It would be composed of the nearly insol- uble silica, kaolin, and other similar products, whether the source were limestone or granite. In the rocks — in granite, for instance — there are minerals which by their decay form salts of potassium, sodium, cal- cium, etc., which are valuable as plant food, and it is these SOILS, CLAYS, FERTILIZERS, ETC. 393 •which the plants absorb from the soil. On the other hand, there are contained in many rocks organic remains, either animal or plant, — as, for instance, the organic contributions forming limestone, — and these are especially rich in plant food. Indeed, during the formation of a soil, organisms, par- ticularly plants, at their death, enrich the soil which has supported them, by returning to it a portion of that which they have extracted from the air and the soil. The decaying vegetation forms a loam, particularly in swampy places, where it is protected from decay and entire dissipation, and the influence of this is felt to a distance of several feet below the surface. At times the conditions favour the formation of an organic soil. This is particularly noticeable in swampy regions, where vegetable growth is rapid and decay slow. Deep loams and peat bogs result, and these, when properly drained, make valuable soils. In the ocean, material is deposited sometimes in the form of organic remains, sometimes as inorganic sediments. When these are raised above the sea, they may be in one of two conditions,- — -either consolidated or loose and unconsoli- dated. If the former, they must be disintegrated before forming soils ; but if in the latter condition, they are suited to the growth of plant life as soon as drained. It becomes a question whether the latter are to be considered indigenous or transported soils ; but, since there is every gradation from these to the typical transported soil, and, on the other hand, between the unconsolidated and consolidated rocks, they may be considered to be intermediate in position. Material is prepared upon the land by disintegration, and transported seawards, where it is assorted and deposited; 394 ECONOMIC GEOLOGY OF THE UNITED STATES. and upon the elevation of that part of the sea-bottom it may again begin the cycle. Instances of such soils are found in the coastal plains extending from New Jersey to the Rio Grande, but most of these are still too swampy to be of use to man. Of the organic indigenous soils, the swamp lands of Florida, the Dismal Swamp, and the innumerable morasses and bogs of the northeastern states are illustrations. A residual soil covers the greater part of the area of the United States south of the glacial belt, and throughout this area the char- acter of the soil is distinctly influenced by the underlying rocks. This soil varies in thickness up to many feet, and in some tropical regions, such as Brazil, this residual soil has a thickness of several scores of feet. Excepting on a plain, it is not strictly accurate to speak of an indigenous soil. Upon hillsides the action of gravity tends to cause the soil to creep slowly down toward the valley, and even upon moderate slopes this creeping action is noticeable. In arid lands the peculiarities of the climate make this more noticeable. Heavy rainfalls occur at rare intervals, and the tendency is to cause a wash of the disinte- grated materials from the base of the mountains out upon the plateau. Gravel slopes are thus formed, as the result of the action of gravity, aided by the wash of the heavy rains. From these types of partly moved soils, there is every gra- dation to the talus soil which forms at the base of a cliff by the constant dropping and subsequent disintegration of rock fragments. Eventually the talus is built up to a point where its slope meets the top of the cliff, or a point where the talus slope is continued in the hill. In other words, the hill wears back by weathering ; and this weathered slope and the talus SOILS, CLAYS, FERTILIZERS, ETC. 395 slope become continuous. If, however, a stream flows at the base of the cliff, and removes the talus, the above condition may for a long time be delayed. The talus soil resembles the indigenous soil in the fact that it has a character resem- bling that of the rock of the cliff, and that it is derived by disintegration. But, on the other hand, it has been removed for some distance, and is very liable to be a commingled product derived from the several kinds of rocks which form the cliff. These soils are very common in the Cordilleras at isolated points. In their passage to the sea, streams take such fragments as they find within their grasp, and transport them down stream, always tending to divide them into smaller frag- ments. In the course of their development, streams build flood plains, and often terraces and deltas, by reason of cer- tain causes which cannot be explained here. These, which are usually excellent soils, are generally fine-grained in tex- ture, and are composed of materials from all parts of the drainage area above the point of deposit. The Mississippi valley furnishes the best illustration of this class of soils, but in a minor way all the smaller rivers are likewise flood- plained. Akin to these soils are the sea-bottom sediments which are raised above the sea, and the lake-bottom deposits which result from the filling and drainage of lacustrine bodies. Another group of transported soils, although of very little importance, is that of aerial or sedlian soils. Even in moist climates, there are times when the dust blows about, and this aids, not only in transportation, but also in the disintegration of rock fragments. In the arid lands this blowing about of sand and dust becomes of much more importance, and all the soils there are in a measure transported by this means. 396 ECONOMIC GEOLOGY OF THE UNITED STATES. Locally, in these regions, where the conditions are favourable, and also along lake and sea shores, blown sands form extensive tracts of sand-dunes which are typical seolian soils, usually barren of vegetation, not alone because of the fact of their constant movement, but also because they are actually barren of plant food. Usually quartz and sand grains predominate, and these form a porous deposit, through which the water passes freely without causing a decay of the minerals and the formation of plant food. Only hardy and sand-loving plants are able to obtain a footing there ; but if these succeed in growing in suificient abundance to prevent the movement of the sand, they soon bring about the disintegration of the grains and the formation of a soil capable of sustaining other forms of vegetation. A final important group is that of glacially formed soils. In certain mountains snow accumulates, and, moving down the valleys, forms a glacier which ploughs against the valley bottom and sides, rasping and grinding off fragments as it moves, and transporting these to its terminus, together with the fragments which fall upon it from the overhanging cliffs. Thus, at any given time, there is beneath a glacier a deposit consisting of large boulders and finer fragments, even fine-grained clay, all mixed intimately. If the glacier should disappear, the valley bottom would be covered with this material, forming a glacially transported soil. At the terminus of the glacier, moraines are formed of the material brought by the ice, and left when it was able to move no farther. From beneath the ice, streams issue ; and these assort the materials, leaving the large boulders behind, car- rying the fine clay some distance from the glacier, and depositing sand plains and terraces between these two points. SOILS, CLAYS, PEETILIZEES, ETC. 397 Almost exactly this same condition has been experienced by the northern sections of this country, north of a line ex- tending approximately from Nantucket, through Long Island, central New Jersey, northwestern Pennsylvania, Cincinnati, Ohio, Wisconsin, and thence northwestward to Dakota. Nearly all of this region was beneath an ice-sheet resembling that of Greenland. Any soil which may have existed before the oncoming of the glacial period was swept away ; and when finally the ice melted, the surface was littered with a glacially transported soil, in some places morainal, in some the general sheet of unstratified till or ground moraine, and elsewhere with sand plains and terraces. In a limestone region the soil contains not only fragments of this material, but of many rocks derived from more north- ern regions. Where the motion of the ice was for a long distance over a limestone belt, as in some of the north and south valleys of New England and New Jersey, the influ- ence of the limestone is markedly noticeable in the soil. But it is not uncommon to find, over a given stratum, a soil almost free from this material. In places the deposit is thick, again it is thin, and, over large areas, no glacial soil was left. The time since the close of the glacial epoch is so short that in such places residual soils have not been formed, and the bare rock outcrops. Where the country rock is hard, well jointed, and not easily disintegrated, as in the granite and gneiss regions of New England, the proportion of boulders in the soil is very great, and agriculture is carried on with difficulty. Thus there is a marked difference in the charac- ter of the soil north and south of the terminal moraine. In soils of all these characters plants of various kinds 398 ECONOMIC GEOLOGY OP THE UNITED STATES. grow. Some are well adapted to nearly all varieties of plants, others support only certain kinds. In a state of nature the plants rob the soil of certain elements, but they return to it not only a part of that which they extracted, but also some of the carbon which they have absorbed from the air. Moreover, they furnish a vegetable coating, which protects the soil from being washed away, and furnishes water percolating through it with certain acids which dis- integrate the particles of rock. It also delays the passage of this percolating water so that it does not sink readily into the soil and wash away the plant food. Man has come into the field with his modern methods and implements, and has begun to rob the soil of its natural stores of plant food. Extravagant and even foolish methods have been introduced, and, in this country in particular, thoroughly prodigal methods have been adopted. The abundance of land, its virgin richness, and the fact that we have not had centuries of experience in tillage, have tended to make us thoughtless of our duty to "the soil and our descendants. The wealth of the nation is largely dependent upon the tillage of the soil, and methods which will ultimately prove disastrous should be avoided. Already in the older settled districts the soil is impoverished, and the time is not far distant when our western farm lands will need to be treated scientifically or be abandoned. At present the average farmer is taking from 'the soil all it will yield and returning nothing to it. Moreover, he is interfering with the natural formation of plant food by the removal of the loam, and by rendering the soil porous by ploughing so that water passes through it as it does through a sand-dune. He should return that part of the SOILS, CLAYS, FERTILIZERS, ETC. 399 vegetation which he does not use, and indeed he must do more. The peat beds, swamp loam, manure, marls, guanos, and phosphates must be more commonly used. Clays} An almost infinite variety of clay occurs in this country, and its abundance is so great that for ordinary purposes it is readily accessible. There are numerous ways in which it is derived, the most common being as a result of rock decay. Beds of clay are found throughout the sedimentary strata, either still incoherent, or consolidated, and sometimes even transformed to slate. These are chiefly formed as sediments, by the deposition of the fine-grained products of rock decay. Ordinarily these are too impure for any but the roughest uses, and some of them cannot be used at all. For some purposes, such as the manufacture of white pottery, pure kaolin is needed, but for tiling and bricks, impure clays may be used. The first stage in the formation of much of the clay is the decomposition of the rock, a process which is every- where in progress. The mineral which is of most impor- tance in the production of the finer grades of clay is feldspar, which, by its decay, loses the sodium, potassium, and other soluble salts, while, as an ultimate product, kaolin, or hydrous silicate of alumina, remains. Such clays in place are very rare, for they are usually mixed with impuri- ties of one kind and another; but in many cases, for the better class of porcelain and other ware, rocks which are 1 The subject of clays is admirably treated by Professor R. T. Hill in the Mineral Mesources of the United States for 1891, pp. 474-528. 400 ECONOMIC GEOLOGY OF THE UNITED STATES. disintegrating, and, in some cases, pure feldspar, are crushed and washed to remove the impurities. More commonly workable clays occur in beds where they have been deposited by sea or lake, in some cases in the form of nearly pure kaolin, but more commonly as impure clays, varying greatly in composition, texture, and colour. From these, bricks, drain tiles, chinaware, furnace linings, pottery, various utensils and ornamental pottery, etc., are manufactured by the aid of heat and partial melting. Not a little clay is used for purposes of adulteration and as a filling for cheap grades of paper. For these several purposes different kinds are needed, and consequently different industries spring up in various localities. Clays known as fire-clays are suited to with- stand high temperatures by reason of the absence of alkaline material. These are particularly abundant in the Carboniferous rocks associated with coal beds, the plants having been instrumental in the withdrawal of the alkalies. Brick clays must be made of a natural or arti- ficial mixture of sand and clay. When a red colour is needed, iron salts must also be present. Certain alkalies are also needful to aid in the partial fusion of the clay when heated. Some brick clays are the result of residual decay; some are worked-over products of disintegration deposited in water, and in this country a large proportion of these clays are directly or indirectly the result of glacial action. As the ice moved over the rocks, they were ground and rasped until a rock flour was produced which was sometimes depos- ited in marginal lakes, or in the river-terrace plains near the ice front, and sometimes deposited directly from the SOILS, CLAYS, FEETILIZEKS, ETC. 401 ice when it melted. The distribution of these clays in the glacial belt is very widespread, and every state and nearly every district has such clays for the manufacture of brick for local demands. Certain large centres which produce brick of an exceptional quality ship some of their output to a considerable distance ; but most of the producers sup- ply only local markets. This is less true of the other clay industries, excepting those producing the coarsest products ; and very fine ornamental ware is sent from one country to another. Clays are of all ages from the Cambrian to the present, but in this country the most important are of Cretaceous, Tertiary, and Quaternary age. The brick clays are chiefly of Quaternary age, being either recently deposited in river valleys, or of glacial origin. Fire-clay occurs abundantly in the Carboniferous, and some in this country occur else- where in the Palaeozoic. In addition to actual clays, flint, quartz, and feldspar are ground up and used as clay. There are large quantities of these minerals, as well as of clay, which are not at present utilized. Notwithstanding the great importance of the industry of brick production, there are no statistics available. In 1891 the value of the potter's materials, including kaolin, fire- clay, ground flint, and feldspar, was over $1,000,000. New Jersey is the most important state in this respect, but many others have valuable pottery industries. Probably the brick industry is many times more valuable than that of the man- ufacture of pottery. The industry of feldspar production for grinding and mixing with clay and for a glaze is centred in Maine, Connecticut, New York, and Pennsylvania. The annual 402 ECONOMIC GEOLOGY OP THE UNITED STATES. product varies from 8000 to 15,000 long tons, valued at about $5 a ton, and this comes from coarse granitic or peg- matite veins. Flint occurs in bands and nodules of con- cretionary origin in limestones and chalk. It is an impure form of silica, and is used extensively in the manufacture of pottery. There are vast quantities in the west and southwest which are not at present utilized. In 1891, 15,000 long tons, valued at 160,000, were produced in the United States. Fertilizers. General Statement. — Various substances are used for the purpose of returning to the soil the elements needed in plant growth, thereby enriching impoverished soils. Manure and other waste products of organic origin are commonly used for this purpose, and there are extensive establishments for the manufacture of artificial guano from the remnants of fish and other animals, obtained during the process of prep- aration for the market. Vegetable products are also made to give up their plant food to the soil. Sometimes the plants which have grown upon the field are allowed to decay there, and at times loam and peat are added to the soil. These products do not come within the scope of this work, and none of them, with the exception of artificial guano, are of more than local importance. There are, however, several classes of important economic products which are of use for returning to the soil needful sub- stances which have been extracted by plants. These are limestone, marl, gypsum, and the various phosphates. Limestone and Marl. — It is a well-recognized fact that limestone soils are rich in plant food, and consequently the SOILS, CLAYS, FERTILIZERS, ETC. 403 addition of this rock to a poor soil is of value. This is due partly to the presence of the carbonate of lime, and partly to other substances of organic origin furnished the limestone by the animals which formed it. For the pur- pose of a fertilizer, limestone is burned to form lime, and then spread upon the soil. A portion of the lime product mentioned in the preceding chapter is used for this pur- pose, while many farmers burn limestone for their own or for local use in regions where it can be easily obtained. There are no statistics for the production of lime for fertil- izing purposes. Marl is a calcareous clay, owing its calcareous nature to the presence of numerous shells of moUusca. Being a soft clay, it is easily obtained; and before the introduction of cheap phosphatic fertilizers, it was extensively used for fer- tilizing purposes, particularly in New Jersey, where it is found most abundantly. This substance occurs locally in many places, in the bottom of swamps, and it should be of more local importance than it is. In the coastal plains of Cretaceous and Tertiary age there are extensive deposits of marl and greensand ; and since these are at present used only for local purposes, statistics of their production are difficult to obtain. During the census year 1880 the value of the marl product was approximately 1500,000, and in 1891 only 167,500, this representing 135,000 tons of marl. This calcareous clay is also of value in the manufacture of Portland cement. Gypsum. — This mineral, the sulphate of lime, is used for two purposes principally, — one as "land plaster" for a fertilizer, the other, and the most important, calcined, to form plaster of Paris. Gypsum occurs in all rocks, in minute quantities ; but in many sedimentary strata, it is suffi- 404 ECONOMIC GEOLOGY OF THE UNITED STATES. ciently abundant to give to water percolating through them a certain peculiarity known as "hardness." The water of nearly all rivers and lakes, and of all oceans, carries it in solution; and when lakes fail to overflow, and are trans- formed to dead seas, this mineral becomes concentrated, and may finally be precipitated in beds. Much of the supply obtained in this country is associated with salt, and has prob- ably originated in this way. In the Cordilleras there are large areas of gypsum, called white sands, in the dried-up beds of extinct lakes ; but this is at present of no value except for local purposes. There is still another way in which this mineral may be formed in the rocks, and some believe that many of the gyp- sum beds are of this origin. This is by the alteration of beds of limestone, through which sulphurous waters are per- colating. It is doubtful how far this can be extended to account for the commercial deposits of gypsum, but some of this mineral is undoubtedly formed in that way. Sulphurous waters are not uncommon, the sulphur being furnished by decaying organic remains or by iron pyrites ; and these, coming in contact with limestone beds, may very readily alter them to the sulphate of lime. The association of gypsum with salt, however, indicates that much of it is the result of precipitation from salt lakes; and for the western deposits this is unquestionably the true explanation. In different parts of the world, different ages have had prevailing conditions of aridity, attended by the formation of dead seas ; but in this coun- try the Permian, Tertiary, and Quaternary have been the most important periods in which arid conditions have pre- vailed. This applies to the western part of the country ; and SOILS, CLAYS, PBETILIZEES, ETC. 405 there is some reason to believe that, during the Palaeozoic, there were periods of aridity in the east. PRODUCTION OF GYPSUM IN THE UNITED STATES, 1891. States. Calcined FOR Plaster. Fertil- izer. Sold Crude. Total Product. Short Tons (2000 Lbs.). Total Value. Michigan Kansas . . ... New York .... Iowa ... . . Virginia Soutli Dakota . California, Ohio, Utah, " and Wyoming . . . $173,175 159,832 53,250 4,938 90,810 128,550 210 53,513 4,845 22,222 4,680 3,336 $22,000 1,280 5,058 352 79,700 40,217 30,135 31,385 5,959 3,615 17,115 $223,725 161,322 58,571 58,095 22,574 9,618 94,146 Total .... §482,005 §117,356 128,690 208,126 $628,051 GYPSUM PRODUCTION OF THE UNITED STATES. 1880 $400,000 1885 . 405,000 1890 428,626 1892 675,000 In 1891 we imported $226,319 worth of gypsum. Phosphatic Fertilizers.^ — Mineral Phosphate. The phosphatic fertilizers may be divided into mineral phosphates, of which apatite is the only representative, and rock phosphates which consist of guano, bone beds, and phosphatic nodules. Mineral phosphate, or apatite, the phosphate of lime, occurs in nearly 1 A valuable treatise on The Nature and Origin of Phosphate of Lime, by R. A. F. Penrose, Jr., forms Bull. 46, U. S. Geol. Survey. 406 ECONOMIC GEOLOGY OP THE UNITED STATES. all eruptive and metamorphic rocks, generally in small grains and crystals, and in such small quantities that it does not sensibly increase the value of the enclosing rock as a soil-producer. In some rocks, principally in the meta- morphic limestones associated with the Archean, apatite is often more abundant, and seems here to be the result of segregation into crystal form of the phosphatic substances originally disseminated through the limestone in the form of organic remains. The bones of vertebrates, the flesh of many animals, and, in some cases, the tests or shells of animals, par- ticularly certain Crustacea, contain some phosphate of lime; and as a result of this, certain limestones are sufficiently phosphatic to make high-grade soils. But there is no reason for believing that the apatite which occurs in igneous and metamorphic rocks is of organic origin ; but, on the contrary, this is probably the original source of the organic phosphatic materials extracted by the intervention of organisms. Apatite is not mined in this country; but in Canada large quantities of it occur in veins in the Laurentian limestones and gneisses, near Ottawa, Perth, and Kingston. Here it is mined, separated by hand, and crushed, chiefly by the farmers who own the land and by small companies. A great decline in this industry has been caused by the competition of the South Carolina and Florida phosphates. Guano. — This is the excrement of birds, such as divers and penguins, which resort in great numbers to some of the islands off the west coast of South America. It is found elsewhere, but the climatic conditions have not favoured its accumulation into extensive deposits. In 1804 Humboldt first called attention to the deposits of guano on the Chincha Islands, off the coast of Peru ; and from 1842 to 1873, when SOILS, CLAYS, FERTILIZERS, ETC. 407 they were exhausted, nearl}' 14,000,000 tons, valued at from f45 to $70 a ton, were exported from there. Since then other islands have been producing guano ; and although the older deposits are approaching exhaustion, the province of Tarapaca and the off-lying islands are still exporting this substance. In 1879 Chili seized these deposits, and still controls them. Chili exported, in 1890, 41,323 metric tons of guano, valued at 11,237,003 ; but the time is not far distant when these islands will cease to produce guano. Smaller quan- tities are obtained in the Argentine Republic and Uruguay. Rock Phosphates. — -In this country the most important fertilizer is the rock phosphate, which exists in the form of bone beds and phosphatic nodules of concretionary origin, usually occurring together; and the recent discoveries of these substances have given to this country the leading rank in the production of natural fertilizers. South Carolina and Florida are the important phosphate-producing states, but deposits also exist in North Carolina, Alabama, and other southern coastal states. These deposits consist of a white phosphatic limestone or a limy marl-like clay containing layers and nodules of more pure phosphate of lime and bones and teeth of mastodons, sharks, and other land and marine animals. The South Carolina deposits were recognized in 1797; but it was not until 1867 that their true value was known, and since then the production of phosphates in this state has rapidly increased. There are two methods of mining these deposits : one dredging in the river beds, the other removing the "land rock" by means of open trenches. The phosphate is then crushed, washed, dried in kilns, and finally converted into superphosphates. Beaufort is the principal locality, and here, as well as elsewhere, there is a 408 ECONOMIC GEOLOGY OF THE UNITED STATES. wide variation in the character, composition, and distribution of the phosphates ; but they are all distinctly bedded with the other strata of Tertiary age. The following table shows the increase in output of phos- phate rock in South Carolina, a marked decrease being noticed since 1889, when the Florida phosphates became of importance. In 1890, 212,102 tons were obtained from the rivers by dredging, and the balance of the 537,149 tons from the land rock. PKODUCTION OF PHOSPHATE EOCK IN SOUTH CAROLINA. Long Tons (2240 Lbs.). 1867 6 1868 12,262 1870 65,241 1875 122,790 1880 190,763 1885 395,403 1889 548,585 1890 537,149 1891 475,506 1892 350,000 Deposits of phosphate of lime were discovered in Florida in 1883, but not until 1888 were they known to exist in large quantities. In this year a fossil tooth was found in a white subsoil, and the latter upon analysis was found to be an important phosphate rock. Great excitement and active exploration followed, and extensive developments have been made which prove that this area is the largest and most im- portant phosphate region in the country. The phosphate is in the form of (1) layers and nodules, called respectively "hard rock" and "land pebble"; (2) less pure phosphatic limestone, filling the spaces between the nodules and layers, called "soft rock"; (8) vertebrate fossils; and (4) "river SOILS, CLAYS, FERTILIZERS, ETC. 409 pebbles," which are derived from the land deposits washed down and accumulated by the streams. The following table shows the remarkably rapid development of the phosphate production of Florida : — Yeak. Value. PHOSPHATE PRODUCTION OF FLORIDA. Pkoduct. Long Tons (2240 Lbs.). 1888 ... . 3,000 125,000 1889 4,100 32,800 1890 46,501 338,190 1891 • . . 112,482 703,013 1892 . . . . . 202,382 The following table of analyses shows the composition of these phosphates : — ANALYSES OF SOUTH CAROLINA AND FLORIDA PHOSPHATE ROCK. lukaville, Flokida. South Carolina. Phosphoric acid (Pfi^) Lime (CaO) . . . . Alumina (AI2O3) . . Ferric oxide (Fe./),) Magnesia (MgO) . . Alkalies (Na^O) . . . Sulphuric acid (SO3) . Fhiorine (Fl) . . . . Chlorine (CI) . . . . Silica (SiO^) . . . . Carbonic acid (CO^) Insoluble matter . . . Moisture 33.91 47.02 2.37 1.46 0.39 0.19 0.36 2.35 0.08 0.10 2.67 5.07 3.96 26.0 to 29.0 35.0 to 42.0 Traces to 2.0 1.0 to 3.0 Traces to 2.0 0.5 to 2.0 1.0 to 2.0 4.0 to 12.0 2.5 to 5.0 2.0 to 6.0' 0.5 to 4.0 1 Organic matter and combined water. 410 ECONOMIC GEOLOGY OP THE XJNITBD STATES. The price of phosphate rock varies greatly according to the proportion of phosphate of lime, but in 1891 it averaged about 16.25 a ton. No doubt these deposits will in time be exhausted, but there are still immense stores in sight and enough to last for long periods of time. France, Belgium, and some other countries, contain phosphate beds of similar character and origin. The origin of these deposits is from organic remains, as is indicated by the presence of bones of vertebrates. For some reason both land and marine vertebrates resorted to the estu- aries and bays, and their remains became commingled. In Florida, at the time of formation of the phosphate beds, there existed above the sea a series of small keys and islets bathed by the warm southern currents ; and in the straits between them marine life abounded, while upon the land, birds and mammals thrived. In the shallow coastal waters and on the shores, the bones of these animals were accumulated. One may obtain a possible clue to the mode of accumula- tion of these remains by a study of the Big Bone Salt Lick of Kentucky to which mammals resorted for salt in large numbers, and, becoming mired or killed by carnivorous ani- mals, their bones have accumulated for ages. Great quanti- ties of bones of all kinds are gathered together in this great mammalian cemetery. Similar conditions may have existed in Florida and South Carolina, and this, added to the excrements of birds, laaj suffice to account for these deposits. The recent (1893) disastrous hurricanes on the Gulf Coast furnish a suggestion concerning the possible accumulation of these land and marine vertebrates. Extensive floods have been produced on the low-lying islets of this coast by the high water accompanying these storms, and many hundred SOILS, CLAYS, FERTILIZERS, ETC. 411 lives have been lost in consequence. The similar typhoons of Asia have caused the destruction of hundreds of thou- sands of human lives. These waves, by stranding the larger marine vertebrates and at the same time drowning many of the land mammals, might readily have caused these phosphate beds. Being in the track of many of the West India hurricanes, these keys were favourably situated for these peculiar conditions ; and, while the storms were fre- quent enough to cause much destruction, they were not frequent enough to completely devastate the region. At least, this is the case at present, since man himself inhabits the similar islets on the Gulf Coast. Secondary changes consisted in grinding the phosphatic material to clay under the action of the waves, and later the concretionary gathering together of the phosphate of lime into layers and nodules. The " river pebbles " repre- sent a still later process of concentration by the action of river erosion. The following tables show approximately the production of phosphate of lime in the world and in the United States for a series of years : — PRODUCTION OF PHOSPHATE OF LIME IN THE WORLD, 1890. Metric Tons (2204 Lbs.)- United States . • 518,835 Belgium . . 280,0001 Venezuela . ■ 60,000 Chili 2 : .... 41,3233 Canada . . . 23,588 Great Britain 18,295 Peru'.= . ... • 17,0001 Uruguay^ . . . • S.^'^ss French Guiana . . • 3,500 1 Estimated. - Guano. ' Exported. 412 ECONOMIC GEOLOGY OF THE UNITED STATES. PRODUCTION OF PHOSPHATE ROCK IN THE UNITED STATES. Metkic Tons (2204 Lbs.). 1880 214,229 1882 . . 337,500 1884 438,830 1886 437,579 1888 455,892 1890 . . 518,835 1891 . . . 597,589 1892 . 651,801 The value of the output for 1892 was 12,361,219. Artesian Wells?- It is usually possible in moist countries to obtain a water supply, sufficient for ordinary purposes, by means of wells of very shallow depths ; and it is not uncommon in such regions to find actual springs outcropping at the surface. These rise through joint planes, or along faults in some cases, but much more commonly they represent the escape of underground water at some favourably situated point on a hillside or at the base of a hill. The most common condi- tion is where a porous stratum is underlain by an impervious layer, such as clay. Water, passing through the porous layer, encounters the impervious stratum and flows over it in the direction of its dip, and if this stratum outcrops on a hillside, a spring is formed. The contact of a deep soil with impervious rock, or of any pervious and impervious layer, 1 A very valuable and comprehensive treatise on artesian wells, prepared by Professor R. T. Hill, is publislied by the Department of Agriculture under the title of The Occurrence of Artesian and Other Underground Waters in Texas, etc. A paper on artesian wells by Professor T. C. Chamberlain is also found in the Eifth Ann. Rept., U. S. Geol. Survey, pp. 125-173. SOILS, CLAYS, FERTILIZERS, ETC. 413 produces the same condition. So common is the association between clay strata and springs that such a stratum is usu- ally indicated at the surface by a line of springs where it outcrops. Springs are usually superficial phenomena, and a series of droughts, or even a single drought, will frequently cause them to disappear, showing how shallow is their ori- gin. There are, however, some which are deep seated in origin, and these usually rise in permanent and extensive flow through fissures in the strata. Still another kind of large spring is the type which forms in limestone regions where much of the drainage is underground. In river valleys, and sometimes on plains, these underground streams reach the surface as extensive springs. Artesian wells are deep-seated springs artificially formed, or, more exactly, deep-seated bodies of water tapped by artificial borings and rising to the surface under natural hydrostatic pressure. A spring which rises along a fault plane closely resembles an artesian well, with the exception that its escape to the surface is provided for by a naturally formed channel, — the fault plane instead of an artificial well. The depth of artesian wells varies from a few score to several thousand feet, and all depend upon a few simple principles. Percolating water divides itself into two parts, one portion escaping, after a very short journey, in the form of springs or by general seepage, the other portion commenc- ing a long underground journey. The latter portion natu- rally seeks the easiest paths, and these are in the porous rocks. Moreover, under the influence of gravity there is a tendency for the water to go deeper into the earth ; but, on 414 ECONOMIC GEOLOGY OF THE UNITED STATES. the other hand, as the depth increases, there is an increasing hydrostatic and rock pressure which tends to force the water to the surface. This is not sufficient to force it upwards through the rocks against gravity unless a channel is fur- nished. If the strata are fissured, the water passes to these fissures and escapes to the surface naturally ; but if they are not, it becomes entombed. In the case of horizontal rocks water percolates through them, but its progress is retarded by the presence of imper- vious layers. The most favourable condition for the accu- mulation of water in the strata is in inclined layers, since here all of the strata outcrop at some point on the surface, and slope downward into the earth with a greater or less angle of dip. Where a porous stratum, such as sandstone, outcrops, the water that falls upon the area of outcrop readily soaks into the ground, and much of it is able to begin an underground journey. Naturally, if the dip is slight, there is a greater area of outcrop than in the case of a steeply inclined bed. Where the sandstone is overlain and underlain by an impervious stratum, such as clay or a clay rock, the water is prevented from escaping to the surface, as it tends to do under the action of the hydrostatic pressure, and also from passing through the underlying bed to lower layers. The sandstone, therefore, becomes a water-bearing stratum, and the water passes down the inclined plane between two impervious beds. When this stratum is pierced by a well, the water rises, theoretically, to the level of the water column in the stratum (Fig. 26) ; that is, nearly to the level of the outcrop of the stratum at the point of entrance of the water into the earth. In reality the water does not rise so high, because of the SOILS, CLAYS, FERTILIZERS, ETC. 415 '^ SO /— . a' "2. "^ !> £, S' ® S^ i o o Z c rt g I- si CD n "^ a a a. ^ g g C o- K o " "■ S c+ CD '^ n (M S * ft &3 3 &3 - O "^ t: ^ & o >: •5' "" a w a ° «■ o w 1 interference of friction. If, therefore, the outlet of the well is above the outcrop of the water-bearing stratum, the water rises only part way to the surface; but, if the outlet is below this, the water may gush out as a fountain, and such wells, artesian wells, are usually permanent and have a strong flow. The slope of the stratum may be very gentle, in which case it may be tapped for great distances from its outcrop without boring to extreme depths ; or it may be steep, and then an artesian well can be obtained only near the outcrop, unless it is driven to a great depth. Generally speaking, therefore, steeply dipping strata are not favourable to the construction of artesian wells. It not infrequently happens that a series of strata, after having dipped at a certain angle for some distance, become horizontal, and then rise to the surface with an opposite dip, forming a syncline ; and, if other conditions are favourable to the forma- tion of artesian water-bearing strata, the centre of the syncline is a very promising place for an artesian well, since the hydrostatic pressure is maintained on two sides and the water supply comes from two outcrops, one on S CD CT^ 3- s » a (D f^ ^ 2" 2. 5, ^ I S & o g- ° q a S o 1 11 I 416 ECONOMIC GEOLOGY OE THE UNITED STATES. either side of the syncline (Fig. 27). It is frequently stated that this is the normal condition for the formation of artesian wells ; but such wells are much less common than those which are found in strata having a monoclinal atti- tude, or, in other words, a dip in only one direction. From the above it will be seen that artesian wells are purely geological phenomena, and that a knowledge of the geology of a country will serve, not only to predict the Fig. 27. — Section showing conditions under which artesian wells are found in a synclinal trough. A, height of water level; B, porous stratum, bounded above and below by impervious strata, and all folded into a syncline ; C, arte- sian wells. (After Chamberlain.) possibility of finding such supplies of water, but also the depth at which it will be found. Even in moist climates artesian wells are frequently desired for a permanent supply of constantly flowing water ; and, in regions of stratified rocks, they can usually be obtained with a force sufficient to cause the water to rise nearly, if not quite, to the surface. Not infrequently they are mineral bearing, and not suited for drinking purposes, but supplies of pure water are often obtained. The above principles of artesian-well occurrence are of value also in obtaining brine from salt-bearing strata, and, as has already been stated, the principles apply in part to the petroleum wells. It is, however, in arid regions that artesian water is of most importance in this country, and every year this is becoming more true of these regions. There are large SOILS, CLAYS, FERTILIZERS, ETC. 417 tracts which, in their present condition, are absolutely unfitted for human habitation, or even for occupation by cattle, because there is no drinking-water. One does not need to travel very extensively in the arid regions to find large tracts where the wild grass has not been touched by the herds of cattle with which the more favourably situated parts of the region are overstocked. The rains come rarely, excepting in a small part of the summer season, and these either sink into the thirsty soil or flow away through chan- nels which are usually dry. The discovery of artesian water in such places opens up an otherwise inhospitable region to settlement. Even where cattle-raising is possible, agriculture is out of the question, because of the aridity and the absence of water for irri- gation, the only supply being from scattered springs, with a small flow, near the mountains. In the mountains a suffi- cient amount of rain falls for some crops, but the country is generally too rugged for cultivation, and the water, excepting from the larger ranges, does not escape beyond the margin of the mountainous tracts, being either evaporated or soaked into the ground. Since the mountain-forming rocks extend beneath the plains, artesian water may be found even where the surface is very arid. Moreover, on the less arid plateaus sufficient water falls, at certain seasons, to cause under- ground water-bearing strata. When these have been found at no great depth, large tracts which were formerly desert and uninhabited are now dotted with small farms irrigated with artesian water. One of the future possibilities of the arid regions consists in the discovery and development of artesian water-bearing belts, a work which is already begun, but hardly more than begun. 418 ECONOMIC GEOLOGY OF THE UNITED STATES. Mr. F. H. Newell 1 states that in the census year there were 8097 artesian wells in the western half of the country, 3930 of which were used for purposes of irrigation. Cali- fornia had 3210; Utah, 2524; Colorado, 596; Texas, 534; and South Dakota, 527 such wells. The average area irri- gated per well was 13.21 acres, and in California and Colo- rado over 18 acres. The total number of acres thus irrigated was 51,896, of which 38,378 were in California. The total 8097 wells represent an investment of about 11,988,461. Mineral Waters.^ A very important industry in this country is the utilization of waters which, having dissolved certain mineral constitu- ents from the rocks, issue from the earth either through natural channels, in the form of springs, or from artificially formed wells. These mineral waters possess some properties which render them of value for medicinal or other purposes. Peale, in the census report above referred to, classifies min- eral waters as thermal and non-thermal, the latter being cold, and the former either tepid, warm, or hot. The thermal springs are generally, though not always, found in regions of recent or present volcanic activity, and are often one of the indications of this activity, — in this country one of the indications of dying volcanic action. All waters issuing from the earth contain mineral in solution ; and it is this which gives to it medicinal qualities, chiefly that of a tonic. No such waters are more common than those containing 1 Eleventh Census Bulletin, No. 193, Artesian Wells for Irrigation. 2 A very valuable discussion and classification of the mineral waters in the United States, from which this summary is chiefly extracted, is found in the Eleventh Census Eeport, on Mineral Industries, pp, 779-787. SOILS, CLAYS, FERTILIZERS, ETC. 419 iron ; but there are numerous other kinds of mineral waters, such as those which contain sulphur, in the form of sul- phuretted hydrogen, lithia, manganese, and many other sub- stances. Many mineral springs are not utilized, and some which are used are of little value. There, are two classes of materials in mineral waters, gaseous and solid substances, although it frequently happens that both of these constituents are present in the same spring. It is upon the basis of the solid constituents that Peale constructs his classification, omitting the temperature, since there is every gradation from hot to cold springs, and since there is no necessary difference between the con- stituents of the two. Each group may be represented by thermal and non-thermal types, the term thermal being applied to those whose temperature is above 70° Fahr. The gaseous constituent is used for minor subdivisions. This classification of mineral waters cannot be given here in detail, but in general the scheme is as follows : (1) Alka- line springs, when they contain carbonates, " whether of alkalies, alkaline earths, alkaline metals, or iron alone " ; (2) alkaline saline springs, those in which carbonates are mixed with sulphates or chlorides ; (3) saline springs ; (4) acid springs, which include the sour water containing alum, sulphuric acid, etc. There are many subdivisions based upon this general scheme. Some of these springs furnish water for bottling, while others are used entirely at the point of issue. It is difficult to obtain exact information concerning the number and value of the mineral springs of the country, but the following table gives the approximate statistics. In 1891 the list of com- mercial mineral springs in the country numbered 288. 420 ECONOMIC GEOLOGY OE THE UNITED STATES. PRODUOTION OF MINERAL WATERS IN THE UNITED STATES, 1891. States. Gallons. Value. New York 2,779,472 1796,047 New Hampshire . . 960,000 502,000 Virgiaia 534,293 215,392 Wisconsin .... 2,882,117 184,133 Michigan .... 2,228,575 149,773 California .... 334,533 135,959 Colorado .... 481,038 133,222 Massachusetts . 841,062 115,591 Total for the United States . . 18,392,732 $2,996,259 It will be noticed that there is no necessary relation be- tween the number of gallons produced and their value, since much depends upon the demand for particular classes of mineral water. MINERAL-WATER PRODUCTION OF THE UNITED STATES. Year. Gallons. Value. 1880 2,000,000 #500,000 1885 9,148,401 1,312,845 1891 18,392,732 2,996,259 The industry is thus a rapidly growing one. Our imports of natural mineral waters, in 1891, were 2,019,833 gallons, valued at |392,894. CHAPTER XVIII. PRECIOUS STONES, ABRASIVE MATERIALS, SALT, MISCELLA- NEOUS MINERALS, AND GENERAL SUMMARY OP MINERAL PRODUCTION. Precious Stones.^ The production of precious stones in this country has never attained especial prominence, although nearly all gems have been occasionally found. Turquoise and pearls are the only gems produced in this country in quantities sufficient to call for especial consideration; but, since there seems every reason to expect that valuable stones may yet be found in our vs^estern region, some mention will be made of these even though at present the production is unimportant. In prehistoric times turquoise was obtained by the Indians from Los Cerrillos, New Mexico, and beads of this mineral are often found with their implements. These turquoise veins are still worked, and recently other veins have been dis- covered in the Burro Mountains, Grant County, New Mexico, some of the gems from these mines being equal in colour to the best oriental turquoise. During the present year (1893), turquoise has been dis- covered in the Jarilla Mountains, in Dona Ana County, New 1 The subject of precious stones Is treated fully by G. F. Kunz in Gems and Precious Stones of North America, by E. "W". Streeter in Precious Stones and Gems, and also in the Eleventh Census Report on Mineral Indus- tries, and the reports on the Mineral Resources of the United States, Day, U. S. Geol. Survey. 421 422 ECONOMIC GEOLOGY OF THE UNITED STATES. Mexico, and it is predicted that this will prove of great value. As in the case of the Grant County gems, the occurrence is in association with intrusive trachyte, the min- eral being the result of an alteration of the kaolin which existed in the veins. The turquoise grew, as it were, in the kaolin, it being a hydrous phosphate of aluminum. All of these turquoise veins were originally worked by the Indians, and their discovery was due to this fact. But as an illus- tration of the lack of knowledge of the rarer minerals on the part of the prospectors, it may be pointed out that the Jarilla deposit was overlooked on the assumption that it was a copper stain. Pearls are frequently found in fresh-water clams belong- ing to the genus Unio, and some of these are of value. Particularly valuable finds have been made in Wisconsin, and Kunz states that pearls of good quality are more liable to be found in creeks which flow through a limestone country. Precious stones, particularly sapphire and diamond, have been occasionally found in the gold-bearing gravels in vari- ous parts of the west, but, until very recently, no systematic efforts have been made to obtain them, nor has any success attended the efforts to find their source in the rocks. Re- cently systematic work has been carried on for the recovery of sapphire from the gravel bars in the Missouri River east of Helena, Montana. These ai'e being carefully washed for gems, but only a small degree of success has rewarded the efforts, since the few gems which are found have not the red colour of ruby, nor the blue of sapphire, but range through lighter colours of blue, red, green, and yellow. Sapphire crystals have been found in an andesite dike crossing the slates upon which the gravels rest, and the source of the PKECIOUS STONES, ABRASIVE MATERIALS, ETC. 423 gems may have been a similar rock, but no thoroughly scien- tific study has been made of the region and its possibilities. At Corundum Hill, North Carolina, some fairly good sap- phires are occasionally found. A few diamonds have been discovered in gravels in North Carolina, Georgia, and California, in well-defined areas, but they have not been traced to their source. Garnets, valuable for gems, have been found in several parts of the country, but the principal supply comes from the Navajo Indian Reservation, where they are obtained from ant-hills. In 1890 opal was discovered in the state of Washington filling amygdaloidal cavities of varying size in basalt, and operations have been pushed with the result of producing some good-sized stones equalling those of Hungary and Australia. Tourmaline gems are found in the Colorado desert, Rumford, Maine, and elsewhere, and some very beau- tiful titanite or sphene crystals of a beautiful yellow colour have been obtained from the Tilly Foster mine in Putnam County, New York. Quartz, either in the transparent condition, or coloured, or containing inclusions, is frequently used for cheap jewelry, and this industry is of considerable importance, particularly in places visited by numbers of tourists, such as the Hot Springs of Arkansas. In several parts of the west there are fossil forests in which petrified trees are composed of agate or jasper, often beautifully banded, and these are made use of extensively for the manufacture of ornaments and jew- elry. Satin spar or fibrous gypsum is also cut into cheap ornaments and jewelry, and there are numerous other minerals used for similar purposes. Several gems, besides those above mentioned, have been found sparingly in the United States. 424 ECONOMIC GEOLOGY OP THE UNITED STATES. The following table furnishes an approximate statement of the value of the precious stone production of this country : — PRODUCTION or PRECIOUS STONES IN THE UNITED STATES. Stohes. • 1884. 1886. 1888. 1890. 1891. Turquoise . Sapphire . . Quartz . . Gold quartz . Smoky quartz Opal . . . Catlinite . . Garnet . . Tourmaline . Agatized wood Diamond $2,000 1,750 11,500 140,000 12,000 10,000 4,000 2,000 800 $3,000 750 11,500 40,000 7,000 10,000 3,250 5,500 60 $8,000 500 11,150 76,000 4,000 5,000 3,500 .... $28,675 6,725 14,000 9,000 2,225 5,000 2,308 2,250 6,000 $150,000 10,000 10,000 6,000 5,000 5,000 5,000 3,000 3,000 2,000 Total . . $222,825 $118,850 $139,850 $118,833 $235,300 The above table, which is in large part merely a rough estimate, probably does not represent the true value of the output of gems and precious stones, since large quantities are sold at the point of production, and cut by locM jewellers, without any record being kept. Moreover, there are many mineral collectors who purchase precious stones for private and public collections, some of them purchasing the entire output of some of the smaller producing localities. It is not improbable that the true value of the industry is fully double that stated in the above table, but, nevertheless, the precious stone production of the United States is extremely limited, and the country is probably by no means up to its possible PRECIOUS STONES, ABEASIVE MATERIALS, ETC. 425 capacity as a producer of these minerals. Now that the west has entered upon a stage of more minute and intelligent exploration, it need not be surprising if gems of value are found. When we compare our precious stone production with our consumption of cut and uncut gems, which in 1891 was valued at over 112,700,000, and with the output of diamonds from the Cape of Good Hope fields, which in 1890 exported £4,162,073 sterling worth, we plainly see the lack of importance of the United States in this respect. Abrasive Materials. General Statement. — There are two classes of materials which serve for abrasive purposes : those used as a powder or a sand, and. those used as stones. In the first class are grouped sand, diamond, corundum, emery, infusorial earth, and some minor substances ; and, in the second class, millstones, grind- stones, and whetstones. Sometimes stones of the latter class are prepared artificially, by the manufacture of a rock con- sisting in part of powdered or granular abrasive substances ; but more commonly they are naturally formed rocks. Sand is used for abrasive purposes in polishing and sawing certain stones, such as marble, the sand being fed to a straight- edged steel saw, which moves back and forth on the stone, and uses the sand for cutting edges. Diamond dust, obtained from the waste made in cutting diamonds, and from black and imperfect diamond bort, is also used for sawing hard rocks and minerals, chiefly in the preparation of gems and the manufacture of ornaments from hard rocks and minerals. Being the hardest known mineral, it is of great value for these purposes. Corundum and emery are used, in the form of granular fragments, and as a fine flour-like powder, for 426 ECONOMIC GEOLOGY OF THE UNITED STATES. smootliing and polishing purposes, as, for instance, in pol- ishing granite and other rocks, and also in the form of artificially made wheels for grinding purposes. Infusorial earth is also used for polishing, but for a finer grade of work than the above materials. Infusorial Earth. — Certain animals, known as Infusoria, and plants belonging to the group of Diatoms, secrete shells or tests of silica, and when they die these durable parts are left behind. When in particular bodies of water these organisms are the predominant forms of life; having durable shells they tend to accumulate in beds, forming diatomaceous or infusorial earth. These forms of life are particularly abundant in fresh-water ponds; and conse- quently their remains are commonly found in the swamps, which are fiUed-up lakes, of the glacial belt in New Eng- land and other northern states. Where these ponds were small, and their banks bordered with reeds and other forms of vegetation, very little sediment entered, and the accumulations were principally organic, and the infusorial beds comparatively pure. A thin layer of this white, pow- dery earth is found in excavations in many swamps, but it is usually not sufficiently abundant to be of value. Infusorial earth, in this country, is principally obtained from Pope's Creek, Maryland, but California, New Hampshire, and New Jersey also produce some. There is not an extensive demand for this substance, and consequently the output is ^limited. It has served, as an absorbent, in the manufacture of dyna- mite ; but wood pulp is replacing it for this purpose. In the form of a soap or a powder, it is used as silver polish and for other cleansing purposes, and also in the formation of a glaze for bricks. PRECIOUS STONES, ABEASIVB MATERIALS, ETC. 427 Corundum and Emery. — These minerals differ from each other very slightly, the former being oxide of aluminum, and the latter being corundum mixed with iron oxide. The former is, therefore, harder and more durable, and hence more valuable, it being the hardest of the minerals which are common enough for extensive use, ranking next to dia- mond in the mineralogical scale of hardness, diamond being 10, corundum 9 (in its pure form sapphire). Emery is found in the metamorphic rocks at Chester, Massachusetts ; and corundum is produced at Laurel Creek in Georgia and Corundum Hill in North Carolina. It occurs here at the contact of gneiss and serpentine, the latter having resulted from the alteration of an olivine rock. There are other minor localities for these minerals. Practically all of the corundum used in the country is of domestic production, but much of the emery is imported, our imports in 1891 having amounted to 1104,199. Grindstones and Buhrstone. — Grindstones are made of a firm, gritty sandstone, and these are principally produced from the Berea grit of Ohio and Michigan, although Cali- fornia and South Dakota also produce some. Although some of the grindstones used in this country are imported, the greater number are of domestic production. The industry of buhrstone or millstone production has rapidly decreased since the introduction of the roller process of grinding grain, but they are still used in many of the small grist mills, and for grinding cement, paint, gypsum, etc. Stones for these purposes are found in this country ; but the grist mills still using buhrstones prefer the French buhr, which is of superior quality to any produced in this country. A buhrstone must be fine grained and very com- 428 ECONOMIC GEOLOGY OP THE UNITED STATES. pact, much more so than grindstones ; but it must not glaze too readily, nor, on the other hand, should its texture be so loose that particles rub off, as in the case of grindstones. A gritty quartzite or a quartz conglomerate are the rocks best adapted for this purpose ; and in this country the chief supply comes from Ulster County, New York, and, in smaller quantities, from Pennsylvania and Virginia. In 1891 we imported $24,039 worth of millstones. Oilstones and Whetstones. — Oilstones and whetstones are chiefly of domestic production. Since 1823 New Hampshire has been the seat of the scythe-stone industry, a valuable grit for this purpose being found in a mica schist in Grafton County. Whetstones are also found in Massachusetts and Vermont. The western grindstone grits furnish some scythe-stones; but they are more gritty and coarser, and hence inferior to those produced by the New Hampshire company, which also operates the Massachusetts and Ver- mont quarries, and exports considerable quantities to Europe. Oilstones are of a still finer texture, and these are also found in New Hampshire; but the most important seat of the oilstone production is in Garland County, Arkansas, where there are extensive beds of novaculite, of Palaeozoic age, occurring stratified with shales and limestones in very much folded strata. These deposits were first made to produce commercially in 1840, although extensive quarries were worked for implements by the aborigines. These stones, known as Washita and Arkansas oilstones, are recognized as the best in the world for sharpening fine tools, and they are extensively used for this purpose both in Europe and the United States. The most important quarries are situated near the Arkansas Hot Springs, and PEECIOIJS STONES, ABRASIVE MATERIALS, ETC. 429 Griswold states i that they are actually deposited sediments of fine-grained quartz, instead of a chemically precipitated deposit, as was formerly believed. There are immense quan- tities of novaculite in this region, but the grade is very variable, and some of it is quite inaccessible at present. An oilstone, known as the Hindostan, is quarried in Orange County, Indiana. It is a very compact sandstone, and, although very good, does not equal the Arkansas novaculite ; but is more cheaply quarried and fashioned, and hence is sold at a lower price. A more coarsely grained sandstone, known as the Shoemakers' sandstone, is also ob- tained from Indiana, and, until recently, this has been of considerable value in shoemaking ; but the introduction of improved machinery has caused the demand to rapidly decrease. Statistics. — In 1891 this country exported $51,500 worth of whetstones, and the following table shows the production of the various abrasive materials for a series of years : — PRODUCTION OF ABRASIVE MATERIALS IN THE UNITED STATES. Materials. 1880. 1885. 1890. 1892. Infusorial earth . . . Corundum and emery Grindstones .... Buhrstones . ... Whetstones and oilstones, $45,660 29,280 500,000 200,000 8,000 $5,000 108,000 500,000 100,000 15,000 $50,240 89,395 450,000 23,720 69,909 $20,000 88,000 500,000 16,000 150,000 Total $782,940 $728,000 $683,264 $774,000 1 The novaculite of this country, and the industry in general, are fully described by L. S. Griswold in a valuable Monograph entitled Whetstones and Novaculites of Arkansas, Ann. Eept. Ark. Geol. Survey for 1890, Vol. III. 430 ECONOMIC GEOLOGY OF THE UNITED STATES. Salt. Our supply of salt comes either from brine or from deposits of rock-salt. At several places in California salt is obtained by evaporating ocean water ; but this source is not as important as might at first be supposed, since more concentrated solutions occur elsewhere. In various parts of the Cordilleras salt lakes exist, and there is every grada- tion in this region, from fresh-water lakes to deposits of rock-salt, which have resulted from the evaporation of salt lakes. There are several salt works located upon the shores of Great Salt Lake, in Utah, and in Nevada, upon the shores of the smaller salt lakes of that state. The salt thus obtained by solar evaporation is used principally for local purposes, particularly in the chlorination process of reducing ores. Some of these lakes have crusts of salt, and, in some cases, in all the arid regions of the west, the water has entirely disappeared under the influence of the arid climate, and here the ranchmen are able to obtain their supply of salt at the surface, from beds of rock-salt produced by the natural evaporation of dead seas. Rock-salt deposits, now buried in the earth, have resulted from the same process as that just described, and these are found stratified in rocks of various ages from the Silurian to the present. Water, in its passage over and through the earth, dissolves many minerals, the most common being salt.^ When these waters, which contain so little salt that they seem fresh, enter an enclosed sea without an outlet, the fresh water is evaporated and the salt is concentrated, until, finally, after a long period of time, it may accumu- 1 The mineralogioal name of salt is halite. PEECIOUS STONES, ABRASIVE MATERIALS, ETC. 431 late in a solid mass of rock-salt either at the bottom of the lake, or in place of the lake, if all of the water is evaporated. Many impurities usually occur with rock-salt, either disseminated through it or concentrated into layers. These represent the impurities dissolved in water with the salt. Other chlorides, particularly those of calcium and potassium, gypsum, iron, and sedimentary deposits of clay or sandstone, are some of the common impurities which must be separated. A bed of rock-salt of considerable extent occurs in the Tertiary deposits on Petit Anse island in Louisiana, where it was discovered, during the Civil War, beneath the site of some salt wells which had been known for a long time. In western New York beds of rock-salt occur in the Silurian over a wide area, in Kansas in the Triassic, and in Texas in the Permian rocks. Some of these rock-salt deposits are actually mined, but some are worked as brines, water being allowed to enter the salt beds from below, through artificial borings; and, after dissolving the salt, the water is brought to the surface either through natural artesian wells or by pumps. Some of these beds are un- doubtedly dried-up salt lakes, but some may be salt deposits which have accumulated in shallow coastal lagoons or upon salt marshes along some ancient shore. However, much of the salt of the country is made from natural brines which occur scattered through rocks of all ages, and are obtained from wells, either by pumping or as artesian water. The most common mode of occiirrence is in beds of sandstone, capped and underlain by more impervious beds. Some of this salt may have been originally built into the rocks when they were deposited in the ocean ; some may 432 ECONOMIC GEOLOGY OF THE UNITED STATES. represent beds of rock-salt subsequently dissolved ; and some are apparently derived in the same manner as petroleum and natural gas, — namely, by accumulation in a porous stratum from some outside source. Associated with the salt in the brine are the same minerals which are found in rock-salt; and brines are also frequently associated with petroleum and natural gas. Some of the impurities, such as gypsum, are injurious ; and one of the chief problems in salt manufacture is how to remove all of these substances without injuring the salt or interfering with its evaporation. Our salt supply comes chiefly from the Salina group of the Silurian in New York and from the Carboniferous in Michigan; but other states and other ages of rocks are also saliferous. The salt is obtained in some places by solar evaporation, in large shallow pans ; in others, by artificial heat obtained by burning wood, coal, or natural gas. The price of this mineral is extremely low, and it is produced at a profit only where it can be obtained very easily and evaporated cheaply. This is very strikingly shown by the fact that sea water can rarely be evaporated, even in arid regions, and made to yield salt at a profit. Nevertheless, both in this country and in Europe this is done in certain very favourably situated localities. The distribution of the salt supply is shown in the follow- ing table ; but this does not represent the distribution of salt, for there is probably vastly more in the Tertiary and recent strata of the Cordilleras than in any other part of the country, but it is too far from the market to be of value. Very pure salt can be obtained by the wagon-load in scores of places in the far West. PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 433 PRODUCTION OP SALT IN THE UNITED STATES. States. 1883. 1886. 1887. 1889. 1892. New York . . 1680,638 $874,258 $936,894 $1,136,503 12,200,000 Michigan . . 2,344,684 2,967,663 2,291,842 2,088,909 1,906,027 Kansas . . . 202,500 698,395 Utah. . . . 100,000 75,000 102,375 60,000 295,000 Ohio .... 231,000 199,450 219,000 162,500 276,000 West Virginia, 211,000 145,070 135,000 130,000 166,800 California . . 150,000 160,000 140,000 63,000 125,000 Louisiana . . 141,125 139,911 118,735 152,000 81,000 Total . . . $4,251,042 $4,825,345 $4,093,846 $4,195,412 $5,879,222 New York has rapidly increased its output, and Kansas has shown a remarkable increase since 1888, when salt first began to be produced there. At the same time, Louisiana and Michigan have decreased; and in ten years there has been a very slight total increase for the country. Our pro- duction of salt is practically what we consume, although we export about $30,000 worth a year ; and in 1892 we imported 1768,734 worth, chiefly for special purposes. The output for 1892 represents 11,585,734 barrels of 280 pounds each. Aside from a certain increase in demand for this mineral in the reduction of ores and in the manufacture of caustic and baking soda, the increase in the salt industry must be depen- dent upon the increase in population, its consumption for cooking, table, and curing purposes being the most important uses of the mineral. 434 ECONOMIC GEOLOGY OF THE UKITED STATES. OUTPUT OF SALT IN THE WORLD, 1891. Metric Tons (2204 Lbs.). Great Britain . 2,077,072 Eussia . . . 1,400,0001 United States . . 1,300,107 Germany . . 666,793 Spain .... 225, 870 '' Hungary . . . . 159,898 Canada . . . 45,021 Italy .... 31,285 Colombia . . 21,644 Bromine. This element is not found free, but in the form of bromides, and the chief source is from rock-salt and salt water. It is produced as a by-product in the manufacture of salt in West Virginia, Michigan, and some other salt regions. During the evaporation of salt, it becomes concentrated, together with some other substances, in the bittern or mother liquor, from which it is extracted. Its chief use is for chemicals, in the manufacture of an aniline colour (eosene) and, in smaller amounts, as a disinfectant. In the past twelve years the product of bromine in this country has varied somewhat; but in 1892, 379,480 pounds were produced, valued at $64,512. Borax. Among the other substances found associated with salt are borax, soda, and gypsum, the latter of which is described in the preceding chapter. Borax exists in the alkaline flats of the arid regions which contain valuable stores of alkaline ' Estimated. 2 Exported. PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 435 substances, the greater part of which no attempt has ever been made to utilize. In Tuscany this substance occurs in hot springs, while in Hungary it is obtained from the rock- salt ; but in our country the source is the beds of desiccated lakes in the desert regions of Nevada and California. The " salines," which contain borax, in the west, probably received their supply from hot springs resulting from the neighbour- ing volcanic activity which was very well developed in the Great Basin during the period of desiccation. The minerals are borate of soda and of lime, mixed with clay, gypsum, salt, and other impurities. There is also borax in fissure veins in California, probably deposited in the tube of a hot spring similar to the Tuscan springs; and the industry of borax production in that state has rapidly increased since the introduction of deep mining. Aside from the European localities, borax is produced also in Thibet, Asia Minor, and Chili, in dried lake bottoms similar to those of the Great Basin of the Cordilleras. The original source of borax is probably in all cases vol- canic emanations, the hot springs of Tuscany illustrating the active stage in its production. These, flowing into the waters of the salt lakes, caused borax to accumulate in the same manner that salt and gypsum accumulate in the same places. In the west the borax permeates the soil, as does ordinary alkali ; and in favourable situations, a crust forms upon the surface. After this has been removed, a new deposit commences to form by the solution of the mineral in percolating waters ; and its rise to the surface by capillary action forms a crust by the subsequent evaporation of the boracic waters. After five or six years a new crust is formed ; but this naturally does not equal, in thickness, the 436 ECONOMIC GEOLOGY OF THE UNITED STATES. original crust which has been accumulating for ages. It is removed, dissolved, and evaporated ; and the process is repeated until crystals of nearly pure borax are formed. Borax is used in v^elding, since it forms fusible salts with most metallic oxides, and it is also used in glazing brick, chinaware, etc., as well as in the manufacture of enamel for ironware, and for the gloss given to starched linen in laun- dry work. As an antiseptic it is important, and it is also used in dyeing, for sanitary purposes, and in drugs. Our consumption of borax about equals the production, which is given in the following table : — PRODtrCTION OP BORAX IN THE UNITED STATES. Pounds. Year. California. Nevada. Total. 1864 24,304 . . . . ' 24,304 1865 251,092 251,092 1875 2,336,000 2,804,000 5,140,000 1880 1,219,948 2,640,800 3,860,748 1885 1,885,300 5,586,104 7,471,404 1890 6,402,034 5,487,794 11,889,828 1892 11,596,574 2,646,525 14,243,099 Since 1864 the total production of the United States has been 128,539,190 pounds, and the price has steadily decreased, with some fluctuations, having remained, however, for the past four years 7^ cents a pound in New York. The value of the borax output at the place of production was, in 1892, 1925,810. PEECIOUS STONES, ABRASIVE MATERIALS, ETC. 437 Natural Soda. This is obtained from the alkaline substances which are so abundant in arid regions, such as those of the Great Basin, the deserts of Africa, Asia, and South America, where it occurs in the form of carbonate and bicarbonate of soda mixed with clay and various chemical impurities. The alkali coats large areas with a snow-white, efflorescent deposit, and sometimes with a thick crust. There are vast quantities of these substances in the deserts, alkali flats, and alkaline pools of the west ; but as yet little has been done to extract them, and only a small amount is produced. This is probably an industry which will assume marked importance in the future, now that the knowledge of methods of extrac- tion has improved and means of cheap transportation are at hand. Magnesite. This mineral, which is a carbonate of magnesia, occurs in a number of places in California, and possibly elsewhere in the Cordilleras. It resembles unglazed porcelain, being hard, fine grained, and white. There are several modes of occurrence, one being in a vein from five to seven feet thick in Childs Valley, while elsewhere it is generally bedded with talcose slates, serpentines, and magnesian carbonates or dolo- mites. Until recently no use has been made of this mineral, but within a few years experiments have been made with the idea of introducing it; and already it is being used as a substitute for chlorine, as a bleacher, in the manufacture of paper from wood pulp, for which purpose it is said to be better suited, as well as cheaper, than chlorine. Other uses are also made of it, and it is expected that it will be possible 438 ECONOMIC GEOLOaY OF THE UNITED STATES. to ship the mineral as far east as Pittsburg and compete with the foreign magnesia used in the manufacture of basic steel. Sulphur. Sulphur is obtained from three sources, — iron pyrite, which has already been described,^ from the waste calcium sulphide produced in the alkali works, and from native sul- phur. Native sulphur is known to exist in various parts of the west, but nearly all of these deposits are so inaccessible, and the cost of transportation to the market so great, that they are not exploited. At present the total supply pro- duced in this country comes from Utah and Nevada. Out- side of the United States sulphur is found in numerous places, chiefly in volcanic regions. Extensive deposits are known to exist in Japan, but they are not favourably situated for profitable production, and our principal supply comes from the island of Sicily, which has produced this mineral for several centuries. It is obtained here from various mines, scattered over a wide area, and worked to a considerable depth by very crude and antique methods. Since 1831 there has been produced from this district nearly 13,000,000 tons of sulphur, valued at not far from $350,000,000. At first thought the explanation of the origin of sulphur seems simple, particularly when it occurs in volcanic regions, where emanations of sulphur vapor are commonly associated with eruptions of lava. Since sulphur deposits are so com- monly associated with recent volcanic rocks, there is good reason to believe that they are frequently the result of this association. But the breaking up of sulphuretted ip. 300. PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 439 hydrogen, produced- from the decomposition of gypsum or of organic remains, will also form sulphur deposits, and such appears to be the origin of at least some of the Sicilian sul- phur and of a bed of sulphur which occurs stratified with sedimentary rocks in a region no less remote from volcanoes than western Louisiana. The demand for native sulphur is decreasing, although the uses to which it is put are increasing. This is due to the increasing use of pyrites in the manufacture of sulphuric acid, and to the production of sulphur from the calcium sul- phide, which was formerly a waste product in the manu- facture of alkalies. The statistics of the production of iron pyrite are given in a previous chapter. We have in this industry the rather anomalous condition of abundant supplies at home, but practically no home produc- tion, notwithstanding a heavy demand for brimstone at a price varying from |22 to |30 a ton. There are other minerals of minor importance which illustrate the same peculiarity ; but in most cases where our mineral supply is good our production is large. These peculiarities are generally, as in the present instance, the result of a failure of railroad transportation to compete with ocean transportation, combined with certain difficulties of mining and transporting materials in our sparsely settled western territory. There are some reasons to hope that the sulphur deposits of the west will eventually become of importance, but at present only those of Utah are of value. Sulphur is used in the manufacture of sulphuric acid, matches, gunpowder, and many minor substances, as well as in its native condition in medicine and for other purposes. In 1892 our production of this mineral amounted to 1825 short 440 ECONOMIC GEOLOGY OE THE "UNITED STATES. tons, valued at $54,750, while we imported, chiefly from Sicily, 100,711 long tons, valued at 12,189,307. During 1890 Sicily exported 344,763 tons, and during 1891, 293,328 tons. Fluorite. This mineral is not uncommon, as a veinstone, in various parts of the world, and it is found sparingly in granites and metamorphic rocks ; but until within a few years it has not been considered of much value. Now, however, it is intro- duced into the reduction of some of the refractory ores, for which it serves as an excellent flux; and it is also used in the manufacture of opalescent glass, in the production of hydrofluoric acid, and for other minor purposes. In this country the only source of fluorite is the galena-hearing limestones at Rosiclare, Hardin County, in the southern part of Illinois. Formerly these deposits were worked for lead, and the fluorite was a waste product, but now the re- verse is true. The mineral occurs in true fissure veins, which have been traced for a distance of several miles. Fluorite is not an uncommon mineral in altered dolomitic limestone, and it is possible that the above deposits will change in character when the limestones are passed through. The output of fluorite from this region has more than doubled in the past ten years, and in 1892 amounted to 9000 short tons, valued at $54,000. No fluor-spar is imported, but it is obtained as a by-product in the reduction of cryolite to aluminum and sodium. This source is decreasing, how- ever, with the introduction of bauxite as a source of alumi- num. In 1892, 8155 long tons of cryolite, valued at 173,847, were imported into this country. PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 441 G-raphite. Plumbago, or graphite, one of the pure forms of carbon, occurs in metamorphic rocks, particularly in limestones, where it is undoubtedly the result of the metamorphism of carbonaceous substances of organic origin. The same is true of the graphitic coals of Rhode Island, where the Car- boniferous coal has been metamorphosed almost to the stage of graphite, and locally actually to this condition. The Rhode Island graphitic anthracites are used to some extent in the manufacture of crucibles and stove-blacking. Graphite has also been mined in Pennsylvania, New Jersey, Michigan, and Wyoming ; but the only important American source of this mineral is at Ticonderoga, New York, where, in the metamorphic rocks, there is a vein of sufficient purity to be used in the manufacture of lead-pencils. This mineral is found in Japan, Russia, Canada, Germany, Austria, and Ceylon, the bulk of our supply coming from the latter region. In every case the source being rocks of metamorphic origin, this fact has led some to hold that for this reason we must consider them to be of sedimentary origin and the graphite to be inorganic in origin; but this is a mere assumption. In 1891 the output of graphite in the United States was 1,559,674 pounds, valued at 1110,000, and in the same year we imported |555,080 worth of plumbago. The better qual- ities of graphite are used in the manufacture of lead-pencils, and much is also used in the preparation of lubricants, while the poorer qualities are manufactured into stove polish, cru- cibles, paint for the protection of iron, and other similar purposes. 442 ECONOMIC GEOLOGY OF THE UNITED STATES. Lithographic Stone. Although this country imports about |100,000 worth of unengraved lithographic stone each year, none is produced here. This is probably not because there is none in the country, but rather because its occurrence has not been detected. There are, in many places, rocks which very closely resemble lithographic stone, but these have not the fineness of quality which fits the Solenhofen stone so well for lithographic purposes. This is a compact, homogenous, fine-grained limestone, of gray or creamish colour, found at Solenhofen in Germany. It varies somewhat in texture, and colour, and some is suited only to low-grade work. Litho- graphic stone is found elsewhere in Europe, but in no case is the quality equal to the German stone. In Texas there is a stratum which is apparently a good quality of lithographic stone, but it is cut by joint planes, which prevent its extrac- tion in good-sized blocks. Below the surface this may be found to be less jointed, but the deposit has been scarcely prospected. Beds of this stone are also reported to occur in Virginia, Indiana, and Arkansas, but nothing can be said at present concerning their value. It seems very improbable that, among all the varieties of rock, of all ages and all kinds of origin, occurring in the west, this particular kind should be absent ; and the most probable explanation of our non-production is ignorance of its character by , the pros- pectors who have explored the region. Mica. The group of micas, which includes a great variety of minerals, all of which are complex silicates of alumina, with PKECIOTTS STONES, ABEASIVE MATERIALS, ETC. 443 varjdng proportions of iron, sodium, potassium, magnesium, etc., is one of the most common groups of minerals, being present in the greater number of metamorphic, many igneous, and some sedimentary rocks. It is, however, of value only when found in considerable quantities, in the form of large sheets ; and these occurrences are relatively rare. The two varieties, biotite and muscovite, are of commercial impor- tance, the former being only semi-transparent in thin sheets, while the latter is quite transparent. Large sheets of these minerals are found, usually in coarse pegmatite veins in granite, in coarse granite, and in thin beds in metamorphic rocks. Mica is obtained from several places in New Hampshire, but chiefly from the Palermo mine in Grafton County, which pro- duces nearly all the supply obtained in this country. Small quantities also come from North Carolina, and a very little from South Dakota and Wyoming. In the table at the close of this section it will be noticed that, since 1884, there has been a marked falling-off in the output of the country. This is due to the importation of a very fine grade of mica from India, where it occurs in extensive deposits which can be so easily worked and so cheaply produced that, even with a duty of 35 per cent ad valorem and the long distance of transportation, it can compete with the mica produced at home. Recently Canada has begun to produce mica in great quantities ; and the mineral, although biotite, and therefore not transparent, can be used for various purposes where trans- parency is not necessary. This biotite is obtained chiefly in Ottawa from the apatite mines, and the industry is succeed- ing that of apatite production which has been seriously 444 ECONOMIC GEOLOGY OP THE UNITED STATES. checked by the important discoveries of phosphates in the United States. During the process of mining, the mica is obtained in as lai'ge pieces as possible; and it is afterward cut into sheet mica, provided the quality is sufficiently good. For this purpose, either wine colour or white is desired, and the sheets must be smooth and free from spots. The price varies according to the size; but of late years there has been an increasing demand for the smaller sizes, since the industry in which it is chiefly employed (panels of stove and furnace doors) now makes use of numerous small sheets instead of one large sheet. Sheet mica is also used extensively in electrical apparatus; and since colour is not important, the dark biotites of Canada are being used for this purpose. This class of mica must be flexible and non-conductive, and the sheets must be of uniform size, although many different sizes are made. There is also a rapidly increasing demand for ground mica, which is made of the scraps and waste produced in the manufacture of sheet mica. One of the most im- portant uses of this material is for the production of the frosted and spangled effect in wall papers, and the finer grades of ground mica are used for metallic white surfaces. Ground mica is also used in the manufacture of lubricants for car and carriage wheels. The production of mica in this country is shown in the following table. Of the output for 1892, New Hampshire produced, approximately, $70,000 ; North Carolina, $25,000 ; and the other $5000 was distributed between several states. The imports come chiefly from India and Canada. .PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 445 PRODUCTION AND IMPORTS OP MICA IN THE UNITED STATES. Yeak. Pounds . Value. Impokts. 1880 1884 1890 1892 81,669 147,410 60,000 75,000 $127,825 368,525 75,000 100,000 $12,562 27,655 146,975 100,846 The waste and scrap material made into ground mica is not included in the above table. In 1892 it amounted to 959,000 pounds, valued at 167,130. Talc and Soapstone. A series of minerals of different varieties, but possessing the same general character, are included in this group. They are hydrated silicates of magnesia, and are soft, with a soapy feeling, a colour usually grayish or greenish, and a greasy lustre. Some, such as fibrous talc, bear a certain resemblance to asbestos; and they are all characterized by their slight expansion during changes of temperature, which adapts them to certain particular uses. In an impure state they are common in metamorphic rocks, often in sufficient quan- tities to produce talcose schists ; and among these, beds of sufficient purity for commercial purposes are sometimes found. Nearly every state in the Union where metamorphic rocks occur has talc deposits; but only a very few produce it. Steatite, or soapstone, is the most common form, and this is found in the metamorphic rocks of Pennsylvania, New Hamp- shire, New Jersey, Virginia, Vermont, and Maryland, but 446 ECONOMIC GEOLOGY OF THE TJNITBD STATES. principally in the two first states. Fibrous talc is mined near Gouverneur, New York, but some comes also from Fairfax County, Virginia. Soapstone is obtained from quarries ; and the large blocks are trimmed into slabs to be used for various purposes, such as hearths, mantels, fire-bricks, linings to stoves, laundry, bath, and acid tubs, etc. Aside from its slight expansion and contraction under changes of temperature, soapstone does not absorb acid or grease, and this makes it valuable for some of the above purposes. The smaller fragments are made into smaller articles, such as slate-pencils and orna- ments. Ground into a powder, it is used as an adulterant of soap, paper, rubber, etc. ; and owing to its extreme fineness of grain, it is valuable for paint, particularly that used for the protection of metal, since it not only adheres closely, but also resists the attacks of acids and solvents. Steatite grease is used as a lubricant, and there are many similar uses for the mineral. The aborigines quarried soapstone extensively for the manufacture of ornaments and pipes, these being easily fashioned because of the softness of the rock. The fibrous talc produced at Gouverneur, New York, is entirely ground to a powder, and used chiefly as a filler of medium quality paper and for increasing its weight. For the purpose of a filler, it is superior to clay, since it is fibrous and makes the paper stronger. It is also used as an adulter- ant of soap and of many white powdery substances. In 1889, 12,715 short tons of soapstone were produced in the United States, and of this 4371 tons came from Pennsylvania, 4250 tons from New Hampshire, 1500 tons from New Jersey, and 1300 tons from Vermont. The pro- duction of talc and soapstone in the United States is shown PRECIOUS STONES, ABEASIVE MATERIALS, ETC. 447 in the following table, in which it will be seen that the industry is a rapidly growing one : — PRODUCTION OF TALC AND SOAPSTONE IN THE UNITED STATES. Yeak. EiBKOus Talc. SOAPSTONE. Short Tons. Value. Short Tons. Value. 1880 . . . 1885 1892 .... 4,210 10,000 51,000 f57,730 110,000 459,000 8,441 10,000 19,000 $66,665 200,000 266,000 Asbestos. There are two species of minerals which have a fibrous habit and marked resistance to heat, — one asbestos, a variety of hornblende, the other chrysotile, a variety of serpentine, and both called asbestos in the market. The first occurs in metamorphic rocks rich in the varieties of hornblende, the second is found in serpentines which have commonly resulted from the alteration of oli vine-bearing rocks. Both are equally valuable for their power of resisting heat, but asbestos is inferior in strength and is not used where great strength is required. There are no deposits of chrysotile which are worked in this country, but asbestos is found in a belt of meta- morphic rocks on the eastern slope of the Appalachians from New York to Georgia. Limited amounts have been produced from here, but the principal source of asbestos in this country is California, although some occurs also in Wyoming. During 1891 this mineral was reported from 448 ECONOMIC GEOLOGY OF THE UNITED STATES. several parts of the Cordilleras, and a company was organ- ized for its production in Gallatin County, Montana. The output of asbestos in this country has steadily decreased, and, in 1891, only 66 tons, valued at $3960, were produced. Our supply comes almost entirely from Canada, which, since 1879, has become an important pro- ducer of chrysotile, the market having previously been supplied from Italy. The Italian asbestos has long fibres and is well suited to weaving. The Canadian chrysotile comes from the serpentine belt of the province of Quebec south of the St. Lawrence. Our imports of asbestos for 1891 were valued at |358,461; and as these are rapidly increasing, it will be seen that the discovery of extensive deposits of this substance in this country is very desirable. In 1891 Canada produced 9279 short tons of asbestos, valued at 1999,878. This mineral is used for fire-proof mineral cloth and paper, fire-proof paints, linings of fire-proof safes, for packing, for covering boilers, and for numerous purposes where fire-proof qualities are desired. Barite. This mineral, the sulphate of barium, also called barytes and heavy spar, is a common veinstone and is remarkable for its great weight. The chief commercial source in this country is from veins and pockets in limestones, principally from Missouri and Virginia, the work of extraction in the former state being done at intervals by farmers. Barite must be free from quartz-grains, which make the powder gritty, and from iron stains, which injure its normal white colour, although it may be made white by boiling in sulphuric acid and thus removing the iron stain. PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 449 Barytes is used as a pigment and as an adulterant for white lead, which it closely resembles in colour and weight, and for other purposes of adulteration. Its great weight and white colour make it valuable for these purposes, and it it said that it does not injure the quality of white lead. It is not distinctly injurious in other forms of adulteration. The United States produced, in 1891, 34,796 short tons of barite, valued at $118,363, and our imports of manufactured barium sulphate were valued at |22,458, and of the unman- ufactured barite, $8816. Of our output, in 1891, Missouri produced $60,000 worth; Virginia, $52,765; and the bal- ance, $5688 worth, came from North and South Carolina. Mineral Paints. Various mineral products, clays, minerals themselves, and compounds manufactured from them, are made use of in the manufacture of paint. Already chromium and cobalt ores have been considered, and, in the discussion of lead, it was stated that one of the most important uses of the metal was the production of white lead, which is of so much value in paint manufacture. In 1891 the white lead product was 78,018 short tons, valued at $10,454,029. The use of barite as an adulterant and the manufacture of zinc- white as a substitute for white lead have been referred to in previous pages. The value of the zinc-white produced in 1891 was $1,600,000. Red lead and litharge are also made artificially, the value of the red lead production in 1891 being $591,730, and of litharge $720,925. Several metallic paints are also manufactured, and many colouring substances are made by chemical processes; but the consideration of these scarcely comes within the scope of this work. 450 ECONOMIC GEOLOGY OE THE UNITED STATES. Natural metallic paint is made from the coloured clay which is sometimes produced by the decay of mineral veins, — copper producing green ; iron, red and yellow earths, etc. Darl^ red and brown paints of this nature are mined in Penn- sylvania, New York, and elsewhere. In 1891, 25,142 short tons of such paint, valued at $334,455, were produced. The production of ochre is also an important industry, and, even by the aborigines, clays coloured bright red and reddish yellow by iron peroxide were used as pigments. There are large deposits of such clays, and they are mined, finely ground, and then mixed in paints, giving both colour and body to them. In this industry Pennsylvania ranks first, but Virginia and Missouri also produce considerable quan- tities. During 1891 the output of 18,294 short tons of ochre was valued at 1233,823. General Summary of Mineral Production. The mineral industry of the United States deserves to rank among the most important of our industries. In 1892 approximately $670,000,000 worth of mineral products were won from the earth, this estimate for most of the minerals representing the value of the product at the mines. The materials thus won serve as the basis for a vast series of manufacturing industries and for a vast amount of exchange. In the industry of producing these materials, and in those industries which are dependent for existence upon the sup- plies of mineral products, a very considerable percentage of our population is employed. Indeed, it would be difificult to imagine the condition of the nation if these supplies were not at hand. Even more difficult is it to estimate the importance of PKECIOUS STONES, ABRASIVE MATERIALS, ETC. 451 these mineral industries in aiding the growth of the nation and our remarkable industrial progress. There are two great primary industries, — the one supplying food and cer- tain products for manufacture, directly or indirectly from agricultural supplies ; the other, the extraction of substances from the earth and the manufacture of materials from them. In both of these industries the United States holds a high rank ; but, while there may be other nations which equal our agricultural industry, there are none which approach us in mineral resources. For the highest industrial development both of these industries should go hand in hand, and this is the case in the United States. While it may be said that industrial progress is largely dependent upon mineral resources, it is equally true that, for the highest development of these resources, a certain measure of progress in industry is first necessary, in the present state of our civilization. Thus it is that the mineral resources of the United States are, with the exception of certain precious and valuable metals and a few minor substances, developed chiefly in the eastern states. This is even more marked when the whole world is considered; for the industry of mineral production of Europe and the United States far exceeds that of all the rest of the world. This is partly due to lack of exploration, cost of transportation, sparseness of population, and other similar causes ; but it is also, in large part, due to the small degree of industrial progress. Why, for instance, do Mexico and the South American nations depend upon the European and American markets for so many products of the mineral industry? Certainly not for lack of opportunities. Japan has recognized this point and has undertaken to learn the lessons of industrial arts which 452 ECONOMIC GEOLOGY OP THE UNITED STATES. Europe and America have learned by centuries of experi- ence in their development. The people of the western part of our own country and the other nations of the American continents have reached the stage of production of crude materials for the use of those who know how to utilize them ; and the materials which are made from them are in part returned to the sections which produced the raw mate- rial. It is true that this is in a measure the result of sparse- ness of population, but only partly so. The southern states are rapidly emerging from this stage, and the west will find this its next step of progress. When this stage is reached, population increases more rapidly, and the demand for materials increases. Our east- ern states have readied the stage where nearly all economic minerals have a market value, and it is for this reason that these states hold so.high a rank in mineral production ; for the region is not rich in mineral resources, and only coal, iron, petroleum, building-stones, and minor substances are of importance. The west is the great mineral region of the country, and, indeed, of the world, but its resources are only partly developed. Iron, coal, building-stones, petroleum, salt, gypsum, and many minor substances are practically not produced in that section, although all of these are abundant. When this region is fully developed, it is doubtful if there will be any necessity of looking beyond the confines of the nation for more than a very few mineral products. Even at present the number of minerals which this country finds it necessary to import is small, and not only do we supply -our own needs, but we export more than we import of most min- eral products. Our total mineral exports are considerably in excess of the imports. PEECIOTJS STONES, ABRASIVE MATERIALS, ETC. 453 The rank of the nation in metallic products is given at the close of Part II. ; but the statistics for non-metallic minerals are less valuable, since many of them are produced for local consumption rather than for exportation. In the production of petroleum, natural gas, and phosphates this country holds first rank, and it is doubtful if any nation has a greater pro- duction of building-stone. The rank of the country in the production of coal is second, and of salt third, among the nations of the world. The following table shows the value of the mineral pro- duction for materials whose total value, in 1892, exceeded 11,000,000: — VALUE OF MINERAL PRODUCTS OF THE UNITED STATES.! Pkodfcts. 1880. 1885. 1890. 1892. Pig iron (N. T.) $101,466,500 $64,712,400 $151,200,410 $186,806,915 Bituminous coal 69,128,840 84,206,009 108,708,000 122,019,610 Anthracite coal . 38,680,250 76,698,000 66,895,772 74,624,614 Silver (coining value) 89,200,000 61,600,000 70,485,714 88,909,210 Building-stone . 18,856,065 19,000,000 47,000,000 45,000,000 Lime .... 19,000,000 20,000,000 35,000,000 38,500,000 Copper (N. T. value) 11,491,200 18,292,999 30,980,800 37,850,000 Gold (coining value) . 36,000,000 81,801,000 82,845,000 83,000,000 Petroleum 24,183,288 19,198,243 85,366,105 80,229,128 Lead (N. T. value) 9,782,600 10,469,431 14,266,708 17,917,000 Natural gas . . 4,867,200 18,742,726 18,000,000 Zinc (N. T. value) 2,277,482 8,539,856 7,474,962 7,708,680 Cement 1,852,707 8,492,600 6,000,000 6,586,098 Salt 4,829,566 4,825,845 4,752,286 5,879,222 Mineral waters 500,000 1,812,845 2,600,750 3,000,000 Phosphate rock . . 1,128,828 2,846,064 3,218,795 2,861,219 Limestone for iron flux 8,800,000 1,678,478 2,760,811 2,097,600 Zinc-white 768,788 1,050,000 1,600,000 1,200,000 Mercury (San Francisco value) , 1,797,780 979,189 1,208,616 1,119,720 Potter's clay 200,457 275,000 756,000 1,000,000 1 Extracted from RothweU's Mineral Industry, 1892, pp. 4-9. 454 ECONOMIC GEOLOGY OF THE UNITED STATES. As will be seen, there has been a considerable change in the rank of importance of the various industries since 1880. The following table shows the total value of the mineral products of the country at intervals during the past thirteen years. This is exclusive of brick clays and some minor products which are not considered in this treatise. TOTAL VALUE OF THE MINERAL PRODUCTS OF THE UNITED STATES. Year. Metallic Pkoducts. Non-Metallic Prodccts. Total. 1880 . . $201,283,094 $165,440,966 $366,724,060 1882 219,860,518 223,408,023 443,268,541 1884 186,468,162 212,697,759 399,165,921 1886 215,658,334 247,208,210 462,866,544 1888 256,623,933 299,988,780 556,612,713 1890 308,641,957 337,696,669 646,338,626 1892 318,638,596 350,959,283 669,597,879 For the ten years ending 1889, the total mineral product of the United States amounted to 14,627,343,630, of which less than one-half, or 12,165,000,310 worth, were metallic products. In the above table it will be noticed that, while there has been a marked increase in the output of both metallic and non-metallic products, the most striking in- crease has been in the last-named group ; and this will probably be more marked in the next decade. The following table, prepared from materials in the Eleventh Census, shows the value of the mineral industries in the fourteen states which had an output of over 110,000,000 PEECIOUS STONES, ABEASIVE MATERIALS, ETC. 455 in 1889. In the case of each state the principal mineral products are given in the order of their importance, based upon their value, but the products of minor importance are not listed although they are included in the total valuation. Thus in Pennsylvania the most important product is coal, the second petroleum, the third natural gas, etc. For each industry the rank which the state holds, in comparison with the other states, is also given in figures : — MINERAL PRODUCTION OF LEADING STATES, 1889. States. Value. Most Important Mineral Products. Pennsylvania . 1150,876,649 11 11 Coal, petroleam,! natural gas, stone. 3 iron ore. Michigan 70,880,524 Iron ore, copper, salt. Colorado . . 41,126,610 1 2 7 1 12 Silver, gold, coal, lead, stone. Montana . . 33,737,775 Copper, silver, gold. Oliio. . . . 26,653,439 8 2 2 8 Coal, stone, petroleum, natural gas. New York . . 24,165,206 8 1 2 2 Stone, cement, iron ore, salt. California . . 19,699,354 2 9 8 1 Gold, stone, silver, mercury. Illinois . . . 17,110,317 Coal, stone. Missouri . . 15,931,575 8 7 12 Coal, stone, zinc ore, lead. Utah . 11,681,019 Silver, lead. 4 15 Iron ore, stone. Minnesota . . 11,542,138 Iowa . . 10,267,068 Coal. 5 18 Iron ore, stone. Wisconsin . . 10,18.3,861 Nevada . . . 10,143,878 Silver, gold. In 1889, of the total output of the country, which amounted to $587,230,662, 1386,616,834 worth came from 1 Including the New York output. 456 ECONOMIC GEOLOGY OF THE UNITED STATES. states east of the Mississippi, and $252,083,744 worth, or nearly one-half of the total, came from those states east of the Mississippi which are partly in the Appalachians or which border the Atlantic. This is not so strikingly shown in the above table as it would have been had the states of minor importance (with an output of less than $10,000,000) been included in the table. The value of the imports and exports of the leading products is shown in the following table. Aside from these, the exports and imports amount to only a few million dollars annually. EXPORTS AND IMPORTS OF MINERAL PRODUCTS, 1891. Minerals. Exports. Imports. Gold coin and bullion Silver coin and bullion $79,086,581 27,692,879 1,592,931 46,174,835 30,736,442 15,703,543 3,000,0001 130,371 173,887 $44,970,110 18,192,750 9,724,716 Petroleum Iron, and steel, and their products . . Tin and terne plate 41,983,626 25,900,305 8,091,363 Copper 1,665,729 Precious stones 12,745,435 Coal 1,800,0001 Cement 4,411,330 Lead Sulphur 2,867,633 2,675,192 Total •$204,291,469 $175,028,189 In this table some manufactured articles are also included. If manufactured tin and the precious stones were omitted, our exports would greatly exceed our imports of mineral products. 1 Estimated. APPENDIX. LITERATURE OF ECONOMIC GEOLOGY. This list does not pretend to be a bibliography, nor is there even an attempt to refer to all of the many valuable general treatises upon the various aspects of economic geology. With the exception of works upon mining methods and metallurgy, these references are usually to works with which the author is personally familiar. For special descrip- tions of localities and individual economic products of this country, the files of the American Journal of Science and the Engineering and Mining Journal are of particular value, and in these there are many hundred articles of this nature. Similar sources in other countries may be resorted to for accounts of the mineral products abroad ; and there, as well as in this country, such descriptions are also found scattered through the geological literature. There is no complete bibliography of the subject.^ The national geological survey reports of the various countries all contain something of economic geology, and such descriptions usually possess great scientific as well as practical value. In the United States very important de- ^ Since the above was written an extremely valuable treatise, entitled Ore Deposits of the United States, by J. F. Kemp, has been published, and one of the most important parts of the work is its very complete and extensive bibliography. 457 458 ECONOMIC GEOLOGY OF THE UNITED STATES. scriptions of the local mineral resources are found in the various state geological survey reports. Nearly every state in the Union has at one time or another supported a geo- logical survey, and at present many states still have such surveys. In these, full description of the local economic geology will be found. Thus the Pennsylvania reports contain very complete descriptions and statistics concerning the coal, oil, gas, and iron industries of the state, the Ohio reports contain the same with reference to that state ; the New Jersey geological survey publishes valuable infor- mation concerning the clays and iron mines; and many other states publish similar reports. These surveys, when in their best development and when properly managed, keep in advance of the development of the state, and show where valuable deposits exist and how they may be obtained. Thus the clay industry of New Jersey is the direct outcome of the work of the geological survey, the bauxite deposits of Arkansas were discovered by the survey of that state, and the oil and coal industries of several states owe much to the work of the state geologists and their assistants. Usually the publications of the surveys merely describe the local deposits ; but one state, Arkansas, has gone farther than this and treated the subject in hand from a broader standpoint. Thus this state publishes monographs upon manganese and novaculites, which not only describe the local deposits, but show the position of these products in general and the probable future of the local industries. This is vastly more valuable than the mere record of local observations and of local development. In the following list of books of reference, individual mention of the special articles in the magazines and the APPENDIX. 459 geological reports is not made, excepting in exceptional cases where the material is of unusual value. Nor is especial effort made to include European works excepting such English and a few continental treatises as are of general interest. TEXT-BOOKS OF MINERALOGY AND GEOLOGY. Dana, System of Mineralogy, 1892. Dana, Text-Booh of Mineralogy. Dana, Manual of Mineralogy and Lithology. Bauerman, Descriptive Mineralogy. Bauerman, Systematic Mineralogy. Brush, Determinative Mineralogy and Blowpipe. Nason, Manual of Qualitative Blowpipe Analysis. Williams, Crystallography. KosBNBUsCH, Microscopical Physiography of the Rock-Making Minerals (translated by Iddings). RosBNBUSCH, Mikroskopische Physiographic der Massigen Gesteine. RuTLEY, The Study of Rocks. Von Cotta, Rocks Classified and Described (translated by Lawrence). Lb Conte, Elements of Geology. Dana, Manual of Geology. Prestwich, Physical and Chemical Geology. Jukes-Browne, Physical Geology. Lyell, Principles of Geology. Geikie, Class-Book of Geology. Geikie, Text-Book of Geology, 1893. GENERAL TREATISES UPON ECONOMIC GEOLOGY. Phillips, Ore Deposits, 1884. Whitney, Metallic Wealth of the United States. Whitney, The United States. Davies, a Treatise on Metalliferous Minerals and Mining, 1892. Da VIES, Earthy and Other Minerals and Mining, 1888. Kemp, Ore Deposits of the United States, 1893. 460 ECONOMIC GEOLOGY OF THE UNITED STATES. Lakes, Geology of Colorado and Western Ore Deposits, 1893. OsBORN, Minerals, Mines, and Mining, 1888. Page, Economic Geology. Ansted, The Applications of Geology. Williams, Applied Geology, 1886. Belt, Mineral Veins. Von Cotta, A Treatise on Ore Deposits (translated by Prime). Von Cotta, Die Lehre von der Erzlagerstatten. Von Gkoddeck, Die Lehre von den Lagersiatten der Erze. Sandbekger, Untersuchungen uber Erzgange. Grimm, Die Lagerstatten der Nutzbaren Mineralien. Serlo-Lattner, Bergbankunde. Burat, Mineraux Utiles. RoTHWELL, The Mineral Industry, etc., of the United States, for 1892. Reports of the Tenth and Eleventh Census on Mineral Industries, etc. Annual Reports upon the Mineral Resources of the United States (Day, U.S. Geol. Survey). SPECIAL ARTICLES. PuMPELLY, Johnson's Cyclopaedia, 1886, VI., p. 22 (article on Ore Deposits). Newberry, Deposition of Ores {Columbia School of Mines Quarterly, 1880, Vol. v., p. 337). Le Conte, Genesis of Metalliferous Veins {American Journal of Science, 1883, Vol. XXVI., pp. 1-19). Raymond, Mining Statistics for 1870, p. 448. Kemp, The Filling of Mineral Veins {Columbia School of Mines' Quarterly, No. 1, XIII.). Wadsworth, State Board of Geological Survey for 1891-92, p. 144. WORKS UPON SPECIAL SUBJECTS. Iron. Pumpelly, Tenth Census, Vol. XV., pp. 1-601. Eleventh Census volume on Mineral Industries. Pumpelly, Geological Survey of Missouri, Report for 1872, Part I. WiNCHELL (N. H. and H. V.), The Iron Ores of Minnesota, BuU. 6, Minn. Geol. Survey, 1891. APPENDIX. 461 Irving and Van Hise, I'he Penokee Iron-bearing Series of Michigan and Wisconsin, Tenth Annual Report U.S. Geol. Survey, pp. 347-458. Summary Final Report, Second Geol. Survey of Pennsylvania, Vols. 1. and II., (also forthcoming volumes). Also scattered reports in Penn- sylvania survey publications. Kendall, The Iron Ores of Great Britain, 1893. Gold, Silver, and Lead. Lock, Gold, its Occurrence and Extraction. AVhitney, The Auriferous Gravels. Smyth, The Gold Fields of Victoria. Annual Reports of the Director of the Mint (for Gold and Silver). Williams, Popular Fallacies regarding the Precious Metal Ore Deposits (Fourth Annual Report U.S. Geol. Survey, pp. 257-267). Lord, Comstock Mines and Mmm*/, Monograph IV., U.S. Geol. Survey, 1883. Becker, Geology of the Comstock Lode, Monograph III., U.S. Geol. Survey, 1882. (Also, in abstract. Second Annual Report U.S. Geol. Survey, pp. 293-325.) Emmons, Geology and Mining Industry of Leadville, Colorado, Monograph XII., U.S. Geol. Survey. (Also, in abstract, Second Annual Report U.S. Geol. Survey, pp. 203-287.) Curtis, The Silver-Lead Deposits of the Eureka Mining District, Nevada, Monograph VII., U.S. Geol. Survey, 1884. (Also, in abstract. Fourth Annual Report U.S. Geol. Survey, pp. 225-251.) Zinc, Copper, Mercury, Manganese, Tin, and Aluminum. Chamberlain, Geology of Wisconsin, 1873-1879, Vol. IV., pp. 367-571. (Zinc.) Irving, The Copper-bearing Rocks of Lake Superior, Third Annual Report U.S. Geol. Survey, pp. 89-188. (Copper.) PuMPKLLY, Geological Survey of Michigan, 1869-1873, Vol. I., Part 11. (Copper.) Becker, Geology of the Quicksilver Deposits of the Pacific Coast, Monograph XIII., U.S. Geol. Survey, 1888. (Also Eighth Annual Report U.S. Geol. Survey, pp. 965-985.) (Mercury,) Eleventh Census volume on Mineral Industries, pp. 202-245. (Mercury.) 462 ECONOMIC GEOLOGY OF THE UNITED STATES. Le Conte and Rising, The Phenomena of Metalliferous Vein-formation now in Progress at Sulphur Bank, California {American Journal oj Science, XXIV., 1882, pp. 23-33). (Mercury.) Le Contb, On Mineral Vein-formation now in Progress at Steamboat Springs, etc. (^American Journal of Science, XXV., 1883, pp. 424-428). (Mercury.) Penrose, Manganese, Annual Report Arkansas Geol. Survey, Vol. I., 1890. (Manganese.) RoTHWELL, Mineral Industry, etc., for 1892, pp. 439-462. (Tin.) Eleventh Census volume on Mineral Industries, pp. 247-265 (Tin.) Richards, Aluminum, its Properties, Metallurgy, and Alloys, 1890. (Aluminum.) Eleventh Census, Mineral Industries, pp. 277-284. (Aluminum.) Mineral Resources of the United States, 1891, pp. 147-163. (Aluminum.) RoTHW^ELi., Mineral Industry, etc., of the United States for 1892, pp. 11-18. (Aluminum.) Coal. Leavitt, Facts about Peat. Shaler, General Account of the Fresh Water Morasses of the United States, Tenth Annual Report U.S. Geol. Survey, pp. 261-338. Willis, The Lignites of the Great Sioux Reservation, Bull. 21, U.S. Geol. Survey, 1885. DuMBLE, The Lignites of Texas, Texas Geol. Survey, special report. Hayden Reports — Geol. Survey of the Territories. Smyth, A Rudimentary Treatise on Coal and Coal Mining. MacFarlane, Coal Regions of America. Lesley, Manual of Coal and its Topography, 1856. Lesquereux, On the Vegetable Origin of Coal. Annual Report Second Geol. Survey of Pennsylvania, 1885, pp. 95-124. Lesley, Forthcoming report Pennsylvania Geol. Survey, Summary Final Report, Vol. HI. Hull, The Coal Fields of Great Britain. White, Comparative Stratigraphy of the Bituminous Coal Field of the Northern Half of the Appalachian Field, Bull. 65, U.S. Geol. Survey, 1891. Eleventh Census volume on Mineral Industries, pp. 343-422. Mineral Resources, 1891 (Day, U.S. Geol. Survey), pp. 177-402. Pennsylvania Geological Survey Reports, particularly Reports AA and AC. APPENDIX. 463 Petroleum. Crew, A Practical Treatise on Petroleum. Orton, The Trenton Limestone as a Source of Oil and Natural Gas in Ohio and Indiana, Eighth Annual Report U.S. Geol. Survey, 1889, pp. 475-662. Tenth Census Report, Vol. X., pp. 1-319. Eleventh Census Report on Mineral Industries, pp. 425-591. White, The Mannington Oil Field, Bull. Geol. Society America, Vol. 3, 1892, pp. 187-216. Lesley, Summary Final Report Pennsylvania Geol. Survey, Vol. II., 1892. Pennsylvania Geological Survey Reports, particularly 1 5, III and Annual Report, 1886, Part n (the latter containing a complete bibliography of Petroleum). Ohio Geological Survey Reports. Btjilding-Stones, etc. Merrill, Stones for Building and Decoration, 1891. Hull, A Treatise on Building and Ornamental Stone of Great Britain and Foreign Countries. BuRNHAM, Limestone and Marble, 1883. Tenth Census volume on Building-Stones. Eleventh Census volume on Mineral Industries, pp. 595-666. Smock, Building-Stone in New York, Bull. New York State Museum, 1888. Shaler, Geology of Cape Ann, Massachusetts, Ninth Annual Report, U.S. Geol. Survey, pp. 529-611. (Granite.) Harris, Granites and our Granite Industries. Da VIES, A Treatise on Slate and Slate Quarrying. Rothwell's Mineral Industry, etc., pp. 49-56. (Cement.) Mineral Resources of the United States for 1891, pp. 529-538. (Cement.) Soils, Clays, Fertilizers, etc. Shaler, The Origin and Nature of Soils, Twelfth Annual Report U.S. Geol. Survey, 1892, pp. 213-345. (Soils.) Johnson and Cameron, Elements of Agricultural Chemistry and Geology. Hill, Mineral Resources of the United States for 1891, pp. 474-528. (Clays.) 464 ECONOMIC GEOLOGY OF THE UNITED STATES. Penrose, The Nature and Origin of Phosphate of Lime, Bull. 46, U.S. Geol. Survey. (Fertilizei-s.) Hill, The Occurrence of Artesian and other Underground Waters in Texas, etc. (Agricultural Dept.). (Artesian Wells.) ChambbrlaIjST, The Requisite and Qualifying Conditions of Artesian Wells, Fifth Annual Report U.S. Geol. Survey, pp. 125-173. Peale, Eleventh Census, volume on Mineral Industries, pp. 779-787. (Mineral Waters.) Miscellaneous Minerals. Streeter, Precious Stones and Gems, 1892. KuNZ, Gems and Precious Stones, 1892. Griswold, Whetstones and Novaculites of Arkansas, Annual Report Arkansas Geological Survey for 1890, Vol. III. Chatard, Salt-Making Processes in the United States, Seventh Annual Report U.S. Geol. Survey, pp. 497-527. Jones, Asbestos, its Properties and Occurrence, 1890. MINERAL STATISTICS. RoTHWELL, The Mineral Industry, etc., of the United States for 1892. Day, Mineral Resources of the United States (Annual Report issued hy the U.S. Geol. Survey). Also earlier volumes edited by Williams, etc. Tenth Census Reports upon Mineral Products. Eleventh Census volume on Mineral Industries. Production of Gold and Silver in the United States (Annual Report Director of the Mint). Taylor (revised by Holdeman), Statistics of Coal. MINING METHODS. Davies, a Treatise on Metalliferous Minerals and Mining, 1892, pp. 314- 490. Gkeenwell, Mine Engineering, 1889. Balch, The Mines, Miners, and Mining Interests of the United States in 1882. Hunt, British Mining, 1884. MiCHELL, Mine Drainage, 1881. Abel, Mining Accidents and their Prevention, 1889. APPENDIX. 466 KuNHARDT, The Practice of Ore Dressing in Europe, 1884. Lock, Mining and Ore Dressing Machinery, 1890. Andre, A Treatise on Milling Machinery, 1877. Bowie, A Practical Treatise on Hydraulic Mining, 1885. Whitney, Auriferous Gravels. Hughes, A Text-Book of Coal Mining, 1892. Andre, A Practical Treatise on Coal Mining, 1879. Pamely, The Colliery Manager's Handbook, 1891. Walton, Coal Mining Described and Illustrated. Booth, Marble Workers' Manual. ALLOYS AND METALLURGY. Brannt, Metallic Alloys, 1889. HioRNS, Mixed Metals, 1890. Bauerman (revision of Phillips), Elements of Metallurgy, 1891. Phillips, Elements of Metallurgy, 1874. Roberts-Austen, An Introduction to the Study of Metallurgy, 1892. Overman, Treatise on Metallurgy. Bloxam, Metals, their Properties and Treatment. Makins, a Manual of Metallurgy. Mitchell, A Manual of Practical Assaying. Ricketts, Notes on Assaying. HiORNS, Practical Metallurgy and Assaying, 1888. Howe, The Metallurgy of Steel, 1891. Greenwood, Steel and Iron. Bauerman, The Metallurgy of Iron. OsBORN, The Metallurgy of Iron and Steel. Gore, The Art of Electro-Metallurgy. EissLER, The Metallurgy of Gold. Eisslee, The Metallurgy of Silver. EissLER, The Metallurgy of Argentiferous Lead. HoPMAN, The Metallurgy of Lead, 1893. Howe, Copper Smelting, Bull. 26, U.S. Geol. Survey. BKRATA. On p. 152, twelfth line from bottom of page, for "his" read "this." On p. 441, tenth line from bottom of page, for "inorganic" read 'organic." LIST OF AUTHORS AND WORKS REFERRED TO IN THE TEXT. PAGES Adams, F. D., Canadian Record of Science, 1891, pp. 463-469 35 Becker, G. F., Monograph U.S. Geological Survey, III., 1882 185, 187 Becker, G. F., Monograph U.S. Geological Survey, XIII., 1888 254, 255 Brannt, W. T., Metallic Alloys 171 Brooks (T. B.) and Pumpelly (R.), Geological Survey of Michigan, 1869-73 124 Brush, G. J., Blowpipe Analysis 27 BuRNHAM, S. M., Limestone and Marble 359 Carll, J. F., Annual Report Pennsylvania Geological Sui-vey, 1886, Part II., pp. 830-895 337 Cakll, J. F., Pennsylvania Geological Survey, Report III., pp. 270-284 340 Chamberlain, T. C, Fifth Annual Report U.S. Geological Survey, pp. 125-173 412 Clayton, J. E., Engineering and Mining Journal, Vol. 45, 1888, p. 108 191 Curtis, J. S., Monograph U.S. Geological Survey, VII., 1884 . 187 DasAjY^. ^., Manual of Mineralogy 3, 27 Dana, E. S., System of Mineralogy 3, 27 DAifA,^.. S., Text-Book of Mineralogy 3,27 Dana, J. D., Manual of Geology 51 Davies, D. C, Earthy and Other Minerals and Mining . . . 199 Da VIES, D. C, Metalliferous Minerals and Mining 80, 96, 199 DuMBLE, E. T., Brown Coal and Lignite of Texas 819 Eleventh Census volume on Mineral Industries . . 138, 151, 155, 176, 274, 283, 312, 337, 366, 383, 421 Emmons, S. F., Monograph U.S. Geological Survey, XIl., 1886 80, 234 Fairbanks, H. W., American Geologist, 1891, VII., pp. 209-222 152 467 468 LIST OP AUTHORS AND "WORKS. PAOXS Foster (J. W.) and Whitnby (J. D.), Report on the Geology of the Lake Superior Land District, Part II., 1851 . . . 124 Geikie, a., Class-Book of Geology 51 Geikie, a., Text-Book of Geology 51, 80 Griswold, L. S., Annual Report Arkansas Geological Survey, 1890,111 429 Gkoddeck, a. von. Die LeJire von dem Lagerstatten der Erze . 199 Hill, R. T., Mineral Resources of the United States (Day, U.S. Geological Survey) for 1891, pp. 474-528 .... 399 Hill, R. T., The Occurrence of Artesian and Other Under- ground Waters in -Texas, etc. (Agricultural Dept.), 1892 . 412 HiORNS, A. H., Mixed Metals 171 Iddings, J. P., translator of Rosenbusch's Microscopical Physiography 4 Irving (R. D.) and Van Hise (C. R.), Tenth Annual Report U.S. Geological Survey, pp. 341-508 124, 125 Jukes-Browne, A. J., Physical Geology 51 Kemp, J. F., Ore Deposits of the United States 80, 457 KuNZ, G. F., Gems and Precious Stones of North America . . 421 Lb Conte, J., American Journal of Science, XXV., 1883, pp. 424-428 255 Le Conte, J., American Journal of Science, XXVI., 1883, pp. 1-19 80, 255 Le Conte, J., Elements of Geology 51, 80 Le Conte (J.) and Rising (W. B.), American Journal of Science, XXIV., 1882, pp. 23-33 255 Lesley, P., Pennsylvania Geological Survey, Summary Final Report, Vol. 1 131 Lesquereux, L., Pennsylvania Geological Survey, 1885, pp. 95-124 322 Lord, E., Monograph U.S. Geological Survey, IV., 1883 . . 182 Merrill, G. P., Stones for Building and Decoration, 1891 . . 359, 383 Mineral Resources of the United States (Day, U.S. Geological Survey), 1891 283, 287, 312, 337, 383, 387, 421 Newberry, J. S., School of Mines Quarterly, 1880 80 Newell, F. H., Eleventh Census Bulletin, No. 193 ... . 418 Ohio Geological Survey Reports 337 Orton, E., Eighth Annual Report U.S. Geological Survey, 1889, pp. 475-662 337 LIST OF AUTHORS AND WOEKS. 469 PAGES Pealb, a. C, Eleventh Census Report on Mineral Industries, pp. 779-787 418 Pennsylvania Geological Survey Reports 337 Penrose, R. A. F., Jr., Annual Report Arkansas Geological Survey, 1890, Vol. 1 262 Penrose, R. A. F., Jr., Bulletin 46, U.S. Geological Survey . 405 Penrose, R. A. F., Jr., Journal of Geology, Vol. I., pp. 275-282 266 Phillips, J. A., Ore Deposits .80, 191, 199, 255, 274 PuJiPELLY, R., Johnson's Cyclopcedia 80 Pumpelly, R., Geological Survey of Missouri for 1872, Parti 126 Pumpelly (R.) and Brooks (T. B.), Geological Survey of Michigan, 1869-1873 124 Raymond, R. W., Mining Statistics, 1870 80 Richards, J. W., Aluminum, its Properties, Metallurgy, and Alloys, 1890 283 Rising (W. B.) and Le Conte CJ.), American Journal of Science, XXIV., 1882, pp. 23-33 255 RosENBUSCH, H., Microscopical Physiography, translated by J. P. Iddings 4 RosENBUSCH, H., Mikroskopische Physiographic der Massigen Gesteine 34 RoTHWELL, R. P., The Mineral Industry, etc., of the United States ior 1892 140,151,257,274,28.3,335,337,387,453 Russell, I. C., American Journal of Science, XLIII., 1892, p. 178 328 Russell, I. C, Journal of Geology, Vol. I., 1893, p. 233 . . . 328 Russell, I. C, National Geographic Society Magazine, III., 1891, pp. 53-204 328 Sandberger, F., Untersuchungen iiher Erzgange ' 73, 86 Shaler, N. S., Twelfth Annual Report U.S. Geological Sur- vey, pp. 213-345 391 SiVER, L. D., Engineering and Mining Journal, Vol. 45, 1888, pp. 195-196, 212 189 Streeter, E. W., Precious Stones and Gems 421 Tenth Census, Vol. X 337, 359 Tenth Census, Vol. XV 119 Van Hise (C. R.) and Irving (R. D.), Tenth Annual Report U.S. Geological Survey, pp. 341-508 ..... 124, 125 470 LIST OF AUTHQKS aJlD -^OEKS. PAGES Wadsworth, M. E., Catalogue of the Michigan Mining School, 1892 79 Wadsworth, M. E., Report of the Michigan State Board of Geological Survey 79, 80 White, I. C, Bulletin Geological Society of America, Vol. 3, 1892, pp. 187-216 344 Whitney, J. D., Auriferous Gravels 155 Whitney, J. D., Metallic Wealth of the United States ... 80, 155 Whitney, J. D., The United States 155 Whitney (J. D.) and Foster (J. W.), Report on the Geology of the Lake Superior Land District, Part XL, 1851 ... 124 Wii,i,iAMS, G. R., Elements of Crystallography 3 Winchell, N. H. and H. V., Bulletin No. 6, Minnesota Geological Survey, 1891 126 INDEX. A. Abrasive materials, 425. production of United States, 429. Acid springs, 419. Adirondack magnetite mines, 142. Adit level, 106, 107. -Slolian soils, 395. Africa, copper in, 219, 220. copper production of, 226, 227. gold in, 165. gold production of, 174, 175. iron ores of, 135. natural soda in, 437. Agate, use of, in jewelry, 423. Agatized yfood, production of United States, 424. Aix la Chapelle, zinc deposits, 245. Alabama, bauxite in, 285. bauxite production of, 291. coal in, 315. coal production of, 317, 333, 334. iron in, 121. iron production of, 138, 139, 144, 145, 307. limestone production of, 379. phosphates in, 407. tin in, 275. Alaska, coal in, 320. gold fields of, 160. gold production of, 161, 173. Alaskan coal district, 313, 319. Albertite, 355. Algoma, Canada, copper mines, 220. Alkali, 434. Alkaline saline springs, 419. springs, 419. Alloys of aluminum, 289. antimony, 297. copper, 222. Alloys of gold, 171. iron, 136. lead, 239. manganese, 270. nickel, 294. silver, 201. tin, 282. treatises on, 465. Almaden, Spain, mercury mine, 255, 256. Almeria, Spain, lead district, 236. Altai Mountains, gold in, 164. Aluminum, 283. alloys of, 289. bronze, 289. cost of, 287. history of, 284, 286. metallurgy of, 286, 287. mineralogical association of, 284. occurrence of, 283. ores of, 25. production of, 290. France, 291. Germany, 290. Switzerland, 291. United States, 290. properties of, 288. treatises on, 462. uses of, 288. Alumnite, 284. Amalgamation, 113, 114. of gold, 113. silver, 113. American copper mines, 221. Amherst, Ohio, buff sandstone, 370. blue sandstone, 370. Amorphous structure, 2. Amphibole minerals in the rocks, 7. Amygdules, 83, 211. Analyses of anthracite, 312. 471 472 INDEX. Analyses of bituminous coal, 312. cements, 388, 389. coal, 312. hydraulic cement, 388, 389. lignite, 312. peat, 312. phosphates, 409. Portland cement, 388, 389. natural gas, 350. Ancient river gravels, 154. Andreasherg, Germany, mining dis- trict, 198, 218, 236. Anglesite, 22, 228. Anhydrous sesquioxide of iron, 119. Annahergite, 14, 292. Anthracite, 311. analyses of, 312. occurrence of, Colorado, 319. New Mexico, 311, 319. Pennsylvania, 315, 316. Rhode Island, 311, 314. production of Appalachian field, 321. New England field, 321. Pennsylvania, 316, 333. Rocky Mountain field, 321. United States, 331, 453. Anticline, 50. Anticlinal Theory for accumulation of petroleum, 344. Antimony, 296. alloys of, 297. occurrence of, Arkansas, 297. California, 297. Nevada, 297. foreign, 297. ores of, 26. price of, 298. production of, Austria-Hungary, 298. Canada, 298. Italy, 298. Japan, 298. Nevada, 307. Spain, 298. United States, 298, 304, 305. the world, 298, 299. uses of, 297. Apatite, 12, 405. Apatite, distribution of, 405. occurrence of, Canada, 406. origin of, 406. Appalachian Mountains, asbestos in, 447. building-stones in, 384, 385. coal district of, 313, 315. coal production of, 321. economic products of, 60. formation of, 68. general characters of, 59. gold fields of, 147, 148. lead in, 229. manganese in, 264. ore deposits, absence of, 95. silver veins in, 192. Appalachian states, copper in, 209. lead production of, 240. slate in, 374. Archean, division of, 66. land areas, 65. rocks, origin of, 40. Arctic, climate of, 328, 329. Argentiferous blende, 180. chalcopyrite, 180. galena, 21, 180, 181, 228. Argentine Republic, guano in, 407. Argentite, 21, 80. Argillaceous hematite, 19. Aroa, Venezuela, copper mine, 218. Arizona, copper in, 209. copper production of, 224, 225, 307. gold production of, 173. lead in, 235. lead production of, 240, 241. onyx in, 382. silver in, 191. silver production of, 204. Arizona Copper Mine, 216. Arkansas, antimony in, 297. bauxite in, 286. lithographic stone in, 442. manganese in, 263, 265. manganese, production of, 271, 307. novaculites in, 428. zinc production of, 251. Arkansas oilstones, 428. Artesian wells, 412. INDEX. 473 Artesian wells, association with syn- clines, 415. cause of, 413. conditions for existence, 414. in arid regions, 416. California, 418. Colorado, 418. South Dakota, 418. Texas, 418. United States, 418. Utah, 418. similarity of petroleum wells to, 343. treatises on, 464. value of, 416. in the United States, 418. Asbestos, 14, 447. distribution of, 447. imports of, 448. occurrence of, 447. production of, Canada, 448. treatises on, 464. uses of, 448. Ashio, Japan, copper mine, 218, 220. Asia, copper production of, 226, 227. iron ores of, 135. natural soda, occurrence in, 487. Asia Minor, borax in, 435. chromium in, 300. Aspen, Colorado, silver mines, 189. Asphalt, 356. Asphaltura, 340, 355. distribution of, 356. imports of, 357. occurrence of, California, 356, 357. Kentucky, 356. Sicily, 356. Texas, 356. Trinidad, 356, 357. Utah, 356. origin of, 356. production of United States, 357. uses of, 357. Atalla, Alabama, hematite, 123. Augite as a rock-forming mineral, 8, 10. Auriferous gravels, California, 153. origin of, 155. Victoria, 162. Auriferous quartz, origin of, 169. Australia, gold coinage, 172. iron ores of, 135. copper production of, 226. manganese in, 267. silver in, 199. tin in, 280. tin production of, 283. Australasia, copper in, 219. copper production of, 226. gold in, 161. gold production of, 163, 174, 175. silver in, 197. silver production of, 206. Austria, bauxite in, 285. copper in, 208, 219. gold in, 165. iron ores of, 134. mercury in, 256. mercury production of, 261, 262. spelter production of, 252. tin production of, 283. zinc production of, 252. Austria-Hungary, antimony produc- tion of, 298. chromium in, 300. coal production of, 335. gold production of, 175. lead in, 237. lead production of, 242. nickel-cobalt in, 293. ozokerite in, 357, 358. silver in, 198, 199. silver production of, 198, 206. zinc in, 237, 246. Azurite, 22, 208. in Russia, 219. B. Babbitt metal, 297. Ballarat, Victoria, gold district, 161. Banca tin deposits, 279. Banded structure in mineral veins, 85, 98, 99. Barite, 17, 448. production of Missouri, 449. North Carolina, 449. South Carolina, 449. 474 INDEX. Barite production of United States, 449. Virginia, 449. uses of, 449. Barometers, use of mercury in, 260. Barrier Range, Australia, silver dis- trict, 197. Barytes, 448. Basic secretions in granite, 362. Batesville, Arkansas, manganese de- posits, 265. Baux, France, bauxite occurrence, 285. Bauxite, 25, 284, 285. occurrence of, 285, 303. Alabama, 285. Arkansas, 286. Austria, 285. Cordilleras, 285. France, 285. Georgia, 285. Germany, 285. Italy, 285. production of Alabama, 291. France, 291. Georgia, 291. Belgium, coal production of, 335. iron ores of, 134. lead in, 237. phosphates in, 410. phosphate production of, 411. spelter production of, 252. zinc in, 237, 245. zinc production of, 252. Bell metal, 222. Benzine, 341, 347. Berea grit, 355. Ohio, grit, 370, 427. Bichromate of potash, 299. Big Bone Salt Lick, Kentucky, 410. Bilboa, Spain, iron deposits, 134. Billeton, tin deposits, 279. Biotite, 8, 443. Birmingham, Alabama, iron produc- tion, 141. Bitumen, 356. Bituminous coal, 311. analyses of, 312. in Appalachian Mountains, 317. Bituminous coal production of Penn- sylvania, 333. United States, 331, 453. Blackband, 119, 132. Black copper mine, Arizona, 216. Black Forest, Germany, zinc deposits, 246. Black HUls, South Dakota, gold in, 158, 168. silver in, 192. tin mines of, 275. Black Jack, 23. Blende, 23, 228, 243. argentiferous, 180. Blind-seams in granite, 365. Blue Ridge, tin in, 275. Bluestone, 371, 372. distribution of, 385. occurrence of, 385. production of New Jersey, 373. New York, 373, Pennsylvania, 373. United States, 373, 386. Bog iron ore, 19, 119, 135. in New England, 121. precipitation of, 82. Bog manganese, 24. Boleo, Mexico, copper mine, 220. production of, 226. Bolivia, copper in, 218. gold production of, 166. silver in, 195. silver production of, 196, 206. tin in, 280. tin production of, 283. Bonanza, 184. Bonanza mines, 159. Bone beds, 405. Borax, 434. occurrence of, Asia Minor, 435. California, 435. Chili, 435. Cordilleras, 435. Nevada, 435. Thibet, 435. Tu.scany, 435. origin of, 435. price of, 436. production of California, 436. INDEX. 475 Borax production of Nevada, 436. United States, 436. uses of, 436. Borneo, mercury in, 257. mercury production of, 261. platinum in, 177. Bornite, 208. Bort, 425. Bosses, 37. Branch-veins, 102. Brandon, Vermont, limonite deposits, 122. manganese deposits, 264. Brass, 223, 249. Braunite, 262. Brazil, gold production of, 166. platinum in, 177. Breccia, 29, 100. Brick clays, 400, 401. Brines, 430. British Columbia, platinum in, 177. British Guiana, gold production of, 175. Britannia metal, 282, 297. Brittany, France, tin deposits, 278. Bromine, 434. occurrence of, Michigan, 434. West Virginia, 434. production of United States, 434. Bronze, 222, 282. Brown hematite, 19, 119, 120. method of mining, 122. occurrence of, 121, 302. Alabama, 121. Georgia, 121. Pennsylvania, 121. Texas, 121. Virginia, 121. production of, 120. Alabama, 139, 144. Colorado, 143. Georgia, 144. Michigan, 139, 144. Missouri, 143. Pennsylvania, 141, 144. Tennessee, 143. Virginia, 142, 144. Wisconsin, 143. Brown stone, 370. Brusa, Asia Minor, chromite deposits, 300. Buddie, 112. Buhr, French, 427. Buhrstone, 427. production of United States, 429. Building-stones, 359. distribution of, 384. occurrence of, 384. production of California, 383, 384, 386, 455. Colorado, 383, 384, 386, 455. Connecticut, 383, 384, 386. Illinois, 383, 384, 386, 455. Indiana, 383, 384, 386. Maine, .383, 384, 386. Massachusetts, 383, 384, 386. Minnesota, 383, 384, 386, 455. Missouri, 383, 384, 386, 455. New Jersey, 383, 384, 386. New York, 383, 384, 386, 455. Ohio, 383, 386, 455. Pennsylvania, 383, 386, 455. United States, 383, 385, 386, 453. Vermont, 383, 384, 386. Wisconsin, 383, 384, 386, 455. treatises on, 463. Burden, New York, iron mine, 132, 142. Burmah, tin in, 280. Butte, Montana, copper mines, 214, 220. silver mines, 190. C. Calamine, 23, 243. Calcining ores, 114. Calcite as a rock-forming mineral, 9, 10. Calcium sulphide, 438. California, antimony in, 297. artesian wells in, 418. asbestos in, 447. asphaltum in, 3-56, 357. auriferous gravels, 153. borax in, 435. borax production of, 436. 476 INDEX. California, building-stone production of, 383, 384, 386, 455. chromium in, 299. chromium production of, 807. copper in, 216. copper production of, 224, 307. diamonds in, 423. gold fields, development of, 150. gold production of, 173, 307, 455. granite production of, 368. grindstones in, 427. gypsum production of, 405. infusorial earth in, 426. lead production of, 240. limestone production of, 879. magnesite in, 437. manganese in, 266. manganese production of, 271. marble in, 381. marble production of, 383. mercury in, 253. mercury production of, 255, 807, 455. metal production of, 305. mineral products of, 455. mineral water production of, 420. natural gas in, 351. onyx in, 382. petroleum in, 337, 388, 840. petroleum production of, 348. platinum in, 176. quartz gold mines of, 148. salt in, 433. sandstone in, 372. silver in, 191. silver production of, 204, 455. slate in, 374. tin in, 276. Calumet and Hecla, Michigan, copper mine production of, 210, 213. Cambrian land areas, 67. Canada, antimony production of, 298. apatite deposits in, 406. asbestos in, 448. asbestos production of, 448. copper in, 220. gold in, 167. gold production of, 167, 175. Canada, iron ores of, 185. iron pyrite in, 301. iron pyrite production of, 301. lead production of, 242. manganese in, 266. manganese production of, 272. mica in, 443, 444. nickel in, 293. nickel production of, 296. natural gas production of, 855. petroleum in, 838, 340. petroleum production of, 349. phosphate production of, 411. platinum in, 177. platinum production of, 178. salt production of, 484. silver in, 193, 194. Cape Ann, Massachusetts, granite in, 365. Cape of Good Hope, copper produc- tion of, 227. Carbon group of minerals, 11. Carbonas, 278. Carbonate of iron, 119. occurrence of, 135, 302. production of, 132. Ohio, 144. Pennsylvania, 141. Carbonic acid, during Carboniferous period, 830. Carboniferous period, carbonic acid in, 330. climate of, 327. coal, 313. conditions existing in, 325, 326. moisture in, 328. submergence of land during, 326. _ vegetation of, 325, 327. Caret, 171. Carrara, Italy, marble imports from, 382. Carrizal, Chili, copper mine, 217. manganese deposits, 267. Cartersville, Georgia, manganese dis- trict, 264. Caspian region, petroleum in, 338, 340. Cassiterite, 25, 274. INDEX. 477 Castner process of sodium production, 287. Catlinite, production, United States, 424. Caucasus Mountains, gold in, 164. manganese in, 267. Cave opening, 230, 232. Cavern tlieory for tlie accumulation of petroleum, 344. Cavities, origin of, 75. of minor importance, 78. resulting from faulting, 77. resulting from solution, 77. Cement, 359, 387. analyses of, 388, 389. exports of, 456. imports of, 390, 456. production of, New York, 455. United States, 389, 453. Central America, silver in, 193, 194. silver production of, 206. Central coal area, 313, 318. production of, 321. Central plains, disturbance in, 62. economic products of, 62. general features of, 61. Central states, building-stones in, 385. sandstone in, 369. Cerargyrite, 21. Cerro de Pasco, Peru, silver mines, 196, 258. Cerrusite, 23, 228. Ceylon, graphite in, 441. Chalcocite, 22, 208. Chalcopyrite, 22, 180, 208. Chamber deposits, 80, 84. Chanarcillo, Chili, silver mines, 197. Chateaugay, New York, iron mines, 129. Chemical ore deposits, 80, 82. Chemically precipitated rocks, .30. Chert, 125. Chester, Massachusetts, emery de- posits, 427. Child's Valley, California, magnesite deposits, 437. Chili, borax in, 435. cobalt in, 294. Chili, cobalt production of, 296. copper in, 209, 217, 220. copper production of, 226, 227. gold production of, 166, 167, 175. guano exports of, 407. manganese in, 267. manganese production of, 272. phosphate production of, 411. silver in, 197. silver production of, 197, 206. China, gold in, 166. gold production of, 174. iron ores of, 135. natural gas in, 352. Chincha Islands, Peru, guano de- posits, 406. Chlorite, origin of, 9. Chrome green, 299. Chrome iron, 177. Chrome steel, 299. Chrome yellow, 299. Chromite, 14, 299. Chromium, occurrence of, 299. foreign, 300. United States, 299. origin of, 299. production of, California, 307. United States, 300, 304, 805. uses of, 299. ChrysocoUa, 22, 208. Chrysotile, 15, 447. occurrence of, Canada, 448. Cinnabar, 24, 253, 260. Clastic, definition of, 28. Clay iron stone, 19. Clay rocks, 29. Clays, 359, 399. distribution of, 401. occurrence of, 401. treatises on, 463. uses of, 400, 401. Clay selvage, 99. Claystone, 29. Clausthal district, Germany, 198, 236. Cleavage, definition of, 6. slaty, 373, 374. Clifton copper district, Arizona, 215. Climate in Carboniferous period, 327. Clinton, New York, red hematite, 123. 478 INDEX. Clinton ore bed, extent of, 123. origin of, 123, 124. Coal, 311. analyses of, 312. Appalachian district, 314, 315. areas in the United States, 313. as a part of the earth's crust, 11. association with iron, 317. consumption of in United States, .331. discovery of in United States, 315. distribution of, 312. exports of, 331, 456. future of, 332. imports of, 331, 456. occurrence of, Alabama, 315. Alaska, 313, 319, 320. Central Area, 313, 318. Colorado, 319. Europe, 312, 320. foreign, 320. Georgia, 315. Kentucky, 315. Maryland, 315. Northern Area, 313, 318. Nova Scotia, 314. Ohio, 315. Pacific Coast Area, 313, 319. Pennsylvania, 315. Rhode Island, 314. Rocky Mountain Area, 313, 319. Tennessee, 315. Texas, 318. United States, 312. Virginia, 315. Washington, 320. Western Area, 313, 318. West Virginia, 315. origin of, 32, 311, 321-326. price of, 334. production of, Alabama, 317, 333, 334. Appalachian field, 321. Austria-Hungary, 335. Belgium, 335. Central field, 321. Colorado, 333, 334, 455. France, 335. Coal production of Germany, 335. Great Britain, 335, 336. Illinois, 333, 334, 455. Indiana, 333. Indian Territory, 334. Iowa, 333, 455. Kansas, 334. Kentucky, 333. Maryland, 333. Missouri, 333, 455. New England field, 321. Northern field, 321. Ohio, 333, 334, 455. Pacific Coast field, 321. Pennsylvania, 333, 334, 455. Rocky Mountain field, 321. Russia, 335. Spain, 335. Tennessee, 334. United States, 321, 331, 333, 334, 335, 336, 453. Washington, 334. Western field, 321. West Virginia, 317, 333. World, 335. treatises on, 462. uses of, 331. Coastal plains, 52. Coast Range, period of formation of, 69. Cobalt, 292. blue, 295. minerals, 13, 26. occurrence of, 294, 303. Chili, 294. New Caledonia, 293, 294. Norway, 293. Pennsylvania, 293. Sweden, 293. origin of, 294. production of. Chili, 296. New Caledonia, 296. Prussia, 296. United States, 296, 304, 305. uses of, 295. Cobaltite, 14. Coeur d'Alene, Idaho,, silver-lead mines, 191, 235, 240. Coke, 332. INDEX. 479 Cologne, Germany, zinc deposits, 236, 246. Coinage gold, character of, 171. Coinage of gold, 172. platinum, 177. silver, 201, 204. Colombia, gold production of, 106, 174. platinum in, 177. platinum production of, 178. salt production of, 434. silver in, 197. silver production of, 206. Colorado, anthracite in, 319. artesian wells in, 418. brown hematite in, 14.3. building-stone production of, 38.3, 384, .386, 455. coal in, 319. coal production of, 333, 334, 455. copper in, 216. copper production of, 224, 307. gold in, 158. gold production of, 173, 307, 455. granite production of, 368. Iron production of, 139, 143. lead in, 233. lead production of, 240, 241, 307, 455. manganese production of, 271, 272. metal production of, 305. mineral production of, 455. mineral water production of, 420. nickel in, 292. petroleum in, 337, 338, 339. petroleum production of, 348. sandstone production of, 371, 372. silver in, 181, 189. silver production of, 204, 205, 307, 455. Columnar hematite, 19. Comb structure, 98, 99. Comstock Lode, 181. bonanzas in, 184. galleries in, 108. heat in, 108, 184. history of, 182. occurrence of ore, 185. Comstock Lode, origin of ore, 186. production of, 159, 184, 205. Concentrated contact ore deposits, 80, 93. Concentration of ores, 103, 110. Concretionary action, 89. ore deposits, 80, 89. Conglomerate, 29. Connecticut, building-stone produc- tion of, 383, 384, 386. granite production of, 368. limestone production of, 380. nickel in, 292. sandstone in, 369. sandstone production, 371. Contact ore deposits, 80, 92. metamorphism, 92. Copper, 208. alloys of, 222. consumption in United States, 224. distribution of, 220. exports, 456. imports, 225, 456. mineralogical association of, 208, 221. native, 22. occurrence of, 208, 221, 302. Africa, 219, 220. Appalachian States, 209. Arizona, 209, 215. Australasia, 219. Austria, 208, 219. Bolivia, 218. California, 216. Canada, 220. Chili, 209, 217, 220. Colorado, 216. England, 208, 219. Germany, 208, 218, 220. Italy, 219. Japan, 218, 220. Mexico, 220. Michigan, 209. Montana, 209, 214. Newfoundland, 220. New Mexico, 216. Norway, 219. Peru, 218. Portugal, 210, 220. 480 INDEX. Copper, occurrence of, Russia, 219. Spain, 209, 216, 220. Sweden, 219. United States, 209. Utah, 216. Venezuela, 217. "Vermont, 209. ores of, 22. origin of, 220, 222. price of, 224, 227. production of, 224. Africa, 226, 227. Arizona, 224, 225, 307. Asia, 226, 227. Australasia, 226. California, 224, 307. Chili, 226, 227. Colorado, 224, 307. Europe, 226, 227. Germany, 226, 227. Japan, 226, 227. Lalie Superior district, 210. Maine, 225. Mexico, 226. Michigan, 224, 225, 307, 455. Montana, 215, 224, 225, 307, 455. New Hampshire, 225. New Mexico, 224. North America, 226, 227. Portugal, 226, 227. Russia, 226. South America, 226, 227. Spain, 226, 227. United States, 224, 225, 226, 227, 304, 305, 453. Utah, 224. Venezuela, 226, 227. Vermont, 225. World, 226, 227. Copper pyrites, 22. Copper Queen mine, Arizona, 216. Copper, treatises on, 461. uses of, 222, 223. Copperfield, Vermont, copper mine, 209. Coquina, 376. Cordilleran region, economic re- sources of, 64. Cordilleran region, general features of, 63. Cordilleras, abundance of metals in, 95, 306. . as a source of lead, 228. bauxite in, 285. borax in, 435. building-stone in, 384, 385. dessicated lakes in, 64. gold fields of, 158. gypsum in, 404. marble in, 381. salt in, 430, 432. silver in, 181. tin in, 275. zinc in, 243. Cornwall, England, copper of, 219. influence of rocli on veins, 102. lead mines of, 237. silver occurrence of, 199. stookwerks in, 89. tin mines of, 277, 278, 280, 281. Cornwall, Pennsylvania, iron mines, 131, 138, 140. Coronado, Arizona, copper mines, 215. Corundum, 13, 25, 284, 425, 427. production of United States, 429. Corundum Hill, North Carolina, cor- undum of, 427. sapphire of, 423. Country rock, 98, 99. Course, 100. Cradle, 111. Creede, Colorado, silver mines, 189. Cretaceous coals, 314, 318, 319, 320. Cretaceous coastal plains, 55. economic products of, 56. Cretaceous land areas, 69. Crimora, Virginia, manganese district, 264. Cross-cuts, 105, 106. Cross-section, 101. Cryolite, 25, 284, 440. Crystalline structure, 2. Cuba, manganese in, 266. manganese production of, 272. Cuprite, 22. Cut-off plane in granite, 365, 366. INDEX. 481 D. Dakota, gold production of, 173, 307. Dalmatia, Oalifornia, gold mines, 152. Dannemora, Sweden, magnetite of, 134. Davis, Massachusetts, iron pyrite mines, 301. Davy, experiments on aluminum, 286. Delaware, granite production of, 368. Delta soils, 395. Dendrites, 24. Developing veins, 105. Deville process of extracting alumi- num, 286. Devonshire, England, copper in, 219. lead in, 237. silver in, 199. tin in, 278. Diahase, use as granite, 367. Diamonds, character of, 12. occurrence of, California, 423. Georgia, 423. Montana, 422. North Carolina, 423. production of. United States, 424. use for abrasive purposes, 425. Diaspora, 284. Diatomaceous earth, 32. Diatoms, 426. Dickerson, New Jersey, iron mine, 143. Dikes, 37. Diorite, use as granite, 367. Dip, 51, 100. Dip-fault, 51. Disintegration of rocks, 391, 392. Disseminated eruptive ore deposits, 80. Divider, 88. • Dolomite, 10, 247. Douglas Island, Alaska, gold deposits, 160. Downthrow of fault, 50. Drainage of mine, 106. Dressing of ores, 103. Drifts, 107. Drive, 106. Droppers, 102. Durango, Mexico, tin in, 281. E. Eastern Archean Mountains, eco- nomic products of, 59. general characters of, 58. Eastern states, spelter production of, 250. zinc production of, 250. Economic geology, treatises on, 459. Effusive rocks, 36. Ekaterinoslav, Russia, mercury in, 257. Elaterite, 355. Electrolytic process of extracting alu- minum, 286, 287. Elements, combinations of, 3. composing the earth's crust, 1. metals and metalloids, 3. native, 1. Emery, 425, 427. imports of, 427. occurrence in Georgia, 427. Massachusetts, 427. North Carolina, 427. production of United States, 429. England, copper in, 208, 219. lead in, 237. tin in, 277. Eruptive ore deposits, 80. Eruptive rocks, geological age of, 42. Erzgebirge, Germany, tin in, 278. Estuary theory for origin of coal, 323. Eureka district, Nevada, 187. Europe, coal in, 312, 320. copper production of, 226, 227. manganese in, 267. silver in, 197, 199. zinc in, 247. Exports of cement, 456. coal, 331, 456. copper, 456. gold, 456. iron, 145, 456. lead, 456. mineral products, 456. petroleum, 456. silver, 456. Extrusive rocks, 36. 482 INDEX. F. Fault, 50. Fault breccia, 29, 77. Faults, effect of on veins, 101. Feeders, 102. Feldspar in the rocks, 6, 10. production of United States, 401, 402. use of for pottery, 401. Ferro-manganese, 270. Fertilizers, kinds of, 402. phosphatio, 405. treatises on, 464. Fibrous talc, 445. occurrence in United States, 446. Findlay, Ohio, gas region, 352. Finland, gold in, 164. tin in, 279. Fire clays, 400, 401. Fissure veins, 80, 84. Flags, 373. Flat openings, 230, 232. Flats, 231. Flaxseed iron ore, 20, 123. Flint, concretions of, 89. production of in United States, 402. use for pottery, 401, 402. Flood plain soils, 395. Florence, Colorado, petroleum field, 339. Florida, phosphates in, 407, 408. phosphate production of, 409. plains, 54. Fluocan, 98, 99. Fluorite, 17, 440. Flux, use of, 114. use of limestone for, 378, 379, 380. Foot wall, 99, 106. Forest of Dean, Great Britain, iron mines of, 133. Forest on Malaspina glacier, Alaska, 328, 329. Fossil hematite ore, 20, 119, 123. Fragmental, definition of, 28. rocks, origin of, 31. Frame, 112. France, aluminum production of, 291. bauxite in, 285. France, bauxite production of, 291. coal production of, 335. lead in, 237, 238. manganese in, 267. phosphate in, 410. manganese in, 267. silver in, 198. silver production of, 206. tin in, 278. Franklin Furnace, New Jersey, zinc deposit, 20, 114, 244, 263. Franklinite, 20, 23, 243. Fredouia, New York, gas wells, 351. Free coinage of silver, 202. Freestone, 370. Freiberg, district Germany, 198, 236. French buhr, 427. French Guiana, phosphate production of, 411. G. Galena, 22, 180, 181, 228. Galena limestone, 229. Galenite, 22. Galicia, Austria, ozokerite in, 357. Gangue, 17, 97. Garnets, 423. production of United States, 424. Garuierite, 292, 294. Gash veins, 80, 84, 230, 2-32. in Mississippi valley, 84. Gasoline, 347. Gems, imports of, 425. Geodes, 83. Geographical zones in the United States, 52. Geological association of ore deposits, 94. history of the United States, 65. map, 100. surveys ; state and national, 457. text-books, 459. Georgia, bauxite in, 285. bauxite production of, 291. brown hematite in, 121. brown hematite production of, 144. coal in, 315. diamonds in, 423. INDEX. 483 Georgia, gold in, 148. granite production of, 368. iron production of, 139, 143. manganese in, 263, 264. manganese production of, 271, 307. marble in, 381. marble production of, 383. red hematite production of, 143. Germany, aluminum production of, 290. bauxite in, 285. coal production of, 335. copper in, 208, 218, 220. copper production of, 226, 227. gold coinage of, 172. gold in, 165. iron ores of, 134. iron pyrite production of, 301. lead in, 236. lead production of, 242. lithographic stone in, 442. manganese in, 268. mercury in, 257. nickel production of, 296. petroleum production of, 349. salt production of, 434. silver in, 197, 199, 294, 295. silver production of, 198, 206. tin in, 278. tin production of, 283. zinc in, 2.36, 245, 246. Germany and Luxemburg, iron pro- duction of, 146. Gibbsite, 284. Gilsonite, 355, 356. Glacial clays, 400. Glacial period, economic effects of, 70. Glacial soils, 396, 397. Glaciation during Pleistocene, 70. Glassy structure, 2. Glens Falls, New York, marble, 381. Globe copper district, Arizona, 216. Globigerina ooze, 31. Gneiss, characters of, 39. use as granite, 366. Gogebic, Wisconsin, iron range, 140, 143. Golconda, Nevada, manganese de- posit, 266, 270. Gold, 20. alloys of, 171. bearing conglomerates in Aus- tralia, 168. origin of, 168. bearing gravels, 154. origin of, 155. bearing sandstone. Black Hills, 168. quartz, origin of, 169. circulation of, 167. coinage, 171, 172. amount of, 172. conditions of accumulation, 147. effect of weathering upon, 103. exports of, 456. extraction by amalgamation, 113. fields of California, development of, 150. early history of, 149. fields of the Cordilleras, 158. foil, 249. foreign regions, 161. future of, 159. imports of, 456. occurrence of, 168, 303. Africa, 165. Alaska, 160. Altai Mountains, 164. Appalachian Mountains, 147. Australasia, 161. Austria, 165. California, 148. Canada, 167. Caucasus Mountains, 164. China, 166. Colorado, 158. Finland, 164. Georgia, 148. Germany, 165. Hungary, 165. India, 166. Japan, 166. Mexico, 167. Montana, 168. Nevada, 159. New South Wales, 162. New Zealand, 162. North Carolina, 148. 484 INDEX. Gold, occurrence of, Nova Scotia, 168. Queensland, 162. Russia, 163. Siberia, 163. South Africa, 164. South America, 166. South Carolina, 148. South Dakota, 158. Tasmania, 163. Transvaal, 164. Urals, 163. Victoria, 161. Yukon valley, 160. origin of, 168. production of, 171. Africa, 174, 175. Alaska, 161, 173. Appalachian field, 148. Arizona, 173. Australasia, 163, 174, 175. Austria-Hungary, 175. Bolivia, 166. Brazil, 166. British Guiana, 175. California, 173, 307, 455. Canada, 167, 175. Chih, 166, 167, 175. China, 174. Colorado, 173, 307, 455. Colombia, 166, 174. Dakota, 173, 307. Idaho, 173. India, 166, 174. Mexico, 175. Montana, 173, 307, 455. Nevada, 173, 307, 455. New Mexico, 173. New South Wales, 162. New Zealand, 162. Oregon, 173. Peru, 166, 167. Queensland, 162. Russia, 164, 174, 175. South Africa, 165. South Carolina, 173. United States, 173, 174, 175, 304, 305, 453. Utah, 173. Venezuela, 175. Gold production of Victoria, 161. World, 174, 175, 203. quartz production of, United States, 424. segregation of, 170. segregation veins of, 152. source of, 147. treatises on, 461. uses of, 170. washing, 155. Gossan, 98. Gothite, 19, 119. Gouge, -99. Gouverneur, New York, fibrous talc deposits, 446. Grahamite, 355. Granite, 360. blind seams in, 365. blotches in, 362. characters of, 360, 361. colour of, 361. distribution of, 384. durability of, 362. green seams in, 365. joint planes in, 363, 364, 365. occurrence of, 361. production of, California, 368. Colorado, 368. Connecticut, 368. Delaware, 368. Georgia, 368. Maine, 368. Maryland, 368. Massachusetts, 368. Missouri, 368. New England States, 368. New Hampshire, 368. New Jersey, 368. New York, 368. Pennsylvania, 368. Rhode Island, 368. South Dakota, 368. United States, 368. Vermont, 368. Virginia, S68. Wisconsin, 368. rift in, 363, 365, 366. sap in, 363. stones sold as, 366. ESTDBX. 485 Granite, texture of, 361. uses of, 361, 367. weathering of, 363. Graphite, 11, 311, 441. imports of, 441. production of. United States, 441. Graphitic anthracite, Rhode Island, 311, 314, 441. Great Basin, natural soda in, 437. origin of, 64. Great Bonanza of Comstock Lode, 185. Great Britain, coal production of, 335, 336. gold coinage of, 172. iron in, 133. iron production of, 146. iron pyrite production of, 301. lead in, 237. lead production of, 242, 243. manganese in, 267. manganese production of, 272. nickel production of, 296. nickel-cobalt in, 293. phosphate production of, 411. salt production of, 434. silver coinage of, 204. silver in, 199. spelter production of, 252. tin production of, 283. zinc in, 237, 246. zinc production of, 252. Great Salt Lake, salt from, 430. Greece, chromite in, 300. Greenland, native iron in, 81, 119. Green seams in granite, 365. Grindstones, 425, 427. occurrence of, California, 427. Michigan, 427. Ohio, 427. South Dakota, 427. production of. United States, 429. Ground mica, 444. Ground plan, 101. Guadalajara, Spain, silver mines, 198. Guadalcazar, mercury mines, 258. Guanajuata, Mexico, silver deposits, 193. Guano, 406. Guano exports from Chili, 407. occurrence in Argentine Republic, 407. South America, 406. Uruguay, 407. Gypsum, 18, 359. association of, with salt, 404, 431, 432. imports of, 406. occurrence of, 403. in Cordilleras, 404. origin of, 404. production of, California, 405. Iowa, 405. Kansas, 405. Michigan, 405. New York, 405. Ohio, 405. South Dakota, 405. United States, 405. Utah, 405. Virginia, 405. use as a fertilizer, 402, 403. use in jewelry, 423. H. Hade, 50, 100. Hanging wall, 99, 106. Harney's Peak, South Dakota, tin mines, 276. Harz Mountains, manganese mines, 268, 270. Heat in Comstock Lode, 184. Heat in mines, 108. Heavy spar, 448. Hematite, 19, 119, 120. occurrence of, 135, 302. Hindostan oilstone, 429. Hibernia, New Jersey, iron mine, 128. Horizontal shaft, 106. Hornblende, as a rock-forming min- eral, 7, 10. Horn silver, 21. Horse, 99. Hot springs, association of, with mineral veins, 86. Huanoavelica, Peru, mercury mine, 267. 486 INDEX. Huanchaca, Bolivia, silver mine, 195. Hungary, borax in, 435. gold in, 165. iron pyrite production of, 301. nickel production of, 296. salt production of, 434. Hydrated sesquioxide of iron, 119. Hydraulic cement, 387. analyses of, 388, 389. production of Indiana, 389. Kentucky, 389. New York, 387, 389. Pennsylvania, 390. United States, 389. Hydraulic elevator, 156. Hydraulic mining. 111, 155. Hydraulic mining, suspension of, 156. I. Idaho, gold production of, 173. lead in, 235. lead production of, 240, 241, 307. silver in, 190. silver production of, 204, 205, 307. Idria, Austria, mercury mine, 256. Igneous rocks, 34. . classification of, 35. position of, 37. the source of metals, 72. variation in, 34. Illinois, building-stone production of, 383, 384, 386, 455. coal production of, 333, 334, 455. lead in, 229. limestone production of, 379, 380. mineral products of, 455. spelter production of, 250, 252. Imports of United States, asbestos, 448. asphaltum, 357. cement, 390, 456. coal, 331, 456. copper, 225, 456. emery, 427. gems, 425. gold, 456. graphite, 441. gypsum, 406. Imports of United States, iron, 145, 456. iron pyrite, 300. lead, 456. marble, 382. millstones, 428. mineral products, 456. mineral waters, 420. nickel, 296. precious stones, 456. silver, 456. sulphur, 440, 456. tin, 456. Impregnation ore deposits, 80, 88. India, gold in, 166. gold production of, 166, 174. mica in, 443. silver coinage of, 204. Indiana, building-stone production of, 383, 384, 386. coal production of, 333. hydraulic cement production of, 389. limestone production of, 379, 380. natural gas in, 351. natural gas production of, 354, 355. oilstones of, 429. petroleum in, 337. petroleum production of, 348. Indian Territory, coal production of, 334. Indigenous soils, 391, 394. Infusoria, 426. Infusorial earth, 32, 425, 426. production of United States, 429. Intruded sheets, 37. Intrusive rooks, 37. Iowa, coal production of, 333, 455. gypsum production of, 405. limestone production of, 379. mineral production of, 455. zinc production of, 261. Iridium, 21,179. Iridosmium, 177, 179. Ireland, lead occurrence in, 237. Iron, 119. alloys of, 136. INDEX. 487 Iron; association of manganese with, 263. association with coal, 317. carbonate, 119. conditions necessary for profitable extraction of, 119. distribution of, 137. exports of, 145, 456. hat, 98. imports of, 145, 456. Mountain, Missouri, iron mines, 126, 136, 143. native, 18, 81, 119. occurrence of, 18, 135, 302. Africa, 135. Asia, 135. Australia, 135. Austria, 134. Belgium, 134. Canada, 135. China, 135. foreign, 133. Germany, 134. Great Britain, 133. Italy, 135. Norway, 134. Portugal, 135. South America, 135. Spain, 1.34. Sweden, 134. ores of, 18, 119. manganiterous, 263. production of Alabama, 307. Colorado, 139, 143. Georgia, 139, 143. Germany and Luxemburg, 146. Great Britain, 146. Michigan, 138, 139, 144, 145, 307, 455. Minnesota, 139, 142, 144, 145, 455. Missouri, 139, 143. New Jersey, 1.39, 143. New York, 1.38, 141, 144, 145, 307, 455. Ohio, 139, 143, 144. Pennsylvania, 138, 140, 144, 145, 307, 455. Spain, 146. Iron production of Tennessee, 139, 143. United States, 144, 145, 146, 304, 305, 453. Virginia, 139, 142, 144, 145. West Virginia, 144. Wisconsin, 139, 142, 307, 455. World, 146. pyrite, 18, 119, 300. concretions of, 89. occurrence of, 301, 303. production of United States, 300, 301, 304, 305. uses of, 300. as a source of sulphur, 438. treatises on, 400. uses of, 136. Italy, antimony production of, 298. asbestos in, 448. bauxite in, 285. copper in, 219. iron in, 135. iron pyrite production of, 301. lead in, 237. lead production of, 242. manganese in, 267, 268. manganese production of, 272. mercury in, 257, 261, 262. petroleum production of, 349. salt production of, 434. zinc in, 237, 246. zinc production of, 252. Japan, antimony production of, 298. copper in, 218, 220. copper production of, 226, 227. gold in, 166. petroleum in, 338, 340. petroleum production of, 349. silver coinage in, 204. silver production of, 206. sulphur in, 438. Jasper, use of, in jewelry, 423. Jean, Spain, lead district, 236. Jig, 112. Jigger, 112. Joint planes, 75. 488 INDEX. Joint planes in granite, 363, 364, 365. in sandstone, 371. Joplin district, Missouri, zinc depos- its, 244. Jura-Trias period of volcanic activity, K. Kansas, coal production of, 334. gypsum production of, 405. lead in, 229. lead production of, 241. limestone production of, 379. salt in, 431. salt production of, 433. spelter production of, 250. zinc in, 244. zinc production of, 250, 251, 307. Kaolin, 7, 10, 25, 399, 400. Karg gas well, Ohio, 352. Kentucky, asplialtum in, 356. coal in, 315. coal production of, 333. hydraulic cement production of, 389. limestone production of, 379. natural gas in, 351. natural gas production of, 354. iron production of, 145. Kerosene oil, 340, 347. Keweenaw Point, Michigan, copper mines, 210, 220. Kootenay Lake, Canada, silver de- posits, 194. Kremnitz, Austria-Hungary, silver mines, 198. Laccolite, 37. Lake Champlain iron mines, 138, 142. Lake Superior region, copper mines of, 210, 212, 213, 221, 225. economic products of, 63. general features of, 63. iron ores of, 124, 138, 139, 140. Lakes desiccated in the Cordilleras, 64. Lakes, Quaternary, 70. La Motte, Missouri, nickel mine, 292. Lampblack, 353. Lancaster Gap, Pennsylvania, nickel mines, 293, 296. Land plaster, 403. Land rock, 407. Lateral secretion, 86. Latin Union, formation of, 201. Laurel Creek, Georgia, corundum of, 427. Lead (a leader), 99. Lead, 228. alloys of, 239. exports of, 456. imports of, 456. mineralogical association of, 228, 238. occurrence of, 238, 302. Appalachian district, 229. Arizona, 255. Austria-Hungary, 237. Belgium, 287. Colorado, 233. France, 237, 238. Germany, 236. Great Britain, 237. Idaho, 235. Illinois, 229. Ireland, 237. Italy, 237. Kansas, 229. Mexico, 238, 240, 241. Missouri, 229. Mississippi valley 228, 229, 231, 248. Montana, 235. New Mexico, 236. New South Wales, 238. Poland, 237. Portugal, 236. Russia, 237. Scotland, 237. Spain, 236. Sweden, 237. Utah, 235. Wales, 237. Wisconsin, 229. ores of, 22, 238. INDEX. 489 Lead production of, 239. Appalachian states, 240. Arizona, 240, 241. Austria-Hungary, 242. California, 240. Canada, 242. Colorado, 240, 241, 307, 455. Germany, 242. Great Britain, 242, 243. Idaho, 240, 241, 307. Italy, 242. Kansas, 241. Mexico, 242, 243. Missouri, 241, 307, 455. Mississippi valley, 240. Montana, 240, 241, 307. New Mexico, 240, 241. Nevada, 240, 241. New South Wales, 242, 243. Russia, 242. Spain, 242, 243. Sweden, 242. United States, 240, 241, 242, 243, 304, 305, 453. Utah, 240, 241, 307, 455. Wisconsin, 241. world, 242. price of, 239. treatises on, 461. uses of, 238. Lead-zinc, gash vein deposits, 84. Leader, 88. Leadville, Colorado, copper occur- rence, 216. manganese occurrence, 263, 265. silver-lead mines, 189, 205, 233. Ledge, 98. Lehigh, Pennsylvania, anthracite area, 316. County, Pennsylvania, brown he- matite, 121, 122. Lift plane in granite, 365, 366. Lignite, analyses of, 312. of Texas, 318. Lime, 359, 378, 379, .380. use as a fertilizer, 403. Limestone, 376. character of, 376, 377. Limestone, colour of, 377. definition of, 377, 378. distribution of, 385. flux, 453. occurrence of, 385. origin of, 31, 376. production of, Alabama, 379. California, 379. Connecticut, 380. Illinois, 379, 380. Indiana, 379, 380. Iowa, 379. Kansas, 379. Kentucky, 379. Maine, 379, 380. Maryland, 379. Massachusetts, 380. Minnesotti, 379. Missouri, 379, 380. Nebraska, 379. New Jersey, 380. New York, 379, 380. Ohio, 379, 380. Pennsylvania, 379, 380. Texas, 379. United States, 379, 380, 453. Vermont, 379. Virginia, 379. Wisconsin, 379. use of term, 377. uses of, 378, 380. as a fertilizer, 402. Limonite, 19, 119, 120, 122, 135. Literature of Economic Geology, 457. Litharge, 238. production of United States, 449. Lithocarbon, 355. in Texas, 356. Lithographic stone, 442. Little Bay, Newfoundland, copper mines, 220. Locating mineral veins, 105. Lode, 98, 106. Longfellow, Arizona, copper mine, 215. Long ton, 133. Los Cerrillos, New Mexico, turquoise in, 421. Louisiana, salt in, 431. 490 INDEX. Louisiana, salt production of, 433. sulpliur in, 439. Lovelock's Station, Nevada, nickel mine, 292. Lower California, copper in, 220. Lubricating oil, 340, 347. Luxemburg and Germany, iron pro- duction of, 146. M. Magnesite, 14, 437. Magnetite, 19, 20. concentration of, 129. distribution of, 127. occurrence of, 128, 131, 302. Michigan, 127. Nevy Jersey, 127. New York, 127. Pennsylvania, 127. Rhode Island, 128. origin of, 130. production of, 127. Michigan, 139, 144. New Jersey, 143, 144. New York, 141, 144. Pennsylvania, 141, 144. segregation of, 130. separation by electricity, 120. Maine, building-stone production of, 383, 384, 386. copper production of, 225. granite production of, 368. limestone production of, 379, 380. slate production of, 376. Malachite, .22, 208. - of Russia, 219. Malaspina glacier, Alaska, forest on, 328, 329. Malay Peninsula, tin in, 279. Maltha, 355. Manganese, 253, 262. alloys of, 270. association with hot springs, 266. with iron, 263. concentration of, 269. distribution of, 262, 268. mineralogical association of, 262. occurrence of, 135, 263, 268, 303. Manganese, occurrence of, Appala- chian Mountains, 264. Arkansas, 263, 265. Australia, 267. California, 266. Canada, 266. Chili, 267. Cuba, 266. Europe, 267. Prance, 267. Georgia, 263, 264. Germany, 268. Great Britain, 267. Italy, 267, 268. Michigan, 265. New Jersey, 264. New Zealand, 267. Pennsylvania, 264. Portugal, 267. Russia, 267. Spain, 267. Sweden, 267. Turkey, 267. United States, 264. Vermont, 264. Virginia, 263, 264. Wisconsin, 265. ores of, 24. origin of, 268, 269. price of, 271. production of Arkansas, 271, 307. California, 271. Canada, 272. Chili, 272, 273. Colorado, 271. Cuba, 272. Georgia, 271, 307. Great Britain, 272. Italy, 272. Michigan, 272. New Jersey, 272. Portugal, 272. Russia, 272, 273. Sweden, 272. Turkey, 272. United States, 271, 272, 304, 305. Vermont, 271. Virginia, 271, 307. INDEX. 491 Manganese, treatises on, 4G2. uses of, 270. Manganiferous iron ores, 203. silver ores, 263. zinc ores, 263. Mansfield, Germany, copper mines, 218, 220, 222. Marble, character of, 39, 380. definition of, 377, 378. distribution of, 384. imports of, 382. occurrences of, 384. California, 381. Cordilleras, 381. Georgia, 381. Maryland, 381. New York, 381. Pennsylvania, 381. Tennessee, 381. Vermont, 380. Virginia, 381. production of California, 383. Georgia, 383. Maryland, 383. New York, 883. Pennsylvania, 383. Tennessee, 383. United States, 383, 386. Vermont, 383. uses of, 382. use of term, 377. Marbleized stone, 375. Marl, character of, 403. occurrence of, in New Jersey, 403. production of United States, 403. use as a fertillizer, 402, 403. use iu Portland cement, 403. Marquette iron district, 124, 140. Marsh gas, 350. Maryland, chromium in, 299. coal in, 315. coal production of, 338. granite production of, 368. infusorial earth in, 426. iron pyrite in, 301. limestone production of, 379. marble in, 381. marble production of, 383. Maryland, serpentine in, 382. slate production of, 376. Mason and Barry, Portugal, copper mine,' 216. Massachusetts, building-stone pro- duction of, 383, 384, 386. granite production of, 368. limestone production of, 380. mineral water production of, 420. nickel in, 292. sandstone production of, 372. whetstones in, 428. Massive eruptive ore deposits, 80. McDonald petroleum field, Pennsyl- vania, 339. Mechanically formed ore deposits, 80, 81, 135. Malaconite, 208. Menominee, iron district, 125, 140, 143. Mercury, 24, 253. mineralogioal association of, 253, 258. occurrence of, 258, 303. Austria, 256. Borneo, 257. California, 253. Germany, 257. Italy, 257. Mexico, 258. Nevada, 253. New Mexico, 253. Oregon, 253. Peru, 257. Russia, 257. Servia, 257. Spain, 255. Utah, 253. origin of, 258. production of, 261. Austria, 261, 262. California, 255, 307, 455. Borneo, 261. Italy, 261, 262. Mexico, 261. Peru, 261. Russia, 261. Servia, 261. Spain, 261, 262. 492 INDEX. Mercury production of United States, 261, 262, 304, 305, 453. world, 261, 262. price of, 260. treatises on, 461. uses of, 113, 260, 262. Merionetshire, England, manganese deposits, 267. Mesaba Range iron district, 126, 140, 142. Metalloids, 96. Metallurgy, 113. of aluminum, 286, 287. treatises on, 465. Metals, 96. In igneous rocks, 72. in sedementary rocks, 73. production of, California, 305. Colorado, 305. Cordilleras, 306. Montana, 305. United States, 304, 305, 306, 307, 454. review of, 302, 304. Metamorphic rooks, 38. geological age of, 41. kinds of, 39. Metamorphism, causes of, 38, 40. contact, 92. Metric ton, 133. Mexico, copper in, 220. copper production of, 226. gold in, 167. gold production of, 175. lead in, 238, 240, 241. lead production of, 242, 243. mercury in, 258. mercury production of, 261. onyx in, 882. silver coinage of, 204. silver in, 193, 199. silver production of, 194, 206. tin in, 281. tin production of, 283. Mica, 8, 10, 442. occurrence of, in Canada, 443, 444. India, 443. New Hampshire, 443. Mica, occurrence of, in North Caro- lina, 443. South Dakota, 443. Wyoming, 443. production of New Hampshire, 444. North Carolina, 444. United States, 444, 445. Micaceous hematite, 119. Michigan, bromine in, 434. copper in, 209, 211. copper production of, 209, 213, 224, 225, 307, 455. grindstones in, 427. gypsum production of, 405. iron in, 124, 127. iron production of, 138, 139, 144, 145, 307, 455. manganese production of, 272. manganiferous iron ores in, 265. mineral production of, 455. mineral water production of, 420. salt in, 432. salt production of, 433, 455. sandstone production of, 372. silver production of, 192. Mill, 107. Millerite, 26, 292. Millstones, 425, 427. imports of, 428. occuiTenoe of. New York, 428. Pennsylvania, 428. Virginia, 428. Mine, character of, 105. drainage of, 106. Mines, heat in, 106. Mining methods, 103, treatises on, 464. terms, 96. Mineral, definition of, 2, 96. paints, 449. occurrence of, in New York, 450. Pennsylvania, 450. products, exports of, 456. imports of, 456. of California, 455. Colorado, 455. Illinois, 465. INDEX. 493 Mineral products of Iowa, 455., Michigan, 455. Minnesota, 455. Missouri, 455. Montana, 455. Nevada, 455. New York, 455. Ohio, 455. Pennsylvania, 455. United States, 450, 451, 453, 454, 455, 456. Utah, 455. "Wisconsin, 455. statistics, treatises on, 464. Mineral veins, 98. formation of, 85. in joint planes, 76. Mineral waters, classification of, 418. imports of, 420. production of, California, 420. Colorado, 420. Massachusetts, 420. Michigan, 420. New Hampshire, 420. New York, 420. United States, 420, 453. Virginia, 420. Wisconsin, 420. treatises on, 464. Minerals, alteration of, 75. common rock-forming, 5. common vein-forming, 15. Mineralogy, text-books on, 459. Mineville, New York, iron mines of, 129. Minnesota, building-stone production of, 383, 384, 386, 455. iron in, 124, 125, 126. iron production of, 139, 142, 144, 145, 455. limestone production of, 379. mineral products of, 455. sandstone production of, 372. Mississippi valley, lead-zinc mines, 84, 228, 229, 231, 240, 244, 248. Missouri, barite in, 448. barite production of, 449. Missouri, building-stone production of, 383, 384, 386, 455. coal production of, 333, 455. iron production of, 139, 143. lead-zinc deposits of, 229, 244. lead production of, 241, 307, 455. limestone production of, 379, 380. mineral paints in, 450. mineral products of, 455. nickel in, 292. sandstone production of, 372. spelter production of, 250. zinc-lead deposits of, 229, 244. zinc production of, 250, 251, 307, 455. Moisture in the Carboniferous, 328. Molly Gibson, Colorado, silver mines, 189. Monocline, 51. Montana, asbestos in, 448. copper in, 209, 214. copper production of, 215, 224, 225, 307, 455. diamonds in, 422. gold in, 158. gold production of, 173, 307, 455. lead in, 235. lead production of, 240, 241, 455. metal production of, 305. mineral production of, 455. sapphire in, 422. silver in, 181, 190. silver production of, 204, 205, 307, 455. Mother Lode, California, 150, 152. Mountains, association of ores with, 60, 94. MuTcia, Spain, lead district, 236. Muscovite, 8, 443. Mysore, India, gold production of, 166. N. Napa Consolidated, California, mer- cury mines, 255. Naphtha, 341, 347. Native copper, 22, 211. iron, 18, 81, 119. 494 INDEX. Native mercury, 24. silver, 21, 180. Natural gas, 337, 349. analyses of, 350. association of, with petroleum, 361. consumption of, 354. distribution of, 337, 350, 351. future of, 352, 353. history of, 351. occurrence of, 337, 350. California, 351. China, 352. Indiana, 351. Kentucky, 351. New York, 351. Pennsylvania, 351. Ohio, 351, 352. Ontario, 352. pressure of, 352. production of Canada, 355. Indiana, 354, 355. Kentucky, 354. New York, 354. Ohio, 354, 355, 455. Pennsylvania, 354, 355, 455. United States, 354, 355, 453. West Virginia, 351, 354. uses of, 353, 354. Natural soda, 437. Nebraska, limestone production of, 379. Nevada, aiitimony in, 297. antimony production of, 307. borax in, 435. borax production of, 436. gold in, 159. gold production of, 173, 307, 455. lead production of, 240, 241. mercury in, 253. mineral products of, 455. nickel in, 292. salt in, 430. silver in, 181. silver production of, 181,204, 205, 307, 455. sulphur in, 438. New Alniaden, California, mercury mine, 253, 254, 255. New Birmingham, Texas, iron mine, 121. New Brunswick, manganese in, 266, New Caledonia, cobalt in, 293, 294. cobalt production of, 296. nickel in, 292, 293, 294. nickel production of, 296. New England, anthracite production, 321. bog iron ores of, 121. coal basin, 313, 314. granite production of, 368. infusorial earth in, 426. iron pyrite in, 301. slate in, 374. tin in, 275. Newfoundland, copper in, 220. iron pyrite in, 301. New Hampshire, copper in, 225. granite production of, 368. infusorial earth in, 426. mica in, 443. mica production of, 444. mineral water production of, 420. oilstones in, 428. soapstone in, 445. soapstone production of, 446. whetstones in, 428. New Idria, California, mercury mine, 253, 254, 255. New Jersey, bluestone production of, 373. buUding-stone production of, 383, 384, 386. granite production of, 368. infusorial earth in, 426. iron in, 120, 127, 128, 135. iron production of, 139, 143, 144, 145. limestone production of, 380. manganese production of, 272. manganiferous zinc ores of, 264. marl in, 403. soapstone in, 446. sandstone in, 369. sandstone production of, 372. spelter production of, 250. zinc in, 243, 244, 248. zinc production of, 250, 251. INDEX. 495 New Mexico, anthracite in, 311, 319. copper in, 216. copper production of, 224. gold production of, 173. lead in, 236. lead production of, 240, 241 . mercury in, 253. silver in, 191. silver production of, 204. turquoise in, 421. zinc in, 251. New South Wales, gold in, 162. gold production of, 162. lead in, 238'. lead production of, 242, 243. platinum in, 177. tin in, 280. New York, hluestone production of, 373. building-atone production of, 383, 384, 386, 455. cement production of, 455. granite production of, 368. vgypsum production of, 405. hydraulic cement production of, 387, 389. .ron in, 127. iron production of, 138, 141, 144, 145, 307, 455. limestone production of, 379, 380. marble in, 381. marble production of, 383. millstones in, 428. mineral paints in, 450. mineral products of, 455. mineral water production of, 420. natural gas in, 351. natural gas production of, 354. petroleum in, 338, 339. petroleum production of, 348, .349. Portland cement production of, 390. salt in, 431, 432. salt production of, 433, 455. sandstone production of, 371. slate production of, 370. New Zealand, gold in, 162. gold production of, 162. manganese in, 267. New Zealand, petroleum in, 338, 340. platinum in, 177. Niccolite, 26, 292. Niocoliferous pyrrhotite, 26, 292. Nictel, 292. alloys of, 294. cobalt, association of, 293. copper alloy, 295. imports of, 296. mineralogical association of, 292, 294. occurrence of, 292, 293, 294, 303. Austrian-Hungary, 293. Colorado, 292. Connecticut, 292. Great Britain, 293. Massachusetts, 292. Missouri, 292. Nevada, 292. New Caledonia, 292, 293, 294. North Carolina, 292. Norway, 293. Oregon, 292. Pennsylvania, 293, 294. Prussia, 293. Sweden, 293. ores of, 26. origin of, 294. price of, 295. production of, 295. Pennsylvania, 307. United States, 295, 304, 305. world, 296. steel alloy, 295. uses of, 294. Nijne-Taguilsk, Russia, copper mines, 219. Non-metallic mineral production of United States, 454. Normal fault, 50. Norrie, Michigan, iron mine, 140. North America, copper production of, 226, 227. North Carolina, barite production of, 449. diamonds in, 423. gold in, 148. iron pyrite in, 301. mica in, 443. 496 INDEX. North Carolina, mica production of, 444. nickel in, 292. phosphates in, 407, 408, 409. tin in, 275. Northern coal area, 313, 818. production of, 321. Norway, copper in, 219. iron in, 134. niclcel-cobalt in, 293. nickel production of, 296. silver in, 199. Novaculites, occurrence in Arkansas, 428. Nova Scotia, coal in, 314. gold in, 168. manganese in, 266. Nuggets, origin of, 157. O. Ochre, 450. production of United States, 450. Ogdensburg, New Jersey, zinc de- posits, 244. Ohio, building-stone production of, 383, 386, 455. coal in, 315. coal production of, 333, 334, 455. grindstones in, 427. gypsum production of, 405. iron ore in, 132. iron production of, 139, 143, 144, 145. limestone production of, 379, 380. mineral production of, 455. natural gas in, 351, 352. natural gas production of, 354, 355, 455. petroleum in, 337, 338, 339. petroleum production of, 348, 349, 455. salt production of, 433. sandstone production of, 371, 372. Oil-pools, 342. Oilstones, 428. occurrence of, Arkansas, 428. Indiana, 429. New Hampshire, 428. Oilstones, production of United States, 429. Old Dominion, Arizona, copper mine, 216. Olivine, 10. Ontario, natural gas in, 852. Utah, silver mine, 190. Onyx, 381, 382. occurrence of, Arizona, 382. California, 382. Mexico, 382. Oolitic iron ore, 123. Ooze, globigerina, 31. red, 31. Opal, occurrence of, Washington, 423. production of United States, 424. Openings, 230. Oregon, gold production of, 173. mercury in, 253. nickel in, 292. platinum in, 176. silver in, 205. Ore channels, 80, 86. Ore, definition of, 15, 96. Ore deposits, association of, with mountains, 60, 94. with younger rocks, 94. classification of, 78. distribution of, 94. geological association of, 94. origin of, 72. Ore pulp. 111. Ores, character of, 15. common, 15, 17. concentration of, 103, 110. mining of, 108. occurrence of, 302, 304. aluminum, 25, 284. antimony, 26, 297. cobalt, 26, 292. copper, 22, 208. gold, 20, 147. iron, 18, 119. lead, 22, 228. manganese, 24, 262. mercury, 24, 253. nickel, 26, 292. silver, 21, 180. tin, 25, 274. INDEX. 497 Ores, occurrence of zinc, 23, 243. reduction of , 103, 113. removal of, 74. transportation of, 109. variation.s of, 102. Organic rocks, 31. soils, 393. Ornamental stones, 359, 360. Orthoclase, 6. Osmium, 21, 179. Outcrop, 97. Overtlirust fault, 50. Overturned fold, 51. Oxygen in the earth's crust, 1. Ozokerite, 357. Pacific coast, coal field, 321. production of, 313, 319. Palatinate, Germany, mercury mines, 257. Palseozoio, history of the United States, 68. Palermo, New Hampshire, mica mines, 443. Palladium, 179. Panulcillo, Chili, copper mines, 217. ParafBn, .340. Park City, Utah, silver mines, 190. Patio process, 196. Paving-blocks, 366. Pay gravels, 154. Pay streaks, 154. Pearls, 422. Peat, 311. analyses of, 312. bogs, 322. bog theory for origin of coal, 322. Pennsylvania, anthracite in, 315, 316. production of, 316, 333. bituminous coal production of, 333. bluestone production of, 373. building-stone production of, 383, 386, 455. coal in, 315, 316, 317. coal production of, 315, 316, 333, 334, 455. cobalt in, 293. Pennsylvania, chromium in, 299. granite production of, 368. hydraulic cement production of, 390. iron in, 121, 127. iron production of, 138, 140, 141, 144, 145, 307, 455. limestone production of, 379, 380. manganese in, 264. marble in, 381. marble production of, 383. millstones in, 428. mineral paints in, 450. mineral production of, 455. natural gas in, 351. natural gas production of, 354, 355, 455. nickel in, 293, 294. nickel production of, 307. petroleum in, 337, 338, 339. petroleum production of, 348, 349, 455. Portland cement production of, 390. sandstone in, 369. sandstone production of, 371. slate production of, 376. soapstone in, 445. soapstone production of, 446. spelter in, 250. zinc in, 244, 245. zinc production of, 250, 251. Penokee-Gogebic iron district, 125, 135. Perak, tin in, 279. Percussion table, 112. Peru, copper in, 218. gold production of, 166, 167. mercury in, 257. mercury production of, 261. petroleum in, 340. petroleum production of, 349. phosphate production of, 411. silver in, 196. silver production of, 196, 206. Petit Anse, Louisiana, salt deposits, 431. Petrified vyood, use of, in jewelry, 423. Petroleum, 337. 498 INDEX. Petroleum, accumulation of, 346. association of salt with, 432. character of, 340. composition of, 341. distribution of, 337, 342. exports of, 456. history of, 338. occurrence of, 337. California, .337, 338, 340. Canada, 338, 340. Caspian region, 338, 340. Colorado, 337, 338, 339. Indiana, 337. Japan, 338, 340. New York, 338, 339. New Zealand, 338, 340. Ohio, 337, 338, 339. Pennsylvania, 337, 339. Peru, 340. Russia, 338, 340. United States, 338. West Virginia, 338, 339. origin of, 340. production of, 347. California, 348. Canada, 349. Colorado, 348. Germany, 349. Indiana, 348. Italy, 349. Japan, 349. New York, 348, 349. Ohio, 348, 349, 455. Pennsylvania, 348, 349, 455. Peru, 349. Eussia, 349. United States, 346, .348, 349, 453. West Virginia, 348, 349. world, 349. resemblance to animal oils, 340. resemblance, in behaviour, to arte- sian water, 343. theories to account for accumula- tion of, 343. treatises on, 463. uses of, 346. Phosphates, 12, 402, 405, 407. analyses of, 409. Phosphates, occurrence of, Alabama, 407. Belgium, 410. Florida, 407, 408. France, 410. North Carolina, 407. South Carolina, 407. origin of, 410. price of, 410. production of, Belgium, 411. Canada, 411. Chili, 411. Florida, 409. French Guiana, 411. Great Britain, 411. Peru, 411. South Carolina, 408. United States, 411, 412, 453. Uruguay, 411. Venezuela, 411. Phosphor bronze, 223. Phosphorus, injurious to iron, 119. Phyllite, origin of, 39. Pig iron, production of United States, 304, 305, 455. Pinches, 101. Pipe lead, 238. Piston jigger, 112. Piston stamp, 110. Pitch, 100, 231. Plagioclase, 6. Plaster of Paris, 403. Platinum, 21. characters of, 177. coinage of, 177. group of metals, 179. occurrence of, 176, 303. California, 176. Canada, 177. Colombia, 177. Borneo, 177. Brazil, 177. British Columbia, 177. New South Wales, 177. New Zealand, 177. Russia, 176. United States, 176. price of, 178. production of, 178. INDEX. 499 Platinum production of Canada, 178. Colombia, 178. Russia, 178. United States, 178, 304, 305. uses of, 177, 178. Pleistocene glaoiation, 70. Plumbago, 441. Plutonic rocks, 37. Pocket theory for accumulation of petroleum, 346. Pointed box, 112. Poland, lead in, 237. spelter production of, 252. zinc in, 237, 246. zinc production of, 252. Pools of oil, 342. Pope's Creek, Maryland, infusorial earth deposits, 426. Portland cement, 387. analyses of, 388, 389. production of, New York, 390. Pennsylvania, 390. United States, 389. use of marl for, 403. Portland,- Connecticut, brownstone, 370. Portsmouth, Rhode Island, coal mines, 314. Portugal, copper in, 220, 226. copper production of, 226, 227. iron in, 135. lead in, 2.36. manganese in, 267. manganese production of, 272. silver coinage of, 204. tin in, 279. Potosi, Bolivia, silver mines, 195, 258. tin mines, 281. Potter's clays, 400, 401. production of United States, 453. Precious stones, 421. imports of, 425, 456. production of, United States, 424. treatises on, 464. Precipitated ore deposits, 80, 82, 135. Prescott, Arizona, onyx deposits, 382. Prospect Hill, Nevada, silver mine, 187. Prospecting, 104. Prospector, 104. Prosser iron mine, Oregon, 122. Prussia, cobalt production of, 296. nickel-cobalt in, 293. Przibram, Austria, silver mines, 102, 198. Pseudomorphs, 88. Psilomelane, 24, 262. Pyrargyrite, 21, 180. Pyrite, 300. production of, United States, 304, .305. Pyrolusite, 24, 262. Pyroxene group, 8. Pyrrhotite, niccoliferous, 26. Q Quartz, gold-bearing, 169. gold mines of California, 148. importance of, as a rock-forming mineral, 5, 10. production of United States, 424. use of, in jewelry, 423. use of in pottery, 401. Quartzite, characters of, 39. Quaternary additions to the United States, 70. coastal plains, 52. economic products of, 54. lakes of Cordilleras, 70. Quebec, Canada, petroleum in, 340. Queensland, gold in, 162. gold production of, 162. tin in, 280. Quicksilver, 253. Quincy, Michigan, copper mine, 213. R. Rammelsberg district, Germany, 198, 236. Ratio of silver to gold, 202. Red hematite, 19, 119. occurrence of, 302. Michigan, 124, 125. Minnesota, 124, 126. Missouri, 126. New York, 123. 500 INDEX. Eed hematite, occurrence of, Wiscon- ' sin, 124. origin of, 126, 127. production of, 122. Alabama, 139, 144. Georgia, 143. Michigan, 139, 144. Minnesota, 142, 144. Missouri, 143. Pennsylvania, 141. Tennessee, 148. Wisconsin, 142, 144. Redington, California, mercury mine, 255. Red lead production of United States, 449. Red ochreous hematite, 19. Red ooze, 31. Reduction of ores, 103, 113. Reef, 98. Replacement ore deposits, 80, 87, 135. Residual soils, 391, 392, 394. Reverse fault, 50. Rhenish provinces, Germany, lead mines of, 236, 245, 246. zinc mines of, 236, 245, 246. spelter, production of, 252. zinc, production of, 252. Rhodium, 179. Rhode Island, anthracites of, 311, 314, 441. granite production of, 368. magnetite in, 128. Ribbon structure, 98. Richmond, Massachusetts, limonite deposits, 122. Virginia, coal, 315. Rider, 99. Rift in granite, 363, 365, 366. Rio Grande, Texas, coal areas, 318. Rio Tinto, Spain, copper mines, 217, 220. River gravels, 154. Rock, definition of, 97. phosphates, 407. salt, 430. Rocks, disintegration of, 391, 392. disturbance of, 48. divisions of, 28. Rocks, geological age of, 41. igneous, 34. sedimentary, 28. metamorphic, 38. Rocky Mountain coal area, 318, 319. production of, 821. period of formation of, 69. silver in, 192. Roll, 101. Roofing-slate, 374, 875, 376. Rosario, Chili, copper mines, 217. Rosiclare, Illinois, fluorite deposits, 440. Roxbury, Connecticut, siderite de- posits, 183. Ruby Hill, Nevada, silver mines, 187. Ruby silver, 21. Run, 100. Russia, coal in, 335. copper in, 219. copper production of, 226. gold in, 163. gold production of, 164, 174, 175. lead in, 237. lead production of, 242. manganese in, 267. mercury in, 257. petroleum in, 339, 340. petroleum production of, 349. platinum in, 176. platinum production of, 178. salt production of, 434. silver in, 199. Ruthenium, 179. Rutland, Vermont, marble in, 380. Saline springs, 419. Salisbury, Massachusetts, iron mines, 142. Salt, 13, 430. association with gypsum, 404. petroleum, 337, 343, 432. lakes, as a source of salt, 430. occurrence in California, 430. Kansas, 431. Louisiana, 481. Michigan, 432. INDEX. 501 Salt, occurrence in Nevada, 430. New York, 431, 432. Utah, 430. origin of, 430, 431, 432. production of, California, 433. Canada, 434. Colombia, 434. Germany, 434. Great Britain, 434. Hungary, 434. Italy, 434. Kansas, 433. Louisiana, 433. Michigan, 433, 455. New York, 433, 455. Ohio, 433. Russia, 434. Spain, 434. United States, 433, 434, 455. Utah, 433. "West Virginia, 433. world, 434. treatises on, 464. uses of, 433. water, 337. association with petroleum, 337, 343, 432. Sandhurst, Victoria, gold district, 161. Sandstone, 29, 369. colour of, 370. characters of, 369. distribution of, 369, 385. occurrence of, 369, 385. Central states, 369. Connecticut, 369. New Jersey, 369. Pennsylvania, 369. production of, California, 372. Colorado, 371, 372. Connecticut, 372. Massachusetts, 372. Michigan, 372. Minnesota, 372. Missouri, 372. New Jersey, 372. New York, 372. Ohio, 371, 372. Pennsylvania, 372. United States, 371, 372, 386. Sandstone production of Wisconsin, 372. quarrying of, 370. texture of, 370. iises of, 371. weathering of, 369. Sand, use of, for abrasive purposes, 425. San Jacinto, California, tin mines, 276. San Luis Obispo, California, onyx of, 382. Sap of granite, 363. Sapphire, occurrence of, Montana, 422. North Carolina, 423. production of United States, 424. Satin spar, use of, in jewelry, 423. Saucon valley, Pennsylvania, zinc mines, 245. Schemnitz, Austria, silver mines, 198. Schist, characters of, 39. Schistose structure, origin of, 40. Schonfeld, Austria, tin mines, 279. Schuylkill, Pennsylvania, anthracite area, 316. Scotland, lead in, 237. Scythestones, 428. Segregated ore deposits, 80, 90, 135. Segregation, nature of, 90. of gold, 152, 170. of iron, 130, 1.35. Serpentine, 381, 382. occurrence of, Maryland, 382. origin of, 176. Servia, mercury in, 257. mercury production of, 261. Sesquioxide of iron, 119. Seville, Spain, copper of, 216. Sweden, zinc in, 246. Shafts, 106, 107. in Comstock Lode, 108. Shales, 29. Sheet lead, 238. Sheet mica, 444. Sheets of intruded rocks, 37. Shenandoah valley, Virginia, iron deposits, 122, 142. tin deposits, 275. Shoding, 104. Shoemaker's sandstone, 429. 502 INDEX. Short ton, 133. Shot lead, 239. Siberia, gold in, 163. Sicily, asphaltum in, 356. sulphur exports of, 440. sulphur in, 438. sulphur production of, 438. Siderite, 20, 119, 132. Sierra Nevada Mountains, period of formation of, 68. silver in, 192. slate in, 374. Silesia, Germany, lead-zinc deposits, 236, 246. spelter production of, 252. zinc production of, 252. Silicon in the earth's crust, 1. Silver, 180. alloys of, 201. character of, 201. coinage of, 201, 205. decline in price of, 202. distribution of, 192. exports of, 456. extraction of, by amalgamation, 113. free-coinage of, 202. imports of, 456. lead ores, 302. mineralogical association of, 199, 200. native, 21. occurrence of, 180, 199, 200, 302. Appalachians, 192. Arizona, 191. Australasia, 197, 199. Austria- Hungary, 198, 199. Bolivia, 195. California, 191. Canada; 194. Central America, 194. Chili, 197. Colombia, 197. Colorado, 181. Cordilleras, 181. Europe, 197, 199. France, 198. Germany, 197, 199. Great Britain, 199. Silver occurrence of Idaho, 190. Mexico, 193, 194, 199. Montana, 181, 190. New Mexico, 191. Nevada, 181, 184, 188. Norway, 199. Peru, 196. Rocky Mountains, 192. Russia, 199. Sierra Nevada Mountains, 192. South America, 195, 199. South Dakota, 192. Spain, 198. Sweden, 199. United States, 181, 189, 199. Utah, 181, 190. ores of, 21. manganiferous, 263. origin of, 199,. 200. production of Arizona, 204. Australasia, 206. Austria^Hungary, 198, 206. Bolivia, 196, 206. California, 204, 455. Central America, 206. Chili, 197, 206. Colombia, 206. Colorado, 204, 205, 307, 455. Ei-ance, 206. Germany, 198, 206. Idaho, 204, 205, 307. Japan, 206. Mexico, 194, 206. Michigan, 192. Montana, 204, 205, 307, 455. Nevada, 181, 204, 205, 307, 455. New Mexico, 204. Peru, 196, 206. Spain, 206. United States, 204, 205, 206, 304, 305, 453. Utah, 204, 205, 307, 455. world, 203, 206, 207. ratio of, to gold, 202. treatises on, 461. uses of, 201. Slate, 373. character of, 374. colour of, 373. INDEX. 503 Slate, consumption of, 375. distribution of, 374, 384. geological age of, 374. occurrence of, Appalachian states, 374. California, 374. New England, 374. origin of, 39, 373. production of, Maine, 376. Maryland, 376. New York, 376. Pennsylvania, 376. United States, 376, 386. Vermont, 376. Virginia, 376. uses of, 374, 375. Slaty cleavage, 373, 374. Slickenside, 100. Slime, 111. Sluice, 111. Smaltite, 13, 26. Smelting, 113, 114. Smithsonite, 23, 243. Smoky quartz, production of. United States, 424. Soapstone, 14, 445, occurrence of, 445. production of. New Hampshire, 446. New Jersey, 446. Pennsylvania, 446. United States, 446, 447. Vermont, 446. uses of, 446. Soils, 391. classification of, 391. impoverishment of, 398. origin of, 391. treatises on, 463. Solenhofen, Germany, lithographic stone, 442. Solution cavities, 77. South Africa, gold in, 164. gold production of, 165. South America, copper production of, 220, 227. gold in, 166. guano in, 406, iron in, 135, South America, natural soda in, 437. silver in, 195, 199. tin in, 280. South Carolina, barite production of, 449. gold in, 148. gold production of, 173. iron pyrite in, 301. phosphate in, 407, 408, 409. phosphate production of, 408. South Dakota, artesian wells in, 418. gold in, 158. grindstones in, 427. gi'anite production of, 368. gypsum production of, 405, mica in, 443. silver production of, 205. South Wallingford, Vermont, man- ganese mines, 264. Southern Atlantic states, tin in, 275. spelter production of, 250. - zinc production of, 250, 251. Spain, antimony production of, 298. coal production of, 335. copper in, 209, 216, 220. copper production of, 226, 227. iron in, 134. iron production of, 146. iron pyrite in, 301. iron pyrite production of, 301. lead in, 236. lead production of, 242, 243. manganese in, 267. mercury production of, 255, 261, 262. salt production of, 434. silver coinage of, 204. silver in, 198. silver production of, 206. spelter production of, 252. tin in, 279. zinc in, 236, 247, zinc production of, 252. Spanish gold mine, California, 151, Spathic iron ore, 119. Specular hematite, 19, 119. Spelter, 249. price of, 249. production of, Austria, 252. 504 INDEX. Spelter, production of, Belgium, 252. Eastern states, 250. Great Britain, 252. Illinois, 250, 252. Kansas, 250. Missouri, 250. New Jersey, 250. Pennsylvania, 250. Poland, 252. Rhine District, 252. Silesia, 252. Southern states, 250. Spain, 252. United States, 250, 252. world, 252. Sphagnum, action of, 322. Sphalerite, 23, 243. Sphene, occurrence of. New York, 423. Spiegeleisen, 270. Springs, cause of, 412. Stamps, 110. Stamping of ores, 110. State geological surveys, value of, 458. Statistics of minerals, treatises on, 464. Statuary hronze, 222. Steatite, 445. Stibnite, 26, 297. St. Ives, England, tin mines, 278. Stockwerk, 89. Stoping, 107. Stora Kopparberget, Sweden, copper mines, 219. Straits Settlements, tin in, 279. tin production of, 283. Stratified, definition of, 28. Stream-tin, 25, 274. Strike, 51, 100. Strike fault, 50. Sublimation ore deposits, 80, 93. Submergence of land in Carboniferous period, 326. Sudbury, Canada, nickel mines, 293. platinum occurrence, 177. Sulphide of silver, 180. Sulphur, 12, 438. imports of, 440, 456. Sulphur injurious in iron ores, 119. occurrence of, Japan, 438. Louisiana, 439. Nevada, 438. Sicily, 438. United States, 438, 439. Utah, 438. origin of, 438. production of, Sicily, 438. United States, 439. uses of, 439. Sulphur Bank, California, mercury mines, 86, 254, 255, 259. Sulphuric acid, use of iron pyrite for, 300. Sumatra, tin in, 280. Surveys, state and national geological, 457. Sutro tunnel, 107, 183. Swamp soils, 394. Sweden, copper in, 219. iron in, 134. lead in, 237. lead production of, 242. manganese in, 267. manganese production of, 272. nickel-cobalt in, 293. nickel production of, 296. silver in, 199. Swells, 101. Switzerland, aluminum production of , 291. Syenite, use of, as granite, 366. Syncline, 51. T. Table Mountain, California, 154. Tailings, 112. Talc, 14, 445. production of. United States, 447. Talus soils, 394. Tamarack, Michigan, copper mine, 213. Tarapaoa, guano deposits, 407. Tasmania, gold in, 163. tin in, 280. Telluride of gold, 159. Tennessee, coal in, 315. INDEX. 505 Tennessee, coal production of, 334. iron production of, 139, 143. marble in, 381. marble production of, 383. Tertiary coal, 314, 318, 319. coastal plains, 54. land areas, 69. mountain folding, 69. river gravels, 154. Texas, artesian wells in, 418. asphaltum in, 356. coal in, 318. iron in, 121. limestone production of, 379. lithographic stone in, 442. silver production of, 205. Tharsis, Spain, copper mine, 217. Thermal springs, 418, 419. Thibet, borax in, 435. Thistle, Utah, ozokerite deposits, 357. Thunder Bay, Canada, silver mines, 194. Ticonderoga, New York, graphite, 441. Tilly Foster mine. New York, titanite from, 423. Tilt Cove, Newfoundland, copper mine, 220. Timbering mines, 108. Time-scale, geological, 45. Tin, 274. alloys of, 282. distribution of, 274. imports of, 282, 456. mineralogical association of, 274, 281. occurrence of, 274, 281, 303. Alabama, 275. Australia, 280. Austria, 279. Banca, 279. Billeton, 279. Bolivia, 280. Burmah, 280. California, 276. England, 277. Finland, 279. France, 278. Germany, 278. Mexico, 281. Tin, occurrence of, New South Wales, 280. North Carolina, 275. Perak, 279. Portugal, 279. Queensland, 280. South America, 280. Spain, 279. Straits Settlements, 279. Sumatra, 280. Tasmania, 280. United States, 275, 277. Victoria, 280. Virginia, 275. origin of, 281. ores of, 25, 274. placers, 274. plate, 282. price of, 282. production of Australia, 283. Austria, 283. Bolivia, 283. Germany, 283. Great Britain, 283. Mexico, 283. Straits Settlements, 283. United States, 283, 304, .305. world, 283. treatises on, 462. uses of, 282. Titanite in New York, 423. Titusville, Pennsylvania, petroleum in, 338. Tombstone, Arizona, silver mines, 191. Tourmaline, 423, 424. Transported soils, 391, 395. Transvaal, gold in, 164. Treadwell, Alaska, gold mine, 160. Trenton limestone, as a source of petroleum, 337, 338, 339. Triassio coastal area, 56. economic products of, 57. volcanic activity of, 57. Tribute system, 109. Trinidad,asphaltum in, 356, 357. True veins, 80, 83. Tunnel, 106, 107. Turgite, 19. Turkey, manganese in, 267. 506 INDEX. Turkey, manganese production of, 272. Turquoise, 421. occurrence of New Mexico, 421. production of United States, 424. Tuscany, borax in, 435. Tye, 112. Type metal, 239, 297. U. Unitite, 355. Unconformity, 45, 46. Underlie, 100. United States, abrasive materials, production of, 429. agatized wood production of, 424. aluminum production of, 290. antimony production of, 298, 304, 305. artesian wells in, 418. asbestos imports of, 448. asphaltum imports of, 357. production of, 357. barite production of, 449. bluestone production of, 386. borax production of, 436. bromine production of, 4.34. buhrstone production of, 429. building-stone production of, 383, 385, 386, 453. catlinite production of, 424. cement exports of, 456, imports of, 390. production of, 453, 456. chromium in, 299. production of, 300, 304, 305. coal consumption of, 331. exports of, 456. imports of, 456. occurrence in, 312. production of, 320, 333, 334, 335, 336, 456. cobalt production of, 296, 304, 305. copper consumption of, 224. exports of, 456. imports of, 225, 456. occurrence in, 209. production of, 224, 225, 226, 227, 804, 305, 453. United States, corundum production of, 429. diamond production of, 424. emery imports of, 427. production of, 429. feldspar production of, 401, 402. flint production of, 402. garnet production of, 424. gems, imports of, 425. geological history of, 65. geological survey, publications of, 457. gold coinage of, 172. exports of, 456. imports of, 456. production of, 173, 174, 175, 304, 305, 453. gold quartz production of, 424. granite production of, 368, 386. uses of, 367. graphite imports of, 441. production of, 441. grindstones, production of, 429. gypsum imports of, 405. production of, 405. hydraulic cement production of, 389. in Archean times, 65. Cambrian times, 67. Cretaceous times, 69. Palaeozoic times, 68. Tertiary times, 69. infusorial earth production of, 429. iron, exports of, 145, 456. imports of, 145. production of, 144, 145, 146, 304, 305, 453. iron pyrite, production of, 300, 301, 304, 305. lead, exports of, 456. imports of, 456. production of, 240, 241, 242, 243, 304, 305, 453. lime production of, 453. limestone production of, 379, 386, 453. litharge production of, 449. manganese, occurrence of, 264. INDEX. 507 United States, manganese production of, 271, 272, 304, 305. marble production of, 383, 386. marl production of, 403. mercury production of, 261, 262, 304, 305, 453. metal production of, 304, 305, 306, 307, 454. mica production of, 444, 446. millstones, imports of, 428. mineral products of, 450, 451, 453, 454, 455. distribution of, 455, 456. exports of, 456. imports of, 466. mineral water, imports of, 420. production of, 420, 453. natural gas, consumption of, 354. production of, 354, 365, 453. nickel production of, 295, 296, 304, 305. ochre production of, 450. oilstone production of, 429. opal production of, 424. petroleum, exports of, 466. occurrence of, 338. production of, 346, 348, 349, 453. phosphate production of, 411, 412, 453. pig iron, 453. platinum production of, 178, 304, .305. Portland cement production of, 389. potter's clay production of, 463. precious stones, imports of, 4.66. production of, 424. quartz production of, 424. red lead production of, 449. salt production of, 433, 434, 453. sandstone production of, 371, 372, 386, sapphire production of, 424. silver, coinage of, 204. exports of, 456. imports of, 466. occurrence in, 181, 189, 199. United States, silver production of, 204, 205, 206, 304, 305, 453. slate production of, 376, 386. soapstone production of, 446, 447. spelter production of, 250, 252. sulphur, imports of, 440, 456. occurrence in, 438, 439. production of, 439. talc production of, 447. tin, imports of, 456. occurrence in, 275, 277. production of, 283, 304, 305. tourmaline production of, 424. turquoise production of, 424. whetstone production of, 429. white lead production of, 449. zinc, occurence in, 244, 247. production of, 250, 251, 252, 304, 305, 453. zinc-white, production of, 261, 449, 453. United Verde, copper mine, Arizona, 216. Upthrow of fault, 50. Urals, chromium in, 300. copper in, 219. gold in, 163. platinum in, 176. Uruguay, guano in, 407. phosphate production of, 411. Utah, artesian wells in, 418. asphaltum in, 356. copper in, 216. copper production of, 224. gold production of, 173. gypsum production of, 406. lead in, 235. lead production of, 240, 241, 307. 455. mercury in, 253. mineral products of, 456. ozokerite in, 357, 358. salt in, 430. salt production of, 433. silver in, 181, 190. silver production of, 204, 205, 307, 465. sulphur in, 438. 508 INDEX. V. Vanner, 112. Vaseline, 347. Vegetable origin of coal, 322. Vegetation in Carboniferous, 325, 327. Vein, 98, 106. Vein rock, 97. Vein wall, 99. Veins, branching of, 102. effects of faults upon, 101. effects of intersections on, 102. influence of country rock upon, 102. variations in, 101, 102. Veinstones, 17, 97. Venezuela, copper in, 217. copper production of, 175. phosphate production of, 411. Vermilion, 24. Vermilion Lake iron district, Minne- sota, 126, 140, 142. Vermont, building-stone production of, 383, 384, 386. copper in, 209. copper production of, 225. granite production of, 368. limestone production of, 379. manganese in, 264. manganese production of, 271. marble in, 380. marble production of, 383. soapstone production of, 446. slate production of, 376. whetstones in, 428. Vertical crevice opening, 230. Vete Grande, Mexico, silver mines, 193. Vete Madre, Mexico, silver mines, 193. Victoria, auriferous gravels of, 162. Victoria, gold in, 161, 162. gold production of, 161, 162. tin in, 280. Virginia, barite in, 448. barite production of, 449. coal in, 315. granite production of, 368. gypsum production of, 405. iron in, 121. Virginia, iron production of, 139, 142, 144, 145. iron pyrite in, 301. limestone production of, 379. lithographic stone in, 442. manganese in, 263, 264. manganese production of, 271, 307. marble in, 381. millstones in, 428. mineral paints in, 450. mineral water production of, 420. slate production of, 376. tin in, 275. zinc in, 245. Volcanic neck, 37. W. Wad, 24, 262. Wales, lead in, 237. Washington, coal in, 320. coal production of, 334. opal in, 423. silver production of, 205. Washita oilstones, 428. Water line, 102. Water, solvent power of, 74. underground, 74. Welcome nugget, 157. Stranger nugget, 157. Western coal area, 313, 318. production of, 321. Westphalia, Germany, lead mines, 236. West Rutland, Vermont, marble in, 380. West Virginia, bromine in, 434. coal in, 315. coal production of, 317, 333. iron production of, 144. natural gas in, 351. natural gas production of, 354. petroleum in, 338, 339. petroleum production of, 348, 349. salt production of, 433. Whetstones, 425, 428, 429. White lead, 238, 239. production of United States, 449. INDEX. 509 White metal, 249. Willeraite, 23, 243. Winze, 107. Wisconsin, building-stone production of, 383, 384, 386, 4.55. granite production of, 368. iron in, 124. iron production of, 139, 14i!, 143, 144, 307, 455. lead in, 229. lead production of, 241 . limestone production of, 379. manganiferons iron ore of, 205. mineral products of, 455. mineral water production of, 420. sandstone production of, 372. zinc production of, 251, 307. Witwatersrand gold district, Africa, 165. World, antimony production of, 298, 299. coal production of, 335. copper production of, 226, 227. gold production of, 174, 175, 203. iron production of, 146. iron pyrite production of, 301. lead production of, 242. manganese production of, 272. mercury production of, 261, 202. nickel production of, 296. petroleum production of, .'j49. salt production of, 434. silver production of, 203, 206, 207. spelter production of, 252. tin production of, 283. zinc production of, 252. Wurtzilite, 355. Wyoming, asbestos in, 447. gypsum production of, 405. mica in, 443. Wyoming, Pennsylvania, anthracite area, 316. Z. Zinc, 228, 243. blende, 23. mineralogical association of, 243, 247. Zinc, occurrence of, 243, 244, 247, 302. Austria-Hungary, 237, 246. Belgium, 237, 245. Cordilleras, 243, Europe, 247. Germany, 236, 245, 246. Great Britain, 237, 246. Italy, 237, 246. Kansas, 244. Mississippi valley, 229, 214. Missouri, 244. New Jersey, 243, 244. Pennsylvania, 244, 245. Poland, 237, 24(). Spain, 236, 247. Sweden, 240. United States, 244, 247. Virginia, 245. manganiferous, 203. ores of, 23. origin of, 84, 231, 214, 247, 248. price of, 249. production of, 249. Arkansas, 251. Austria, 252. Belgium, 252. Eastern states, 251. Great Britain, 252. Iowa, 251. Italy, 252. Kansas, 2.50, 251, .307. Missouri, 250, 251, 307, 455. New Jersey, 250, 251. New Mexico, 251. Pennsylvania, 250, 251. Poland, 252. Rhine District, 252. Silesia, 252. Southern states, 250, 251. Spain, 252. United States, 250, 251, 252, 304, 305, 453. Wisconsin, 251, 307. world, 252. treatises on, 461. uses of, 248. Zincite, 23, 243. Zinc white, 248, 251, 449, 453. TEXT-BOOKS ON GEOLOGY AND CONNECTED SUBJECTS Published by MACMILLAN & CO. ADAMS (L. E.). —British Land and Fresh Water Shells. Illustrated with coloured plates. $2.00. B. BLACK'S School Atlas of Modern, Ancient, and Physical Geography. A series of 41 Maps, fully coloured, with Index of 15,000 Names, and Clue Index. 4to, cloth. ^2.75. Black. 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