GIFT OF C- ECONOMIC GEOLOGY McGraw-Hill DookCompany Electrical World The Engineering andMining Journal Engineering Record Engineering News Railway Age G azettx? American. Machinist Signal E,ngin N. / ." x ' ^- ' f ' . //.r- ^V// 1 / > 7 ur.'* /f^^fcAl^ /S, N / .\v.(-/ f Cv;<-l^ <' 'V-"."- .'"'< jtv^wii ^ ; ^Sfel / -.'\> 'I.--!-'-'--. '-.' .v / ; % V;.-g,'.':ii :A;K ? -VvS;' :/ -^ V.x-r.'-\v.V.-/.'vvA-^ .;;' /,(" FIG. 9. Quartz vein along the foot wall of a porphyry dike, with stringers running off into the porphyry. (After Lindgren.) Veins. The United States Supreme Court has denned a vein as any belt or zone of mineral rock lying within the boundaries 12 ECONOMIC GEOLOGY clearly defined as separating it from the surrounding rock. Mineral veins fall into three distinct classes: (1) Fissure Veins or True Veins of Fracture. A fissure is of indefinite length traversing strata independent of bedding, generally nearly vertical and filled with mineral matter. The fissure is not parallel to the bedding. The walls may or may not coincide, and are nearly parallel with each other. The fissure was in the rock prior to the filling. The fissure vein then is the filled fissure, which is of indefinite length. It is from the fissure veins that our largest supply of the precious metals comes. (See Fig. 9.) (2) Gash Veins. Gash veins are represented by a metalli- FIG. 10. Gash vein in the magnesian limestone of Wisconsin. (After Chamberlain.) ferous deposit found only in limestones and confined to a single layer or formation. They are the most common in the bedding and the joint planes. (See Fig. 10.) (3) Segregated Veins. These correspond to the planes of bedding or stratification and in many respects are not unlike true fissure veins or gash veins. These veins vary in thickness and direction. Their irregularities are many. They are often pinched out as by forcing the walls together, or by the ex- pansion due to tension of the rock masses, or solution of the walls of the original channel. These veins also vary much in richness. The hanging wall is that part of the country rock lying geologically immediately above a vein or bed. The foot ORE DEPOSITS 13 wall is the lower boundary of a lode. The selvage is the zone of clay or decomposed rock, or both, separating the vein material from its walls (Fig. 11). The Occurence of Metalliferous Veins. (1) Metalliferous veins occur mostly in disturbed and highly metamorphosed regions. The tilting and the folding causes fissures that may be subsequently filled with mineral matter. Mineral veins therefore occur most frequently in mountainous regions or in the regions dis turbed by igneous activities. The lead deposits of Missouri are an exception to the rule for these occur in undisturbed and fossiliferous Paleozoic limestones. FIG. 11. A vein with its ores extending into the altered country rock. (2) These veins are more abundant in the older geological formations. There is no relation between the occurrence of min- eral veins and age alone. The connection is with metamorphism, which is more common in the older terranes. In the Pacific coast belt metalliferous veins often occur in Jurassic, Cretaceous and Tertiary formations. But these terranes have been sub- jected to folding and metamorphism. (3) Parallel veins usually have the same metallic content. (Veins at right angles may in some cases be exceptions.) The parallel fissures were formed by the same causes, at the same time and filled with similar material. Fissure veins not parallel with 14 ECONOMIC GEOLOGY each other (save perhaps at right angles) were formed at different times and filled under different conditions. The east and west veins at Cornwall, England, carry tin and copper and are pre- Triassic. The northeast and southeast veins are post-Triassic, but also contain tin and copper. The north and south veins are Cretaceous and contain lead and iron. The Richness of Veins. (1) If two mineral veins intersect each other one or both are generally richer at the point of inter- section. This increased value may be due to the reaction of waters bearing different bases in solution in the two fissures. FIG. 12. Section showing the form of the ore body in the, Victor, Smuggler Lee and Buena Vista miners, Cripple Creek district, Colorado. A, Ore. (After Penrose.) (2) Mineral veins are likely to be richer near their intersection with either acid or basic intrusives. This is especially true in regions that have suffered much metamorphism. It shows the influence of heat upon the metallic contents of the veins. (3) A change in the character of the county rock which a vein traverses may determine a change either in the contents or in the richness of the vein material. A vein may be well defined in the sedimentaries in close proximity to an acid or basic intrusive but upon invasion of the igneous rocks the vein is often subdivided into numerous branches. Irregularities in Veins. (1) Fissure veins are often irregular, as shown in Fig. 12. The vein often divides into numerous ORE DEPOSITS 15 White Porphyry Blue Limestone |': r -y-:V.' : -^;| Gray Porphyry Vein Material White Limestone FIG. 13. Section on the gold ore chute of Iron Hill, Leadville, Colorado. (After Blow.) FIG. 14. A troop of horses with the vein passing around it on both sides. A, Country rock; H, horse; F, fault. 16 ECONOMIC GEOLOGY branches. This is especially true as a vein passes from the sedi mentaries into the associated intrusives (Fig. 13). FIG. 15. Ore bearing quartz vein, somewhat lens-shaped. The country rock is altered, but contains no ore. (After Lindgren.) (2) Veins often dividing may come together as one vein and enclose a portion of the country rock. Such an enclosed portion is called a " horse. " Several masses of rock may appear within FIG. 16. A vein brecciated on one side and banded on the other. the vein and then they are called a "troop of horses," as shown in Fig. 14. ORE DEPOSITS 17 (3) Veins may pinch together by the creeping of the strata of the wall. In such cases the walls are mashed and the veins filled in part at least by the pressure of the superincumbent weight. (4) Veins may widen out and rise to lens-shaped ore masses within the vein (Fig. 15). (5) They may also be made irregular by repeated crustal movements, which break the rock into rubble-like material. The filling of these incipient fracture planes gives rise to the brec- ciated veins, as shown in Fig. 16. (6) Irregularities are also formed by the solution of limestones by percolating waters, charged with carbon dioxide. Granite. Altered Schor/aceous Granite. Peach with Cassiterite. 'ombs of Quartz. Siliceous Iron Ore Combs of Quartz Peach with Cassiterite. Altered Schor/aceous Granite. Granite FIG. 17. Structure of a lode at the Bellau mine, St. Just, Cornwall, Eng- land. (After Thomas and MacAlister's Geology of Ore Deposits.) Ribbon Structure. A banded or ribbon structure is not uncom- mon in the veins. In fact, according to LeConte, it is as common in veins as the columnar structures is in dikes. The layers upon the two sides usually correspond with each other in color or in composition, and, therefore, gives rise to a beautiful striped ap- pearance. Sometimes these successive layers are of different 2 18 ECONOMIC GEOLOGY materials. Occasionally where the gangue is quartz the layers are of agate, save the center, which presents a comb-like structure of interlocking quartz crystals, as shown in Fig. 17. Sometimes there appears to have been successive openings and fillings of the fissure both with the gangues and the metallic minerals. This is considered by many geologists as conclusive proof of the filling of fissures from solutions. Age of Veins. The age of veins is determined by the manner of their intersection. The intersecting vein is always younger than the intersected. The geological period to which fissure veins belong must be determined by the fossil content of the as- sociated terranes and by the stratigraphical position or the litho- logical similarity of the contiguous areas in which the fissures were formed. The filling of the fissure with gangue and metallic min- erals is a slow, subsequent operation. Classification of Ore Deposits. The classification of ore de- posits is a matter of convenience. It generally depends upon the purpose desired. They may be classified as to their mode of occurrence, as fissure, lens-shaped, bedded, etc. The following classification is based mainly upon use. Metals, precious and useful. PRECIOUS. Gold, silver, platinum, etc. USEFUL. Copper, iron, aluminum, zinc, and lead. Fuels: coal, petroleum, gas, naphtha, paraffine. Lubricants: graphite and oil. Structural: granite, limestone, sandstone, clay. Orna- mental: phosphates, onyx, marble, amber. Fertilizers: limestone, marl, feldspars, phosphate. Explosives: diatomaceous earth. Miscellaneous: asbestos, paint. They may be classified as to origin for the origin of economic products is as widly different as the products themselves. Prof. J. F. Kemp gives the following terse order: Solution, igneous, suspension. Prof. Franz Prosepny gives them Idiogenous, that is contemporaneous, xenogenous, that is later than the rock. Prof. W. 0. Crosby gives them Igneous, aqueo-igneous, aqueous. The following classification has been arranged by W. H. Weed. A. Igneous magmatic segregation, (a) Siliceous. 1. Masses. Aplite masses. Ehrenberg, Shartash. 2. Dikes. Beresite or aplite. Berezovsk. 3 . Quartz veins . Alaska, Randsburg, B lack Hills, S . D ORE DEPOSITS 19 (b) Basic. 1. Peripheral masses. Copper, iron, nickel. Sud- bury, Ontario. 2. Dikes. Titaniferous iron. Adirondacks and Wy- oming. B. 3. Igneous emanations. Deposits formed from gases above or near the critical point, e g., 365 C. and 200 atmospheres for H 2 0. (a) Contact-metamorphic deposits. 1. Deposits confined to contact. Magnetite deposits (Hanover, New Mexico); chalcopyrite deposits, Kristiana type; gold ores, Bannock, Idaho, type. 2. Deposits impregnating and replacing beds of contact zone. Chalcopyrite deposits, pyrrhotite ores, magnetite ores, Canada type; gold tellurium ores, Elkhorn type; arsenopyrite ores, Similkameen type. (b) Veins closely allied to magmatic and to Division D. 1. Cassiterite. Cornwall, Eng. 2. Tourmaline copper. Sonora, Mex. 3. Tourmaline gold. Helena, Montana; Minas Geraes, etc. 4. Augite copper, etc. Tuscany. C. Fumarolic deposits. (a) Metallic oxides, etc., in clefts in lava. No commercial importance. Copper, iron, etc. D. Gas-aqueous or pneumato-hydato-genetlc deposits, igne- ous emanations, or primitive water mingled with ground water. (a) Filling deposits. 1. Fissure veins. 2. Impregnation of porous rock. 3. Cementation deposits of breccia. (b) Replacement deposits. 1. Propylitic. Comstock, Nevada. 2. Sericitic, Kaolinic, calcitic, copper-silver, silver- lead. Clausthal, De Lamar, Idaho. 3. Silicic dolomitic, silver-lead. Aspen, Colorado. 4. Silicic calcitic. Cinnabar, California. 5. Sideritic silver-lead. Coeur d' Alene, Idaho; Slocan, B.C.; Wood River, Idaho. 6. Biotitic gold-copper. Rossland, B. C. 20 ECONOMIC GEOLOGY 7. Fluoric gold tellurium. Cripple Creek, Colorado. 8. Zeolitic. Michigan copper ores. STRUCTURE, TYPES OF THE CLASSIFICATION UNDER D Fissure veins: San Juan, Colorado. Volcanic stocks: Nagyag and Cripple Creek. Contact chimneys: Judith. Dike replace- ments and impregnations. Bedding or contact planes: Mercur, Utah. Axes of folds: Synclinal basins, anticlinal saddles. Bendigo, Elkhorn. E. Meteoric waters. (Surface derived.) (a) Underground. 1. Veins. Wisconsin lead and zinc. 2. Replacements. Iron ores, Michigan. Lead, zinc, Mississippi Valley. 3. Residual. Gossan iron ores, manganese deposits. Virginia. (b) Surficial. 1. Chemical. Bog iron ores, sinters Some bedded iron ores, etc. Clinton ore, New York. 2. Mechanical. Gold and tin placers. California, Alaska. F. Metamorphic deposits. Ores concentrated from older rocks by metamorphism, dynamo or regional. What Constitutes a Mine? (1) In the broadest sense a mine may be said to consist of a body of ore sufficiently large and rich to pay for the original purchase price of the property, all costs of mining, transportation, reduction plant, together with a large percentage of interest on the investment. (2) In determining what constitutes a mine, it is necessary to consider each item of possible expense chargeable against the property, all physical and geological conditions, and such ore bodies as are developed, together with their bearing upon future ore bodies. (3) The situation of property is exceedingly important. In this connection it becomes necessary to consider availability of water, for power, for the treatment of the ore, and for the removal of slimes; fuel as a source of heat, and as a source of power; and timber for the shafts and underground workings. It is necessary to consider the accessibility of property both ORE DEPOSITS 21 for the purpose of shipping supplies to the mines and marketing the ore or bullion; the question of dumping ground for the re- moval of waste; the position of the mill for the reduction of the ore, and position of the smelter for roasting the ore. (4) The geological and physical problems in connection with determining the mine deal perhaps more with the future of the mine than with the actual cash value. In this connection one must consider not only the enclosing rocks, their resistance, definition and influence upon the mineralization, but must consider also the fissure deposits, if they are present, the faults, because in the majority of deposits the ore actually occurs in fissures and faults, or as fissure veins. (5) Fissures and faults are additionally important because in many cases the continuity of the ore body must be determined. If faulted by intersecting fissures, this must be known and the con- sequence actually determined. It is a well-known fact that ore bodies are more often irregular in dip, strike, and formation than otherwise, the valuable portion of ore being controlled by some physical fact such as the intersection of the fissure with certain strata whose definition is known, intersection of fissure with the igneous rocks, and intersection of one fissure with another of dif- ferent age. In a known district it is often possible by careful observation of these facts to calculate the exact position of valu- able bodies. At Rico, Colorado, vertical veins intersect a zone of disturbance rich at the point of intersection. This has been proven generally true. Therefore, wherever vertical veins in- tersect a plane of disturbance, rich ore deposits are more likely to be encountered. (6) Ore above or below water level is important on account of the method of treatment of the ore. Above water level there are frequently high-grade ores that can be quickly and cheaply reduced by a simple mill upon the ground, whereas below water level the milling process may be involved and expensive as it may be necessary to smelt the ores before reduction to the metallic state. These are very important items in the cost of reduction because of the additional expense required and the uncertain factor or the cost of reduction. (7) It is also necessary to say whether the ores are primary or secondary in origin. Often there is a zone in the vein wherein are deposited, below water level, very rich bodies of ore which under normal conditions might reasonably be considered perma- 22 ECONOMIC GEOLOGY nent. Experience has shown that the deep ores even at a greatly increased expense of mining may be mined at a profit. Butte shows a zone of oxidation, a zone of sulphide enrichment, and a zone of permanent value in which the workings may be carried far below the surface and still obtain a definite value of metal. The Michigan copper mines and the gold mines on the west coast of British Columbia are examples of mines far below the surface carried on at a profit in the zone of permanent value, as the owners know exactly what to depend upon. (8) The gross value of ore deposits is to be determined only by actual measurement^ ores blocked out and the determination of the values by careful and conscientious sampling with sufficient precaution to assure the owner that the results are absolutely correct. It is a very easy matter to guess on the quantity of ore, but it would be an easy matter to make an overestimate or under- estimate, for the only estimate that can receive credence is that based upon the ores actually blocked out. It is an easy matter in the sampling of ore chutes to arrive at an erroneous conclusion by a failure to sample the material of an entire vein and find where the value lies. If the purpose is to find out the value of an entire vein, samples are collected in different places; one from near the center, one near the hanging wall, one near the foot wall, one from across the top of the adit, one from the center, and one from near the bottom of the vein exposed. This method will not only tell where the pay streak lies, but also give the average of the entire face. Ore bodies like other bodies have three dimensions and there- fore can be blocked out only by actual development. These ore bodies must be cut and drifted upon at sufficient intervals to determine length, thickness, and form of the valuable chutes. The ore bodies may be divided into three classes: (1) Ore actually in sight; (2) ore technically in sight; and (3) ore that under the conditions existing should be expected with proper development of the property. (10) The next step is the determination of the method of min- ing and treatment of the ores for all time and whatever grade and kind, and to calculate the cost of converting ore into money. Here are 11 factors: Cost of mining, labor and supplies; cost of development, labor and supplies; cost of reduction; teaming; milling; loss in mill; loss in smelting; commission paid to smelter; cost of equipment of mine; cost of equipment of mill; cost of ORE DEPOSITS 23 equipment of smelter; cost of mill; cost of smelter; cost of managing smelter; cost of normal litigation that may arise from ore bodies coming from other than the ground in question; amount of interest on the money advanced for the original purchase and equipment at nominal rates; and, lastly, a large percentage of profit. To be a profitable mine the sum total of these costs must not exceed the gross value of the ore as calculated. CHAPTER II ORIGIN OF ORE DEPOSITS Meteoric Origin. In the light of the new planetesimal hypothe- sis of the earth's origin which has been so admirably worked out by Prof. T. C. Chamberlain there seems to be a continuous shower of extraterrestial material falling upon the surface of the earth. If this material strikes the land it mingles with the soil almost unnoticed. If it falls into the sea its high specific gravity carries the material to the ocean bottom where it is buried in the muds ot the sea floor. If it falls upon the Arctic snow fields it enters into the ice and imparts the peculiar banded appearance characteristic of so many glaciers. Wherever this shower of meteoric dust may fall it becomes a possible source of ore deposits through segregation by vadose waters. Number of Meteorites. According to Prof. C. A. Young from 15,000,000 to 20,000,000 of meteorites enter the earth's atmosphere every 24 hours. One of the most noted of modern meteoric masses is that of the Canyon Diablo which fell in eastern Arizona. C. R. Keyes says that 20 miles east of the San Francisco mountains, in the midst of the vast level plain forming the general surface of the high plateau, is a low mound called Coon Butte. The center of this butte contains a crater- like depression about 1000 ft. across. In the vicinity of this hill such large amounts of meteoric iron have been found from time to time as to give rise to the theory that the crater was produced by an enormous meteorite striking the earth at this point. The impact caused the fragments to scatter in all directions. Meteorites are scattered over widespread areas rather than of local occurrence. The reports of the Challenger expedition cite a great abundance of chondrones of cosmic origin in the abyssmal deposits of the ocean. Nordenskjold cites the presence of minute, black, metallic particles in the Arctic snow fields. C. R. Keyes calls attention to hailstones containing fine metallic particles composed mainly of iron, nickel, cobalt and copper. He also cites the constant occurrence of meteorites 24 ORIGIN OF ORE DEPOSITS 25 in the desert regions of the Mexican plateau situated many miles from the mountains and far away from igneous rocks. Metallic Content of Meteorites. Nearly all of the common metals have been found in meteorites and gold has been reported. As these particles reach the earth they mingle with the soil, oxidize in the presence of moisture, pass into solution and are transported to a deeper zone by the circulating ground waters. It is probable that a part at least of the widely diffused metallic content of sedimentary rocks is of meteoric origin, and that this extraterrestrial material is the primary source of many vadose ore deposits. Segregation. Many ore bodies are so intimately associated with masses of igneous rocks as to lead the observer to the XwC>\*7 *^;p */$.** r JT JT * V >r -V W * * -V * ^ C 3 Sr . *^i * AW* ***' v. w **w* 'vg ;^.v>X FIG. 18. Example of a contact deposit between two different kinds of rock. conclusion that such deposits resulted without doubt from the solidification of homogeneous or heterogeneous magmas through various causes of differentiation. Such deposits are so closely related petrographically to the rock masses as to lead to the conclusion that they form one heterogeneous complex. Magmas may be either homogeneous or heterogeneous. If the magma be homogeneous under the same conditions of temperature and pressure, there is uniform mobility in the various portions of the material. If the magma be heterogeneous then the more fluid portions may move readily toward the surface and the heavier and more basic material migrate toward the lower portion of such a magma. These magmas in which a perfect segregation may occur are deep-seated deposits brought into view through the erosion of a considerable amount of super- 26 ECONOMIC GEOLOGY incumbent strata. (See Fig. 18.) In the process of segregation of the ecomonic minerals three classes of ore deposits are formed : (1) The metals; (2) the oxides of the metals; and (3) the sulphides of the metals. Following the separation of the metallic content, the oxides and the sulphides of the metals, there appears the solidification of the ferro-magnesian minerals as the pyroxenes, the amphiboles, etc. After the solidification of the ferro- magnesian minerals comes a more acidic product as the feldspars and the last to separate is quartz. (See Fig. 19.) The causes of segregation are: (1) Fractional crystallization of the various ^ Mica Syenite Porphyry ^Igneous Vein showing 5^ marginal segregation FIG. 19. Vein of mica syenite-porphyry, showing marginal segregation oi ferro-magnesian minerals and iron ores. (After J. H. L. Vogt.) constituents of the magma. (2) The separation of the magma into two immiscible solutions, that is, solutions that will not mix, like water and oil. The completeness of the segregation may be determined by the rate of cooling of the magma as a whole. (3) The degree of viscosity. The viscosity will depend largely upon the chemical composition of the masses, varying with the relative amount of the ferro-magnesian and acidic minerals present. A segregation of the magma is not impossible before its appearance as an intrusive and this gives rise to ore bodies not unlike those segregating from homogeneous magmas, but the segregation is less complete. ORIGIN OF ORE DEPOSITS 27 We may consider one type in the segregation of ore bodies from an ultra-basic magma traversing the Appalachian belt from Alabama to Nova Scotia, appearing often in the Carolinas, Maryland, -Pennsylvania, Vermont and Quebec in a belt of Paleozoic rocks pierced here and there by peridotite. The segregation in the Thetford and Black Lake districts, Quebec, is as follows, as shown in Fig. 20. (1) The metals, chromium and iron, become oxidized and form lens-shaped masses of chromite and magnetite. There is a tendency for the chromite and magnetite to migrate toward the periphery of the mass and to appear often as lens-shaped ore bodies in the midst or in the border of the basic peridotite. The peridotite, rich in ferro magnesian minerals was the second FIG. 20. Section to illustrate the segregation of chromite and magnetite as lens-shaped ore bodies, Troy, Vermont. A, Perdotite; B, sericite schist. mass to solidify. The peridotite consists almost entirely of the ferro magnesian mineral olivine. If a difference existed in the constituents of the magma the pyroxenites would appear third in the process of solidification. The next product in the order of the solidification was acidic in character, light in color, of lower specific gravity, and the product a granite containing crystals of the potash feldspar, orthoclase, with granules of some ferro magnesian minerals, usually horn- blende. The final product as a rock mass from solidification is the most acidic and ribbed by veins of aplite, in which the feld- spars, micas and amphiboles are apparently absent. The final product through the differentiation of the ultra-basic magma gives free silica or quartz. 28 ECONOMIC GEOLOGY No scientist has ever worked more indefatigably in the prod- ucts of magmatic segregation than J. H. L. Vogt. His classification gave us: (1) The segregation of the native metals; (2) the segregation of metallic oxides; and (3) the segregation of metallic sulphides. In the segregation of the metals, the pre- cious metals, gold, silver, and platinum are formed. (1) Silver, the least frequently occurring as an original mineral, is in such form and quantity as to lead to the conclusion that the metal followed the law of solidification of magmas from the basic to the acidic. Gold is found in considerable quantities in the basic rocks as diabases and diorites, and in such acidic rocks as the granites and syenites; examples of the latter are found in the pegmatites of Australia and Alaska. The platinum is a product of segregation from such ultra-basic rock masses as the peridotites and the modern form or appearance is as grains of platinum associated with the metamorphic products. In serpen- tine platinum is almost always associated with the segregation of chromite, although all chromite does not contain platinum. The most important segregation of metallic iron is manifested at Disco Island, on the western coast of Greenland where large masses having the appearance of meteoric iron have been discovered. It was not until the ore body was subsequently discovered in place that its true nature was known, viz., segrega- tion from the basic intrusive basalt. Cobalt and nickel are more or less common and wherever one is found the other is present. Perhaps in New Zealand is found the best illustration of ore bodies of cobalt and nickel segregating from a molten magma. This generally carries a certain per- centage of iron, so it becomes an alloy of cobalt and iron. (2) The second class of products segregating from molten magma is the metallic oxides. Types of chromite and magnetite are among the more important and more common. In many cases the titanium is so abundant in magnetite as to lead to the conclusion that the titanium oxide plays the role of an acid, and the iron that of the base. Illustrations are common in the formation of such ore bodies in the Adirondack Mountains in New York. Another mineral sometimes segregating as an original mineral is cassiterite. In general, however, it is associated with pegmatite, an acid product in the solidification of some magma. In certain sections the character of the ore body is such as to ORIGIN OF ORE DEPOSITS 29 lead one to the conclusion that it is an original mineral. In the peridotite belt that stretches from Alabama to Nova Scotia, in North Carolina especially, corundum occurs in considerable abundance as an original mineral and emery is found in Massa- chusetts. The former has the formula A1 2 03 and the latter contains hematite or magnetite intimately mixed with corun- dum. These original minerals, surpassed in hardness only by the diamond, are worthy of mention here for their use as abrasives. (3) The third class as worked out by Vogt was that of the metallic sulphides. The segregation of metallic sulphides is characteristic of several types of igneous rocks as a result of dif- ferentiation either before or after intrusion. They are common FIG. 21. Section to illustrate the mode of occurrence of sulphidic segre- gations connected with norite intrusions. 1, Norite; 2, pyrite; 3, gneiss. (After Thomas and MacAlister's Geology of Ore Deposits.} products of segregation from magmas rich in ferro magnesian minerals. The sulphides commonly occurring with igneous origin are copper, iron, cobalt and nickel. (See Fig. 21.) Associated with these are the arsenides of a few metals. These are less im- portant and need not be further considered. The sulphide of copper most commonly segregating is chalcopyrite, CuFeS 2 . Bornite and chalcocite may also occur as primary minerals. Pneumatolysis. Pneumatolysis demands the formation of ore bodies from both acid and basic intrusives through the agency of gases dissolved in the magmas. Because the gases were present at the time of the intrusion, they were under high pressure and above their critical temperature. The magmatic vapors and 30 ECONOMIC GEOLOGY steam are liberated during the consolidation of deep seated intru- sives. The action takes place, not before consolidation begins, but during the process of consolidation and ceases altogether when solidification is complete. The vapors extract the metals from the cooling magma and deposit them as oxides and sulphides. Without pneumatolytic action the metals within the magma would remain as accessory minerals in the form of oxides, sul- phides, or silicates, distributed through the rock. If these metals be present in sufficient quantities to become essential, they pro- duce a massive segregation. Pneumatolysis, therefore, is the process of extracting metals from deep seated magma by the agency of superheated gases. The ores are deposited in the fissures and joint planes, both in the igneous rocks and the adjacent metamorphic aureole. The character of the minerals in the lodes is determined by the type of magma from which they were derived. The classification of such ore deposits depends upon: (1) The nature of the rock giv- ing rise to the ores. (2) The particular metals contained in the cooling magma. (3) The minerals associated with the ore bodies! The gases are called carriers or mineralizers. Each magma has its own mineralizer, and whether the metals will be deposited as oxides or sulphides depends upon their chemical affinity and the presence or absence of sulphur. Tin, as will be shown later, is most abundant as the oxide even when sulphur is present in the magma, while lead is most abundant as the sulphide. By the active magmatic gases the metalliferous minerals spar- ingly scattered through the cooling mass are withdrawn and more or less concentrated in the partially consolidated intrusive. The gases are then liberated and the ores concentrated in the lodes in which they are found, either in the intrusive or in the walls. The third step is the liberation of thermal waters. The tran- sition from concentration of minerals to liberation of thermal waters is gradual. The character of the ore bodies is deter- mined by the nature of the fissures, joints, faults, breccias, bed- ding planes, or other cavities in which deposition has taken place. The form of the deposit is of the utmost importance to the miner. To the geologist the altered walls of the lode and the minerals of the lode determine the character of the magma from which the ore was derived. According to Thomas and MacAlister, the most typical pneumatolytic ores are cas- siterite, wolframite, and scheelite, which may be associated with ORIGIN OF ORE DEPOSITS 31 sulphide of copper, iron, and arsenic, and less commonly ores of the other metals. (See Fig. 22.) Cassiterile. Lodes of tin are characterized by the presence of minerals bearing fluorine. This active element is able at high temperature to form a volatile compound with tin, which at a lower temperature is deposited as cassiterite according to the equation : SnF 4 +2H 2 O = Sn0 2 +4HF. Fluorine bearing minerals in the country rock owe their exist- ence to the presence of free hydrofluoric acid. Boron, chlorine, FIG. 22. Tin lode at the Bunny Mine, St. Austell, Cornwall, England. (After Thomas and MacAlister's Geology of Oie Deposits.) "The vein infilling is coarse cavernous quartz, with a distant resemblance to comby structure. It is a pegmatite vein containing cassiterite and wol- framite, some feldspar in the vein is kaolinized and the adjacent granite is altered to greisen, A little fluorite and tourmaline are present." carbon dioxide, and occasionally sulphur aie piesent. These vapors also assist in the extraction of the metals from the magma. Fluorine also forms a volatile compound with silicon and the silica associated with tin veins may have been formed accord- ing to the equation: 32 ECONOMIC GEOLOGY When the intruded rock is traversed by numerous joint planes, the vapors decompose its various constituents and readily form new minerals. If the country rock is not traversed by joints the process begins along planes of bedding or cleavage planes of min- erals and the alteration is easily effected. Feldspars are kao- nized and micas chloritized. Silicification of the country rock and greisenization also are not uncommon, but the character of the change depends upon the nature of the magmatic vapors. Fluorine belongs to the earliest emanations but boron, carbon dioxide, and hydrogen sulphide may belong either to the early or later emanations. Order of Deposition. At Cornwall both the oxide of tin and the sulphide ores were simultaneously deposited. The presence of copper ores upon previously formed cassiterite leads to the conclusion that copper ores continued to be deposited after the deposition of tin had ceased. In other instances where tin and copper ores arrived simultaneously, cassiterite was deposited first. Thomas and MacAlister give the order of deposition: (1) Cas- siterite and wolframite, together with the sulphides of copper, iron and arsenic. (2) The sulphides of copper, iron and arsenic, associated with those of lead, silver and cobalt. (3) Silver sul- phides and the oxides and carbonate of iron. (4) Nickel, anti- mony, and manganese minerals. The intrusion came in as large batholites of granite cutting sedimentaries of Ordovician Age. At Central and East Corn- wall they cut through Devonian rocks. The smaller batho- lites at Devonshire cut Devonian and Carboniferous strata. The ore is concentrated either in the periphery of the granite batholith or the metamorphic aureole. The copper ores, containing chalcopyrite, chalcocite and bornite, where tin does not occur, are often of pneumatolytic origin. In Norway where copper lodes are associated with a greisenized granite, the ore is unquestionably formed under the principles of pneumatolysis. At Copperfield, Strafford and Corinth, Vermont, the chal- copyrite, associated with tourmaline, occurs in saddle-shaped bodies in mica schist, or in chimneys at the contact of granite veins with mica schist. Pyrite and pyrrhotite are the associated sulphides. These sulphides were formed under pneumatolytic conditions. ORIGIN OF ORE DEPOSITS 33 Gold. Gold is sometimes found in copper-tourmaline veins connected with intrusives. It is found principally in the quartz and the tourmaline lies near the walls of the vein. This is especially true in Thelemarken. In Ontario auriferous-tourma- line veins occur in which the walls of the country rock are well tourmalinized. Titanite, rutile, anastase, and brookite are minerals often formed by pneumatolytic action associated with fluorine and boron-bearing minerals. Molybdenite is also found in quartz veins, pegmatites and granites in such manner as to show pneu- matolytic action. The Basic Intrusives. Ore bodies associated with the basic intrusives, gabbros and diabases, are often markedly pneumat- olytic, but not as common as in the granites, yet the process is the same. The principal agent or mineralizer is chlorine instead of fluorine or boron. Titanium would be extracted as the chloride and deposited as the oxide according to the equation : TiCl 4 +2H 2 = Ti0 2 +4HCl. Iron is similarly extracted: Fe 2 Cl6+3H 2 = Fe 2 3 +6HCl. The reactions of phosphorus and lead are similar: PbCl 2 +H 2 S = PbS+2HCl. Fluorine and boron are rare in the basic, but common in the acid intrusives. Hydatogenesis. Hydatogenesis is the process by which ore bodies connected with the intrusives of basic and acidic magmas are formed outside the metamorphic aureole. In point of time they are generally post-pneumatolytic. If it happens to be contemporaneous then it must take place beyond the zone of metamorphism. If they appear in the aureole or in the igneous rock itself, they were not formed until solidification and meta- morphism were complete. When the zone of metamorphism is free from minerals indicating mineralizers, the lode may be considered to belong to the hydatogenetic class. The ores are sulphides and oxides of the metals, the former predominating. To determine whether the ore body is of pneumatolytic or hydatogenetic origin, the geologist must look first to the nature 34 ECONOMIC GEOLOGY of the irruptive rock from which the minerals were derived; second, to the nature of the minerals in the lode, and third, to the character of the non-metalliferous minerals both in the lode and the metamorphic aureole. The magma may have been either basic or acid, deep-seated or superficial, irruptive or eruptive. In the classification of hydatogenetic deposits, it is customary to select the most important economic mineral. Many deposits are catalogued as gold ores that are strictly pyritic lodes charac- terized by a small amount of gold. Primary Gold Veins. Hydatogenetic gold veins are associated FIG. 23. Section to illustrate the formation of auriferous quartz lenses in alaskite. (After Thomas and MacAlister's Geology of Ore Deposits.) with granite, porphyry, andesite, trachyte and rhyolite. (See Fig. 23.) The chief gangue is quartz, but calcite, siderite and magnesite may be present with the quartz. Barite and fluorite may form the gangue; tourmaline and orthoclase may also be present. In what form the gold was extracted from the rocks and transported is perhaps uncertain. The solutions were di- lute and the gold reduced to the elemental state by the accom- panying sulphides. The presence of carbon or hydrocarbons in the walls of the ore body aids in its enrichment. In the secondary concentration near the surface melanterite has been the precipitant. Gold may occur as a. telluride of gold, or ORIGIN OF ORE DEPOSITS 35 telluride of gold and silver, or free gold in the presence of other tellurides. It occurs with the auriferous silver ores and with the sulphides of other metals in which the gold is present in the elemental state not as a sulphide. Primary Copper Ores. Chalcopyrite, chalcocite and bornite appear as primary minerals of hydatogenetic origin. The native copper is either metamorphic or metasomatic in origin. The chalcopyrite is by far the most important contributor to the world's supply of copper, but not all chalcopyrite is primary. The sulphides are derived from either acid or basic intrusives and precipitated by the action H 2 S in the heated waters. Primary Lead and Zinc Ores. The sulphides of lead and zinc, when filling fissures, appear to be connected with acid intrusives and are most abundant in the Paleozoic rock although they appear in the rocks of all ages. It is from these intrusives that the lead and zinc minerals appear to have been derived. Primary Silver Ores. True silver veins are characterized by the presence of original argentiferous minerals as native silver and argentiferous alloys together with the chlorides, iodides, bromides, selenides, tellurides, antimonides, arsenides of silver and other metals. In Butte, Montana, the silver seems to have been derived from dikes of quartz porphyry cutting granites. At Cobalt, South Lorraine and Gowganda, Ontario, the silver is derived from diabase and gabbro; therefore primary silver deposits may be associated with either acid or basic intrusives. The sulphides of the other metals also appear as primary ores, when derived from some magma and precipitated by hydrogen sulphide. Two carbonates appear as hydatogenetic minerals, siderite and rhodochrosite; one hydrosilicate garnierite is derived from a peridotite magma in its transition to serpentine and de- posited in the numerous fissures by the combined action of lateral secretion and hydatogenesis. Metasomasis. According to Le Conte, metasomasis is the process by which change in the mineral composition of a rock is effected. It may be produced in three ways: (1) By the alter- ation of the original minerals; (2) by the replacement of the original minerals; (3) by the crystallization of the minerals. The three changes may be effected separately or conjointly. If a limestone should be replaced in part by magnesium carbon- ate and therefore converted into dolomite, such a dolomitization 36 ECONOMIC GEOLOGY would represent a metasomatic replacement. The replacing material is introduced by circulating meteoric waters. The sol- vent action of the water is increased by the presence of carbon FIG. 24. Contact deposits in limestone beneath shale. dioxide under pressure, sulphides and silicates, together with the humic acid of the soil. Where sedimentaries lie in contact with igneous rocks, iron is leached out of the intrusive and by chemical action deposited FIG, 25. Iron ores of Michigan interbedded with sedimentary rocks. (After Emmons.) as an iron ore wherever an equivalent amount of limestone has been dissolved and transported elsewhere by percolating waters (Fig. 24). Metasomatic metalliferous minerals are most com- mon in the sedimentary rocks. They may be deposited soon ORIGIN OF ORE DEPOSITS 37 after the deposition of the sediments on the floor of the sea, or some later period, either before or after these sedimentaries have become land masses. Ore deposits thus formed are divided into two classes: (1) Bedded deposits, in which the ore body conforms with the strata FIG. 26. Iron ores of Michigan interbedded^with igneous and sedimentary rocks. (After Emmons.} in which it lies, as shown in Figs. 25, 26, and 27. (2) Fissure deposits, in which the ore conforms to the fissures and joints of the strata which may cross the sedimentaries at any angle. The former type embraces the most important iron and man- FIG. 27. Geological section in the manganese region of north Arkansas. The block bands represent beds of manganese that were deposited in layers alternating with the accompanying rocks. ganese formations, while the latter includes the silver, lead and zinc deposits. There are three ways of recognizing a metasomatic ore body: (1) The absence of symmetrical banding of its vein material. (2) The absence of breccias cemented by gangue minerals. (3) Lack of definition between the country rock and the ore body. 38 ECONOMIC GEOLOGY Metasomatic Iron Ores. The ores of iron that owe their origin to chemical action through solution and precipitation are the carbonate (siderite), the oxide (hematite) and the hydrous oxide (limonite). (See Fig. 28.) The source of the iron is generally some neighboring intrusive or pyritiferous sedimentary. The iron is dissolved by percolating waters. The solutions may find their way into strata capable of effecting the chemical change suggested, or find their way into FIG. 28. Section to illustrate the usual occurrence of iron ore deposits in the Mesabi range. It is below the glacial drift and resting upon quartz- ite. (After Winchell) standing waters where the iron can be extracted and deposited by metasomatic action. Pyrite will oxidize readily to melanterite, FeSO4,7H 2 O. Solu- tions bearing calcium carbonate will bring about the reaction through which the iron would be precipitated as the carbonate and the calcium sulphate will be precipitated as gypsum, CaSO4,- 2H 2 O, or transported elsewhere. FeSO 4 + CaCO 3 = FeCO 3 + CaS0 4 . If the percolating waters bear chlorine, the chloride of iron, Fe 2 Cl6, will be formed and calcium carbonate acting upon the ORIGIN OF ORE DEPOSITS 39 chloride of iron will precipitate the iron as the oxide (hematite), according to the equation: The iron ore replaces the lime- stone in the metasomatic de- posits molecule by molecule. Thomas and Mac A lister divide the iron ores of metaso- matic origin into two classes: (1) Contemporaneous, in which the replacement oc- curred either during or im- mediately after the deposition of the original rock. (2) Sub- sequent, in which the replace- ment occurred after the depo- sition and consolidation of the original rock. The former in- cludes the bedded deposits and the latter the irregular patches and veins. The oolitic Clinton iron ore of central New York, Pennsylvania and Alabama is a representative of the contemporaneous de- posits. The ore lies above the Medina sandstone in lime- stones of Silurian age. The Lake Superior iron ores lie upon the Archean complex and in the Keweenawan ter- ranes. They form the best American representative of subsequent replacement. (See Fig. 29.) The source of the iron seems to have been the ancient igneous rock of the Lake Superior region. The iron was precipitated as siderite. The siderite then passed into hematite and insensibly into ferruginous quartz schists, jaspers, magnetite and limonite schists. In the 40 ECONOMIC GEOLOGY Mesabi district the iron was originally deposited as the silicate, greenalite. Metasomatic deposits of Bauxite. The Georgia- Alabama baux- ites are found in -Paleozoic limestones above pyritiferous shales. Meteoric waters oxidize the pyrite to ferrous sulphate and sul- phuric acid. The free acid attacks the aluminum silicates of the shales producing alum and aluminum sulphates which are carried upward by ascending currents. These solutions, in contact with the overlying limestones, form calcium sulphate and bauxite. Lead and Zinc Metasomatic Deposits. Lead and zinc form metasomatic ores in the form of the sulphides, sul- phates, carbonates and silicates. The sulphides are of most importance. Such deposits are common in the Car- boniferous limestone but may occur in the limestones of any age. In Cumberland, England, the ore takes the form of and replaces the calca- reous fossils. The molecular replace- ment has been so perfect that the ore preserves not only the external form but often the internal structure of the fossils it has replaced. The source of the lead and zinc min- erals is often in some igneous rocks or sulphide-bearing sediments. These may be beneath the surface or exposed to weathering agencies at the surface. The transporting waters are meteoric and carry the solutions downward where deposition takes place (Fig. 30). Metasomatic Copper Deposits. Chalcopyrite, CuFeS 2 , is the most important copper ore of metasomatic origin. The materials came from some igneous magma during the later stage of its cooling. The aqueous emanation transported the minerals in the form of sulphates. The solutions are either ascending or descending and the chalcopyrite would be precipitated by hydro- gen sulphide and alkaline sulphides. If the solution percolated through the limestone, then malachite and azurite would be formed. Metasomatic Gold Deposits. According to Thomas and Mac- Alister, in the Transvaal district, siliceous gold-bearing solutions FIG. 30. Diagrammatic section showing the contact of porphyry and limestone and the zone of ore deposi- tion, Maginnis mine, Judith Mountains, Montana. (After Weed and Pirsson.) ORIGIN OF ORE DEPOSITS 41 acting upon pyrite below the permanent water level, in the pres- ence of a deficiency of oxygen caused a partial oxidation of the pyrite and a consequent metasomatic deposition of the gold. Precipitation. Precipitation is the process by which certain constituents of a solution are rendered insoluble in that solution. This is effected in the laboratory by the lowering of the tempera- ture, by the evaporation of the solvent, or by double decomposi- tion. In nature the fall of temperature occurs with rising ther- mal waters, but ores thus precipitated would be rare. The evaporation of the solvent is common and metallic ores may thus be thrown out of solution. The most common cause of precipi- tation is the mingling of different solutions in the trunk channels. Siderite and rhodochrosite are held in solution in waters charged with carbon dioxide. If the carbon dioxide be extracted by relief of pressure, or by any other cause, these metals are repre- cipitated as carbonates and remain as such in the absence of oxidizing agents. The sulphides of many metals are precipitated from their sulphate solution by the action of organic matter, or by the action of hydrogen sulphide upon their acid solution, while others are precipitated as sulphides from their alkaline solutions. Precipitated bedded ores may occur as sheets be- tween sedimentaries, or as crystals, grains, or nodules in the sedimentaries. These deposits may be recognized: (1) By parallelism with the enclosing sedimentaries; (2) by their occurrence in different horizons; (3) their margins are clearly defined; and (4) they do not shade into the barren country rock. Iron and Manganese as Oxides. These occur as bog-ores. Iron and manganese are thrown out of solution as a mixture of hydrated oxides by the action of algae and bacteria. Siderite may be brought into solution by percolating waters and when oxidized thrown out of solution as ferric hydroxide, according to the equation: 4FeC0 3 + 2 +3H 2 O = Fe 2 (OH) 6 +Fe 2 3 +4C0 2 The primary source of the iron and manganese is the ferro- magnesian silicates of the igneous rocks. The pyrite of the sed- imentaries also is oxidized or decomposed by humic acid and rendered available for precipitation. These minerals of iron and manganese had their primary source in the igneous rocks which furnished the detritus from which the sedimentaries were formed. 42 ECONOMIC GEOLOGY In carbonaceous shales the iron and manganese minerals are precipitated as carbonates by the loss of carbon dioxide from their solutions and the reducing action of organic matter. The ore deposits thus precipitated occur either as continuous sheets or as bands of concretionary minerals. (See Fig. 31.) The sulphides of these metals occur as precipitates in bedded deposits either through the action of H 2 S upon their solutions or by the reduction of their soluble sulphates. In the Harz Mountains, the sulphide of copper occurs in bedded deposits that appear to have been reduced from sulphate solutions by the action of decomposing organic matter. Gold is precipitated in siliceous sinter in Queensland, Australia, FIG. 31. Limonite concretions in the Kittany Valley, Pennsylvania. (Photograph by T. C. Hopkins.} where the sinter has been deposited from highly alkaline siliceous waters. This ore has yielded over $350 per ton in gold. A few precipitates as silicates are well known. Illustrations may be cited in the greenalite of the Mesabi iron district, Min- nesota, and the glauconite or green sand marl, of New Jersey. Metamorphism. Metamorphism is the process by which a complete or nearly complete chemical change has been effected in an ore body. These changes may take place either in the upper part of lodes and bedded masses exposed to percolating meteoric waters or at considerable depths below the surface by thermal and dynamic agencies. The first implies the downward trans- ference of minerals in solution for the subsequent enrichment of metalliferous deposits; the second, the reconstruction of an ore ORIGIN OF ORE DEPOSITS 43 body or rock mass by the influence of high temperature or by shearing stresses of sufficient intensity to generate considerable heat. The heat necessary for metamorphism may arise from the intrusion of a fluid magma or from the internal heat of the earth. Dr. F. W. Clarke, in his "Data of Geochemistry" cites the follow- ing changes as the most important: (1) Molecular Rearrangement. By this process a pyroxene is converted into an amphibole. (2) By Hydration. The conversion of a peridotite or a pyrox- enite into a serpentine or steatite would represent the change. (3) By Dehydration. Limonite, 2Fe 2 03,Fe 2 (OH) 6 , is converted into hematite, Fe 2 03, and bauxite, A1 2 03,2H 2 0, into corundum, A1 2 3 . (4) Oxidation and Reduction. Through oxidation ferrous com- pounds become ferric. Through reduction hematite, Fe 2 0s, be- comes magnetite, Fe 3 04. (5) Changes other than hydration produced by percolating solu- tions. The transference of some cement into a sandstone and its conversion into a quartzite would be an example. (6) Metamorphism by the action of gases and vapors, the so-called "mineralizing agents." The process generates new minerals and introduces new solutions. (7) Metamorphism by Igneous Intrusion. By this process new minerals are developed in the metamorphic aureole. The ores associated with metamorphic rocks may be divided: (1) Into those which occur as layers or lenticles in the crystalline schists, and (2) those which occur as metamorphosed metaso- matic deposits of irregular shape. In the crystalline rocks, hematite and magnetite are often of commercial significance. The hematite is produced by the dehy- dration of limonite and the magnetite by the reduction of hema- tite or by the decomposition of siderite through a loss of carbon dioxide. As sulphides, chalcopyrite, galenite, sphalerite and pyrite are common in Scandinavia. While not of so great importance in themselves alone, they have been the source of the material for the enrichment of the lodes, traversing the district. The magne- tite ore bodies of the Adirondacks, New York, represent a meta- morphosed deposit in the older schists and gneisses. (See Figs. 32 and 33.) Another illustration may be cited in the famous hematites and 44 ECONOMIC GEOLOGY FIG. 32. Iron mine, Lyon Mountain, New York. (Photograph by T. C. Hopkins.) FIG. 33. Iron mine, Lyon Mountain, New York. (Photograph by T. C. Hopkins.) ORIGIN OF ORE DEPOSITS 45 magnetites of Constantine, North Africa, noted for their remark- able freedom from sulphur and phosphorus. The zinc-manganese mineral franklinite at Franklin Furnace, N. J., occurs in a metamorphosed limestone with zincite, wil- lemite and rhodochrosite. Corundum, ruby, sapphire and emery occur in the metamor- phosed schists and limestones. The famous emery deposits on FIG. 34. Map of the district of Persberg, showing the association of ' the ore with metamorphosed calcareous rocks. (After Sjorgren.) the Island of Naxos in the Grecian Archipelago occur in a meta- morphosed limestone. Metamorphic ore deposits may be recog- nized by their associated minerals and their mode of occurrence. Metamorphic contact deposits are not distributed over large areas but rather confined within the metamorphic aureole in which the change has been effected through the influence of some intrusive. The changes produced in an ore body are along the lines of de- 46 ECONOMIC GEOLOGY hydration and recrystallization. The intrusives may also bring in new minerals by means of the heated solutions given off by the magma during the last stages of its consolidation which bridges the gap between pneumatolysis and metasomasis. (See Fig. 34.) Metamorphic masses of hematite, magnetite and pyrolusite occur in association with the intruded porphyry at Santiago, in Cuba. The copper deposits at Bisbee, Arizona, must in part be catalogued as metasomatic, yet these copper ores occur within as well as without the metamorphic aureole and associated with a porphyry magma. At Deep Creek, Utah, gold occurs as a metamorphic contact deposit in masses of granite and porphyry intruding the limestone. At the contact of the intrusive with the limestone, garnets and tremolite occur in abundance. The gold occurs both in a finely divided state in the recrystallized limestone and in threads in masses of tremolite. Secondary Changes. Secondary changes in ore bodies are effected; (1) By oxygenated meteoric waters, and (2) by waters derived from depth. The process often involves solution and the transference downward of the more soluble minerals for enrich- ment of the lodes at the lower levels. The extent to which the alteration will extend depends upon: (1) The relation of the rock to drainage; (2) the level of the ground water, and (3) the humidity of the climate. By glacial erosion in northern areas and continental denudation everywhere, the changes are carried progressively to lower levels. In the secondary changes by ascending solutions the older min- erals are replaced by the newer, as at Comstock Lode, Nevada, where calcite is replaced by quartz. The change is generally effected by solutions of a later period of mineralization. The possibility of these deep-seated changes was pointed out by J. H. L. Vogt, who showed that by either hot air or super- heated steam, argentite may be converted into native silver and sulphur dioxide according to the equations: Ag 2 S+H 2 = 2Ag+H 2 S+0. or on copper ores: 2Cu 2 S+60 = 2Cu 2 O+2SO 2 . Cu 2 S+2Cu 2 O = 6Cu-}-2SO 2 Ag 3 AsS 3 +3H 2 O = 3Ag+As+3H 2 S+3O. ORIGIN OF ORE DEPOSITS 47 Weathering changes effected in the upper part of lodes are in part oxidation and in part reduction. The upper part com- prises a zone of oxidized minerals. Beneath this there is a zone of enriched ores, often the richest portion of the entire lode, be- neath which there is a zone of permanent value. In the oxidation of chalcopyrite, ferrous sulphate is formed, which is readily oxidized to ferric sulphate. The ferric sulphate reacts upon the chalcopyrite, reducing the mineral to chalcocite, and by further influence of the ferric sulphate the chalcocite is converted into the sulphate of copper, according to the equation : Cu 2 S+5Fe 2 (S0 4 ) 3 +4H 2 0=2CuS0 4 +10FeS0 4 +4H 2 S0 4 . The copper sulphate in solution is transferred downwards to be reduced by the pyrite or other sulphides according to the equa- tions 7CuSO 4 +4FeS 2 +4H 2 = 7CuS+4FeSO 4 +4H 2 S0 4 HCuS0 4 +5CuFeS 2 +8H 2 0=8Cu 2 S+5FeS0 4 +8H 2 S0 4 . The copper sulphate in the presence of either pyrite or troilite may be converted into chalcopyrite, as, for example, on Vancouver Island. The carbonates of copper are less soluble than the sul- phate. If calcium carbonate in solution is transported downward in the copper lode, malachite or azurite and calcium sulphate would be formed with the liberation of carbon dioxide. The chalcanthite in solution may be reduced to tenorite, 2CuS0 4 + 2CaC0 3 = 2CuO+2CaS0 4 +2C0 2 , which in contact with ferrous sulphate solutions would be reduced to cuprite, Cu 2 0, and ulti- mately to native copper. Cerussite and anglesite, the carbonate and sulphate of lead, are similarly formed direct from galenite, while native silver is often produced by the reducing action of decomposing pyrite upon the sulphate of silver. Detrital Deposits. Detrital deposits are those resulting from the disintegration of rock masses through atmospheric agencies. The more resistant the parent rock the shallower the deposits become. If the gradient of the stream in the valley is small, the deposit will concentrate near the source of the ore. The higher the gradient and the greater the velocity of the stream, the farther down the valley the metalliferous minerals will be carried (see Fig. 35). The composition of the detrital deposit will depend upon the nature of the overlying country rock and the assorting power of the associated waters, as shown in Fig. 36. 48 ECONOMIC GEOLOGY Placers represent the concentration of the heavier economic minerals in the order of their decreasing density. In shallow FIG. 35.-^-Theoretical section showing the origin of auriferous gravels. The dark lines represent gold-bearing veins of which the coarser and heavier materials accumulate in the valleys. Gabbro Schists Etc. Limestone with Iron Ores FIG. 36. Map to illustrate the influence of ore-bearing rocks on the alluvia of streams and rivers. (After Thomas and MacAlister's Geology oj Ore Deposits.) placers the metalliferous mineral is confined to one level. In the deep leads there are two or more levels at which the values may be ORIGIN OF ORE DEPOSITS 49 obtained. Deep leads therefore mark a cessation in the deposi- tion of sediments. It may be that the stream was turned into some other channel by geological changes and subsequently re- turned again to the same valley. (See Figs. 37 and 38.) Laterite is the name applied to deposits arising through the FIG. 37. Section through Tuolumue County, California, showing old river auriferous gravels covered by a bed of lava, and the method of tunneling to reach them, at the sides are shown river gravels_of_a later age. solution and oxidation of certain minerals. The metalliferous minerals in such cases lie near the base of the hills, composed largely of basic intrusives which have been the source of the ore. Such deposits are represented in the Appalachian belt, India, Madagascar and elsewhere. i FIG. 38. Section through the Red Point and Damm Channels from El Dorado Canyon (right) to Humbug Canyon, California, showing the auriferous gravels covered by lava, and the method of reaching them by tunneling. The dotted lines at the sides suggest the ancient outlines of the hills. Gold. Placer deposits are one of the most important sources of this precious metal. In the Black Hills of S. Dakota, and in Alaska the gold has been concentrated by wave action. It is derived from pre-Cambrian metamorphics traversed by quartz veins. 50 ECONOMIC GEOLOGY In the detrital deposits of the Transvaal it is considered by some authorities that by the absence of nuggets the gold must have been deposited by subsequent infiltration into the conglomerate with which it is associated. The arguments in favor of its de- trital origin are: (1) Gold is restricted to the conglomerate; (2) the coarser the conglomerate the richer it is in gold content; (3) it was present in the conglomerate before much erosion took place; (4) it is independent of dikes and faults; and (5) it is inde- pendent of those sulphides which serve as precipitants for gold. In Australia the detrital gold deposits have furnished one nug- get weighing 233 lb., but as a mass of gold weighing 140 Ib. has been found in quartz reefs, the larger nugget may be of detrital origin. However, through chemical affinity, small particles of gold are often welded together. Platinum. Platinum is derived from two types of rocks, the ultra-basic and the basic intrusives, while detrital gold is often derived from both the acid and basic igneous rocks. The rare metals of the platinum group as osmium and iridium are also found in the platinum placers. The Ural placers are the richest in the world in platinum, but placers containing both platinum and gold are found in California. Iron. Iron occurs abundantly as beach placers in the United States and New Zealand, but it is seldom present in considerable quantity in other forms than oxides. The black sands of many river valleys are auriferous but they consist essentially of mag- netite derived from the basic intrusives associated with its genesis. Tin. The most important tin deposits of the world are de- trital. The oxide of tin, cassiterite (Sn0 2 ), stoutly resists dis- integration. During the erosion of the granites, pegmatites and contact metamorphics the tin finds its way toward the bottom of the detritus. It has been found in beach placers in England and in torrential placers in Bolivia. The tin deposits of the Federated Malay States are the most important in the world. The acid intrusives forming the high lands have suffered decomposition and erosion and cassiterite has become the chief detrital placer mineral. On the Islands of the Banka and Billiton the tin deposits occur in two forms; (1), "shoad" deposits in which the ore is found near the lodes from which it was derived; and (2), the deep lead placers which may extend over considerable area and varying depths. Assorted Minerals. These are often of no economic significance ORIGIN OF ORE DEPOSITS 51 in themselves alone but their constant occurrence in a placer im- plies the presence of a precious or useful metal. Cinnabar and wolframite indicate that the placer may carry gold; topaz and tourmaline signify the possible existence of tin; while chromite is an invariable associate of platinum. CHAPTER III PRECIOUS METALS GOLD, SILVER AND PLATINUM Properties of Gold. Gold, symbol Au, is a soft yellow metal unaffected by either moist or dry air. It is insoluble in all single acids save selenic. It surpasses all other metals in its malleability and ductility. Its specific gravity is 19.3; melting-point, 1065 C. and atomic weight, 197.2. Ores Containing Gold. Native gold: Pure Au is sometimes found but most of the native gold contains a small amount of silver platinum, etc. Petzite (Ag,Au) 2 ,Te: In ratio of 3 : 1 the gold content would be 25.5 per cent. Hessite (Ag 2 Te) : Gold is often present replacing a part of the silver. Sylvanite (Au,Ag)Te 2 : If the ratio is 1:1 it would give 24.5 per cent. gold. Calaverite (Au,Ag)Te 2 : with ratio 7:1 it would contain 39.5 per cent, gold. Krennerite (Ag 2 Te,Au 2 Tes) : The per cent, of gold is 35.5. Nagyagite (Au 2 ,Pbi4,Sbs,Te7,Si7). Some samples have given upon analysis 12.75 per cent, of gold. Occurrence. Gold occurs native encased within quartz. Sometimes in a finely divided state, sometimes in particles of considerable size, as nuggets, grains, scales, plates, threads and wires in quartz rock. It is often encased in pyrite, chalcopyrite, arsenopyrite, magnetite and hematite. It occurs also in a finely divided state in schistose rocks, often in too small quantity to pay for profitable extraction. It has been observed in the process of deposition at Steamboat Springs, Nevada. It is present in sea water, especially along the coast of Norway. It has been detected in many saline minerals, as sylvite, kainite, halite, and carnallite. It has also been found in the ashes of sea weeds. An attempt was made several years ago to reclaim the gold from the sea waters of the northeastern coast of the United States, and although the metal appeared in considerable quantity, the effort proved futile. The percentage of gold in sea water varies. It is present in greatest abundance where meteoric waters, flowing freely through 52 PRECIOUS METALS 53 gold-bearing belts, reach the sea. In the Appalachian belt, there is gold in the schistose rocks. Therefore along the Atlantic coast it is manifestly present in the sea water. Australia has many gold deposits, and meteoric waters flowing in rivers to the sea naturally carry some gold to the sea. The compounds of gold occurring as minerals of economic im- portance are few. The combination is generally with telluruim as petzite, (Ag,Au) 2 Te, in which the silver and the gold vary some- what but represent the unit structure in the mineral. Hessite shows no gold in the formula, Ag 2 Te, but gold may re- place the silver to a considerable extent. There is theoretically at least every gradation between the true telluride of gold on the one hand and the telluride of silver on the other. In the telluride of gold, silver is generally present and in the telluride of silver, gold is usually found. Calaverite, sylvanite, krennerite and nagyagite are also important sources of gold. The last named mineral is best catalogued as a sulpho-telluride of lead and gold. Kalgoorlite and coolgardite are examples of the tellurides of gold, silver and mercury. Gold occurs also as an amalgam with mer- cury, and as an alloy with copper, bismuth, platinum and rhodium. A word may be said here with reference to the occurrence of gold as a sulphide. The proofs of its occurrence as such are inadequate. The sulphide of gold is exceedingly unstable when- ever the precipitation occurs in chemical laboratories or the labo- ratory of nature by the action of hydrogen sulphide upon the neutral or slightly acid solution of the metal. Its instability favors its immediate reduction to the elemental state, provided any reducing agent is present. The sulphide of iron which is an exceedingly common associate with gold serves as such a reducing agent. Therefore whenever gold is found encased in pyrite, it is always present as free gold and not as a sulphide. Therefore the existence of auric sulphide, Au 2 S 3 , in nature may be questioned. Gold is found widely diffused in nature although one of the scarcer metals. It appears both in the igneous rocks and the sedimentaries, and manifests itself in the metamorphic rocks both of igneous and sedimentary origin. When occurring in igneous rocks the ore is of primary origin; when in fissure veins it is of pneumatolytic origin; when in sedimentary rocks it is of secondary origin. Its favorite gangue mineral is quartz often associated with fluorite and pyrite. Its occurrence in the granites of Mexico 54 ECONOMIC GEOLOGY and their metamorphic derivatives proves that gold is more likely to be found in the acidic than in the basic rocks. It ha.s, however, been found in basic rocks, and this occurrence is not rare. The auriferous quartz veins are doubtless free from silver in most cases. In some cases, it has been suggested by J. E. Spurr of the United States Geological Survey, that they represent PRECIOUS METALS 55 magmatic segregation. The same idea has been advanced by C. R. Van Hise of the University of Wisconsin. Again it has been shown by Thomas and MacAlister in their " Geology of Ore a ^ '% ^ o , A <>Oe>QO^C><>^'OOO44 < jA*.xi^/\,. ^^IAAX.^A-'AOA V.^ A ^ a ^.^ ^ * A " 4. 4. + + 4-4. ^ 4 *-t+-+-f4-f-4--hf4--- V.* .+ + *. A A ^A^ A A 4 A.A y,- 4 * -O ^^1 * * A *t** A FIG. 44. Horizontal section in the Elkton mine, Cripple Creek district, Colorado, showing the relation of the vein a to the dike b and to the country rock c. (After Penrose.) The third class of gold ores is auriferous copper ores. These are widely distributed throughout the United States and much of the chalcopyrite is gold bearing. Yet in many cases the yellow 60 ECONOMIC GEOLOGY metal is not present in sufficient quantity to warrant its extraction. These auriferous copper ores are especially abundant in Colorado, Utah, Montana and British Columbia. Also at Gold Hill, North Carolina and in Newfoundland. The fourth class of gold ore is auriferous lead ores. The per- centage of lead is large and the gold content often small. They are refactory ores like the copper ores. By ref actory ore is meant one that requires roasting before amalgamation will take place. The heavy sulphides as copper, lead and antimony require this method of treatment, that is the condition of the gold in the min- eral will not allow of its immediate union with mercury upon the amalgamation plates. The fifth class of gold ores comprises the gold-telluride group. The gold telluride ores occur with silver, or with silver, lead and antimony, or as native gold accompanied by other, tellurides. These ores are often sent direct to the smelters for treatment. Geographical Distribution of Gold. Gold is widely distributed in nature. It is present in almost all rocks, but only in a few localities in sufficient quantity for profitable extraction. If a line is drawn from Lake Winnipeg on the north southwesterly to the eastern base of the Rocky Mountains and from thence southerly to the Rio Grande River, nine-tenths of all the gold of the United States lies west of that line. The American belt then may be divided into five areas : (1) The Appalachian region, (2) the Black Hills region; (3) the Cordilleran region; (4) the Pacific Coast belt, and (5) the Alaskan belt. Appalachian Region. The Appalachian field stretches in a northeasterly direction from Alabama on the south, to New- foundland on the north. It carries varying quantities of gold. The richest portion is in the southern part of the belt. Hundreds of samples from this belt have shown traces of gold in almost all cases. In the northern portion of the belt, at Newport, Vermont, samples from Cambrian sericite schists have contained over $20 in gold per ton of ore. Near Lisbon, N. H., is found the best rep- resentative of gold deposits in the northern half of the belt. Samples containing more than $500 in gold per ton have been assayed. A small mill is treating some of the ore but the output is small. The ore occurs in a fissure vein traversing the crystal- line rocks. The gangue is quartz, and in the upper portion of the lode the associated pyrite has suffered much oxidation. The Southern Appalachian Field : The gold fields of the South- PRECIOUS METALS 61 ern Appalachians are situated in an area of crystalline rocks whose general strike is northeast and southwest. The auriferous rocks consist of granites, gneisses, schists, slates and shales. The auriferous quartz veins coincide imperfectly with the dip and strike of the strata. In Alabama there are 3500 square miles of auriferous crystal- line rocks in Chambers, Chilton, Clay, Cleburne, Coosa, Elmore, Randolph, Talladega and Tallapoosa Counties. The gold is encased in glassy quartz associated mainly with pyrite. In Georgia the auriferous belt extends in a northeasterly direction across the entire state. The associated rocks are sheared acid and basic intrusives. Certain bands of gneisses and am- phibolites have been produced in the shearing, and their fissures are filled with auriferous quartz associated with pyrite. The southern Appalachian gold field reaches its maximum im- portance in the Carolinas. From the northern part of South Carolina it extends across the entire state of North Carolina in a northeasterly direction to Virginia. It has a maximum width of 50 miles, and is flanked upon the west by an extensive granitic area and upon the cast by Jura-Trias terranes. The gold occurs in fissure veins with a quartz gangue, and as pyritic impregnation deposits with irregular and lenticular quartz intercalations in the schists and slates. The age of these ores is in all probability Algonkian for their deposition took place subsequent to the development of the schis- tosity of the Algonkian slates. The gold in the Jura-Trias conglomerate must have been pre-Jura-Triassic. The South Mountain belt is situated in the western part of North Carolina. The principal mining region is 25 miles long and about 12 miles wide. The terranes are chiefly bio tit e schists and hornblende gneisses. The schists are regarded as metamorphosed granites and diorites. They are often garnetif- erous and of special interest as they bear the rare minerals ziroon, monazite and xenotime. The strike of these terranes is northeasterly and their dip is about 25. The gneisses contain isolated masses of pyroxenite and amphibolites often metamorphosed into talc and serpentine. The auriferous quartz veins are noted for their remarkable regularity. Their general strike is N. 60 to N. 70 E. and dip at a steep angle to the northwest. The veins are exceedingly narrow averaging less than 6 in. The gangue is usually a milky 62 ECONOMIC GEOLOGY quartz and somewhat cellular from the oxidation of pyrite. The veins were filled from ascending gold-bearing solutions. The pyrite would serve as a reducing agent for the gold thus held in solution. The principal mining ground is in placers which, according to E. T. Hancock, may be divided into three classes. (1) The gravel of the stream and bottom lands, deposited by fluviatile action. (2) The gulch and hill-side deposits or accumulations due to disintegration and motion induced by frost action and gravity. (3) The upper decomposed layers of the country rocks in place. The Virginia belt extends from North Carolina in a northeast- erly direction to Montgomery County, Maryland, and is from 10 to 20 miles in width. The terranes consist largely of mica schists and gneisses, often garnetiferous, talcose and chloritic. The auriferous veins conform largely to dip and strike of the schists. They are very irregular, lenticular and narrow, seldom exceeding a few feet in width. The chief gangue is quartz but the wall rocks are often impregnated with auriferous pyrite. The Fisher lode in Louisa County is the most persistent. This lode has been opened for a distance of more than 5 miles, but the maximum depth to which the lode has been worked is approximately 250 ft. Black Hills District. The Black Hills are situated in Lawrence County in the western part of South Dakota. The auriferous ores are in the northern Black Hills. The gold of South Dakota was first discovered in the placers which occupy depressions in the pre-Cambrian schists. The region in one of peculiar interest for it represents some of the earliest known and worked placers of the United States. After the placers became somewhat exhausted at the surface, the workings were carried downward into the con- glomerate that marks the base of the Cambrian series of rocks. Some geologists are of the opinion that the origin of the placer gold is from the reefs formed by the Homestake ledge in the Cambrian Sea. Other geologists consider that the gold was chemically precipitated by the action of the sulphides of iron and therefore not a true detrital deposit. A reason for this conclusion lies in the fact that the matrix of the auriferous conglomerate is pyrite rather than quartz; also that the gold occurs along frac- ture planes stained by iron oxides. Homestake District : The Homestake belt is the most impor- PRECIOUS METALS 63 tant field in the Black Hills. It has been a steady producer of gold for many years. The Homestake ore bodies occur in the Algonkian slates which are for the most part of sedimentary origin. One variety has howev-er been recognized as a metamorphosed igneous rock and catalogued as an amphibolite because amphibole is the most prominent constituent. The amphibolites occur as dikes or irregular masses in the other Algonkian rocks. The associated FIG. 45. Banded siliceous ore in No. 2 shaft Union mine, Black Hills district, South Dakota, showing preservation of sedimentary bedding in the ore, the banding being continuous with the inclosing stratified rocks. (After J . D. Irving, U. S. Geological Survey.) metamorphosed sediments are quartzites, quartz-schists, mica- schists, phyllites and graphitic, garnetiferous and chloritic slates. More recent eruptives cut through all these rocks as well as the ore bodies themselves. The later eruptives are of two types. (1) A rhyolite porphyry, which is by far the most common rock. It not only cuts through the Algonkian terranes but spreads out in sheets or sills in the nearly horizontal strata of the overlying Cambrian series. (2) The second eruptive is a trachytoid phono- 64 ECONOMIC GEOLOGY lite which appears at the 800-ft. level of the Homestake mine and is a common rock in various parts of the northern Black Hills (Fig. 45). According to J. D. Irving, the ores of the Homestake zone are poorly denned masses of rock sufficiently impregnated with gold to pay for working, but otherwise hardly to be distinguished from the country rock in which they occur. They are singularly bar- ren of the usual ore minerals. The gold occurs in so finely divided a state that the particles are invisible even with a magnifying glass. Leaf gold has, however, been found but without evidence of crystalline structure. Pyrite and arsenopyrite are the only other metallic minerals present. The former is more abundant. Quartz is the most abundant gangue mineral. It occurs in veins or lens-shaped masses often of considerable size and of sev- eral different periods of formation. Calcite and dolomite are also present as gangue minerals usually of secondary origin, but not universally present. Origin of The Homestake Ores : There is no definite evidence as to the source of the gold and pyrite. Irving considers them to have been leached from the rocks at some distance below the sur- face by percolating waters and to have been precipitated in con- tact with graphitic matter and possibly also with original pyrite, present in the slates. A second period of mineralization came after the later intrusion of the rhyolite porphyry, followed the same general channels and deposited the gold and pyrite. This intrusive did not stop at the Cambrian contact, but continued on through cracks and fissures into the Cambrian rocks and deposited gold and pyrite abun- dantly in the basal conglomerate of the Cambrian series and in the calcareous terranes immediately overlying the outcrop of the Homestake belt. In the conglomerate, wolframite replaces some- what, the pyrite but there is no evidence of pneumatolytic action. The secondary enrichment of the ores by surface leaching has been of relatively small importance. There is little evidence of decrease in value of ore with depth. In fact the size of the ore body appears to be increasing rather than decreasing with descent. The ore as a whole averages between $5 and $6 per ton. According to J. D. Irving, the ore occurs in three distinct var- ieties. (1) Banded ore: That is, ore wherein the mineralization has not been accompanied by distortion of the original structures of the rock. (2) Contorted ore: That is, ore where the original PRECIOUS METALS 65 66 ECONOMIC GEOLOGY rock has undergone very great distortion. (3) Massive ore: Where few, if any, traces of either the original structure or the original constituents of the Algonkian rocks can be observed. Cordilleran Region. This vast area stretches through British Columbia on the north southward to Mexico and includes prac- tically all States traversed by the Rocky Mountains. Its best development is in Colorado. Each of these western States is subdivided into fields and districts, and each is worthy of a de- tailed description but only a few of the most important fields are considered. Cripple Creek. This district is situated 10 or 12 miles from Pikes Peak, Colorado, but in the foot hills of the same mountain FIG. 47. Small vein of andesitic breccia, Independence mine, Cripple Creek, Colorado. An, Andesitic breccia; P, pyrite; F, fluorite; Q, quartz; V, valencianite. (After W. Lindgren, U. S. Geological Survey.) mass. The field is the most important as a gold producer in the Cordilleran belt. Its importance is testified to by the fact that it has already produced more than $200,000,000 in gold. It is essentially a gold field for the ore contains from 1 to 10 oz. of silver per ton. The district consists of a series of highly metamorphosed mica schists bearing sillimanite, of pre-Cambrian age; the Pikes Peak granite, characterized by its microcline; the Cripple Creek granite also bearing microcline; and the Spring Creek granite which carries the commonest of the feldspars, orthoclase. In the metamor- phics there also appear some differentiation products of an olivine- syenite magma. The volcanics of the area consist largely PRECIOUS METALS 67 of tuffs and breccias of Tertiary age. These are cut by dikes of phonolite, latite-phonolite, syenite, dolorite, and even the more basic rocks. (See Fig. 46.) The ore bodies occur in two forms. (1) Lodes or veins, and (2) irregular replacement deposits. The veins are exceedingly narrow fissures incompletely filled. They are essentially in the volcanics and present a radical appearance. They are short and nearly vertical (Fig. 47). Some of the most productive fissures have been only a few hundred feet in length. In fact the entire field is circular in form with a radius of 2 or 3 miles. The lodes may occur in both the eruptives and the irruptives. Scale 10 20 feet FIG. 48. Sheeted zone and flats of the Apex vein, Ajax mine, Cripple Creek district, Colorado. (After W. Lindgren and F. L. Ransome, U. S. Geological Survey.) In the former case they favor the breccias and in the latter the granites, as shown in Fig. 48. The fissures seem to have been formed by compressive stresses associated with the cooling igneous rocks. The fissures are particularly small and narrow and may occur in any rock in the series. (See Fig. 49.) The replacement deposits usually occur in the granite. The principal gold ore is the telluride, petzite or calaverite which upon roasting brings the gold to the surface forming beautiful museum specimens. Pyrite is associated with the tellurides. Near the surface and in the oxidized zone in general the gold appears as brown, spongy gold while the tellurium has been con- verted into tellurites. The common gangue minerals are quartz, fluorite and dolomite 68 ECONOMIC GEOLOGY with the sulphides of lead, zinc, antimony and molybdenum spar- ingly present. The ores were deposited from hot alkaline solu- tions. Fluorine was an important mineralizer. The rich tellu- ride ore is shipped to Pueblo for smelting, while the lower grades are chlorinated or cyanided at the mines (Fig. 50) . The banner production of this small area was reached in 1900 when an out- put of more than $18,000,000 was credited to the district, but the output has since declined to nearly $10,000,000 per annum. San Juan District: The San Juan mining belt covers a large a b a b a E FIG. 49. Section in the Victor, Smuggler Lee, and Buena Vista mines, Cripple Creek district, Colorado, showing the parallel ore bodies A . (After Penrose.) FIG. 50. Section showing the forms of the veins in the Blue Bird mine, Cripple Creek dis- trict, Colorado, a, Ore; b, country rock. (After Penrose.) area of mountainous territory in the southwestern part of Colo- rado. It embraces the counties of Dolores, Hinsdale, La Plata, Ouray, San Juan and San Miguel. The continental divide traverses the area with several peaks surpassing 14,000 ft. in altitude. The base of the geological series is Archean. The over- lying Tertiary sedimentaries are capped with andesites, diabases, diorites, etc. Masses of rock composed of volcanic ejectamenta are not infrequent. Many V-shaped valleys of incision traverse the area. The whole field presents the appearance of a deeply cut volcanic plateau. PRECIOUS METALS 69 Telluride District : In the vicinity of Telluride there is a very interesting development of veins. The Smuggler vein is very persistent. It is definitely known that it extends four miles across the high divide that separates the Marshall basin from the valleys of Canon Creek. Many of the veins consist of closely spaced fissures filled with ore. The pay portion rarely comprises the entire vein but rather forms a narrow strip following either the hanging wall or the footwall. The gold is often encased in pyrite and chalcopyrite with quartz gangue. The silver is in the galenite and freibergite, but the double sulphides of silver with antimony and arsenic, as polybasite, stephanite and proustite are known. According to F. L. Ransome the downward percola- tion of meteoric waters dissolved the alkalis from the andesites and rhyolites as sulphides. These solutions rose in temperature as they approached the magma and became charged with sulphuric and carbonic .acids derived from volcanic sources. These acids gathered the metals and their gangue minerals from the more basic material and while penetrating the open spaces of the fis- sured zone, deposited the metals and gangue minerals at higher altitudes. The carbonates were deposited upon the walls of the fissures while the gold, to some extent, penetrated the walls. Silverton: The Silverton district lies to the east of the Tellu- ride. The Tertiary volcanics are separated from the Carbon- iferous terranes by a conglomerate. According to H. Ries, the ore depoits fall into three classes. (1) Lodes, which include most of the known productive deposits, (2) stocks, which in- clude most of the ore bodies formally worked on Red Mountain, and (3) metasomatic replacements, which comprise a few de- posits in the limestones or rhyolites. The lodes occur in all terranes from the pre-Cambrian to the Tertiary irruptives. The Tertiary fissuring is most pronounced in a northeast and southwest direction. The lodes are simple fissure veins. Some- times these veins bear both native gold and silver. The gold is often encased in chalcopyrite and the silver in galenite, tetrahe- drite and enargite. The common gangue minerals are quartz and calcite. The ores were deposited from hot ascending solutions with depth of origin unknown. Ouray District : The Ouray district surrounds the picturesque city of Ouray. The terranes comprise limestones, conglomerates quartzites, sandstones and shales overlain by Tertiary volcanics. 70 ECONOMIC GEOLOGY Fissure veins are the most pronounced and persistent type of ore deposits in the district. Some of these may be traced for more than a mile along the line of their outcrop. Sometimes they reach a width of 75 to 100 ft. and are well mineralized throughout. Much free gold occurs in the Camp Bird, Revenue Tunnel, Atlas and Torpedo-Eclipse mines. Samples from the latter mine have assayed over $50,000 per ton. The ore is often associated with tellurium also encased in chalcopyrite with a gangue of country rock and clay. Quartz, calcite, fluorite and bariteare common gangue minerals. The silver occurs in part native, in part with galenite and tetra- hedrite and in part as stephanite. Less important replacement deposits occur in the quartzites, sandstones and limestones. These deposits in the sandstones are more or less irregular but in the limestones they occur as broad flat ore bodies associated with the fissure veins that penetrate the limestones. The fissuring appears to be late Tertiary and the mineralization in some period later than the introduction of the volcanics. Georgetown District: This district is in the Continental Range in Clear Creek County, about 50 miles west of Denver. The base of the Geological series consists of pre-Cambrian schists of sedimentary origin which are overlain by highly metamor- phosed schistose rocks of igneous origin. This series of terranes was later penetrated by both acid and basic intrusives. The latest irruptives of probably late Cretaceous or Tertiary age, consist of porphyry dikes. These porphyries are of special interest because they stretch in a northeasterly and southwesterly direction nearly the entire length of the state. The lodes occur in fissure veins that cut the pre-Cambrian schistose rocks. Auriferous pyrite with a quartz gangue predominates in the neighborhood of Georgetown. These veins may or may not bear silver. At the Silver Plume mine much fine-grained argentiferous galenite is encountered. At Idaho Springs the prevailing ore is an argentiferous galenite-sphalerite which contains but little gold. According to J. E. Spurr, descending meteoric waters have effected from the wall rock a mixture of quartz, calcite, kaolin and sericite. The walls of the fissure appear to have been the source of the gangue minerals, while the gold and silver were contributed to the veins by magma tic waters. The gold-bearing veins appear at the lower level and the silver at the higher altitudes in this deeply incised region. The former PRECIOUS METALS 71 72 ECONOMIC GEOLOGY metal therefore is found most abundantly in what may be only the lower portions of the argentiferous veins. Sierra Region: Goldfield is situated in the southwestern part of Nevada in Esmeralda County. (See Fig. 51.) According to F. L. Ransome the base of the geological series consists of pre- Cambrian metamorphics. These suffered denudation until the close of the Jurassic Age, when the intrusive alaskite and granite were introduced. This was followed in Tertiary time by eruptives ranging from rhyolite to basalt. The dacite is the most produc- tive extrusive, while some rich ores are found in the andesites. The ore bodies are noted for their remarkable richness and irregu- larity. The fissures are usually irregular, small and intersecting fracture-flows passing into brecciated material. Faulting seems to be absent. After the dacite lode solidified unknown stresses developed this intricate fracturing. The ores are free gold and auriferous pyrite associated with silver, copper, antimony, arsenic, bismuth and tellurium minerals. Magmatic waters contributed the gold to the fissures. These ascending solutions bore H 2 S and CC>2 Near the surface the hydrogen sulphide was in part oxidized to H 2 SO4- The downward trend of these acid solutions through the shattered dacites and andesites and their subsequent mingling with ascending solutions caused the precipitation of their metallic contents. The gold would be precipitated by alka- line carbonates, as native gold. The freshly formed pyrite would serve as a reducing agent upon its encased gold. A second stage of fracturing and mineralization seems to have occurred in this field (Figs. 52 and 53). Comstock Lode: The Comstock Lode is situated in the south- western part of Nevada on the eastern flank of. Mt. Davidson in the vicinity of Virginia City, Washoe County. The geology of this region has been a matter of much study on the part of able scientists like Becker, Von Richthofen, Hague and Iddings. Von Richthofen considered the ore body as filling a fissure on the contact between a syenite foot-wall and an eruptive propylite hanging wall (Fig. 54). Clarence King considered that the vein filled a fissure between a syenite and the Tertiary eruptives poured out upon the flank of Mt. Davidson. Arnold Hague and J. P. Iddings, from an exten- sive study of the rock masses, concluded that the Comstock Lode occupies a line of faulting rocks of the Tertiary age and cannot be considered as a contact vein between two different rock masses. PRECIOUS METALS 73 74 ECONOMIC GEOLOGY I cf O O PRECIOUS METALS 75 The vein itself is a true fissure vein about 4 miles long, and several hundred feet wide, branching in the upper portions, and faulted 3000 ft. in the center. The faults gradually die out as the ends of the veins are reached. The lode contains gold and silver and the chief gangue mineral is quartz. According to Von Richthofen, the ores and gangue minerals were brought up by ascending solutions. Fluorine, chlorine and sulphur were the agents of solution. The ore occurs in bonanzas of remarkable richness. One of these bonanzas is said to have furnished $110,000,000 in gold and silver. The ores are marked also by great irregularity. Gold pre- dominates over silver in the ratio of 3 : 2. The mine has yielded nearly $400,000,000 and is still a steady producer (Fig 55). FIG. 54. East-west section through the Comstock lode in Nevada showing the position of two of the ore bodies, and of the Sutro tunnel. The Pacific Coast Region. This belt extends along the Pacific coast from Lower California northward through California, Oregon, Washington and British Columbia. The California field is the most important of all for it furnishes an annual out- put of approximately $20,000,000. The belt is characterized by quartzose ores and auriferous sulphides. In the more northerly portion of the belt silver occurs with the gold and the auriferous sulphides are without free gold. The region is characterized by many placers which have been derived from the weathering of the upper portions of the quartz veins (Fig. 56). The Mother Lode Belt: This belt comprises a large series of quartz veins stretching in a northerly and southerly direction for 76 ECONOMIC GEOLOGY FIG. 55. View of a portion of Mercur, Utah, and the Mercur mine. (By permission of the Macmillan Company, from Ries' Economic Geology.) FIG. 56. Lowest bed of coarse and bouldery gold-bearing gravel at Cherokee mine, Butte County, California. (After W. Lindgren, U. S. Geological Survey.} PRECIOUS METALS 77 113 miles. The mines are situated in Amador, Calaveras, El Dorado, Mariposa and Tuolumne Counties. These counties furnish three-fourths of the milling ores of the State. The aver- age recovery per ton is much less than in other counties where the veins are smaller and richer. The average recovery from all the counties in the Mother Lode district is less than $4 per ton while in Nevada County the amount exceeds $10 in gold and silver per ton of ore mined. One characteristic of the Mother Lode is the permanancy of the ore with increasing depth. In Amador County the mines are now 3500 ft. deep and the ore is as good as that found at the surface. The ores occur in fissure veins in steeply dipping slates and altered volcanics of Carboniferous and Jurassic age. The ores are found at so great a distance from the granitic rocks of the Sierra Nevadas that they are supposed to bear no genetic rela- tion to them. The veins occur both in the slates and at their contact with diabase dikes. The veins show a remarkable ex- tent and uniformity. In the tilted layers of the slate there lay planes of weakness which the mineral-bearing solutions followed. The chief gangue mineral is quartz, and the ore is native gold and auriferous pyrite. Nevada County: The Grass Valley district of Nevada County still continues to be the leading quartz- mining section of the State. None of the other counties, even those of the famous Mother Lode, approach it in its production of gold. The deep mines of the county are yielding per annum about 2,000,000 tons of free milling ores and 500,000 tons of auriferous copper ores that are treated at the smelters. The veins are quartz and occur along the contact between a grano-diorite and diabase prophyry. They also cut the igneous rocks. Two systems of fissuring are known. The gold is either native or associated with metallic sulphides. The width of the vein seldom exceeds 3 ft. The lode ore oc- curs in well-defined bodies or pay shoots. W. Lindgren believes that the ores were leached out of the rock at a considerable depth and deposited by hot solutions while the wall rocks contained the rare metals in a disseminated condition. The Alaska Field. The region may be divided into: (1) The Sitka district; (2) the Juneau and Douglas Island district North- east of Sitka; (3) the Fairbanks district in the central part of Alaska and; (4) the Seward Peninsula in the western part of Alaska, as shown in Fig. 57. 78 ECONOMIC GEOLOGY Gold placers -fGold and silver lodes D Copper +Tln lode* /X Tin placer. Coal e Petroleum FIG. 57. Map showing mineral deposits of Alaska. After Brooks. (By permission of the Macmillan Company, from Ries' Economic Geology.) Cabbro A/bite Diorite Slate traversed by veins of ra versed by veins Ca/cife d .Ouartf FIG. 58. Gold ore in transverse veins in the Ready Bullion mine, Tread- well, Alaska. (After A. C. Spencer, U. S. Geological Survey.) PRECIOUS METALS 79 It is of interest to note that the United States paid $7,200,000 for the Alaskan territory. It was catalogued as the " white elephant" on the hands of the United States government. Yet the total gold brought out of Alaska exceeds $150,000,000 with an output in 1910 of $20,947,600 or nearly three times the amount paid for the territory. The Lodes: Gold quartz lodes occur most abundantly along the coast, especially near Sitka and on Douglas Island. The ore bodies are dikes of diorite traversing black slates. The hang- ing wall of the ore body is a much altered intrusive greenstone and the foot wall is a black slate. (See Fig. 58.) Treadwell Mine FIG. 59. Section through the Alaska Treadwell mine, Douglas Island, near Juneau, Alaska. Two sets of fractures at right angles to each other seem to have been incident to the epirogenic movements of the region. According to Spencer, the mineralization was caused by hot as- cending solutions of magmatic origin. Secondary concentra- tion is not in evidence. The actual depth to which the ores can be worked depends more upon the increased cost of mining at great depths than upon the exhaustion of the ore body. An almost continuous ore body has been developed for more than half a mile. (See Fig. 59.) The Placers: Gold occurs most abundantly in Alaska in placers. The placer deposits of Seward Peninsula alone are about equal in area to those of California and approximately ten times 80 ECONOMIC GEOLOGY as large as those of the Klondike field which lies east of the Inter- national boundary. Mining in Klondike is said to have passed its zenith while the maximum yearly output of Seward Peninsula is still to be reached. The Klondike placers were discovered in 1896 and those on the Seward Peninsula in 1897. According to A. H. Brooks, three conditions are usually opera- tive in the formation of placers: (1) The occurrence of gold in bed rock to which erosion has access; (2) the separation of gold from bed rock by weathering or abrasion; and (3) the transporta- tion, sorting and deposition of the weathered and eroded auriferous material. Origin: In some parts of Europe, in the tropics and in the southern Appalachians some workable placers have been formed solely by the weathering of the bed rock in place. T. A. Rickard recognized placers in Australia that have been concentrated through the agency of the wind, the lighter material having been removed. In the formation of the true placers transportation, sorting, and deposition of material furnished by the weathering of the rocks are important agents. Uplift may revive the forces of erosion and render these agencies repeatedly effective, which results in the reconcentration of the alluvial gold. The classification of placers should be based both upon origin and form. According to their origin there are three types of placers: (1) Residual; (2) sorted placers; and (3) re-sorted placers. The residual placers are those in which there has been no water transportation, the concentration of gold being due solely to rock weathering. The gold of the sorted placers is the result of trans- portation, sorting and deposition of auriferous material by water. Re-sorted placers are those in which the gold has passed through two or more cycles of erosion before its final deposition. Residual placers are practically all of one type. Sorted placers may be subdivided into hillside, creek and gulch, river bar, gravel plain, bench and high bench deposits. Re-sorted placers may be divided into creek and gulch, beach and elevated beach deposits. Intermediate types may be found which belong to either one of the last two groups. Hillside placers occur on hill slopes and do not occupy any well-defined channels. They grade on the one hand into placers of residual origin and on the other into placers of the stream or gulch type. Creek and gulch placers occur both in material that has been assorted once and in that which has passed through several cycles of erosion. PRECIOUS METALS 81 Gold in the Placers: The gold has usually been deposited where the current of a stream has been checked. A broad basin above a steep-walled canyon is more likely to carry gold than the valley below the canyon, provided the bed rock source of the gold is above the basin. Coarse gold is more likely to be found at the head of a filled basin than near its outlet. The same holds true of a stream that debouches on a coastal plain which will deposit the coarse gold it may carry near the head of its delta. A. J. Collier and F. L. Hess give the following classification of the placers in Seward Peninsula: (1) Creek Placers: Gravel deposits in the beds and interme- diate flood plains of small streams. (2) Bench Placers : Gravel deposits in ancient stream channels and flood plains which stand from 50 to several hundred feet above the present streams. (3) Hillside Placers: A group of gravel deposits intermediate between the creek and bench placers. Their bed rock is slightly above the creek bed and the surface topography shows no sign of benching. (4) River-bar Placers: Placers on gravel flats in or adjacent to the beds of large streams. (5) Gravel-plain Placers: Placers found in the gravels of the coastal or other lowland plains. (6) Sea-beach Placers: Placers reconcentrated from the coastal plain gravels by the waves along the seashore. (7) Ancient beach Placers: Deposits found on the coastal plains along a line of elevated beaches. Klondike. This important mining field lies a little to the east of the Alaskan boundary and in the valley of the Yukon. The auriferous gravels of the district occupy about one-tenth the area of those in Seward Peninsula. In fact the number of miles of creeks bearing placer gold in the Klondike has been catalogued as 50 in comparison with 750 on Seward Peninsula. The placers of such creeks as the Eldorado and Bonanza averaged richer than any deposits on Seward Peninsula. It was the exploitation of these almost fabulously rich and relatively shallow placers that the Klondike gold output went up with a bound, and it is their quick exhaustion that has caused so marked a decline in their annual yield. There are extensive deposits of lower grade gravels, but these are not likely to make the annual yield again equal to that of the banner year. (See Fig. 60.) 82 ECONOMIC GEOLOGY FIG. 60. Dredges on No. 104 below, on Bonanza Creek, Yukon Territory, Hydraulic plant in operation on hill in the distance. (After D. D. Cairnes, Canadian Geological Survey.) FIG. 61. The Dome mill, Porcupine district, Ontario, for cyaniding gold. Showing inclined conveyor. PRECIOUS METALS 83 Porcupine. The porcupine district represents a new field. It is situated in the northern part of Ontario. The most important counties thus far exploited are Doloro, Shaw, Tisdale and Whitney. In these four counties practically all of the ground has been staked. The Dome mines represent the pioneer work in this field. Within the first 100 ft. from the grass roots the company is said to have actually blocked out $8,000,000 of gold. The field bids fair to be a large producer. for three reasons. (1) Its own native richness; (2) the great number of scattered free gold discoveries, and (3) the completion of the railroad to Por- cupine during the summer of 1911. The geology of the district is represented by a series of pre-Cambrian metamorphics traversed FIG. 62. Structural arrangement of the Silurian slates and sandstones at Bendigo, Australia, in which the auriferous saddle-reefs are found. (After Thomas and MacAlister's Geology of Ore Deposits.} by a diabase of post-middle Huronian age. The gold is free mil- ling and the most important gangue is quartz. (See Fig. 61.) The Geological Horizon of Gold: Gold may be found in small quantities in nearly all, if not all, geological formations. It is especially abundant in the pre-Cambrian, Ordovician, Cretaceous and Tertiary formations, that is, in general, in the older rocks, but the last two are among the younger formations. The Silurian Devonian and Carboniferous terranes are not known to carry gold in paying quantities in the United States, but in British Columbia gold occurs in the Carboniferous strata. However it is possible that some of the gold-bearing rocks of the Appalachian belt are as late as the Carboniferous, but in the main they are Cambrian and Ordovician. (See Fig. 62.) 84 ECONOMIC GEOLOGY Methods of Placer Mining. In the early history of placer mining, only a few feet of earth next to the bed rock and the up- per surface of the bed rock itself was panned, washed or sluiced, for the richest portion of the entire placer lies near the bed rock. The earliest method of reclaiming the gold was by panning. This was followed by the rocker, the long-torn and sluice-box, the ground sluice, drift mining, the monitor, the hydraulic elevator and the electric dredge. In the hydraulic process, the entire placer is washed by carrying the auriferous gravel into sluices across which riffles are placed for the extraction of the gold. In FIG. 63. American Hill Placer mine, Elk City, Idaho. (After W. Lindgren, U. S. Geological, Survey.} some cases mercury is placed upon the riffles and the free gold unites with the mercury in the formation of an amalgam. (See Fig. 63.) More than one-fourth of the gold mined in California at present is obtained through dredging, mostly from ground previously mined. The electric dredge has solved the problem of mining the gravels below the water level and in rapidly flowing streams (Fig. 64). The chief difficulty of placer mining in the Klondike is the permanently frozen ground, which has led to certain peculiarities in PRECIOUS METALS 85 the method adopted. Every yard of the gravel which is sluiced must first be thawed either by artificial means or by exposing it to the rays of the summer sun, after stripping off the muck that overlies the auriferous gravels. It is impossible to work the frozen FIG. 64. Hydraulic mine at Cherokee; Butte County, California. (After J. S. Diller, U. S. Geological Survey.) ground with pick and spade, or even with explosives to loosen the gravel. Steam thawing is the most efficient method now in use. Iron pipes, 4 to 6 ft. in length, tipped with steel nozzles, are inserted into the gravel and then steam is forced through them at a pres- sure of about 120 Ib. per square inch. These pipes are known as 86 ECONOMIC GEOLOGY points, one point being inserted in each square yard, and driven gradually by a hammer. Each point will thaw from 2 to 5 cu. yd. of gravel per day. The washing of the gravel is usually done by sluices. These are long wooden troughs made in 12-ft. lengths, and about 10 in. broad. The bottom is lined with wooden riffles consisting generally of longitudinal bars, by which the gold and heavy minerals are caught. The common sluice head has a fall of 8 in. in the 12 ft. and has a capacity of 120 cu. ft. per minute. Water is very scarce in some districts and must be used econom- ically. In some instances the water is conducted for long dis- tances in sluice boxes. In case the valley is wide and the pay streak is on the opposite side of the valley from the stream, the water is raised by centrifugal pumps to a height of 30 or 40 ft. and conveyed across the valley by a long flume. In the final wash-up by which the gold is recovered from the sluice boxes the riffles are re- moved and a copious stream of water sent down the sluice which carries away the fine gravel and leaves the gold and the heavy black sand that accompanies it. When dry, the sand is removed by blowers. The placer mining upon creeks and hillsides is somewhat dif- ferent. On a creek a shaft is sunk down to bed rock. Four lat- eral drifts are driven from the shaft along the surface of the bed rock, and opened out in a fan-like manner, to the limits of the claim. The outermost portions are worked first, and the ground is mined toward the shaft, or retreating. During the retreat the rock and the overlying muck are allowed to cave and settle down to the bed rock. Timbering is thus entirely avoided. The frozen grounds require no support, and chambers often 100 ft. square are found covered by an icy roof of muck. Amalgamation. For amalgamation, the ore must be free mill- ing, that is, not require roasting before the gold or silver will unite directly with mercury. The ore is first crushed to a size varying from 1 to 2 in. in diameter. It then passes with water to the stamps where it is reduced to an impalpable pulp. It is then carried over plates covered with silver-plated amalga- mated copper. From these plates it passes directly to concen- trating tables or Frue vanners where the sulphides are separated by their higher specific gravity and shipped direct to the smelter. The tailings comprise that portion that goes into the streams as waste. The plates were formerly made .of copper, but the copper PRECIOUS METALS 87 did not catch all the gold. The silver-plated amalgamated cop- per plate, which has taken its place, saves 15 per cent, more gold than the old copper plates, and the gold caught above the blankets is 16.72 per cent, greater. The old copper plates were in- efficient for three reasons: (1) They tarnish quickly, and the amalgam passes over the tarnished surface. This has to be re- moved by washing the plates with KCN solution. (2) The amal- gam is loosened from the plates by the washing with KCN and mechanically lost. (3) The chemical loss of amalgam by the same agent through solution is great. The total loss of gold FIG. 65. Iron Crown quartz mill, Newsome Creek, Idaho. (After W. Lindgren, U. S. Geological Survey.) is frequently 10 per cent., but by improved methods in washing and general treatment of the ore 95 to 98 per cent, of the total gold content is recovered. (See Fig. 65.) Cyanide Process. The ore is crushed and treated with a solu- tion of KCN, when a double cyanide of gold and potassium is obtained. The double cyanide is often catalogued KAu(CN)2, and from this solution the gold is precipitated by metallic zinc. One-half pound of zinc is required per ton of solution, the total cost then per ton for precipitation is 12 cents; and a profit can be obtained where only 3 grains of gold exist in a ton of solution. 88 ECONOMIC GEOLOGY The zinc may be used in the form of zinc dust, shavings, granu- lated zinc or sheet zinc, but the zinc dust is generally preferred because it exposes a larger percentage of the surface to the action of the solution. The following equation shows the re- action that might take place. 2KAu (CN) 2 +Zn = K 2 Zn(CN) 4 -h2Au. The process is applicable to certain free milling ores, to refrac- tory ores, but was designed especially for the treatment of tail- ings which were allowed to flow to waste for many years. Many western plants now have their cyanide plant in connection with their amalgamation plant. Chlorination Process. This is not applicable to free milling ores carrying nuggets, but to sulphides carrying large quantities of free gold. The ore is crushed, roasted, weighed and then charged into barrels with 18 tons capacity, 6| ft. in diameter and 15 ft. long. Nascent chlorine is the solvent. The solution from the barrels passes to a filter tank for the removal of the sand. From the filter tank it passes to a settling tank for the removal of the fine particles held in suspension; from the settling tank it passes to the precipitation tank, in which is placed zinc ribbons, scrap zinc, or zinc dust. Hydrogen sulphide is sometimes passed into these tanks, and the resulting gold is reasonably pure, but charcoal is the most efficient reducing agent, and the gold ob- tained is 0.995 fine, Reduction by Sodium Thiosulphate. A solution of Na 2 S 2 3 for the extraction of gold and silver has far greater solvent power than potassium cyanide and is non-toxic in its physiological effect. It can be prepared in large quantities at low price according to the following formula: 2 parts. Na 2 S 2 3 ; 2 parts. CH 3 C0 2 Na; 3/4 part. FeCl 3 ; add 10 times the volume of H 2 0. This will dissolve from 15 to 20 times as much gold in 10 hours as a 2 per cent, solution of potassium cyanide, 2 per cent, being the maximum strength allowable in cyanide solutions. The gold can be recovered from the solution by zinc shavings, zinc dust, zinc ribbons, and by electrolysis. The cost of treatment by this process is estimated at $2.75 per ton. Reduction by Electrolysis. Gold is readily separated by elec- trolysis from its various solutions, and in this method of treat- PRECIOUS METALS 89 ment, silver-plated amalgamated copper plates are not as effective as the older type. Copper, iron and lead plates are used in the order of their efficiency. Copper is more effective than iron and iron is more effective than lead. The silver-plated amalgamated copper plates are profitable only when a current of low density is employed. Uses of Gold. Gold is used in the various arts and industries, for coinage; for jewlery, spectacles, and pen making; in den- tistry, and in chemical and photographic work. The beaten gold leaf is used for gilded letters of signs, for lettering on book bind- ings, for book edges, for mirror frames and picture frames, for gilding metals. Gold dust is used in the moulding of furniture or room decoration. The Japanese use gold largely in the manu- facture of lacquers. Gold is drawn into wire and used for gold lace, and other decorations. It may be of interest to know the relative proportion that enters into these different fields: For coinage, 44 per cent.; for jewlery, 24 per cent.; for exportation, 10 per cent.; watch cases, 10 per cent.; gold leaf, 2 1/2 per cent.; watch chains, 1 3/4 per cent.; pens, dentistry and mechanical work, 11/4 per cent.; for gold plate, 3/4 per cent. All these uses may be catalogued as its use in American arts and industries. This will give for indust- ries 40 per cent., coinage 44 per cent.; exportation 10 per cent. These are based directly upon the coining value of the metal, or $20.67 per Troy ounce. SILVER: ITS PROPERTIES, SOURCE AND USES Properties. Silver, symbol Ag, is known as the white metal. It is pure white and susceptible of very high polish. When it is in the form of a powder, it has a gray or earthy appearance. It is malleable, ductile, and sectile, so that it can be rolled or ham- mered into thin sheets and readily drawn out into extremely fine wire. It is the best conductor of electricity known and its con- ductivity is increased by the process of annealing. It is harder than gold, and softer than copper. It is, therefore; alloyed with copper in coinage. For United States coinage the standard is nine parts of silver to one part of copper. Its specific gravity is 10.50 when cast, and 10.57 when struck by the die in coinage. Its melting point is 955 C., and its atomic weight is 107.88. Ores of the Metal. Silver occurs native containing small quantities of gold, copper, iron, cobalt and antimony. It occurs 90 ECONOMIC GEOLOGY as threads or plates through the reduction of other ores of silver, or it may occur deposited as a film over other minerals or rocks, as copper or carboniferous shale. The other ores of silver are as follows : Argentite, Ag2S, containing 87.1 per cent, silver, the only black and sectile sulphide of silver, the most unstable of all the sul- phides of the commoner metals; pyrargyrite, 3Ag2S,Sb2S3, con- taining 59.9 per cent, silver; stephanite, 5Ag2S,Sb2Ss, containing 68.5 per cent, silver; polybasite, 9Ag2S,Sb2S3, containing 75.6 per cent, silver; proustite, 3Ag2S,As2Ss, containing 65.4 per cent, silver. Silver occurs also in association with copper minerals ; as tetra- hedrite, 4Cu2S,Sb2S3; although no silver is present in the for- mula, samples of this ore have given 500 Ib. of silver to the ton; tennantite, 4Cu2S,As2S3, sometimes bears silver. Silver occurs abundantly in argentiferous galenite. All gale- nite is more or less argentiferous, but the finely crystalline variety contains more silver than the coarse mineral. Silver occurs with tellurium in hessite, Ag 2 Te, containing 63.3 per cent, of silver; in petzite, displacing gold, for petzite is a telluride of gold (Ag,Au)r Te. It occurs in combination with selenium in naumanite, PbSe,- 13Ag 2 Se. and also as the selenide alone, Ag2Se. It occurs with bismuth, copper and mercury, but perhaps more important as the amalgam. This implies varying combinations of silver and mer- cury. Instead of the direct union in the line of atomic weights, seems to unite with mercury in almost all proportions. The amalgam contains 27.5 per cent, to 95.8 per cent, of silver. Silver occurs again in combination with the halogens. The most important haloids of silver are: Cerargyrite, AgCl, with 75.3 per cent, of silver; embolite, 3AgCl,AgBr, containing 66.9 per cent, silver; bromyrite, AgBr, containing 57.4 per cent, of silver; iodyrite, Agl, containing 45.2 per cent, silver. All of these haloid minerals are soft and sectile. Silver is very widely distributed in nature. It is produced by practically all countries of the world, although many of them pro- duce only a small quanity of the metal. It has been observed as a natural constituent of igneous rocks. It has been detected in common salt, in sea weed, in sea water, and in corals. In most cases native silver is of secondary origin, the metal being derived from the reduction of the sulphides and antimonides of silver. Organic matter is a common reducing agent effecting the precipi- PRECIOUS METALS 91 tation of silver in a metallic state. Pyrite, chalcopyrite, and many other sulphides, reduce silver solutions readily to the metallic state. According to Dr. F. W. Clarke, the metal will be precipitated by any reaction in which nascent hydrogen is brought in contact with a silver solution. The nature of silver solutions in metalliferous veins is not positively known. Silver sulphate is readily formed by the oxidation of the sulphide, and that will be transformed into the chloride by percolating chlorine-bearing waters. The antimonides, arsenides, and selen- ides of silver are rarer minerals, and are of only small impor- tance in the production of the metal. These by subsequent enrichment might become of commercial importance. Character of Ore Bodies. At Butte, Montana, the ore occurs as native silver, with galenite in veins of quartz-bearing manganese. These are true fissure veins cutting irruptive granite. At Granite Mountain, 20 miles from Butte, the ore is ruby silver associated with gold in a true fissure vein cutting a gray granite. At Neihart, the ore occurs in veins in gneiss and other igneous rocks, mostly as replacement deposits which have been subsequently fractured and secondarily enriched. Argentiferous galenite is common in Montana as contact deposits between porphyritic igneous rocks and Carboniferous limestone. In the production of silver, Colorado ranks high, the chief sil- ver-producing region of the state being Leadville. This district is situated in the Mosquito Range near the headwaters of the Arkansas river. It began its history in 1860 as a gold camp, but upon exhaustion of the gold resources the camp lost -its significance as such. It then became a silver-producing camp which position it lost nearly a decade ago when Leadville became a lead and zinc camp. Eight or ten different metals are produced within the camp at the present time. The Geology of Leadville. The base of the mountain consists of a series of Archean granites, gneisses, schists and amphibolites. These are overlain by a series of Cambrian quartzities and shales which in turn are covered by Silurian limestones and quartzites. Above these there appear limestones, shales and grits of Carbon- iferous age. Associated with this vast series of sedimentaries there appears also many late Mesozoic and Tertiary irruptives (Fig. 66.) The uplift of the Mosquito Range, of which the Leadville dis- trict forms the western slope, resulted in a series of anticlinal and 92 ECONOMIC GEOLOGY synclinal folds with many faults that have the same general direction as the axes of the fold. They do not coincide exactly with them but pass into folds at their extremities. The folds are nearly vertical on their western slope and less inclined on the east. It is along the higher and steeper slope that the greatest amount of fracturing has taken place. (Fig. 67.) Faults: The displacement in general has been toward the east. The maximum upthrow in any one fault is recorded in the FIG. 66. View from the top of Carbonate Hill, Leadville, Colorado, looking toward Iron Hill. The valley in center ground marks position of the Iron fault. Shaft house is that of the Tucson shaft, and ridge in distance fault scarp of Mosquito Range. (By permission of the Macmillan Company, from Ries 1 Economic Geology.) Mosquito fault, measuring about 5000 ft. The mineral veins themselves have been folded and faulted with the enclosing sedimentary and eruptive rocks. This fact alone would prove that the mineral deposition took place prior to the dynamic movements that formed the Mosquito Range itself. (See Fig. 68.) Mode of Occurrence: The typical form of the Leadville de- posits seem to be a contact sheet whose upper surface is the Lead- PRECIOUS METALS 93 FIG. 67. View from south end of Carbonate Hill, Leadville, Colorado, overlooking California Gulch in foreground and town of Leadville in the valley, Sawatch Range in distance. (By permission of the Macmillan Com- pany, from Ries' Economic Geology.) Gray Porphyry White Limestone Blue Limestone l'-Vv- v -'J Oraand Vein Material Lower Quartzi FIG. 68. East-west section through the McKeon shaft, Leadville, Colorado, showing the faulted ore bodies along the contacts. (After Blow.) 94 ECONOMIC GEOLOGY ville porphyry with a regular and well-defined upper limit to the ore body. The ore occurs in the blue limestone of Carboniferous age. The lower surface of the ore body is irregular and often ill defined. It sometimes occupies the entire thickness of the lime- stone formation. The ore sometimes occurs near the contact of the gray porphyries with the blue limestone, sometimes in both the calcareous and siliceous beds, sometimes in the porphyries themselves either near contact surfaces or along joint and fault planes. As a rule the argentiferous lead ores occur in the blue magnesian limestone while the auriferous pyrites and the copper ores are more frequently found in the quart zites and porphyries. Leadville Minerals : Native gold in flakes or leaflets; the silver minerals are argentiferous galenite, cerargyrite, embolite and native silver; the lead minerals are galenite, cerussite, anglesite, massicot minium, and wulfenite; the accessory minerals are sphalerite, calamine, stibnite realgar, bismuthinite, malachite, chrysocolla, wulfenite, a vanadate of lead and zinc, pyrite, and hydrous and anhydrous oxides of iron. The gangue minerals are quartz, pyrite, siderite, barite, gypsum and hydrous silicates of aluminum. Origion of the Ores: According to S. F. Emmons, the ores were derived from a descending aqueous solution. The ores de- rived their metallic content from the neighboring eruptive rocks. Mr. Emmons further contends that the metals must have been formed beneath a thickness of at least 10,000 ft. of superincum- bent rocks and an unknown amount of sea water; that if they had been deposited from hot ascending solutions as the result of the relief of pressure it would naturally be expected that the bulk of the deposit would have been found in the upper part of this mass of rocks where the pressure was the least, rather than at the base; that at the time of deposition the sedimentary beds were horizontal and relatively undisturbed; that if the deposits had been made from ascending currents the process of deposition would have acted from the bottom upward instead of from the upper surface downward as is shown in the case of the blue limestone which carries the bulk of the ores; that in the region of the greatest ore development there is a noticable absence of channels extending downward through which ascending solu- tions might have come; that the vast majority of irruptive bodies are in the form of horizontal sheets parallel with the stratifica- tion; and that the few approximately vertical bodies afford no PRECIOUS METALS 95 evidence that their walls form part of a channel through which the ore currents came up from below. Since the work of Mr. Emmons was done at Leadville, other eminent geologists have been in the field with better opportunity to study the origin of the ore deposits. The finding of fissure ores in the Cambrian quartzite leads them to the conclusion that the ores may have been brought in by solutions ascending directly from the intrusives. In 1859, placer gold was found in California Gulch, worked out in 1863 and deserted. The owners were much troubled with heavy rock, the composition of which was unknown to the miners, but later discovered to be cerussite, the carbonate of lead, rich in its silver content. In 1875 these deposits were reopened and worked for their silver content. The silver occurs as argentite, native silver, cerargyrite and embolite at the surface and in galenite at greater depths. Masses of auriferous galenite have been found 100 ft. in thickness. At Aspen, oxidized lead and silver ores occur in highly folded and faulted Carboniferous limestone. According to W. H. Weed, the accumulation of ore at the intersection of fault planes is the result of a secondary enrichment rather than of primary concen- tration. At Creede, the silver ores occur in fissure veins pene- trating igneous rocks. At Red Mountain the silver ores occur in true fissure veins traversing Jura-Trias terranes. Utah. Third in order of importance as a silver producer is Utah. In both Cottonwood canons, oxidized lead-silver ores occur near the surface in bedded veins in Carboniferous lime- stone. In Beaver County oxidized lead and silver ores occur in contact fissures in the Horn Silver mine; in " chamber deposits" in Carboniferous limestone at the Cave mine; in fissures at the Carbonate mine; in Park City, as silver and lead oies in Carboniferous limestone, sandstone; and shales. The ores bearing lead and copper are oxidized, the others appear mostly as bedded deposits in the limestone, often with siliceous walls separating one deposit from another. These are frequently associated with porphyritic igneous rocks. In Idaho at Coeur d' Alene the ore galenite is found with siderite gangue in highly folded quartzites and mica schist. Nevada The Comstock lode, Nevada, represents the largest auriferous silver- bearing deposit ever discovered. It lies in a 96 ECONOMIC GEOLOGY great fissure vein several hundred feet in width and four miles long with branching ends. The fissure follows a fault line, and at the center where the displacement is the greatest the width is 300 ft. The mine reaches a depth of nearly one mile. All the veins were originally opened for silver, for they contain silver at the surface. As the veins were worked to lower depths copper ores appeared. The silver soon became refractory and the per- centage too small for profitable extraction. The ore occurs in true fissure veins bearing native silver and the silver sulphides, associated with zinc and manganese. The gangue consists of rhodonite, rhodochrosite, and quartz. Probably there were no open fissures before the deposit occurred for the ore is deposited along fractures or cracks impregnating and partially replacing the wall rock, so that there is a gradual joining of the vein and the wall rock with no sharp line of demarcation between them. The surface ore is black due to such manganese compounds as pyrolusite, MnO 2 , resulting from the breaking down of manganese minerals. At the lower depths the mineral remains pink, the natural color of rhodonite and rhodochrosite. A conical peak 2000 ft. above the valley is cut by a pure white vein of quartz containing ruby silver in little red specks with traces of pyrite, galenite and sphalerite. This locality is remarkable for the depth of the oxidation of the ore reaching 1400 ft. on the sides and 1000 ft. in the center of the mound. This was a very important field in the production of silver before the decline in the price of the metal. The country rock is basic, diabase and diorite. In the Eureka district, oxidized lead and silver ores, auriferous to a considerable degree, occur in a brecciated Cambrian lime- stone and shale. New Mexico. In the Lake Valley district there occur galenite, cerussite and embolite in Paleozoic limestone. At Silver City in the Breman mine, argentite and cerargyrite occur at the contact of shale and limestone impregnating both. At Lone Mountain cerargyrite, bromyrite and embolite occur in a gangue of quartz. In Wardner County and Bitter Root Mountain, Idaho, galenite occurs in quartzite and mica schist in large chutes impregnating the fissured hanging walls. This is one of the most productive regions of the world. In the Thames district the gold-silver lodes consist mainly of quartz, in which both metals are present in threads, foils and PRECIOUS METALS 97 grains. The district is cut through by two Pliocene faults, and the ores are associated with Tertiary eruptives. The ores are of hydatogenetic origin. In the Freiberg district the lodes occur in metamorphic acidic intrusives. The ores are native silver, argentite and proustite. The silver ores of Japan belong to the acidic type associated with Tertiary eruptives. Ontario, Canada. In the Province of Ontario there are three important silver districts. In the order of their discovery they are Cobalt, South Lorrain and Gowganda. The rocks are essen- tially alike in the three fields. The sedimentaries consist of conglomerates, slates and schists of pre-Canbrian age. The intrusives are diabases, gabbros and granites. The silver lodes traverse the irruptives and often the veins penetrate the sedimen- taries. The veins vary in width from a fraction of an inch to two feet or more. The ores are of hydrothermal origin. The silver minerals are native silver, argentite, pyrargyrite, and breithaup- tite, associated with smaltite, niccolite, pyrite, chalcopyrite, erythrite and annabergite. The principal gangue mineral is calcite. Quartz is sometimes present in subordinate quantity. There seems to have been a distinct order of deposition of miner- als in the Cobalt district. According to Prof. Wm. Campell of Columbia University, smaltite was first introduced into fissures in the diabase, etc. This introduction was followed by niccolite and small quantities of other ores. Then there came a period of disturbance in which the vein materials were brecciated. The infiltration of calcite and the deposition of native silver in plates and threads and grains followed later. Finally bis- muth ores were introduced into a few veins. The author has worked out the same order for several mines in the Gowganda district. Geographical Distribution of the Ore. Silver occurs in all countries. It is most abundant in Mexico, United States, Canada, Australia and Germany, arranged in order of importance. In the United States the distribution of silver is in five distinct belts: (1) The Appalachian; (2) the Lake Superior district; (3) the Cordilleran; (4) the Pacific Coast belt; and (5) Alaska. However, 90 per cent, of all the silver produced in the United States comes from Montana, Colorado, Idaho, Utah and Nevada. Therefore, the area of greatest importance is the Cordilleran section. 7 98 ECONOMIC GEOLOGY Geological Horizon. Silver ores occur in the rocks of all ages. It is not restricted, therefore, to any one horizon. However, it is especially abundant in the pre-Cambrian, Cambrian, and Car- boniferous rocks. It occurs in Colorado in Jura-Trias rocks. The character of the deposits may be classified as follows: (1) Most of the silver veins are true fissure veins; (2) the silver occurs as bedded deposits in limestone; and (3) as contact deposits between igneous and sedimentary rocks. Extraction of the Metal. There are five well-known processes used in the extraction of the white metal from its various ores; (1) Amalgamation; (2) smelting; (3) lixiviation; (4) cyanida- tion process; and (5) the electrolytic process. The Amalgamation Process. This is applicable to native silver, embolite, cerargyrite, bromyrite, iodyrite. These crushed to a powder, and ground directly with mercury without any special preparation readily form a silver amalgam. The haeloids are decomposed with a formation of silver amalgam and haloid compounds of mercury. In the case of the sulphide, argentite, metallic silver is set free and a sulphide of mercury is formed, but the process is far slower than in the case of native silver or the halogens. In the case of the arsenides and antimonides, the process is so slow that it seems advisable to roast the ore with common salt prior to amalgamation. Some form of the amalgamation process has been known for a long time. The arrastra was introduced into America in 1557. It was used for a long period of time in Mexico. The pro- cess is simple. The ore is finely crushed, treated with water, placed in iron pans where by revolving machinery it is ground to an- impalpable powder, and mixed with mercury. The revolving machinery is kept in motion four to six hours, when the mixture is complete. The amalgam is then collected and mercury dis- tilled at a temperature of 350, and the silver fashioned into bullion. The "cazo" or " caldron" process is a simple method for treat- ing surface ores containing silver, either native or in the form of chlorides or bromides. The ore is first crushed, and then finely ground in the arrastras and charged into amalgamating vessels with salt and mercury. The small receptacles originally em- ployed consisted entirely of copper. The fondon took its place. This is a larger receptacle with wooden sides and copper bottom. In the fondon, two copper blocks are fastened to arms attached PRECIOUS METALS 99 to the vertical revolving shaft and dragged around on the copper bottom by motive power. It was the tendency of the amalgam in this process to adhere to the copper plates' which first gave the idea of the introduction of silver plated amalgamated copper plates in the gold milling industry. Perhaps the pan amalgamation process is the direct outcome of the cazo and fondon processes with the improved machinery as introduced by Frazer and Chalmers of Chicago. The process is continuous, and the ore is roasted before the effective amalgama- tion takes place, that is, amalgamation takes place far more readily and completely in the presence of roasted ore. Smelting Process. This refers to that method of treatment carried out largely in North America and in Germany, where the object is to obtain a solution of silver in lead. The smelting is carried on in the blast furnace of moderate size with a mixture of ore, fuel, and fluxing material. The smelting of silver ore with lead is most satisfactory under the following conditions: (1) Where there is an abundance of bituminous coal or natural gas to serve as a supply of fuel; (2) where limestone, low in magne- sium, is available ; and (3) where large quantities of silver-bearing galenite abound. The process is not applicable to cupriferous ores and ores free from lead or poor in silver. The process admits of a continuous discharge of lead through a siphon into some bowl or vat, while the slag is run continuously into iron kettles mounted on tracks so that the cone-shaped slags may be easily transported to the waste yards. Later the slags are run into troughs in which there flows a strong current of water. As the slag strikes the water it is immediately granulated. It is used for certain indus- tries, as in the manufacture of cement. The lead can be ladled from the bowl, or tapped from it, or allowed to run continuously. The Pattinson process depends upon the fact that the alloy of silver and lead can be fused easily and the silver crystallized from the lead. Silver does not form an alloy with lead to any considerable extent as the solution cools. Silver dissolves rapidly in lead at the temperature of fusion of the white metal. In the Pattinson process, when the metal is molten and allowed to cool the lead is ladled out of a large iron pot into kettles upon one side growing richer and richer in silver, and upon the other side poorer and poorer in silver. The material first to crystalize would be pure lead. The material last to solidify is the silver, and between the two, varying amounts of silver and lead are 100 ECONOMIC GEOLOGY present. This material is all remelted and recrystallized. This process is continued until only about 0.002 per cent, of silver remains in the lead. The Rosan process is largely like the Pattinson only the liquid alloy is drawn off leaving the solidified portion. The process is less delicate or efficient than the Pattinson, giving 0.003 per cent, of silver waste in the lead. The Parke's process depends upon the formation of compounds of zinc and silver when these metals are melted together. The alloy of zinc and silver is formed containing about 12 per cent, of silver. The zinc is added in small amounts at different times. In the first solidification practically all the gold and copper so- lidify with the zinc. Upon the addition of more zinc the silver unites directly with the zinc in the formation of the alloy AgZni2. The efficiency of this method is proven by the amount. of silver remaining in the lead which is about 0.005 per cent. The final step in the treatment of the alloys thus obtained is cupel- lation, in which process the lead is volatilized, and the gold or silver remains in the cupel. Lixiviation Process. The silver is dissolved, and after filtering, is precipitated from the clear liquid into metallic form by some reagent. The process is as follows: In the treatment of argentiferous copper matter the Ziervogel process has been largely utilized, in which copper, iron and silver are present and converted into their sulphates, then into their oxides. The iron is the first to oxidize, copper second, silver third. Just as the silver begins to oxidize it is treated with water, and the silver is precipitated by scrap copper. The copper still in solution is recovered by the more electro-positive metal, scrap iron. The process is complete when the solution yields with ammonium hydroxide only a faint blue coloration, and when no dense white curdy precipitate is obtained upon the addition of common salt. In the treatment of the ores containing copper and iron, so- dium chloride was first used for the conversion of the silver into silver chloride. This process is known as the Augustine proc- ess. This, because of its general inefficiency, was supplanted by the sodium thiosulphate, otherwise known as the Patera process. This process is more efficacious, because of its greater solvent power, especially upon the arsenates, and antimonates of silver which are practically insoluble in the presence of the sodium PRECIOUS METALS 101 chloride. The sodium thiosulphate meihp$ Ji^s, given w,ayj very largely to the calcium thiosulphate method', 'winch is pra'cbically identical in apparatus and method of trsafmen^/^-V^y/ith (Cal- cium in place of sodium as a solvent. The latter "process is known as the Kiss process from its inventor. But all these in which calcium thiosulphate enters as a solvent are now replaced by the cyanide process. Cyanide Process. This method of treatment is based upon the fact that when silver sulphides, arsenides and antimonides, are treated with a solution of potassium cyanide or sodium cyanide, a double cyanide of silver and potassium, or silver and sodium is formed. The solution is far more concentrated than in the H FIG. 69. Nevada Hills mill, Fairview, Nevada, for cyaniding silver. case of the treatment of gold-bearing ores with potassium cyanide, because the silver minerals are less soluble in a cyanide solution than the gold ores. The solution is filtered to remove all sedi- ment, and allowed to settle to a perfectly transparent liquor. It is then drawn off into precipitating tanks, and the metal reduced to the elemental state by granulated zinc, zinc shavings, zinc dust, as in the treatment of gold. (See Fig. 69.) Electrolytic Process. Silver is separated from argentiferous copper ores electrolytically by sulphuric acid and copper sulphate. The copper and iron are dissolved at the anode, while gold, silver and platinum are precipitated at the cathode. In the modifica- tion of this process, known as the Moebius process, large amounts 102 ECONOMIC GEOLOGY of silver are now ;re;ne,d in the United States. The bath con- sists of a solution of nitric acid, silver nitrate and copper citrate. The. silver anoV copper are both dissolved at the anode. The copper remains in solution, the silver is precipitated at the cathode, the gold remains undissolved. Uses of Silver. Silver was used by the ancients practically as early as gold. Silver is used very extensively in the arts and sci- ences, as in jewelry, tableware, coinage, silver bullion as a me- dium of exchange, photography, mirrors, for optical apparatus, in plating and in very many alloys. Copper lowers the melting- point of silver and makes the metal harder, but does not decrease the malleability, or materially impair the color. This is by far the most important of the silver alloys, and in coinage nine parts of silver to one part of copper produces a coin that resists wear through friction. Silver mixes with lead in all proportions when molten but segregates upon cooling. Therefore, silver- lead alloys lose their homogeneity. Silver alloys readily with cadmium, producing a soft, white, malleable, and ductile alloy. Silver alloys readily with mercury and produces silver amal- gams. Silver unites with tin, zinc, and bismuth in the forma- tion of important alloys, generally ductile and malleable. With platinum, silver forms a hard alloy, that is used very extensively in dentistry. Silver unites with palladium and with rhodium; in fact, silver unites with all useful metals save iron and cobalt. PLATINUM: ITS PROPERTIES, OCCURRENCE AND USES Properties. Platinum, symbol Pt, is one of the rare metals. It has a specific gravity of 21. 46, silver white with a grayish tinge, ductile, malleable, sectile, with a luster less brilliant than that of silver. Its melting point is 1780 C. Its atomic weight is 195. In the finely divided state it is black. The presence of minute impurities render platinum hard and brittle. In the electric crucible Moissan volatilized it, but its boiling point is unknown. It is unaffected by heat in both dry and moist air. It is insoluble in all single acids, but is readily soluble in aqua regia. Ores of Platinum. Native platinum; sperrylite, PtAs2, which is the most important ore of the metal; platiniridium, an alloy of platinum and iridium; osmiridium, an alloy of osmium and iridium; native osmium and irridium contain small quantities PRECIOUS METALS 103 of platinum; it occurs in covellite, which is a sulphide of copper, CuS; and in laurite, which is the sulphide of ruthenium, RuS 2 . Geographical Distribution. Platinum occurs in small quan- tities in the gold-bearing sands of California and Oregon. It occurs in limited quantities in Arizona, Colorado, Georgia, Idaho, and Montana. It is reported from Mexico, Santa Domingo, Brazil, and in placer deposits in Colombia. The world's princi- pal supply of platinum comes from the Siberian side of the Ural Mountains. In Brazil at the Congo Soco mines it occurs in the decomposed schistose rocks associated with gold. It is also found in small quantities in the placer gravels of Alaska. The platinum production in the United States has come from the placer mines in Butte, Humboldt, Siskiou, Trinity, Calaveras, Sacramento, and Del Norte Counties, California. Three-fourths of the amount has been obtained from Butte County alone. The most noteworthy event of the platinum industry in recent years is the discovery of the comparatively new mineral, sperry- lite, the arsenide of platinum, PtAs2, which occurs in association with nickel-bearing ores of Sudbury, Ontario, and in the Rambler mines, Wyoming. Importance is also attached to the discovery of the metal in association with several copper minerals, as covellite, the sulphide of copper, CuS. This result may lead to the discovery of plat- inum of commercial importance in other members of the copper group. With the present high price of platinum, more than twice the value of gold, we may expect a persistent search for platinum ores : (1) Among the placer gravels of the serpentine rocks, especially those resulting from the metamorphism of large masses of per- idotite; (2) in the members of the copper group, and (3) in the nickeliferous peridotites. Geological Horizon. Platinum is associated with the pre- Cambrian, Cambrian and Ordovician terranes. The origin of the ore bodies is largely through the decomposition of the superincumbent rocks, which allows platinum to be carried into the valleys where it sinks to the lower portion of the gravel and into the cracks and the crevices of the upper portion of the underlying rock. It is, therefore, intimately associated with gold in placer deposits, and may be reclaimed by the same method as gold. The common parent rock is the ultro-basic 104 ECONOMIC GEOLOGY ferro-magnesian rock known as peridotite. Many platinum placers have been traced back directly to the decomposition of such a rock. However, all peridotite does not bear platinum. Methods of Extraction. (1) By placer mining. Platinum is obtained by panning the lower gravels of placers or by hydraulic- ing and dredging the entire gravels of the larger placers for the gold. (2) The wet method. The ores of platinum are treated with hot aqua regia which dissolves all of the platinum and part of the iridium. After evaporating the excess acid the platinum is precipitated by ammonium chloride as an ammonium chloro- platinate (NH^PtCle. Ammonium chloride and chlorine are volatile upon ignition and the platinum is left behind as a spongy metal. (3) Recovery from waste solutions. The waste solution is boiled to expel any excess of nitric acid; it is then filtered to remove any platinum sponge that may have been left. Barium chloride is added to precipitate any sulphuric acid that may be present. The platinum salts now in solution are reduced to the elemental state by concentrated hydrochloric acid and zinc. Electrolysis may be substituted in place of zinc. Uses of Platinum. According to Pliny, platinum was known to the ancients, for it occurred in many alluvial beds associated with gold, and remained with the yellow metal after the washing of the gold. In 1735 it was recognized in Columbia, S. A. In 1740 it was exported from Jamaica to Europe. Near the middle of the eighteenth century, the Spanish government forbade its further extraction and ordered all the platinum thrown into the seas to prevent its use as an adulterant of gold. In 1819 platinum was discovered in serpentine rocks on the Siberian side of the Urals. Until 1823 the world's supply of platinum came solely from South America. Since 1824 Russia has been practically the only producer. Platinum was used by the ancients as an adul- terant of gold. It is used in many forms of chemical apparatus in which a high melting-point is necessary. It is the only avail- able metal which will withstand the continuous heat of baking, and for this reason, used extensively as pins to hold artificial teeth together. It is also used for filling teeth; platinized paper for photographic purposes; jewelry, and in coinage when alloyed with 2 per cent, of iridium, especially in Russia, where it was first introduced in 1824, on account of its malleability, its unadulter- ability, and its intrinsic value. Platinum is also used in the manufacture of contact points of telegraph keys; for stills or PRECIOUS METALS 105 retorts in the manufacture of crude sulphuric acid, in which case it is alloyed with 2 per cent, of iridium. On account of its infus- ibility and the fact that its coefficient of expansion is nearly the same as glass, platinum is used to connect outside copper wires with the carbon filament in incandescent lamps. The thickness of the filament varies from 0.01 to 0.012 in. Platinum is used in the manufacture of platinum spoons, dishes, crucibles, combs, foil and wire. Liebig, in his chemistry letters, states that with- out platinum it would be impossible in many cases to make an analysis of many silicates, and thus the composition of most minerals would remain unknown ; without platinum the composi- tion of our organic compounds would likewise remain unknown. Platinum is used extensively by balance makers for weights ; is used in surgical and scientific instruments of precision; for the points of stylographic pens; for the balance wheels and hair springs of non-magnetic watches; for obtaining a silver color on porcelain; for platinum plating; for oxidizing silver; for the fuses of electrolytically exploded cartridges; for use with high-grade explosives like dynamite. It is used with iridium as an electrode for the electrolysis of alkaline chlorides, where an alloy of 15 per cent, of iridium can be rolled to a thickness of 0.007 of a milli- meter and yet have sufficient resistivity to be used on an indus- trial scale. Platinum is used also in the manufacture of the platinum salts of commerce. It is also used in the making of platinized asbestos. The United States dental and electrical uses of platinum equal 50 per cent, of the world's output. The Alloys of Platinum. Platinum alloys readily with gold and silver, and these alloys have been discussed in the treatment of silver. Platinum alloys readily with copper in all proportions at high temperatures. The alloys are extremely hard and less liable to tarnish than the ordinary brasses and bronzes. With 81.25 per cent, copper the alloy is a golden yellow, closely resem- bling 18 carat gold. It is both malleable and ductile and sus- ceptible of a high polish. Both platinum and copper alloy read- ily with about 4 per cent, of zinc. The alloys are extensively used in jewelry; mathematical instruments, and chronometer wheels. Platinum bronze is an alloy of platinum, nickel, and tin. With nickel, platinum forms a white, malleable, magnetic alloy. This is capable of a high polish and is permanent in moist and dry air. The presence of 3 per c.ent. platinum prevents steel from rusting, and is therefore of great industrial importance in the manufac- 106 ECONOMIC GEOLOGY ture of cutlery and instruments of precision. The alloys of plat- inum with antimony, arsenic, bismuth, cadmium and tin are generally brittle. With iridium the alloys are hard and elastic, permanent in moist and dry air, and susceptible of a high polish. This is especially true when less than 25 per cent, of iridium is present. Above that point it becomes difficult to draw the alloy into wire or to hammer it into sheets. An alloy of platinum with 10 per cent, of iridium resists the corrosive action of metals far better than pure platinum. It has been stated that up to the beginning of the present century 25 per cent, of all platinum used in the United States was iridium. We use alloys of platinum and iridium under the name of platinum. Platinum does not amal- gamate readily with mercury. Here it is unlike gold and silver. Palladium. Palladium, symbol Pd, has the color, luster and appearance of platinum, but takes a finer polish. It is malleable and ductile, and is the most easily fused of any metals of the platinum group. It is usually found in the metallic state, some- times with gold and silver, and also associated with platinum in the ores of the latter metal. Palladium can scarcely be distin- guished from platinum by its color. It is chiefly noted for its great tendency to absorb hydrogen. It is with difficulty soluble in nitric acid. It dissolves in boiling sulphuric acid, being more easily attacked in the finely divided state. It melts at 1586 C., and at a higher temperature yields a green vapor. It forms alloys with gold, silver, copper, mercury, nickel, antimony, arsenic and the platinum metals. Palladium is used chiefly for the grad- uated surfaces of physical instruments and for coating silver articles, especially mirrors, because it retains a polish and does not tarnish. Its atomic weight is 106.7. Osmium. Osmium, symbol Os, has a specific gravity of 22.47. It is a bluish metal, harder than glass and infusible in the oxyhydro- gen flame. It crystallizes in cubes or rhombohedrons and is the heaviest of all known solids. It burns in the air to the tetroxide, which has a peculiar penetrating odor and is injurious to the eye. It alloys with metals, notably iridium. It is found in the Ural Mountains, Brazil, California, Borneo and Australia. It is used in pointing gold pens and as bearings for compass needles. Its melting-point is 2500 C. Its atomic weight is 190.9. Iridium. Iridium has a specific gravity of 22.42 and a fusion- point of 1950 C. It is a hard, white, lustrous metal resembling steel. It is malleable at red heat. It melts only in the oxhy- PRECIOUS METALS 107 drogen flame. It is brittle and very hard. It is a powerful catalytic agent when finely divided. It is obtained by igniting ammonium chloriridate, which is obtained from osmiridium or the platinum residues by a complicated process. It is found in the Ural Mountains, Brazil, California, Borneo and Australia. Its atomic weight is 193.1. Rhodium. Rhodium, symbol Rh, is a white, malleable, ductile metal. Its specific gravity is 12.1 and its fusion-point is 2000 C. It is insoluble in acids and unchanged in air. It is prepared from platinum residues by first converting it into rhodium chloride and then by reducing this by heating it with sulphur in a carbon crucible. It forms alloys with platinum, gold, bismuth, and lead. It is the most costly of all the metals, being worth five times as much as gold. It occurs in small quantities in platinum ores and in some native gold. It is found in the Ural Mountains and in Brazil. Its atomic weight is 102.9. METALS OF THE PLATINUM GROUP At. wt. Sp. gr. F. melting- point C. melting- point. Platinum Indium 195.0 193 1 21.5 22 33 3225 3892 1780 1950 Osmium Palladium 190.9 106 7 22.47 11 4 4532 2732 2500 1586 Rhodium Ruthenium . . 102.9 101.7 12.1 12.26 3272 3632 2000 1950 The members of the platinum group occur intimately associated with each other. Where one is present the other members in larger or smaller quantity are usually present. Native platinum contains from 16 to 40 : per cent, of the other metals of the group. These often alloy with each other as in iridosmine and platinirid- ium. They are all white or grayish- white, lustrous, ductile and malleable metals. They are all permanent in the ordinary atmos- phere. Osmium alone burns when strongly heated. All the others are scarcely affected by oxygen at any temperature. Save palladium, they are insoluble in any single acid, and often aqua regia is without solvent action upon iridium and ruthenium. Palladium fuses at the temperature of wrought iron, and is, therefore, the easiest fused of any members of the group. The order of fusibility of the other metals is, palladium, platinum, ruthenium, iridium, osmium, the last of which has never suffered 108 ECONOMIC GEOLOGY fusion. All these minerals occur native and as alloys, principally as scales or granules in the placer gravels, in the same location as described under the caption of platinum. The geological horizon is the same as given for platinum. LOSSES OF PRECIOUS METALS The losses of precious metals may be classed as follows: (1) Hoarding. The quantity hoarded is indeterminable, and the loss is largely retrievable. (2) The amount put out of circu- lation as objects of art and ornamentation. (3) Wear and tear. This represents an irretrievable loss. It occurs in the wear of the coin whereby the medium of exchange to-day meeting the stand- ard of weight, to-morrow becomes too light, as its edges and sides have become smooth. The coin is not suitable as a medium of exchange, and it goes back to the United States mint for recoin- age. This loss also occurs in the gold leaf, silver leaf, wire, and in the pure metals used extensively for plating. (4) Loss in the useful metals, that is, ores containing too low a percentage of gold, or silver, or both, to separate with a profit. A small per- centage of these metals goes into the useful metals as copper and iron, from which it is never removed. (5) The concentrates from milling processes from which other metals are recovered may carry so small a percentage of either gold or silver that they are thrown directly into the waste, thereby losing, for all commercial purposes, a certain quantity of silver and gold. (6) In the extraction of the metals, as reducing the ore to a pulp too rapidly, in crushing the ore too coarsely for amalgamation to take place, and in the employment of cheap labor. (7) Loss in tailings. In some plants estimation has been made that from 50 per cent, to 60 per cent, of the actual gold and silver present in the ore is lost in the tailings from the mill. If the loss in 1 gal. of water is 0.018 cent, and if 576,000 gal. of water per day represents the amount of waste, the actual loss for one year would be represented by the following: 576,000 X 0.018 X 360 X 2 = $74,649.60. (8) By crushing the ore too finely. This produces a flour gold and silver, both of which are carried away on the surface of the water. (9) By filling the holes in the stamps and pans with amal- gam. (10) By cleaning the plates too quickly. (11) Byremov- PRECIOUS METALS 109 ing the amalgam from the plates too thoroughly, for the amalgama- tion is not complete when the plates are new or perfectly free from the amalgam, that is, " experienced " plates are far more efficient in the extraction of the gold and silver than the " inexperienced." (12) By using too slow a current of water. If the current be too slow, the plates become covered with slime, and this prevents the gold and the silver from coming directly in contact with the amalgam. (13) By using too rapid a current of water. This pre- vents the metal from being caught on the amalgamating plates, that is, the heavy current of water simply carries it away. (14) By not keeping the mercury clean. This prevents the amalgama- tion from taking place. Whenever mercury is covered with oil from the machinery, or oily exudations from the hands, it must be redis- tilled or treated with lye to cut the oil. (15) By the flouring of the mercury, that is, the reduction of the mercury to so fine a state of subdivision that it will not adhere to the amalgamating pans. (16) By too few amalgamating machines, as where the ore is rich and the quantity required to pass over the plates is too great for one machine to do the work. (17) By too short sluices or plates; by using the blankets too long; and by leaving the plates in front of the stamps so long that they become charged with mud and other debris and prevent the uniform feeding of the gold upon the amalgamating plates. CHAPTER IV USEFUL METALS (GROUP I) LEAD AND MERCURY Properties. Lead, symbol Pb, is a soft, bluish-white metal. Its freshly cut surface has a bright metallic luster. The metal upon exposure quickly becomes coated with a film of the oxide. Lead, unlike the other metals, is sufficiently soft to be scratched with the thumb-nail. It even leaves a lead gray streak upon paper. Lead is fashioned into foil or wire by rolling and pressing. It is readily soluble in nitric acid but the other mineral acids are without special solvent effect upon the metal at ordinary temperatures. Its specific gravity is 11.3. Its melting-point 327 C. Its atomic weight 207.10. Ores of Lead. Native lead occurs in small quantities in many localities both in the United States and in foreign countries. It is always of secondary origin, the product of reduction from other lead minerals through volcanic action. Galenite, PbS, 86.6 per cent, of lead. Anglesite, PbS04, 68.3 per cent, of lead. A white or gray sulphate. Cerussite, PbCOs, 77.5 per cent, of lead. A white or pink carbonate. Pyromorphite, 3Pb 3 (PO 4 )2,PbCl 2 . Often in small hexagonal crystals. Cotunnite, PbCl 2 , 74.5 per cent, of lead. Massicot, PbO, 92.8 per cent, of lead. A buff powder. Minium, PbsO^ 90.6 per cent, of lead. A vivid red powder. Plattnerite, Pb02, 86.6 per cent, of lead. An iron black oxide. Crocoite, PbCr04, 65 per cent, of lead. Wulfenite, PbMo0 4 , 57 per cent, of lead. Stolzite, PbWO 4 , 44.9 per cent, of lead. Galenite is by far the most important ore of lead. It crystallizes in the isometric system in perfect cubes and regular octahedrons. It also occurs massive and granular. Silver sulphide, Ag 2 S, 110 USEFUL METALS 111 is often intimately associated with galenite and isomorphous with it. All galenite is more or less argentiferous but the coarsely crystallized variety like the galenite of Rossie, St. Lawrence Co., N. Y., is low in its silver content, while much of the finely crystal- lized galenite of the Cordilleran section is highly argentiferous. The last seven minerals are not important as ores of lead, but the artificial massicot, minium and crocoite are important in the arts and industries. Wulfenite and stolzite are interesting molybdenum and tungsten salts of the metal. There are also many compound minerals playing only a minor role in the metal- lurgy of the metal. Origin of the Ores. As already noted, native lead is always of secondary origin, the direct product of the reduction of other ores. The sulphide of lead is precipitated in the laboratory whenever a solution bearing H 2 S comes in contact with neutral or slightly acid solutions bearing lead salts. Galenite appears to have been formed in most cases from mineralized solutions by hydro-chemical reactions, or by hydatogenetic reactions at temperatures which are not excessively high. Mayencon has reported galenite as a product of sublimation in a burning coal mine, Lacroix and Zambanini both report galenite as a Vesuvian sublimate formed during the eruption of April, 1906. Anglesite is a common oxidation derivative of galenite in the presence of water or moist atmosphere. The carbonate, cerus- site, is derived from the oxidation of other ores of lead in the presence of carbonated waters in the upper level of ore bodies. Therefore anglesite and cerussite are generally present in the oxidized zone of an ore body bearing lead minerals. The rich- ness of the ore varies with the extent of the decomposition that has taken place. If it is limited to the breaking down of galenite the ore is sometimes very rich. If the associated country rock has also suffered decomposition the ore has absorbed so much carbon dioxide in the formation of earthy carbonates that it is often too poor in lead to pay for profitable extraction. The oxides are always of secondary origin and result directly from the decomposition and reduction of Other lead minerals. The chloride of lead, cotunnite, is a volcanic mineral produced by sublimation. Character of the Ore Bodies. Primary galenite appears to be connected with the acid intrusives of all ages. Minerals which characterize ores of pneumatolytic origin are absent and 112 ECONOMIC GEOLOGY the galenite is hydatogenetic (Fig. 70). According to Thomas and MacAlister the Derbyshire galenite assumes a variety of forms which they have classified as rakes, pipes, flats and serins. The FIG. 70. Section exposed in a breast of the Enterprise mine at Rico, Dolores County, Colorado. (After Rickard.} rakes are true fissures, often faults; the serins are mineralized fissures crossing them; the flats are mineralized bedding planes; the pipes are irregular pipe-like bodies of ore. FIG. 71. Ideal section through flats and pitches of the lead and zinc region of Wisconsin. (After Chamberlain.} In the United States, lead minerals occur in veins which may be tilted to almost any angle with the strata which the fissure vein traverses. In Missouri, galenite occurs filling large cavities as USEFUL METALS 113 chamber deposits and as gash veins; also it occurs in what is known as flats and pitches. (See Fig. 71.) The most important lead deposits of the United States are of : ?-.'s : Vy* ffiffiffifr* Pf ~- SO I LAND RESIDUARY OAY UPPER GALENA -"- MIPPLE GALENA LOWER GALENA BLUE L1ME5TOME, LIMESTONE PETER'S 5ANDSTQNE FIG. 72. Ideal section in the lead and zinc region of Wisconsin, showing the forms of ore deposits at the different horizons. (After Chamberlain.) Greywackt Diorite Colette, Quartz Galena Blendi FIG. 73. Section of the Adelbert lodes, Pribam, Bohemia. (After J, Zadrizil.) metasomatic origin. They occur in the limestones of all ages (Fig. 72). Fossils have been replaced by galenite retaining both the external form and internal structure of the organism. Such 114 ECONOMIC GEOLOGY instances have been reported from Sardinia, England, and Westphalia. The mineralizing solutions in most cases of metasomatic galen- ite belong to the descending ground-water currents. There are, however, examples of metasomatic replacement deposits that have resulted from the action of heated solutions rising from below in accordance with the theory of the ascensionists. Both of these deposits usually occur in limestones which interact upon percola- ting waters charged with solutions of lead salts. The limestones did not originally contain the galenite. Its source was some associated igneous rock or sulphide-bearing sediment. Alkaline sulphides may have aided in effecting the solution of the lead, and the lead in solution was doubtless transported as a sulphide and deposited in the place of the dissolved limestone. Galenite is usually associated with several other minerals, common among which are calcite, dolomite, siderite, sphalerite, pyrite, rhodonite and quartz, as shown in Fig. 73. Geographical Distribution. Lead in its various ores is widely distributed. The mineral galenite is found in almost all countries, but few are of great importance. It occurs in the United States, England and Sweden in limestones. In the Harz Mountains it occupies veins in clay slate; in Freiberg it occurs in veins in gneiss; in Spain as veins in granite. The United States is the largest producer of lead. The Ameri- can area may be divided into three distinct fields: the Appala- chian; the Missippi River belt, and the Cordilleran region. (1) The first district is of the least importance. It extends from Alabama on the south to Maine on the north. The ores are associated with Cambrian or Cambro-Ordovician metamor- phics. The belt comprises a highly folded and often faulted series of crystalline schists and limestones. In Pennsylvania galenite occurs in many places in these crystallines and is often argentiferous, varying from $2 to $2000 per ton in silver. Lan- caster, Chester, Northumberland and Wayne Counties are most important sections. In New York, at Rossie, St. Lawrence Co., galenite occurs in veins 3 or 4 ft. in width. The crystals are often very large and assiciated with a calcite gangue. In Vir- ginia the terranes associated with lead at Austin's Mines and Sterling are Cambrian and Ordovician. It is not likely that any of these localities in the Appalachain belt will ever become great producers of this useful metal (Fig. 74). USEFUL METALS 115 (2) The Mississippi River belt comprises the following states : Minnesota, Missouri, Illinois, Iowa, Kansas, Kentucky, and Ar- kansas. The Missouri-Kansas district is the most important of them all. It is further divided into three distinct fields: (a) The southeast; (b) the central; and (c) the southwest. In the first two fields the ore is distinctively galenite. In the third district the ore is associated with zinc. Joplin is in the southwest district. The ore occurs in lime- stones and chert of Mississipian age intimately associated FIG. 74. Open cut in barren ground near lola, Marion County, Arkansas, showing jointed dolomite. (After G. I. Adams, U. S. Geological Survey.) with the slates and shales of the Coal Measures. The ore bodies are often massive and sometimes hundreds of feet in diameter. The ore occurs massive and granular and in crystals of the isometric system. The associated minerals are chert, calcite, dolomite, barite and pyrite. These are all of secondary origin. The country rock is sometimes massive and sometimes fragmental (Fig. 75). In this district the ore is associated with sphalerite, ZnS, which sometimes has a resinous luster; sometimes it is the ferriferous sphalerite, containing 10 per cent, or more of 116 ECONOMIC GEOLOGY iron and known by the miners as black jack. Calamine, the hydrous silicate of zinc, and smithsonite, the carbonate of zinc, appear as associated minerals. Both of these are classified in the trade as silicates. The lenticular, tabular and cylindrical forms are more common in the southeastern and central districts than in the southwestern. USEFUL METALS 117 In the Doe Run mine in southeast Missouri, the ore is galenite in limestone. The ore body is sometimes from 50 to 90 ft. in diameter. It is generally in layers parallel to the stratification, but sometimes in vertical or inclined seams and occasionally dis- seminated through the limestone with calcite and nickeliferous pyrite, bearing pyrite or pyrrhotite as accessory minerals. The sedimentaries rest unconformably upon Archean granite and gneiss. Mine La Motte, Bonne Terre, and Doe Run are the most important mines in this district. In southern Illinois and Kentucky the gangue mineral is fluorite, which is occasionally mined and sold to iron blast- furnace operators. (3) The Cordilleran District: In Colorado, Leadville is the most important locality. Here the galenite is oxidized at the surface and is argentiferous. The associated rocks are Lower Carboniferous limestones and dolomites, Ordovician limestones and dolomites, and Cambrian quartzites resting on Archean granite. These terranes are all traversed by sheets and dikes of Cretaceous and post-Cretaceous age. The white and gray por- phyries are older and more important. The main ore body lies in the limestone of the Lower Carboniferous age. The blue lime- stone at or near its contact with the Leadville porphyry is the most important horizon. According to S. F. Emmons, they con- stitute a contact sheet, whose upper surface, formed by the base of the porphyry sheet, is comparatively regular and well defined. The lower surface is irregular and ill defined. There is a gradual transition from ore into unaltered limestone. The ore sometimes occupies the entire thickness of the blue limestone. (See Fig. 76.) The ore also occurs in irregularly shaped bodies or in transverse sheets not always connected with the upper or contact surface of the ore-bearing bed or rock. It also occurs sometimes at or near the contact of sheets of gray or other porphyries with the blue limestone. Less frequently it occurs in both the calcareous and siliceous sedimentaries. According to Hancock the main mass of the argentiferous galenite lies in the limestones and dolomites while the ores containing gold and copper are more pronounced in the siliceous beds, in porphyries and in the crystalline rocks. From an economic standpoint, the most important mineral is the argentiferous galenite with its secondary cerussite and cerargyrite. Lead also occurs here as the sulphate, anglesite, as the phosphate, pyromorphite, and in the form of the oxides 118 ECONOMIC GEOLOGY massicot and minium. Native silver and embolite are both as- sociated with the Leadville ores. The gangue minerals are quartz, siderite, pyrite and gypsum. S. F. Emmons in Monograph XII of the United States Geologi- cal Survey Reports states: " That the ores must have been formed beneath a thickness of at least 10,000 ft. of superincumbent rocks and an unknown amount of sea water. If they had been deposited from hot ascending solutions as the result of the relief of pressure, it would naturally be expected that the FIG. 76. Map showing approximate distribution of the principal silver, lead and gold regions of Colorado. After Spurr. (By permission of the Macmillan Company, from Ries' Economic Geology.) bulk of the deposit would have been found in the upper part of this mass of rocks where the pressure was least instead of at its base. If the de- posits had been made from ascending currents, it would naturally be expected that the process of deposition should have acted from the lower surface of the beds upward, instead of from the upper surface downward, as is shown in the case of the blue limestone which carries the bulk of the ores. The few approximately vertical ore bodies that have come under observation afford no evidence that their walls form part of a channel through which the ore currents came up from below. A downward current seems best to suit the facts thus far observed in the Leadville deposits." USEFUL METALS 119 The ore therefore seems to have been derived from the porphy- ries by leaching and deposited in the limestone by metasomatic replacement. The aqueous solutions traversing the joint planes and bedding planes of the limestone deposited the ore in later Cretaceous times. Newbery and LeConte have suggested that the ores were derived from ascending solutions bearing lead salts or ores consisting of cerussite (the carbonate), galenite (the sulphide), and anglesite (the sulphate) of lead (Fig. 77). Aspen is another important locality in Colorado in which is FIG. 77. General view of Rico, Colorado, and Enterprise group of mines. (By permission of the Macmillan Company, from Hies 1 Economic Geology.) found argentiferous lead ores. According to H. Ries, the ores are oxidized and occur in folded and faulted Carboniferous limestone, although the section involves rocks ranging from the Archean to the Mesozoic in age. Two quartz porphyries, one at the base of the Devonian and the other in the Carboniferous at present ap- pear to bear no special relation to the ore bodies. At the close of the Cretaceous the rocks were folded into a great anticline, with a syncline on its eastern limit. Contemporaneous with the folding there were produced two faults parallel with the bedding of the Carboniferous dolomite. At the same time much 120 ECONOMIC GEOLOGY cross faulting occurred. The ore is found chiefly at the intersec- tion of these two sets of fault planes. According to J. E. Spurr, the ores were deposited by magmatic waters ascending vertically along these faults and were precipi- tated by the reaction between the solutions and certain wall rocks, chiefly shales. The mingling of solutions at the intersection of the fissures also played an important role in the formation of the ore bodies. According to W. H. Weed, the richer ore at the intersection of >Sv/: : :;^^^ /A : '\v/^-/'|.v./:-v FIG. 78. Sketch showing structure of Silver Shield lode, northeast face of stope. (After J. M. Boutwell, U. S. Geological Survey.} these fault planes was due to secondary deposition, while Spurr finds little evidence of secondary sulphide formation. The ores are peculiarly free from other metals (Fig. 78). In Utah and Nevada, argentiferous galenite yields much lead as a by-product (see chapter on the precious metals). In Idaho the bulk of the lead has been from the Coeur d'Alene district in Shoshone County. This district has for many years been one of the leading lead-producing sections of the country. The USEFUL METALS 121 FIG. 79. Map showing location of Coeur d' Alene, Idaho district. After Ransome. (By permission of the Macmillan Company, from Ries' Economic Geology.} Areas in which occur Areas in which occur Area in which Principal auriferous Productive minos Prospects or mine* lead-silver deposits of lead-silver deposits of occur cppper area s not of primary known primary secondary importance deposits importance' importance so far as at present known FIG. 80. Geologic map of Coeur d' Alene, Idaho district. (After Ransome. (By permission of the Macmillan Company, from Ries J Economic Geology.) 122 ECONOMIC GEOLOGY Bunker Hill Mine, The Federal Mining and Smelting Company, and the Hercules Mine are some of the principle producers. Ninety-nine per cent, of the lead and the same per cent, of the silver in the Coeur d'Alene District comes from the Revette quartzite and Burke sandstones, quartzites and shales (Figs. 79 and 80). According to F. L. Ransome, there are no sediments in the dis- trict younger than the Algonkian, except the fluviatile deposits some of which may be of Tertiary age. The post-Algonkian intrusives are monzonite and syenite. The ore deposits of the district are divided into three classes: (1) Lead-silver deposits; (2) gold deposits, and (3) copper deposits. The lead-silver deposits occur in metasomatic fissure veins formed largely by replacement along zones of fissuring or of com- bined fissuring and faulting, and partly by the filling of open spaces. The ore bodies are tabular and the mineralized fissures have the characteristics of faults. They differ from the great faults of the region in that the more important faults are not ore bearing. Fissuring and cleavage are so closely related to each other that the structure may be termed a shear zone. Ries con- siders that the metamorphism was adequate to produce new minerals. The most characteristic minerals are galenite and siderite, the carbonate of iron. Sometimes the galenite replaces the sericitic quartzite. Sometimes the quartzite is replaced by siderite and in turn by galenite. The galenite was not all deposited during one period for some- times the masses of coarsely crystallized galenite is traversed by veinlets of a more compact variety of the same mineral. The lead minerals found in the oxidized zone are cerussite and pyromor- phite ; the silver minerals, native silver and cerargyrite ; the copper minerals, azurite and malachite ; and the hydrated oxide of iron, limonite. Geological Horizon. Lead minerals are not confined to any geological horizon. They occur widely distributed in the rocks of all ages. They are, however, most abundant in the Cambrian, Ordovician, Carboniferous, and Cretaceous ages. Extraction of the Metal. (1) The Reduction Process. Lead oxides are readily reduced to the metallic state by carbon accord- ing to the equation PbO+C = Pb+CO. (2) The Roast-reaction Process. The ore is crushed and intro- duced into a reverboratory furnace in small quantities. The ore USEFUL METALS 123 is first oxidized to the sulphate according to the equation PbS+ 20 2 = PbSO 4 . The oxygen acting upon the lead sulphate formed in the presence of a new charge of ore reduces the sulphate to the oxide. The oxide reacts also upon a new charge of ore when some metallic lead is formed and sulphur dioxide is set free ac- cording to the equation 2PbO+PbS = Pb+SO 2 . The reduced metal sinks to the bottom of the furnace, runs through an inclined trough into an iron kettle from which the metal is dipped into moulds. The process is applicable to galenite that is fairly free from the sulphides of the heavy metals. (3) The Precipitation Process. In this process the ores may be charged in the raw state into a blast-furnace or calcined to remove volatile acid radicles or impurities. If the ore is the sulphate, anglesite, it will produce lead oxide and sulphur trioxide, thus: PbSO 4 = PbO + S0 3 . If the ore is the carbonate, cerussite, it will yield lead oxide and carbon dioxide, PbC0 3 = PbO+CO 2 . If the ore is the sulphide, galenite, it will yield lead oxide and sulphur dioxide, PbS + 30 = PbO -f SO 2 If the ore be the oxidation prod- uct, massicot, some volatile impurities may be removed. The oxide is then introduced into a blast-furnace with coke, scrap iron, or the sulphide of iron. At a high temperature the entire mass is melted. The silicate of iron rises to the surface as a slag and may be drawn off as in ordinary copper smelting. The sulphides of iron, tin, antimony, and copper, will be formed provided these metals are present and may be drawn off at a lower level. The sulphides often found are the black sulphide of copper, CuS, the sulphide of antimony, Sb 2 Ss, of tin, SnS, and of iron, FeS. At the bottom of the furnace is found the metallic lead. An equation represent- ing the reduction to the elemental state in the presence of iron would be PbS + Fe = FeS + Pb. The lead thus obtained is impure and is subsequently refined. If it contains silver in commercial quantities the lead is desilverized by the Pattinson process. (4) The Lime-roasting Process. This method is comparatively new and depends upon the treatment of galenite with lime or gyp- sum under conditions favorable for oxidation. The percentage of lead and silver saved by this method is said to be larger than that obtained by the preceding method while the cost of treatment is no greater. Uses of Lead. One of the most important uses of lead is in the manufacture of white lead. Lead is used also in the manu- facture of other lead pigments under the name of litharge, red lead, 124 ECONOMIC GEOLOGY orange mineral and sublimed blue lead. Lead is used in the manu- facture of lead pipe, shot, etc., and in many alloys that are of great commercial significance. Sheet lead is used extensively for lin- ings to withstand the corrosive action of acids or acid vapors. In the manufacture of sulphurous and sulphuric acid the chambers and towers are lined with sheet lead. Lead is also used for the barrels utilized in the chlorination of gold and for the linings of many vats. In former years sheet lead was used for roofing and for jointing but other metals have largely taken its place. It has been used in the glazing of windows, and now an exceedingly im- portant use is for coverings for electric cables. This use perhaps more than any other is responsible for the increasing domestic consumption. Shot was early manufactured in Missouri and Wisconsin. Pos- sibly this is the earliest use of lead in America. In times of peace and war a continuance of that use is very important. Lead is used also in storage batteries and in many forms of chemical works. Among the alloys type metal, britannia ware, and the various form of babbitt known as antifriction alloys are exceedingly im- portant. It is used also in the various grades of solder as fine, medium and coarse; in the composition of organ pipes; in the fus- ible alloys used in electric lighting systems; in fireprotection sprinklers and in alloys with the precious metals, some of which are of commercial significance. White lead is the most important of the lead pigments. It is used directly as a pigment and as a source of other pigments. White lead has to meet the competition of zinc white .and heavy spar. These three pigments are sometimes used together. Ninety per cent, of all the white lead of commerce is manufactured by the Dutch process at New Kensington, Pa., by the Sterling White Lead Company. Their product is surpassed by none in its opac- ity, its covering power, and in its durability as a pigment. The process is based upon the fact that acetic acid has a strong corrosive effect upon lead. The lead is therefore immersed for several months in dilute acetic acid or vinegar, when in the presence of carbon dioxide and heat the corrosion is complete. The liquid is drawn off. The residue is placed in drying rooms which are of the filter type not used elsewhere in the world. The heat required in drying is small, only enough to remove what moisture cannot pass through the filters. Chestnut and oak bark are used in the process. The bark is exhausted only to its USEFUL METALS 125 most effective point. The spent tan resulting therefrom is of superior quality and its concentrated extract is sold to the leather tanneries. Litharge is another important lead pigment. Its most impor- tant use is that of a pigment. It is used also as an ingredient in the compounding of rubber, in the manufacture of glass, in assay- ing, mixed with glycerine to hold pipes and table tops together. It may be manufactured from several lead salts by roasting them to drive off the volatile acid radicle. The powder obtained is a buff yellow, but if heated to the point of fusion reddish-yellow scales of the oxide appear. This product is known in the marts of trade as litharge. It is obtained in large quantities during the desilverization of lead. Another lead pigment of considerable importance is red lead. It is not only used as a pigment but also in the manufacture of flint glass, and very extensively in the production of structural steel. It is also used as a pipe-joint cement. It can be manu- factured by heating for a considerable time various salts of lead at a temperature of 450. Orange mineral is another lead pigment of less commercial significance. It can be manufactured by the treatment of soluble salts of lead with sodium oxy chloride in the presence of an alkaline hydrate. Sublimed blue lead is obtained as a by-product in the sublima- tion of galenite and consists of a mixture of lead oxide, lead sulphide, lead sulphite, zinc oxide and carbon. It is used in the manufacture of rubber goods. Lead arsenate is used also in the destruction of the gypsy moth. The production of lead includes base bullion, pig lead, bars, sheets and old lead. Pig lead is reported by all smelters operating in the Mississippi Valley. Refined lead embraces all of the de- silverized lead produced in this country, and the pig lead recov- ered from the Mississippi Valley lead industry. Antimonial lead is derived from the treatment of gold and silver ores bearing antimony. In the process of extraction of the precious metals the antimony combines with the lead in the formation of anti- monial lead. For this product there is quite a large demand and the two metals are never separated. In 1885 there began in the United States the treatment of for- eign ores and base bullion largely from Mexico. Part of this prod- uct is smelted and exported, but a considerable quantity is con- 126 ECONOMIC GEOLOGY sumed at home. Some lead is brought in duty free. This has considerable influence upon the annual statistics of the metal. The total valuation of metallic lead and all the pigments derived therefrom has in some years exceeded $60,000,000. Mercury : Its Properties, Occurrence and Uses. Properties. Mercury, symbol Hg, is a bright, silver white, metal, liquid at ordinary temperatures. It was this physical property that gave the metal the old name of quicksilver. It is the only metal liquid at ordinary temperature. Bromine is the only other element liquid at normal temperature. At 38.8 below zero mercury crystallizes in the isometric system. The malleable and ductile cubes are of higher specific gravity than the liquid metal. The liquid metal emits vapor at ordinary temperatures. It does not tarnish upon exposure. It is not attacked by HC1, nor by concentrated ^H^SO 4 without heat. It is readily soluble in HNOs. Its specific gravity as a liquid is 13.59, as a solid it is 14.19. Its boiling point is 357. Its atomic weight is 200. Ores of Mercury. Native mercury, Hg, is rare but sometimes reported in considerable quantity. Cinnabar, HgS, 86.2, per cent, of mercury. The only cochineal red mineral entirely volatile before the blowpipe. Metacinnabarite, 86.2 per cent, of mercury. The black sul- phide of mercury. Calomel, HgCl, 84.9 per cent, of mercury. Most abundant in Carniola and Spain. Tiemannite, HgSe, 71.7 per cent, of mercury. The selenide of mercury which was once worked in the Lucky Boy claim in Utah. Living stonite, HgS,2Sb 2 S3, 24.8 per cent, of mercury. A double sulphide of mercury and antimony that has furnished a small amount of the metal in Mexico. Amalgam, HgAg, is an alloy of silver and mercury in varying proportions. The mercury may be as low as 5 per cent, or as high as 73.6 per cent. Origin of the Ores. Mercury, unlike the precious and most of the useful metals is not very abundant nor widely diffused in nature. It must, however, be remembered that owing to its volatility minute traces of the metal may be easily overlooked. USEFUL METALS 127 Native mercury occurs in small globules scattered through cinnabar and metacinnabarite as a product of reduction by organic matter. Bituminous substances, as idrialite and napa- lite, are commonly associated with cinnabar. A. Liversidge re- ports native mercury from the hot-spring deposits of New Zealand. According to J. D. Dana, native mercury is found in Venetian Lombardy in the marl beds regarded as a part of the nummulitic beds of Eocene age. It has also been observed in the drift in Transylvania. Cinnabar appears to have more than one method of forma- tion. According to F. W. Clarke, mercury and sulphur, under the influence of heat, unite directly, and the product upon sub- liming is of scarlet hue. The black sulphide when acted upon by solutions of alkaline sulphides can be converted into the red form. The solubility of mercuric sulphide manifestly depends upon conditions of temperature, pressure, concentration, and the nature of the solution employed. G. F. Becker has found that mercuric sulphide is precipitated again from solution in alkaline sulphides upon dilution. Relief of pressure may in some cases be the equivalent of dilution as a precipitant. A. Liversidge has reported mercuric sulphide in the hot-spring deposits of New Zealand. Cinnabar has also been observed in the process of deposition by solfataric action at Sulphur Bank, California and Steamboat Springs, Nevada. The black sulphide is precipitated whenever H 2 S meets neutral or slightly acid solutions of mercury salts in the mercuric state. It does not follow that the mercurial solutions have been the same in all localities. They must have varied both in their chemical com- position and in the physical condition under which they canie to the surface. Their properties would be modified by the dif- ferences in the rocks traversed by the solutions themselves. Calomel is a product of secondary origin in Idria in Carniola, Almaden in Spain, Horzowitz in Bohemia, Belgrade in Servia. Amalgam is often formed where veins of mercury and silver intersect each other. Character of the Ore Bodies. The ore bodies bearing mercury in some cases fill fissures, fractures, or cavities in sedimentary rocks. In some instances cinnabar forms impregnation deposits in sand- stones or limestones. These terranes are usually in the vicinity of igneous rocks from which the mercurial ores were originally derived. Deep-seated granites may have been the principal 128 ECONOMIC GEOLOGY source of the mercury. The ores of mercury occur in regions of crustal movement and are newer than the disturbed rocks. They are not confined to any particular formation, nor to any type of rock. .Geographical Distribution. Mercury has a wide geographical range but its occurrence is often in so small a quantity that only a few localities have become actual producers. California has been the only large mercury producer in the United States. It occurs in many western states, New Mexico, Nevada, Oregon, Texas and Utah. According to H. Ries, the California ores occur chiefly in meta- morphosed Cretaceous or Jurassic rocks, and some even are as late as the Miocene and Quarternary. The deposits are in fissured zones. Eruptive rocks seem in many cases to be in- volved in the ore formation. At the New Almaden mine a rhyolite dike extends parallel with the ore body. The ore oc- curs along the contact between serpentine and shale, filling in part the interstices of a breccia. Branch fissures have ore-bear- ing channels extending into the country rock. The chief gangue minerals are quartz, calcite and dolomite. The ore is cinnabar with a little native mercury. The new Almaden mine has been one of the most important mercury deposits of the world. It has been worked to a depth of nearly 3000 ft. and the deposits are diminishing in their mercurial content. This locality is named from Almaden, Spain, where the metal has been obtained for years in great abundance. The New Idria mine, named from Idria in Carniola, has been worked almost continuously since 1853. The ore occurs in the metamorphic shales and limestones of Lower Cretaceous age. The ore is irregularly distributed between a false hanging wall of clay and a foot wall of shale. The ore is cinnabar-bearing pyrite, with a gangue of silicified and brecciated shales and sandstones. It also occurs as impregnation deposits and in reticulated masses. Below the zone of oxidation the ore body contains tabular masses of cinnabar. Other deposits occur at Clear Lake, Sulphur Bank, and the Great Western mine. At the Great Western mine the ore occurs as chimney deposits in opalized quartz. At Steam- boat Springs, Nevada, cinnabar is intimately associated with hot springs and occurs as impregnation deposits in decomposed granite. In Texas cinnabar occurs in Cretaceous limestone often faulted, in fissure veins with a gangue of calcite. USEFUL METALS 129 The most important deposits of mercurial ores in the world are situated in southern Spain at Almaden. The terranes con- sist of highly tilted and metamorphosed quartzites and shales of Devonian and Silurian age. The ore bodies occur in the quartz- ite as impregnation deposits, or as stringers running through the quartzite beds. The impregnations die out suddenly where the quartzites are in contact with the shales. The ore is cinnabar with some native mercury, pyrite and chalcopyrite. Another important mine is situated at Idria in Carniola, Austria. It occurs in limestones, sandstones, shales, marls, dolomites, and conglomerates. The ore body is an impregna- tion deposit in the limestones and dolomitic breccias. The ore is cinnabar with a little native mercury. The gangue min- erals are quartz, calcite, dolomite and fluorite. The richest deposits occupy fissures. Geological Horizon. The ores of mercury are not confined to the rocks of any particular age. The Almaden mine in Spain is in Silurian and Devonian terranes. The New Almaden in California is in the Cretaceous. The Peru terranes bearing mercurial ores are Jurassic. Methods of Extraction. (1) Distillation. The globules of elemental mercury as obtained from its associated gangue min- erals or in pockets in the vein are contaminated with certain impurities that may be left in the retort upon distillation. The metal distills at a temperature of 350 as free from other metals. In this process the metal must be kept free from oil or oily surfaces for these " deaden" the mercury. This proc- ess is utilized in the recovery of mercury from the amalgams of gold and silver obtained in the reduction of the precious metals. (2) Roasting. The ores of mercury are crushed and roasted in large furnaces of from 40 to 50 tons capacity per day until the last traces of the metal are driven off. The temperature used is a bright red heat. This high temperature is needed in order to warm the furnace air and the new feeds of ore. In this process the sulphur is oxidized to sulphur dioxide, which when conducted into water forms sulphurous acid used so largely in the manufacture of paper by the sulphite process. (3) Sublimation. As calomel volatilizes without suffering de- composition it is only necessary to crush the rock bearing this secondary mineral and drive off the chloride of mercury as a 130 ECONOMIC GEOLOGY vapor by heat. The calomel condenses in the cooling chambers as a white sublimate. Uses of Mercury. The most important use of mercury is to form amalgams. Most metals amalgamate with mercury. Sodium and potassium amalgams are used in organic analysis. Tin amalgams are used in ordinary mirrors, gold and silver amalgams in filling teeth. A common amalgam for this purpose consists of silver, copper and tin with enough mercury to amal- gamate the mixture. Copper and zinc likewise amalgamate with mercury. The largest single use lies in the extraction of the precious metals from their various ores. Mercury is used in thermometers but these are not accurate at temperatures exceeding 30 below zero. Mercury is used also in the arts, as in the electrolytic process for the manufacture of sodium and chlorine. The metal is unattacked by a large number of gases, therefore it is used in collecting and measuring gases which are soluble in water. Mercury compounds are used in medicine of which calomel is the most important. The bichloride of mercury, known as corrosive sublimate, is used in mercurial ointment and as an antiseptic for dog bites and snake stings. The sulphide is used as a pigment under the name of vermilion. The unit of measure for mercury is different from that of the other useful metals. The liquid metal is put up in flasks. Each flask contains 75 Ib. The value of the metal is determined by the market at San Francisco. An average quotation is about $45 per flask. The output of mercury in the United States in 1910 was 1,612,500 Ib. There are two conditions that oppose a large production of the metal. One is that many of the cinnabar deposits are situated far from transportation and fuel. The other is that small capital is not likely to be attracted to such localities. CHAPTER V USEFUL METALS CONTINUED (GROUP II, SUBGROUP A) BISMUTH, COPPER AND CADMIUM Bismuth: Its Properties, Occurrence and Uses Properties of Bismuth. Bismuth, symbol Bi, is a silvery white metal with a reddish tinge. Unlike the other metals, save antimony, it is extremely brittle. It is unoxidized at the ordinary temperature in dry air while it is slowly oxidized in moist atmosphere. The reddish tinge on the exposed surfaces of the metal is the result of such oxidation. It expands 2 per cent, upon cooling and this property is responsible for its exten- sive use in the manufacture of safety plugs for boilers. Chem- ically it is closely allied to arsenic and antimony. It is soluble in HC1; specific gravity, 9.8, melting point, 269 atomic weight, 208, and crystallizes in the hexagonal system. Ores of Bismuth. Native bismuth, Bi, 100 per cent. It is often associated with gold, silver, and several of the useful metals. Bismuthinite, Bi 2 S 3 , 81.2 per cent, bismuth. Guanajuatite, Bi 2 Se3, 63.7 per cent, bismuth. Tetradymite, Bi 2 Te3, 51.9 per cent, bismuth when sulphur free. Bismutite, Bi 2 3 ,H 2 C03, 80.6 per cent, bismuth. A basic carbonate of doubtful composition. Bismutosphaerite, Bi 2 03,Bi 2 (C03) 3. Bismite, Bi 2 0s, 96.6 per cent, bismuth. There are also arsenates of bismuth, a tellurate, a vanadate, a silicate and an oxychloride of the same base, but these are rare minerals. The native metal and the sulphide, bismuth- inite, are the most widely distributed of the bismuth minerals and therefore the most important ores. Origin of the Ores. Native bismuth results from the reduction of other ores of the metal. The important deposits of bismuth in Bolivia may be primary. The bismuth is intergrown with 131 132 ECONOMIC GEOLOGY cassiterite, and wolframite may sometimes be present. The sul- phide of bismuth is sparingly soluble in the alkaline sulphides and in that way may be transported some distance from the original ore body. The artificial sulphide is precipitated in the chemical laboratory whenever hydrogen sulphide comes in con- tact with a neutral or slightly acid solution of the metal. Ac- cording to F. W. Clarke, the precipitated sulphide of bismuth heated with an alkaline sulphide at a temperature of 200 has given crystals of bismuthinite. The carbonates of bismuth are of secondary origin. The action of carbonated waters upon other bismuth minerals has produced bismutite. In Aus- tralia bismutite has been observed as an ocherous deposit around a thermal spring. Bismite is also secondary in origin, the oxida- tion product of bismuthinite. According to Mayengon, bis- muthinite occurs as a product of sublimation from burning coal mines. Character of the Ore Bodies. There appears to be no well- marked group of bismuth veins. The bismuth ores are best re- garded as subordinate constituents of other mineral-bearing veins, yet occurring occasionally in such commercial quantities as to establish exceptional modifications of those veins. Veins of bismuth minerals occur in gneiss and other crystalline rocks, also in clay slate, accompanying various ores of silver, cobalt, lead and zinc. In Queensland auriferous bismuth ores are con- nected with granite intrusives. In New South Wales auriferous bismuth veins occur near the contact of granite and slate. In Bolivia the tin-bismuth veins appear to be connected with dikes of dacite and trachyte traversing altered clay slates. Geographical Distribution. The best known locality for bis- muth minerals in the United States is in Colorado. Lake County is the best producer of the brittle metal. According to H. Ries, some of the gold ores on Breece Hill near Leadville contain from 5 to 8 per cent, of bismuth. In the same state near Golden at Bismuth Queen Lode bismuth ores are encoun- tered. It is found also at Beaver City, Utah, and near Tucson, Arizona. In fact, the Cordi Reran section bears many scattered occurrences of bismuth ores. Bolivia, Germany and Austria are the large producers of the metal. Geological Horizon. The ores of bismuth do not appear to be confined to any geological horizon, but are more abundant in the older geological formations. USEFUL METALS 133 Methods of Extraction. Bismuth is obtained in large quan- tities as a by-product in the treatment of gold, silver and lead ores. Two methods that are applicable to the treatment of bismuth ores may be outlined as follows: (1) Roasting. The ore is crushed, and then heated in re- torts. The molten metal drains off through inclined iron pipes. The crude metal thus collected is dissolved in nitric acid, form- ing the nitrate of bismuth, Bi(N0 3 ) 3 . This product is treated with water and the subnitrate of bismuth is formed according to the equation, Bi(NO 3 ) 3 +2H 2 = BiO, N0 3 ,H 2 0,+2HN0 3 . After the precipitate has thoroughly settled the supernatant liquor is drawn off, the precipitate dried, and the oxide, Bi 2 O3, is formed. This oxide when roasted in large crucibles yields elemental bismuth and carbon monoxide according to the equa- tion, Bi 2 3 +3C = 2Bi+3CO. (2) Chlorination. The bismuth ore is crushed, pulverized, and placed in a series of wooden vats and leached with chlorine solutions. The disengaged chlorine dissolves the bismuth. The resulting solution is clarified by filtering. It is then con- ducted into water when the bismuth oxy chloride, BiOCl, is formed. The bismuth oxychloride thus precipitated may be dried and sold directly or it may be roasted with lime when chloride of lime and elemental bismuth are obtained. There are several other processes for the manufacture of metallic bismuth in foreign countries but owing to the minor importance of the metal they are omitted. Uses of Bismuth. Bismuth is used in the treatment of the precious metals for, like lead, it acts as a collecting agent for these metals. Its recovery power is very high for both gold and silver. The most important use of bismuth is in the manu- facture of many alloys which are capable of wide industrial application. Perhaps the most important of these is Wood's fusible metal which melts at 65. The alloy consists of 4 parts of bismuth, 2 parts of lead, 1 part of tin and 1 part of cadmium. The melting-point is far lower than that of any of its constituents. Bismuth melts at 269, lead at 327, tin at 232, and cadmium at 321.7 C. Other alloys are Lippowitz' metal, fusing at 60; Dorocot's metal, fusing at 93; Newton's fusible metal, fusing at 134 ECONOMIC GEOLOGY 94.5; Rose's metal, fusing at about 100. The range of the melting point of these alloys between 60 and 100 renders them capable of industrial application, as on passenger and freight trains where gas is used for lighting and as safety fuses for elec- trical apparatus. Britannia metal is an alloy which carries 1.8 per cent, of bismuth. One variety of type metal carries 7.6, per cent, of bismuth. With zinc the alloys of bismuth are always of definite composition. The alloys of bismuth expand upon cooling, therefore they make fine, hard, sharp castings and are used for safety plugs to fill blow holes in boilers. These alloys are used also in the production of wood cuts. Some of the alloys known as bis- muth solders have so low a melting point that they can be used directly under hot water. Bismuth is used also in the manu- facture of clique metals. It is utilized in the preparation of glass of high refractive power. Bismuth unites with mercury in the formation of dental amalgams. Bismuth is used quite extensively in medicine, the subnitrate being the most important compound. It is used in cosmetics, in calico printing and several of its salts in the chemical trade. Bismuth is one of the most objectionable constituents in brass. The world's supply of bismuth has long been controlled by Johnson, Mathey & Co. of England, who have regulated abso- lutely the production of bismuth, the price of the metal, and the supply of its ores. An attempt has been made to establish a price that would be renumerative to both the mine owners and the producers. The price of bismuth ores in London depends upon the bismuth content. With the metal at $1.25 per pound the following values would be attached to the ores: 10 per cent. ore would be worth $150 per ton; 15 per cent., $200; 20 per cent., $350; 30 per cent., $550; 35 per cent., $650; 40 per cent., $750; 45 per cent., $850; 50 per cent., $1000. The small amount of bismuth ore produced in the United States was formerly sent abroad for reduction. Plants have recently been established at St. Louis, Missouri and Grasselli, Indiana, for the recovery of bismuth from lead ores. Bismuth, as already noted, is contained in other ores than lead, but most of the bismuth passes into the atmosphere through the smelter flues unrecovered. It is estimated that 880 Ib. of bismuth are thrown off in every 24 hours in the smoke and gases of the Washoe smelter. USEFUL METALS 135 Copper : Its Properties, Occurence and Uses Properties of Copper. Copper, symbol Cu, is a copper red to red- dish-brown, soft, ductile and malleable metal. Its color as copper red is best seen by reflected light. It is extremely tough, there- fore, capable of being drawn out into exceedingly fine wires or hammered out into thin leaves. Its ductility and malleability are greatly diminished by the presence of impurities. As an electrical conductor it is second only to silver. The metal slowly tarnishes in dry air but in a moist atmosphere it is readily coated with a basic green carbonate. It is readily soluble in the mineral acids. Its specific gravity is 8.9. It melting point is 1065. Its atomic weight 63.57. Ores of Copper. Native copper, Cu, 100 per cent, copper but often alloyed with gold, silver, lead and mercury. Chalcocite, Cu 2 S, 79.8 per cent, copper. A gray sulphide. Covellite, CuS, 66.4 per cent, copper. An indigo blue sulphide. Bornite, Cu 2 S,CuS,FeS, 55.5 per cent, copper. Known as horseflesh ore by miners. Chalcopyrite, CuFeS 3 , 34.5 per cent, copper. The most im- portant source of the metal. Tetrahedrite, 4Cu 2 S,Sb 2 S 3 , 30.4 per cent, copper. Often argentiferous. Tennantite, 4Cu 2 S,As 2 S 3 , 57.5 per cent, copper. Enargite, 3Cu 2 S,As 2 S 5 , 48.3 per cent, copper. Chalcanthite, CuSo 4 ,5H 2 O, 25.4 per cent, copper. A natural blue vitriol. Brochantite, CuS0 4 ,(3CuOH) 2 , 62.4 per cent, copper. Cuprite, Cu 2 0, 88.8 per cent, copper. The red oxide of copper. Tenorite, CuO, 79.8 per cent, copper. The black oxide of copper. Malachite, CuC0 2 ,Cu(OH) 2 , 57.4 per cent, copper. The green carbonate. Azurite, 2CuC03,Cu(OH) 2 , 55 per cent, copper. The blue carbonate. Nantokite, Cu 2 Cl 2 , 64.1 per cent, copper. Atacamite, CuCl 2 ,Cu(OH) 2 , 59.4 per cent, copper. Dioptase, CuSi0 3 ,H 2 0. Chrysocolla, CuSi0 3 ,2H 2 O. Origin of the Ores. Copper is widely distributed in nature. The metal is easily oxidizable and also easily reduced. It there- 136 ECONOMIC GEOLOGY fore occurs both as native copper and in its numerous compounds. Copper is found in small quantities in the igneous rocks and there- fore in the sedimentaries derived from them. It is a common constituent of sea water, and the green color of the sea has been attributed to its presence. Copper has been obtained in the ashes of sea weeds and found in certain varieties of corals. According to F. W. Clarke, native copper is commonly, if not always, of secondary origin, either deposited from solution or formed by the reduction of some solid compound. Pseudo- morphs of copper after cuprite are well known. W. S. Yeats has described pseudomorphs of copper after azurite from Grant County, New Mexico. W. Lindgren states that the vein of metallic copper at Clifton, Arizona, appear to have been derived from Chalcocite. T. Carnely has shown that native copper is soluble in saline water. Small quantities of native copper have been found at both the Ely mine in Vershire, Vermont, and in the Corinth mine in Cornith, Vermont, that appear to have been formed from very dilute sulphate solutions. The greatest known deposits of metallic copper are found in the Lake Superior region. F. W. Clarke states its original home was, perhaps as sulphide, in the unaltered igneous rocks, but its concentrates are now found in the sandstones, conglomerates, and amygdaloids. In the sandstones and conglomerates it acts as a cement. It 'also re- places pebbles and even boulders a foot or more in diameter. A. C. Lane has cited a corroded quartz crystal which was mainly replaced by copper. Frequently native copper has been reported as holding enclosed nodules of native silver. According to F. W. Clarke, if these metals had been deposited from a fused magma they should not have solidified separately, but as an alloy. R. Beck mentions native copper filling the marrow cavities of fossil bones in the Peruvian sandstones of Corocoro, Bolivia. E. Haworth cites films of copper in the shales near Enid, Oklahoma, which were precipitated by organic substances. The largest single mass of native copper ever found was dis- covered in the Minnesota mine, Michigan, in February, 1857. It was 45 ft. long, 22 ft. wide and 8 ft. thick. It weighed 420 tons. It was 90 per cent, pure copper and contained an appre- ciable amount of silver. The value of that single specimen at the average price of copper would be about $83,000. Chalcopyrite is the most important ore of copper. Bornite and chalcocite are next in importance at least among the sulphides. USEFUL METALS 137 These three minerals have been repeatedly indentified as of mag- matic differentiation. They are doubtless the primary com- pounds from which the other ores in most cases were derived. B. Lotti has reported chalcopyrite, bornite and chalcocite in Tuscany as original segregations in serpentinized rocks. J. F. Kemp has reported primary bornite in a pegmatite vein near Princeton, British Columbia. The various sulphides of copper are often of hydatogenetic origin. Sulphides of more electro- positive metals may have served as precipitating reagents. Cu- pric solutions formed in the upper part of copper- bearing ore bodies reacting upon pyrite precipitate chalcocite. Covellite may be precipitated from copper sulphate solutions by the reaction of chalcocite. Chalcocite may alter into chalcopyrite and bornite. According to Thomas and MacAlister chalcopyrite may be of metasomatic origin. The mode of deposition of chalcopyrite in a certain number of deposits like those formed in limestone or at its contact with other rocks leads to this conclusion. The same authors state that the solutions may have come from above or below. The solutions were transported in the form of sulphates, either due to the oxidation of pyrite in the neighboring rocks, or in the form of aqueous emanations from an igneous magma dur- ing the later stages of its cooling. They also state that the metasomatic chalcopyrite deposits are due to ascending or de- scending solutions of sulphides carrying hydrogen sulphide and alkaline sulphides. The sulphates of copper are formed by the oxidation of the surface ores of copper and iron and the concentration of the mine waters. At Wicklow, Ireland, and Rio Tinto, Spain, chalcan- thite thus formed has been a workable deposit. According to H. Ochmichen, chalcanthite occurs in Chili as an impregnation deposit in partially decomposed granite rocks with the hydrous carbonates and silicates as associated minerals. Brochantite is far more common than is usually supposed and can be easily formed by natural reaction. The two basic carbonates of copper, malachite and azurite, are common copper ores of secondary origin. They are formed in the upper portion of ore bodies by the action of carbonated waters upon copper compounds or by the reactions between cuprous solutions and limestone. At Corinth, Vermont, the author has found fine specimens of both malachite and azurite formed from chalcopyrite by the action of carbonated waters. 138 ECONOMIC GEOLOGY L. Michel has reproduced azurite by leaving a solution of copper nitrate in contact with a crystal of calcite for several years. The carbonates have also been observed in the patina of ancient bronzes. Nantokite, the cuprous chloride, is rather rare, but atacamite, especially in Chili, is important. According to J. D. Dana, it may be formed by the oxidation ofnantokite. F. W. Clarke states, that it has been observed upon ancient coins and bronzes. The fumes of HC1 acting upon tenorite has produced a hydrous chloride that is not far from atacamite in composition and cor- responds very closely to the hydrous chloride found at Mount Vesuvius as a product of volcanic emanation during the eruption of 1872. The two oxides, cuprite and tenorite, are always of secondary origin. They may be formed by the oxidation and reduction of other copper minerals. Cuprite is far the more important species. It has been observed as an incrustation upon ancient objects of copper or bronze. Of the two silicates of copper, dioptase and chrysocolla, the first is rare but the second becomes an important copper ore in certain localities. According to F. W. Clarke, chrysocolla is formed by the action of silica-bearing waters upon soluble com- pounds of copper. Also that the mineral may possibly be pro- duced during the processes of secondary enrichment. H. Ries gives the following classification of the origin of cop- per ores: (1) Magmatic segregations. No workable deposits of mag- matic origin are known in the United States. (2) Contact deposits in crystalline limestone along contact with igneous rocks. The copper has been introduced by vapors from the igneous rocks. (3) Deposits formed by ascending circulating hot solutions, depositing ores in fissures, pores, spaces of brecciation, and by replacement of rock. (4) Lens-shaped deposits in crystalline schists representing a concentration of material from a disseminated condition in the surrounding rocks. The last two are by far the most important, but even here the ores have been enriched by oxidation and the transference of soluble compounds of copper to lower levels to be reprecipitated by limestone and the sulphides of copper and iron. USEFUL METALS 139 Character of the Ore Bodies. Primary copper sulphides are found at Cornwall, England, in veins containing cassiterite. In Norway, where primary sulphides occur : tin is absent and the ores are associated with greisen and derived from acid irruptives during their solidification. In Telemarken in Southern Norway copper ores occur with tourmaline in granites, gneisses and schistose rocks. At the Ely mine in Vershire, Vermont, the chalcopyrite is associated also with tourmaline. The ore occurs FIG. 81. Polished specimen of copper ore from Rambler mine, Wyom- ing. The dark mineral in corellite. The light is kaolinized feldspar. (After Mineral Resources, 1902, U. S. Geological Survey.) in saddle-shaped bodies along the folds in the Vershire schists or in long chimneys at the contact of the intrusive granite with the Vershire schists. Pyrite and pyrrhotite are the common associated sulphides. The granite was the parent home of the copper and the chalcopyrite was deposited under pneumatolytic conditions. This mine was known and worked before copper was discovered in the Lake Superior region. In the earlier days with 16 per cent, copper ore the mine was capable of pro- 140 ECONOMIC GEOLOGY ducing 10,000,000 Ib. of copper per annum, but in the later years much of the ore has not exceeded 3 per cent, copper. According to Thomas and MacAlister, sulphidic copper ores occur in South Australia in veins sometimes 30 ft. in width and of hydatogenetic origin. They occur in the mica schists of Cam- brian age and the associated minerals are pyrite, hematite and molybdenite. They also describe in New South Wales the exist- ence of interbedded veins of a cupriferous pyrrhotite with chalcopyrite, chalcocite and magnetite present. Metasomatic replacements of copper ores occur at Bisbee, Arizona, and in the Lake Superior region. The high grade cop- per ores of northern Italy are considered by some to be of the same origin (Fig. 81). The form then that the various copper deposits assume are veins, contact zones, impregnations and replacements in sedimen- tary rocks. Geographical Distribution. The copper ores of the United States form five distinct belts: (1) The Appalachian belt; (2) the Lake Superior region; (3) the Cordilleran section; (4) the Pacific Coast belt, and (5) the Alaskan belt. (1) The Appalachian Belt. This belt extends from Alabama on the south in a northeasterly direction to Newfoundland on the north. The richest deposits occur in Tennessee, Vermont and Newfoundland. The largest producing mine in the belt is at Ducktown, Tennessee. The ore occurs as true fissure veins in the crystalline schists. It consists chiefly of chalcopyrite in pyrrhotite and pyrite with a little quartz and is the richest where the pyrrhotite is the most abundant. According to H. Hies this district was one of the earliest producers of copper in the United States. The operations were commenced as early as 1850. The ores resulting from secondary enrichment were soon worked out and it was not until 1890 that the underlying low-grade sulphides were successfully worked. Since that time the mine has been a steady producer. At Gold Hill, North Carolina, chalcopyrite occurs in true fissure veins found along sheeted planes in the metamorphics. Pyrite is associated with the copper ore. At Virgilina, Virginia, the ore is bornite with a little chalcopy- rite and pyrite. It occurs in true fissure veins filled with quartz and sulphides. The veins conform to the banding of the mica schists. Replacements of the wall rock are rare. In Green USEFUL METALS 141 County, Virginia, segregations of native copper, together with the oxides, cuprite and tenorite, and the carbonates, malachite and azurite, occur along sheared zones in the altered rocks of Algonkian age. In Pennsylvania, New Jersey and Connecticut, deposits of native copper are found along the contact of diabase and the intruded sandstones. The mines in these states have never been large producers (Fig. 82). The four copper mines worked from time to time in Vermont are the Ely mine in Vershire; the Corinth mine in Corinth; the Elizabeth mine and the Strafford mine in Strafford, Vermont. These are all in Orange County, and are now idle owing in part FIG. 82. Ely mine, Copperfield, Vermont, showing the large slag beds in the foreground. (By courtesy of the Vermonter.) to the depletion of the available ore bodies and in part to the distance from railroad. The chief ore in each was chalcopyrite associated with pyrrhotite and pyrite. The ore is in saddle- shaped bodies in the Vershire schists and in chimneys at the contact of the granite with the Vershire schists. The schists and the associated limestones are of Ordovician age. Tour- malines and garnets are abundant (Fig. 83). The copper ores of the Appalachian belt are somewhat aurifer- ous. The early attempts to work the ores for both the gold and the copper content resulted in failure. The Vermont ores averaged about $2 per ton in gold. The Newfoundland ores are higher in their gold content. Much of that ore assays from $2 142 ECONOMIC GEOLOGY to $6 in gold. Some of the veins on the eastern coast of New- foundland are true fissure veins traversing sandstones and con- glomerates. Intrusive diabase appears to be the home of the copper ore. Chalcopyrite and pyrite are the chief minerals. Chalcopyrite occurs in considerable quantity at Capleton, Province of Quebec, in a sheared amygdaloid. The mine has been a steady producer for a number of years. (2) The Lake Superior Region. This region was discovered by Douglas Houghton in 1830. It has since that time produced more native copper than all other localities put together. In fact it has become one of the most famous copper producing districts of the world. The rocks, known as the Keweenaw series, consist FIG. 83. Dump piles of the Ely mine, Copperfield, Vermont. (By courtesy of the Vermonter.) of interbedded lava flows, sandstones and conglomerates. The conglomerates consist of rounded fragments of a reddish quartz porphyry of igneous origin. The ore is native copper occasionally associated with native silver. It occurs, according to H. Hies: (1) As a cement in the conglomerate, or replacing the conglomerate; (2) as a filling in the amygdules of the lava beds; and (3) as masses of irregular and often large size in veins with calcite and zeolitic gangue. (See Fig. 84.) According to A C. Lane, the original lava flows was the home of small percentages of copper, and while these basaltic rocks were still heated they absorbed sea waters charged with sodium USEFUL METALS 143 144 ECONOMIC GEOLOGY chloride. Meteoric waters transferred the sodium chloride down- ward and in their downward transition they dissolved the copper as copper chloride. Reactions between the original minerals of the volcanics and the copper solution gave rise to native copper, calcium chloride and soduim silicates. The following assemblage of facts bearing on the source of the copper in the Lake Superior district is taken directly from the masterly work of A. C. Lane on the Keweenaw Series of Michigan. (A) The dissemination of copper in small quantities through- out the formation. The average from several thousand feet of drilling at the Clark-Montreal mine was 0.02 per cent. Hardly a single amygdaloid fails to carry less than 0.02 per cent, copper, and when the copper content reaches 0.5 per cent, it is nearly an ore. (B) The occurrence of native copper in similar formations of the red rock associated with salt waters and lavas elsewhere, notably in the New Jersey Triassic, in the Bolivian Puca sandstone, in Nova Scotia, around Oberstin, in the Naho melaphye region, and in Alaska. (C) The general absence of native copper outside the Keween- awan, in the Lake Superior region, but (D) Native copper has been found in iron ore (generally thought to be formed by the action of downward working waters) in a few places. (E) The water in the formation is of three kinds. (a) At and near the surface soft and fresh with sodium in quantities more than sufficient to combine with the chlorine. (6) At some distance (generally 500 to 2000 ft., before it attracts attention, unless especially sought) the chlorine is higher and the water is charged with common salt. The line between the two classes of waters is often quite sharp. (c) At greater depths a strong solution of calcium chloride contains some copper. (F) The middle water b often contains more salt than it could possibly have were it a mixture of a and c. (G) The lines between the different kinds of waters are not regular, yet the lowest water probably always comes within 2000 or 3000 ft. of the surface. (H) The amygdaloids seem, other things being equal, to contain rather stronger (more saline) water than the conglomerates. (I) An unequally heated solution corresponding to mine water USEFUL METALS 145 c will precipitate copper on the same minerals, prehnite, datolite, etc., on which it occurs in the mine, as Fernekes has shown. (J) The traps contain combustible gases, as R. T. Chamberlain has shown. (K) Certain beds are abnormally rich in copper for many miles. (L) Copper often replaces chlorite, and in the Calumet & Hecla, pebbles chlorite replaces felsite, and the copper the chlorite. (M) Copper may even replace vein quartz. (N) Copper is formed generally after those minerals which are the products of alteration and contain lime, and before those sec- ondary minerals which are the products of alteration and contain soda and potash. (0) Therefore at the time the copper formed the mine water might have lost lime but could not have lost sodium. The rock might have lost both. (P) The Calumet & Hecla lode averages less rich (very rich in spots) near the surface, attains its greatest richness at a cer- tain depth, say about 2,000 ft., and then gradually decreases in richness. (Q) The silver occurs more abundantly in the upper levels. In producing the copper solution and guiding it in its circula- tion Lane considers the following factors: (A) The waters were originally contained in the lava. (B) That which early filled it, whether it was buried on land or beneath seas, may have included condensed volcanic vapors containing copper chloride, as in Stromboli, or in the evaporation of desert pools. (C) The absorption of water in the hydration of the rocks. (D) The absorption of water in the cooling of the formation (water in cooling shrinks more than rock) . (E) Faults in the formation facilitating the intermingling of solutions of different compositions. (F) Erosion of the formation and concentration of the copper contained either in pools on the land surface or in the water which found its way down into the rocks, while the deposition of the Keweenawan as a land formation was going on. (G) The ordinary circulation of the water entering at the higher parts and emerging in springs. (3) The Cordilleran Section. (See Fig. 85.) Butte, Montana, is the most important mining camp in this district. In fact it is 10 146 ECONOMIC GEOLOGY one of the largest producers of copper in the world. Its output has been approximately 2,000,000,000 Ib. of copper. It has further- p^^tsi r Mi SILVER VEINS COPPER VEINS [ i ..;;;| Pal - ALLUVIUM AND WASH PLEISTOCENE |jf;3 Nrl - INTRUSIVE RHYOLITE NEOCENE Eliil ap- APLITE ) >- POST CARBONIFEROUS fcyv) qr- GRANITE J FIG. 85. Map of the eastern part of Butte, Montana, district, showing distribution of Veins and geology. (By permission of the Macmillan Company, from Ries 1 Economic Geology.) more produced more than 100,000,000 oz. of silver and 500,000 of gold. The camp began its mining career as a gold producer in 1864. It held this recognition until 1875 when it became a USEFUL METALS 147 silver camp. It maintained this position until about 1880 when it became a copper camp. It will always remain in the literature of mining geology as distinctively a copper camp (Fig 86) . The primary ore was chalcopyrite and pyrite. It is the enor- mous deposits of secondary chalcocite that have been the large producers of the metal. Other copper minerals appearing as ores are bornite, enargite, covellite and tetrahedrite. The veins are FIG. 86. Geologic map of the western half of Butte, Montana, district. (B.y permission of the Macmillan Company, from Ries 1 Economic Geology.} quite largely replacement deposits along fissures in the sheeted granite. The country rock consists of two types of granite. One is a dark hornblendic granite or quartz monzonite known as the Butte granite. The other is an acid granite or better an aplite termed the Bluebird granite. These granites are intersected by dikes of quartz porphyry. Dikes of both intrusive and extru- sive rhyolite intersect the copper veins. 148 ECONOMIC GEOLOGY According to H. Hies, the veins exhibit a curious uniformity of direction, most of them striking nearly east and west, and few of them departing more than 15 or 20 degrees from the vertical. I -3 3 O 4 r^ 02 w . a a T They show considerable variation in width, ranging from a few feet to 150 ft. where the altered country rock is impregnated with chalcocite. In some instances there is no distinct hanging wall USEFUL METALS 149 and the distinction between the vein and the country rock be- comes commercial. The surface material consists of a red or brown quartz. Beneath CSJ fl o O ?S5 N 4. A rare mineral in varying shades of hya- cinth red. The first mentioned mineral, chromite, is the sole source of the metal of commerce. It is widely diffused in the basic igneous rocks rich in magnesium. It has been found in placers derived from their decomposition. It has been observed adherent to an interpenetrating platinum magnet. The rare mineral, daubreelite, Cr 2 S 3 ,FeS, has been observed in several meteorites. Origin of the Ores. S. Meunier has suggested that whenever an alloy of chromium anol iron is brought up from the zone of flowage it oxidizes as it nears the surface. The theory is objectionable because no such alloy is known to exist in nature. Chromite is essentially a primary magmatic mineral. It is one of the first minerals to segregate from an ultra-basic magma like peridotite. Its associate in this differentiation is magnetite. Microscopic slides of the magnetites and chromites of northern Vermont and Megantic County, Quebec, have been prepared to ascertain which of these ores solidified first but the problem is still unsolved. Ore bodies sufficiently large to be of commercial significance are definitely recognized as a product of magmatic USEFUL METALS 231 differentiation in northern Vermont and Megantic County, Quebec. The mines in the Canadian territory are still worked, but those in Vermont are idle, although a considerable amount of ore was at one time mined in the town of Troy. The larger ore bodies of Pennsylvania lie in the same peridotite belt and possess the same mode of origin. J. H. Pratt has assigned magmatic segregation to the chromite deposits of the southern Appalachians. Chrome ocher may result from the alteration of chromite. Character of the Ore Bodies. Chromite occurs in irregular pockets, veins, and lens-shaped masses segregating near the periphery of a peridotite magma. It is also found in placers in association with platinum where it has been derived through the decomposition of peridotite. Geographical Distribution. There are two distinct belts of chrome iron ore in the United States: The Appalachian dis- trict and the California district. The first of these districts may be subdivided into three dis- tinct fields. The southern lies in north Carolina and Maryland; the central has reached its best development in Pennsylvania and the third in northeastern Vermont and Canada. Deposits of chromite occur in the western part of North Carolina and in Baltimore County, Maryland, but these ores are no longer worked. The Wood's mine in Lancaster County, Pennsylvania, was opened in 1828 and worked continuously until 1869, when the mine filled with water. At one time this mine produced practic- ally all the chromite in the world. The ore was also worked at one time in Chester and Delaware Counties, but these mines have also been abandoned. Chromite ores were worked in the early 60's in the northeastern part of Vermont, but distance from the railroad led to the abandonment of these mines also. In Megan- tic County, Quebec, and in Newfoundland where the ores occur in the same peridotite belt they are still extensively mined. In the California district the deposits of chromite reach their best development in San Luis Obispo and Shasta Counties. In the former county the mines like those of the Appalachian belt have been abandoned. The ores of Shot Gun creek in the latter are still worked for their chrome content. According to H. Ries the ore occurs in serpentine in a series of five lenses, each contain- ing from 200 to 1500 tons of chromite. Each lens is connected by vein-like stringers in a nearly vertical shear zone. The ore con- 232 ECONOMIC GEOLOGY tains 43.87 per cent, of chromic oxide. In 1908 an important deposit of chromite was discovered in Converse County, Wyoming. The most important chromite deposits of the world are found in Asia Minor. According to Thomas and MacAlister the ore exists as stocks or dike-like masses, and ultra-basic patches in serpentine formed from the alteration of peridotite. Similar deposits exist in the neighborhood of Kraubat, in Upper Styria. It occurs also in a fairly fresh peridotite in Norway. In New Caledonia, deposits are commercially increasing in importance. The deposits of chromite in Southern Rhodesia are peculiarly interesting, for they are associated with platinum in small pro- portions with the sulphides of cobalt and nickel. Geological Horizon. Chromite is confined in its workable ore bodies to the pre-Cambrian, Cambrian and Ordovician deposits. Therefore its association is with the older ultra- basic intrusives. Methods of Extraction. The electrolytic method: The ore is crushed and fashioned into a large crucible where its complete electrolytic reduction requires one hour. The only manufacturers of chromium in this country are the Baltimore Chrome Works at Baltimore, Maryland, and the Kalion Chemical Works at Phila- delphia, Pennsylvania. Much of the ore treated at Baltimore comes from Scotland, and for Philadelphia from Quebec and Newfoundland. Uses of Chromium. Raw chromite is used in the manufacture of refractory brick. These bricks are used for lining basic, open-hearth furnaces in the steel industry and as a hearth lining for water-jacket furnaces in modern copper smelting. Its merits are as follows: It is infusible; it does not become friable when heated and cooled; is unaffected by sudden heating and rapid cooling; is not affected by the products formed in the fusion of copper ores; it wears away very slowly under the flow of the molten metal. Its use should continue to increase, for the life of the brick is many times greater than that of any other refractory linings and bottoms in the iron or copper in- dustries. This use has been thoroughly tested in the water- j acket furnaces both in New England and in Tennessee. The chro- mite deposits therefore of California should find extensive use in the furnaces for the treatment of the various copper ores in the Cordilleran section. In the linings of one furnace where raw chromite was used over 400 heats were turned out before the basic chromite bricks had to be repaired or removed. Therefore USEFUL METALS 233 the manufacture of refractory bricks in various forms, owing to its own refractoriness, will demand a larger use for chromite than the known American deposits can supply. Chromite brick are made of chromite and coal tar or some other binding material. They are superior to magnesite brick in many particulars. Chromite is used as a mordant in producing shades of red, green, buff, brown and black. Chromium is used in the manufac- ture of the red and yellow chromates for commercial trade and in electrolysis. Some of the chromates are used directly as a pig- ment. Chromium salts are used in printing, dyeing, and in wall paper. Chromium is also used as an oxidizing agent and in tan- neries. Chrome-tanned leather will resist the heating of high- speed belts than any other leather known. It will stand a harder usage. Chromium is also used in the manufacture of pottery. Some chromium salts find a use in medicine. Chromium is used in the manufacture of steel. Here its spe- cial value is its freedom from carbon, and by its use steels high in chromium and low in carbon can be manufactured. Such steels are extremely hard and tough, resist shocks and are of great tensile strength. They are especially to be desired wherever these properties play an important part. It is sometimes stated that scales of chromium separate out and make such steel in- capable of welding and that only an adhering union results. However, the welded zone is equally as strong as the unbroken steel. Chromium is used very largely in the manufacture of alloys. The ferro-alloy is used with ferro-nickel in the manufacture of chrome steel for armor plates, and armor-piercing projectiles, trolley car wheels, crusher jaws, stamp mill shoes, so-called burglar proof safes, tires, axles, springs, magnet steel, cutlery, mechanical implements and bridge steel. The ferro-chrome alloy is produced under the intense heat of an electric furnace from high-grade chrome ores low in silicon. The iron, chromium, tungsten and nickel alloy is especially valuable for high-speed tools on account of its resistance to heat and abrasion. The value of chromite depends largely upon the percentage of chromic oxide, Cr 2 C>3 present. The standard ore contains 50 per cent, of this oxide. It increases in value $1 per ton for every unit above 50 per cent. It decreases in value for every unit less than the standard 50 per cent. When the percentage of chromic 234 ECONOMIC GEOLOGY oxide falls below 30 per cent, it decreases at a far more rapid rate. Ores carrying from 40 to 50 per cent, of the oxide are readily marketable provided they are low in silicon. In spite of the value of the metal in its numerous alloys and its wide application in pigments the output is exceedingly small and most of the ores are imported. CHAPTER VIII USEFUL METALS CONTINUED (GROUP IV) COBALT, NICKEL, MANGANESE, ZINC Cobalt: Its Properties, Occurrence and Uses Properties. Cobalt, symbol Co, is a hard, bluish-white metal somewhat suggestive of nickel, but without its characteristic yellowish tinge. At a high temperature, unlike iron and nickel, it retains its magnetism. The metal is malleable, sectile, and very ductile when heated. In the massive form it is permanent in ordinary atmosphere but when in the pulverulent state it is rapidly oxidized. Its specific gravity varies from 8.54 to 8.7. Its melting point 1530 C. Its atomic weight is 58.97. Ores of Cobalt. Cobalt occurs in the native state in very small quantities in meteoric iron. Jaipurite, CoS, 64.6 per cent. Co. Used in enameling various shades of blue on gold and silver. Linnceite, Co 3 S 4 , 21.34 per cent. Co. If none of the cobalt were replaced by nickel the theoretical per cent, of cobalt would be 57.9. Smaltite, CoAs 2 , 28.2 per cent. Co. Usually with some nickel present. Safflorite, CoAs 2 , 28.2 per cent. Co. Nickel and iron present in varying amounts. Skutterudite, CoAss, 20.7 per cent. Co. With traces of iron. Cobaltite, CoS 2 , CoAs 2 , 35.4 per cent. Co. Erythrite (cobalt bloom), 3CoO,As 2 6 ,8H 2 0, 37.47 per cent. Co. Asbolite (black cobalt ocher). Composition variable. Cobalt is widely diffused in the igneous rocks but in much smaller quantities than its associate nickel. It is present also in both the meteoric and terrestrial iron. It has been found also in the ashes of sea weeds. Origin of the Ores. The sulphides of cobalt may be formed by either the wet or the dry processes. The arsenides of cobalt 235 236 ECONOMIC GEOLOGY according to F. W. Clarke do not represent igneous segregations. They may have been leached out from their accompanying erup- tive rocks, or may have been brought up from below. The sul- phate and carbonate of cobalt are secondary minerals. Erythrite arises from the oxidation and hydration of the arsenides and is a common mineral in the oxidized zone of ore bodies bearing cobalt as arsenides in the lower levels. Asbolite is an alteration product of cobaltiferous ores and in many respects closely resem- bles wad, or bog manganese. Character of the Ore Bodies. The principal ores occur in well- defined fissure veins traversing both intrusives and much-altered sedimentaries. The chief gangue mineral is calcite. Geographical Distribution. The cobaltiferous arsenopyrites are widely scattered along the Appalachian belt. Analyses of this variety, called danaite, from Franconia, N. H., gave 6.45 per cent, cobalt. The scattered occurrences of nickeliferous minerals in the Cordilleran section bear cobalt. The most important cobalt deposits of America are found in the Province of Ontario, Canada, near the boundary line of Quebec and west of the northern end of Lake Temiskaming. It was during the construction of the Temiskaming and Northern Railroad that the deposits of cobalt and silver minerals at Cobalt were discovered. This was followed by a similar discovery at South Lorrain and another at Gowganda. These fields have given to Ontario a position amongst the leading silver camps of the world. The geological' section at Cobalt has as its base a series of highly folded diabases, granite porphyries, etc., that are intruded by granites. This series is Kewatin in age. This series of ter- ranes is separated from the Lower Huronian conglomerates and slates by an erosional unconformity. Above the Lower Huronian rocks is a series of conglomerates, quartzites and arkoses of Middle Huronian age. Post-Middle Huronian diabases appears in sheets and sills. Above the diabases there occurs Niagara limestones and glacial drift completing the geological section. The ores occur in the conglomerates, the diabases and the underly- ing Kewatin series, although the lower formations are not so productive of silver and cobalt. According to W. G. Miller the ores were deposited by highly heated impure waters circulating through the cracks and fissures following the intrusion of the post-Middle Huronian diabase. USEFUL METALS 237 Two possible sources of the ores are suggested. (1) The metals may have been brought up from great depths by these waters. (2). The metals may have been leached out of the disturbed and folded Kewatin series of terranes. The arsenides appear to have been the first minerals deposited, after which the veins suf- fered some disturbance which resulted in the formation of cracks and minute fissures favoring the deposition of the silver at a later time. A proof that disturbance preceded the deposition lies in the fact that the silver cuts the arsenides and that the undisturbed veins are non-argentiferous. The veins are small, varying from 1 in. to 1 ft. or more in thickness. Some of them are of remarkable richness. A single sample from the Gow- ganda camp assayed by E. E. Burlingame & Co. of Denver, Colorado gave 27,066 oz. of silver per ton of ore. Geological Horizon. The commercial deposits of cobaltif- erous minerals are found in the older geological formations from the pre-Cambrian to the Ordovician. Method of Extracting. The ores are roasted, smelted into a matte, and subsequently refined by electrolysis. Uses of Cobalt. Metallic cobalt finds little application in the arts and industries. Cobalt steel has a high elastic limit and tensile strength but it is far more costly to manufacture than man- ganese or nickel steel and therefore does not possess so wide an industrial application. Cobalt is extensively used as a pigment in the manufacture of glass and pottery. The beautiful blue color known as smalt blue is imparted to the glass by the oxide of cobalt. Zaffre, the roasted cobalt ore, cobalt oxide, arsenide, phosphate and sulphate are used in the coloring of glass and the painting of porcelain. Sympathetic inks are made of cobalt acetate and cobalt nitrate. These inks are colored when heated and colorless when cold. This is said to be due to a change in the color of the salts upon the absorption of water. Cobalt and potassium nitrate are used as an oil and water pigment for painting on glass and porcelain. Cobalt nitrate is used in medicine. The salts of cobalt are an antidote for the deadly prussic acid. The nitrate of cobalt is also used in chemical mineralogy in the detection of aluminum, tin, zinc and magnesium. Cobalt is also used in storage batteries but it is expensive for that purpose. Cobalt is used in the manu- facture of gold and silver ornaments. The banner domestic production including cobalt oxide in 238 ECONOMIC GEOLOGY ore and matte came in 1903 with 120,000 Ib. Since 1908 the out- put has been included with nickel. Nickel: Its Properties, Occurrence and Uses Properties. Nickel, symbol Ni, is a lustrous white metal with a faintly yellowish tinge. The metal is ductile, malleable and sectile but extremely hard and tenaceous. It is permanent in the massive form in dry atmosphere but in the presence of moisture it quickly becomes coated with a film of the oxide, NiO. The metal is magnetic but loses this property at high temperatures. It is soluble in mineral acids. Its specific grav- ity when cast is 8.35 and 8.6 to 8.9 when rolled. Its melting point is 1484 C. Its atomic weight is 58.68 Ores of Nickel. Native nickel, Ni, 100 per cent. Ni. Often alloyed with iron. Millerite, NiS, 64.6 per cent. Ni. Occurring in capillary crystals and tufted coatings. Beyrichite, Ni 3 S 4 , 54.23 per cent. Ni. Polydimite, Ni 4 S 5 , 59.4 per cent. Ni. Pentlandite, (Fe, Ni)S, 22 per cent. Ni. Pyrrhotite, Fe n S n +i. Sometimes containing 6 per cent, nickel. Niccolite, NiAs, 43.9 per cent. Ni. Chloanthite, NiAs 2 , 28.1 per cent. Ni. Rammelsbergite, NiAs 2 , 28.1 per cent. Ni. Gersdorffite, NiAsS, 35.4 per cent. Ni. Annabergite, 3NiO,As 2 O5,8H 2 (nickel bloom). Garnierite, (Ni,Mg)O,Si0 2 ,H 2 0. Genthite, 2NiO,2MgO,3SiO 2 ,6H 2 O. To this list there might be added the terestrial minerals, awaruite, FeNi 2 , which occurs in the drift of George River, emptying into Awarua Bay on the west coast of the south island of New Zealand; Josephenite, FeNi 2 , from Josephine County, Oregon, and the nickel alloy FeNi 3 as found in the auriferous sands of the stream Elvo, near Biella, Piedmont, Italy. Origin of the Ores. Nickel occurs in both the terrestrial and meteoric irons. Some of these are best classified as nickel alloys for the percentage of nickel exceeds that of the iron. Nickel is one of the commonest of the minor constituents of the igneous rocks. According to F. W. Clarke in 262 analyses of USEFUL METALS 239 igneous rocks made in the laboratory of the United States Geological Survey an average of 0.0274 per cent, nickel oxide was found. The sulphides and the arsenides of nickel may be formed by either the wet or the dry processes. Where capillary millerite appears on dolomite crystals lining geodes it is unquestionably crystallized from solution. Where it occurs as a radiating in- crustation upon secondary minerals as in Pennsylvania, it too must be of secondary origin (Fig. 119). The origin of nickeliferous pyrrhotite is perhaps an open question. According to J. H. L. Vogt it represents a distinct segregation from a molten magma. This has long been con- FIG. 119. Evans mine, Canadian Copper Company, Copper Cliff, Ontario. (After A. E. Barlow, Canadian Geological Survey.} sidered the origin of the Sudbury, Ontario, pyrrhotite. The order of segregation has been most carefully studied by R. Bell, H. B. von Foullon, T. L. Walker, A. P. Coleman, A. E. Barlow and others. The order suggested is chalcopyrite near the wall rock, then pyrrhotite bearing nickel, and lastly nickel sulphide; the matrix being norite. According to D. H. Browne the occur- rence of the ores at Sudbury is comparable to the phenomena observed in a cooling copper-nickel matte, in which the copper sulphides concentrate along the margins of the mass, and the nickel sulphides at the center (Fig. 120). According to W. Campbell and C. W. Knight the Sudbury ores were all formed from solution. The order given is as follows : 240 ECONOMIC GEOLOGY First magnetite, then pyrite and gangue, then pyrrhotite. The mass is then fractured and in the cracks there appears pentlandite. These ores are all fractured and in the cracks thus formed chalcopyrite is deposited. According to F. W. Voit the nickel ores of Dobschau, Hungary, were deposited from solution in a gangue of calcite at or near contacts of diorite. C. R. Keyes considers the nickel mineral, linnaeite at Mine La Motte, Mo., of secondary origin. It occurs in limestones as a metasomatic replacement deposit with lead and copper. - FIG. 120. Roast yards near Victoria mine, Mond Nickel Company, Sudbury district, Ontario. (After A. E. Barlow, Canadian Geological Survey.) The famous Temiskaming mining district in Ontario was dis- covered in 1903. The sulphides and arsenides of nickel and co- balt were all formed through solutions from heated waters asso- ciated with the basic intrusives of post-Middle-Huronian age. The native silver of Cobalt and Gowganda was the last mineral to form from solution in the ore bodies for it cuts the smaltite and the gangue mineral calcite. According to W. G. Miller these deposits are analogous to those of Annaberg, Saxony, and Joachimsthal, Bohemia. The ores may represent a leaching of the accompanying basic eruptive rocks, or they may have been USEFUL METALS 241 brought up from below. At all events they are not primary segregations. Morenosite, the sulphate of nickel, and zaratite, the carbonate of nickel, are formed by the oxidation and carbonation of the sulphides and other ores of the metal. The hydrous silicates of nickel, which are rarely, if ever, definite mineral species, but rather a mixture of the silicates of nickel with magnesium compounds and free silica, are entirely unlike the sulphides and arsenides in their genesis. They form a distinct class of ores. They are associated with masses of serpentine or other hydromagnesian rocks. They represent a concentration of the nickel in a peridotite magma, but especially one rich in nickeliferous olivine. Character of the Ore Bodies. Millerite occurs as an incrusta- tion upon other minerals and as capillary crystals in cavities among quartz crystals. The nickeliferous pyrrhotite occurs as a contact deposit between quartzite and norite; also in irregular masses of large dimensions. The sulphides and arsenides appear in well-defined fissure veins traversing the basic intrusives and their adjacent terranes. Garnierite and genthite, together with other hydrous silicates of nickel occur in enormous deposits which in part result from precipitation and in part from the transition of a peridotite magma to serpentine. The deposit near Noumea, the capital of New Caledonia, is perhaps the most noted nickel-bearing ore body in the world. The ores are particularly free from sulphur, arsenic and copper, three constituents injurious to nickel. There are two distinct varieties of these hydrous silicates present. The one is green and the other is chocolate brown. The green variety carries from 45 to 48 per cent, of nickel oxide; the brown variety carries from 43 to 46 per cent, of the oxide of nickel. Both contain small quantities of cobalt. The green variety was long mistaken for the green hydrous carbonate of copper, malachite. The brown variety was thrown away as worthless earth which was supposed to be colored by the hydrated oxides of iron. The green variety is now regarded as deposited from solution from above, while the brown variety tells its tale of the transition of the country rock peridotite to serpentine. The method of mining at Noumea is simply open cut work. The ore is taken out in benches having faces about 30 ft. high so that the appearance of the quarry is not unlike the risers and 16 242 ECONOMIC GEOLOGY treads of a stairway. The ores are blended to a shipping grade, and sent to the lowlands on aerial rope ways, conveyed to the coast by ground trams, transferred to lighters, and then con- veyed to ships. The quantity of ore seems to be inexhaustible. The ores are shipped to England, France, Holland, Germany and Australia. Geographical Distribution of Nickel. There are three distinct belts of nickel-bearing ores in the United States: (1) The Ap- palachian district; (2) the Central district; and (3) The Cordil- leran section. (1) Appalachian belt: But little nickel has ever been produced in this section. The largest deposit is in Lancaster County, Pennsylvania, where the nickeliferous pyrrhotite is associated with the altered intrusive, amphibolite, encased in mica schist. J. F. Kemp regards the amphibolite as an altered gabbro or norite, and the deposit as originally magmatic. In the southern Appalachian belt in Webster County, North Carolina, the hydrous silicates of nickel appear in connection with the transition of a peridotite magma (dunite) to serpentine. The olivine of the original peridotite bears nickel. The nickel ore occurs in small fissures with talc and gymnite. (2) Central district (Mo.) comprises the Mine La Motte, Fredericktown district, which furnishes annually a small amount of nickel as a by-product from the lead industry. Nickel was mined and smelted to a small extent by the North American Lead Company. (3) Cordilleran section: This section embraces Arizona, Idaho, Oregon, Washington, and Wyoming, each of which have from time to time reported the existence of nickel-bearing minerals, but none have ore bodies that have yet assumed the dimensions of commercial importance. The most noted of these occurrences are those of Nickel Mountain, Oregon. According to H. Ries the ore is genthite associated with a quartz gangue. It occurs as a flat-lying deposit on the surface of a post-Cretaceous, pre- Eocene peridotite, or as veinlets in the peridotite and resulting serpentine. It is thought that the genthite represents an alteration product of the peridotite, for nickel has been found in the fresh peridotite. Other Districts. At Sudbury, Ontario, is by far the largest, the best known and the most important nickel-bearing ore body in America. From this nickeliferous pyrrhotite comes nearly all USEFUL METALS 243 of the nickel consumed in the United States. In fact, practically the entire production is said to be imported into the United States. However a small balance goes to England. New Caledonia, as elsewhere noted, is the largest single producer of nickel-bearing minerals in the world (Fig. 121). Nickel also occurs at Revda, southwest of Ekaterinburg, in the Urals nickelif- erous minerals in connection with antigorite serpentine which , is associated with metamorphic limestones and mica schists; also at Frankenstein, in Prussian Silesia, in association also with serpentine. FIG. 121. Main pit Creighton mine, Sudbury district, Ontario. (After A. E. Barlow, Canadian Geological Survey.) The association of the nickeliferous minerals points to one thing of especial interest. Their home is everywhere shown to be connected with the ultrabasic and basic intrusives a4, is a tungstate of manganese; reinite, FeWO^ stolzite, PbWO^ cuprotungstite, Cu- WO 4 ; scheelite, CaW0 4 , and tungstite, WO 3 . 270 ECONOMIC GEOLOGY Origin of the Ores. Wolframite is both a primary and a secondary mineral. In the Cornish tin mines, wolframite is a companion of cassiterite, the most important ore of tin. The. two minerals may appear as primary segregations. While tungsten is an annoying impurity, a by-product is obtained which is used in the manufacture of the sodium tungstate of commerce. According to J. D. Irving, wolframite occurs with cassiterite in the Etta tin district of the Black Hills, South Dakota. Primary wolframite has been observed in quartz veins cutting granite; and secondary wolframite in associated limestones, apparently formed by metasomatic replacement. At Oscola, Nevada, the tungstate of manganese is abundant in veins of quartz cutting a porphyritic granite. Scheelite, the tungstate of calcium, is also present in the same veins. Htib- nerite occurs with scheelite and wolframite in similar veins in the Dragoon Mountains, Arizona. At Trumbull, Conn., the ores are wolframite, scheelite and tungstite. At Longhill, Conn., scheelite occurs along the contact of limestones with hornblende gneiss and diorite. Scheelite occurs in the Province of Quebec in quartz veins cutting slates and sandstones. Its association is with the acid intrusives, as granites and pegmatites, rather than the ultra-basic rocks, as peridotite. Character of the Ore Bodies. Tungsten minerals occur as masses (lens-shaped) in the early segregation of an acid magma; in veins cutting acid intrusives; in limestones, by metasomatic replacement; and as contact deposits between limestones and their intrusives. Geographical Distribution. There are three belts of tungsten minerals in the United States: the New England, the Cordilleran, and the Western belt. Geological Horizon. The ores seem to be confined to the acid intrusives of the older geological formations. Method of Extraction. The metal is most easily extracted from scheelite, the tungstate of calcium. Uses. The largest and the most important use of tungsten is in the manufacture of tool steel. It imparts both hardness and toughness to the steel. It is this use which renders the mining of tungsten minerals profitable. According to F. L. Hess : " The introduction of tungsten into steel gives it the property of holding a temper at a much higher temperature than high-carbon steels. When lathe tools are made from tungsten steel, the lathes may be speeded up until the chips leaving the tool are so hot that they turn blue." THE RARE METALS 271 The percentage of tungsten in tool steel varies with the manu- facturers. Some use from 1J to 3J per cent.; others from 16 to 20 per cent, of tungsten. According to C. A. Edwards, the hard- est steel recorded contained 19.37 per cent, tungsten. Tungsten is added to steel in the form of an alloy of tungsten and iron carrying from 40 to 82 per cent, of the former metal. Alloys of tungsten with copper and aluminum are well known, and of considerable technical value. A small quantity of tungsten added to aluminum greatly improves its resistance to erosion, and increases its tensile strength. Tungsten is used in the manufacture of crucibles for electric furnaces. Powdered tung- sten is mixed with carbonaceous matter in the form of a paste, pressed into the desired shape, and sintered. Tungsten is used as a filament in incandescent electric lamps. The extreme whiteness of the light renders it far superior to that of the carbon incandescent lamp, which it is rapidly supplanting. It is far more efficient than the tantalum lamp. The drawback is the brittleness of the filament, and much material is lost in shipment. The advantages are its whiterlight, its longer life, and its use in either alternating or direct currents. Metallic tungsten has been used in arc-lamp electrodes. Tungsten is used in rendering curtains, draperies and papers fire-proof. It is used as a mordant in dyeing, also in weighting delicate fabrics. As sodium tung- state has approximately the same ratio of expansion for moderate temperatures as platinum, it is used for sealing platinum appa- ratus for making water determinations in rock analysis. Tung- sten is used as a pigment in the manufacture of glass, also of gold and violet bronze powders. Calcium tungstate is used as a screen to make X-rays visible. Economics. The production of tungsten is so closely related to that of pig iron, from which tungsten steel is manufactured, that the output for 1908 was far below that of 1907. The value of its production is as follows: 1905, $268,676; 1906, $348,867; 1907, $890,048; 1908, $229,995; 1909, $559,900; 1910, $844,526, and 1911, $407,985; 1912 ; $492,000. Titanium Properties. Titanium, symbol Ti, is a rare metal, extremely difficult to isolate in a pure state, owing to the fact that it unites directly with nitrogen, forming a nitride. Its melting point is 272 ECONOMIC GEOLOGY 3,000 C.; its specific gravity is 3.543, and its atomic weight is 48.1. Mode of Occurrence. Titanium is often catalogued as one of the rarer elements; yet it is almost invariably present in the igneous rocks, and in the sedimentaries derived from them. According to F. W. Clarke, out of 800 igneous rocks analyzed in the laboratory of the U. S. Geological Survey, 784 contained titanium. It is found in nature only in the oxidized state (Fig. 133). Olir/ne-hyperite Hornblende Rock. Mica, FIG. 133. Titaniferous apatite vein in gabbro. (After J. H. L. Vogt.) Ores of Titanium. Ilmenite, FeO, TiO 2 , is a faintly magnetic iron-black mineral, with a black or brownish-red streak. Several varieties have been recognized, based on the relation of the iron to the titanium. The true ilmenite carries from 26 to 30 per cent, of titanium. Menaccanite carries from 20 to 25 per cent, of titanium. Leucoxane is a metamorphic decomposition-product of ilmenite and its numerous varieties. It occurs as a white or reddish mineral surrounding ilmenite. Rutile, Ti02, shades in color from reddish-brown to black. It occurs in tetragonal crystals, often twinned. THE RARE METALS 273 Nigrine, TiO 2 , is a black variety, containing from 2 to 3 per cent, of Fe 2 3 . Ilmenorutile is a black variety from the Ilmen Mountains, containing 10 per cent, or more of Fe 2 03. It carries too much iron to be classified as rutile, and too much titanium for ilmenite. Octahedrite, TiO 2 , occurs in definite octahedrons of the tetrag- onal system. Brookite, TiO 2 , crystallizes in the orthorhombic system. Perovskite, CaO,TiO 2 , is a calcium titanate. Titanite, CaO,TiO 2 ,Si0 2 , often called sphene, on account of its wedge-shaped crystals. The oxide, Ti 2 0s, has not been observed as an independent mineral. Origin of the Ores. Ilmenite is widely diffused throughout both the acid and the basic intrusives, and on account of its basicity is one of the earliest minerals to segregate from a cooling magma. Leucoxane is always secondary in origin. Rutile is a common constituent of the acid intrusives, and is occasionally found in limestones, dolomites and slates. The variety octahe- drite is always of secondary origin. Perovskite is associated with both eruptive and metamorphic rocks. Titanite is a pyrogenic mineral in the older secretions of the acid intrusives, as granites, syenites, etc. Character of the Ore Bodies. The titaniferous iron ores occur in considerable quantities in the State of New York. They are mined chiefly for their iron content, and occur in more or less lens-shaped masses. Titaniferous magnetite is a common mineral in New York and New England. In Nelson County, Va., large dikes of pegmatite, sometimes hundreds of feet thick, cut a biotite gneiss. Rutile and ilmenite occur in these dikes, asso- ciated with the potassium and sodium feldspars, amphibole, hornblende, quartz and apatite. In the pegmatite itself, the titanium ores are not sufficiently abundant to become a commer- cial consideration; but the pegmatites are cut by veins or dikes of rutile, ilmenorutile, and apatite, which F. L. Hess considers as a later phase of the pegmatites. At Roseland, Virginia, in the same county, the rutile comprises about 4 per cent, of the pegmatite. The rock is crushed and concentrated together with the decompo- sition-products that overlie the pegmatite, to a product containing approximately 98 per cent. Ti0 2 . 18 274 ECONOMIC GEOLOGY Geographical Distribution. There are three belts of titanium- bearing rocks in the United States: (1) The Appalachain belt. The -maximum development occurs, as above noted, in Nelson Co., Virginia. In Chester, Pa., rutile occurs in exceptionally pure crystals, which have brought high prices for the dental trade and for museum specimens. It occurs in New York, where large quantities of titaniferous iron abound, and in Vermont, where many fine crystals of rutile have been obtained. (2) The North- ern Belt, where titaniferous ores have been mined in Minnesota in considerable quantity. (3) In Wyoming, where the ore is similar to that found in Minnesota. In foreign countries rutile is found in Norway, South Australia, and Queensland. Geological Horizon. Titanium minerals are more abundant with the pre-Cambrian, Cambrian, and Ordovician terranes than with the later geological formations. Uses. The most important use of titanium is in the manufac- ture of steel and cast-iron, to which it imparts hardness and toughness. The alloy ferro-titanium, containing 10 to 20 per cent, of titanium, is first manufactured. This is added to the molten iron so as to produce a steel bearing 0.1 per cent, titanium. Steel rails thus formed resist the wear of heavy traffic much longer than ordinary rails. Titanium-thermit is another form in which titanium is introduced into steel. Cupro-titanium is an alloy of titanium used in the manufacture of bronze and other castings containing copper. Titanium is used in the manufacture of electrodes for arc-lights. The chloride of titanium, TiCl 2 , is used in dyeing. The sulphate, ^(SOJs, is used both as a striper and a mordant. The titanous potassium oxalate is used as a yellow dye and a mordant in the treatment of leather. Ti(S04)2 is used in ihe detection of fluorine. The tile industry also utilizes rutile. It gives a soft, beautiful yellow color in tile and brick. Rutile is also used to give to artificial teeth an ivory tint. The nitride of titanium is sometimes formed in smelting titaniferous iron ores. This compound has commercial possi- bilities as a fertilizer. Rutile finds some use as a gem. ZIRCONIUM Properties. Zirconium, symbol Zr, is a rare element closely allied to titanium. Its melting point is 1500 C ; its specific grav- ity is 4.15, and its atomic weight is 90.6. THE RARE METALS 275 Ores of the Metal. Zircon, ZrSiO-i, is the most important source of the element and its compounds. Unlike the other rare minerals to which it is allied, it occurs chiefly as a silicate widely diffused in the igneous rocks. It is easily distinguished from all other minerals by its crystal form; viz., that of a tetragonal prism terminated by a tetragonal pyramid at either extremity; by its color, which shades through brown and yellow to green; and by its hardness of 7.5. Zircon is one of the least alterable of all minerals, for it contains no protoxides, and only the most insoluble of dioxides. It, how- ever, passes into the hydrous state, producing amorphous and iso- tropic species or varieties. This is effected by the loss of silica, and the addition of iron oxides through infiltrating waters. Auer- bachite, calyptolite, cryptolite, malacon, oerstedite, and tachy- aphaltite are all altered varieties of zircon. In some instances, zircon seems to have been of pneumatolytic origin. According to F. W. Clarke, it is one of the earliest minerals to crystallize from a cooling magma, and the first of all silicates to thus solidify. The varieties of zircon mentioned above are all of secondary origin, arising through the hydration and metamorphism of zircon. Beccarite is an olive-green variety of zircon from Ceylon. Braddeleyite, Zr0 2 , is an oxide of zircon found in Brazil and Ceylon. Geographical Distribution. Zircon is one of the commonest constituents of all classes of igneous rocks. It is more abundant, however, in the acid than in the basic intrusives. It is especially abundant in the granites, pegmatites, syenites, gneisses, diorites and pyroxenites, and in the younger eruptives. The most noted American locality is in Burke, McDowell, Henderson, Polk and Rutherford Counties, N. C., where it occurs in the gold- bearing monazite sands, due to the disintegration of granite and gneissoid rocks. At Grenville, Canada, it occurs in a crystalline limestone, in association with wollastonite, titanite and graphite. Geological Horizon. Zircon is not restricted to any horizon, for it occurs in the igneous rocks of all ages. Method of Extraction. Zircon is separated from its matrix by rough crushing and washing. A clean separation can be made with electrical machinery and by careful washing. A small quantity of zircon is obtained as a by-product from the monazite concentrates. 276 ECONOMIC GEOLOGY Uses. The metal is obtained in two forms, one amorphous, the other crystalline. The former burns readily in the air, the latter only at the high temperature of the oxyhydrogen flame. The oxide, ZrO 2 , is the most important salt. It is reported to have been used in the tile and pottery industries. The demand for zircon is small. It has been supplied in the United States by the intermittent working of the mines near Zirconia, N. C. The crystals of Zircon are larger in Henderson County, where they occur in pegmatites, than elsewhere when associated with monazite. The crystals of zircon are larger also in the peg- matites than they are in the granitic, gneissoid, or hornblendic rocks. Only a few hundred pounds of zircon are obtained during an entire year, and in some years there seems to be no recorded output of the mineral. Vanadium Properties. Vanadium, symbol V, is a rare element closely allied to phosphorus. It acts both as an acid and a base. The metal is permanent at ordinary temperatures, but is rapidly oxidized to V 2 O 5 when heated. Its melting point is 1680 C.; its specific gravity is 5.5, and its atomic weight is 51.2. Ores of Vanadium. Vanadinite, 3PbO, V 2 O 5 , PbCl 2 , is the most common vanadium mineral. Desdoizite, 4RO, V 2 O 5 , H 2 0. (R = Pb, Zn, in ratio 1 : 1.) Cuprodescloizite, 4RO, V 2 5 , H 2 O. (R = Pb, Zn, Cu.) Pucherite, Bi 2 0s, V 2 0s, is a vanadate of bismuth. Mottramite is a vanadate of lead and copper. Carnotite is a vanadate of uranium and potassium of some commercial significance where it occurs as canary yellow impreg- nations in the sandstones of western Colorado and eastern Utah. Roscoelite is a vanadium silicate of the mica family, where vanadium occurs displacing aluminum. The color ranges from a clove-brown to a dark greenish-brown. There are many rare minerals bearing small percentages of vanadium. These are most common in the ferromagnesian rocks. They are present in the titaniferous magnetites, and in rocks of nearly every class, whether of igneous or of sedimentary origin. Vanadium has been observed in bauxite, cryolite, rutile, peat, lignite, and in the ashes of wood. THE RARE METALS 277 Origin of Ores. Small quantities of primary vanadium may occur in the segregation of titaniferous magnetites. Carnotite occurs as impregnation deposits in sandstones. It occurs also in the pegmatite veins of Radium Hill, South Australia. Where carnotite occurs on or near partially altered vegetable matter, organic substances have acted as precipitants for vanadium. Mottramite occurs as an impregnation deposit in England, where it has attained some commercial significance. Roscoelite is found sparingly in the gold veins of Boulder County, Colorado, and in Granite Creek, California, several pounds of roscoelite were wasted in the extraction of the included gold. Geographical Distribution. Workable deposits are chiefly confined to the Cordilleran belt. Colorado and Utah are the most promising; but vanadinite ores have been produced com- mercially in Arizona and New Mexico. Geological Horizon. Small quantities of vanadium may be found in the rocks of all ages; but the workable deposits of western Colorado and eastern Utah are in Jurassic and Cretaceous sandstones. Uses. Like titanium, vanadium finds its most important use in the manufacture of steel. Even small quantities of the metal impart a remarkable toughness to the steel. In the manu- facture of steel it removes both oxygen and nitrogen, and forms carbides, with beneficent effect upon the finished product. Vanadium steel resists both shock and fatigue far better than ordinary steel. It is therefore well fitted for saws, springs, and mechanical tools in general. Vanadium is introduced into steel either as an alloy with chromium, or with manganese, or both. To these alloys nickel is sometimes added. Each metal present tends to make the resulting steel both hard and tough. Vanadi- um is also used in the manufacture of cast iron, brass and bronze. When 3 to 5 parts per 1,000 are added to steel, vanadium communicates remarkable properties. It doubles the coefficient of resistance to fracture under all circumstances (as shock, crush- ing, elongation, etc), and at the same time imparts such extreme hardness as to make it possible to reduce the armor of vessels in thickness almost one-half. The reason that the effect of 0.5 or 0.3 per cent, of vanadium is so general and intense on steel lies in the extreme avidity vanadium has for oxygen. The presence of minute traces of the metal in a bath of molten steel would lead to an immediate and absolute reduction of every trace of iron oxide. 278 ECONOMIC GEOLOGY Now, the rupture of the best prepared steel is due to traces of the oxides of Fe, even microlites of Fe 2 O 3 act like the stroke of a diamond on the thickest glass. Vanadium steel acquires its maximum hardness not by tempering, but by annealing at 700 to 800 C. A planing machine with vanadium steel cutting edges can be set at work with the greatest velocity, and even when heated at red-heat, it still continues to take off shavings of iron or casting without exhibiting any signs of exhaustion. This property is of vital importance in projectiles. The shock they receive upon striking their mark raises them to a very high tem- perature, yet vanadium steel retains all its sharpness, and its pene- trating force remains intact. Ordinary steel softens and loses its cutting power. Vanadium is destined to cause a revolution in armaments. The salts of vanadium have considerable commercial signifi- cance. F. L. Hess states that metavanadic acid is used as a substitute for gold bronze in paint; that vanadium chloride is used as a mordant in printing fabrics; that vanadium trioxide is used as a mordant in dyeing; and that vanadium pentoxide is used as a reducing agent in the treatment of organic compounds in an acid bath. This anhydride is also used in the place of platinum in the contact process for the manufacture of H 2 SO 4 , and as a photographic developer. Vanadin is a medicinal prep- aration with potassium chlorate. Vanadium salts are also used as fertilizers, in coloring glass, and in the manufacture of a water- proof black ink. Economics. The price paid for vanadic acid in 1910 was about $2.50 per pound according to purity. The price paid for the alloy ferro-vanadium was about $5 per pound of vanadium content. UEANIUM Properties. Uranium, symbol U, is a rare and heavy metal. Its melting point is 800 C; its specific gravity is 18.7, and its atomic weight is 238.5 the highest of all known elements. Ores of the Metal. Uraninite, xU0 2 , yU0 3 , with some PbO, and a little N. It crystallizes in isometric octahedrons, but usu- ally occurs massive and granular. The color varies in shades of gray, green and black. In uraninite, helium was first discovered and later polonium. Both uranium and its compounds are THE RARE METALS 279 radioactive, and uranium itself may be the progenitor of its more highly active companion, radium. The mineral is remarkable in that it presents the only instance in which nitrogen has been found belonging to the original crust of the earth. Uranniobite is the crystallized variety of uraninite in which the element nitro- gen occurs in its maximum percentage, 2.6 per cent. Broggerite, U0 2 , U0 3 , Th02, occurs in octahedral crystals. Cleveite, U0 2 ,U0 3 ,ThO 2 , Y 2 3 , the trioxide, UO 3 , is present in larger percentage in cleveite than in the preceding minerals. It crystallizes in hexahedrons, often modified by other funda- mental isometric forms. Nivenite, U0 2 , U0 3 , Th0 2 , Y 2 3 , occurs massive, velvet-black in color and is more soluble than the other varieties of uraninite. Pitchblende, U0 2 , U0 3 , is massive uraninite. Th0 2 and the rare earths are absent, while nitrogen is sparingly present, if represented at all. Coracite is an alteration product of uraninite in its transition to gummite. Gummite, (PbCa)U 3 , SiOi 2 , 6H 2 0, is an alteration product of uraninite which occurs in rounded or flattened pieces, closely resembling gum. Carnotite is cited by H. Ries as occurring in Montrose County, Colo., and also in Utah. Carnotite is a vanadate of uranium and potassium which occurs in canary-yellow impregnations in sand- stones in western Colorado and eastern Utah. It is second in importance of the uranium-bearing minerals. There are several well known hydrous arsenates and phosphates of uranium and the alkaline earth metals, but they are not of commercial significance. Origin of the Ores. Most of the minerals bearing uranium are of secondary origin. The columbates and tantalates of iron containing uranium are primary constituents of pegmatites. Character of Ore Bodies. Uraninite is sometimes obtained from metalliferous veins, but more often it is found in association with acid intrusives, granites and pegmatites. In Colorado it is obtained from a schistose granite which in places gives way to porphyry. Uranium is chemically unlike vanadium, with which it is associated in one of its most important ores; viz., carnotite. Uranium has been found in coal; in an anthracitic mineral in a pegmatite vein in Canada; in anthracitic -bitumen from Sweden; and in the ashes of seaweeds. Carnotite occurs as impregnation 280 ECONOMIC GEOLOGY deposits in sandstones. It occupies the interstices between the grains, and occurs in thin coatings in the cracks and crevices of the rocks. In some instances, lumps of several inches in thick- ness have been obtained. These lumps are very pure. Geographical Distribution. Uraninite and gamotite occur in Montrose County, Colorado, and also in Utah. Pitchblende is found in Gilpin County, Colo. Carnotite occurs in Montrose, San Miguel, Dolores, Rio Blanco, and Routt Counties, Colo., and in the eastern part of Utah. Geological Horizon. In southwestern Colorado, the carnotite deposits are in Jurassic sandstones, and in northwestern Colorado in Cretaceous sandstones. Extraction of the Metal. Uranium salts have been extracted at the Haynes plant near Cedar, Colo.; but the haul both for ore and supplies is long and expensive. The ore is of low grade, and the problem of commercial extraction is difficult. Uses. Uranium, unlike the other rare metals considered above in this chapter, does not find its most important use in the manu- facture of steel. This use will be considered later. Uranium minerals and their salts are radioactive. They have given rise to the study of radiology, and to a new method for the determination of the age of the earth through radium emana- tions. A careful study of the data published along this line places the age of the earth at approximately 100,000,000 years. A pocket-knife, keys, coins, or any piece of metal may be covered with uraninite and placed on a photographic plate in a dark room; and in a few days, upon the development of the plate, photographs of the objects will be obtained. Uranium hardens and toughens steel, like its associate, vana- dium. It is used in Germany in the manufacture of steel and ferro-alloys, and of gun-barrels. The salts of uranium are used in the manufacture of pottery glazes and iridescent glass. The double acetate of uranium and sodium is used in the determination of phosphates. Uranyl acetate is used in medicine as a precipitant for proteids, and in the chemical laboratory in the volumetric determination of zinc. In this determination, the nitrate may be substituted for the acetate. The nitrate is also used in the manufacture of glazes; in photog- raphy; in the chemical laboratory in the determination of arsenic and phosphoric acid, and in the detection of morphine. The THE RARE METALS 281 trioxide is used to paint porcelain red, and is also used in calico printing. Columbium Properties. Columbium, symbol Cb, is a rare acid-forming element, closely allied to tantalum. Its melting point is 1950 C, its specific gravity is 7.2, and its atomic weight is 93.5. Ores of the Metal. Columbite, FeO, Cb 2 O 5 , is a columbate of iron. It crystallizes in the orthorhombic system. Its color is brownish-black to black. Manganocolumbite, MnO, Cb 2 05, is a columbate of manganese, in which manganese has displaced the iron of normal columbite. Iron may be present in considerable quantity. Samarskite, R" 2 , R'" 3 , (CbTa) 6 2 i, where R" = Fe, Ca, U0 2 and R'" = Ce,Y. The mineral is a rare columbate and tantalate of iron, calcium, uranium, and the rare earth metals. Euxenite is a columbate and titanate of the rare earths. It is an altered samarskite. Pyrochlore is a metacolumbate of calcium and cerium. Fergusonite is a metacolumbate of Y, Er, Ce and U. Sipylite is a columbate of erbium. There are several other rare minerals of which columbium is a constituent. Character of the Ore Bodies. Columbite is a primary mineral, found in the acid intrusives, granites and pegmatites. In these veins single masses of columbite have been obtained weighing more than 2000 pounds. Geographical Distribution. Columbite is found sparingly in the Appalachian belt in North Carolina, Virginia, Pennsylvania, New York, New Hampshire, Connecticut and Maine. In Maine, columbite is associated with cassiterite. In New Hampshire, at Acworth, it is associated with beryl; in New York, at Green- field, it is associated with c'hrysoberyl. The Appalachian belt is scarcely of commercial significance. Columbite occurs in Colo- rado near Canon City, and at the Etta mine in the Black Hills, South Dakota. The largest masses found in America occurred in the Etta mine in association with cassiterite. Uses. The interest attached to columbium at present is due to the incandescent lamp industry. There is little if any pro- duction of columbite other than for the tantalum present, and for museum and laboratory materials. 282 ECONOMIC GEOLOGY TANTALUM Properties. Tantalum, symbol Ta, is an acid-forming element closely allied to columbium, with which it is generally associated. It is ductile, malleable, sectile, hard, tough, and readily with- stands corrosion. Its melting point is 2250 C., its specific gravity is 10.4, and its atomic weight is 181. Ores of the Metal. Tantalite, FeO, Ta 2 5 , is a tantalate of iron. It occurs in orthorhombic crystals; is black with a cin- namon-brown streak. It is the most important source of the tantalum of commerce. Manganotantalite, MnO, Ta2Os, is a tantalate of manganese, in which manganese has displaced the iron of normal tantalite to a considerable extent, if not entirely. Ixiolite is a rare tantalate of tin. Samarskite, mentioned under Columbium, is a rare mineral rich in tantalum. There are many tantalates of the rare earth metals known in mineralogy, but they are rare minerals. Origin of the Ores. Tantalite, like its associate, columbite, occurs as a primary mineral in the acid intrusives, as the granites and pegmatites. Some of the rare tantalates are decomposition- products of tantalite, and therefore of secondary origin. Geographical Distribution. Tantalite is found in practically the same localities as columbite. Massive tantalite has been found in Coosa County, Alabama; and manganotantalite of ex- ceptional purity in western Australia. The American supply is mainly obtained from Scandinavia and Australia. Separation. The columbates may be separated from the tantalates by fusion with HKS04 or KOH, and treating the fused mass with HC1 and metallic zinc. When diluted with an equal volume of water, a permanent and intense blue coloration is obtained. In the case of the tantalates thus treated, the blue color soon disappears. Uses. F. L. Hess states that the only practical use to which tantalum is put is in making filaments for incandescent electric lamps. More than twenty thousand 20-candrle-power incandes- cent electric lamp filaments can be made from a single pound of tantalum. The tantalum lamps used in America are manufac- tured from imported tantalum. The cost of the metal is more than $300 per pound. The metal is ductile, malleable, hard, tough, and strongly THE RARE METALS 283 resists corrosion. These properties ought to lead to new uses of commercial significance. A small tonnage of tantalum-bearing minerals is produced by the Western Reduction Company of Omaha, Neb. The source of the ore was near Keystone, South Dakota. Selenium Properties. Selenium is a non-metallic element closely allied to sulphur. Its association with copper, silver, lead, mercury, bismuth and thallium, together with its relation to tellurium, a semi-metallic element, has led to its consideration in this work on the metallics. Selenium is known in four allotropic modifi- cations: (1) A brick-red amorphous powder; (2) a black crystal- line powder; (3) in dark red translucent monoclinic crystals; and (4) a black, shining, brittle, amorphous mass. It is a con- ductor of electricity. The conductivity is twice as great in the presence of light as in the dark. The melting-point of selen- ium is 217; it boils at 680 C., and burns with a blue flame to Se0 2 . Its specific gravity varies from 4.26 to 4.8, and its atomic weight is 79.2. Ores of Selenium. Native selenium, Se. Selen-sulphur, SeS, an orange-red or reddish-brown mineral, consisting of mixtures of selenium and sulphur in unknown proportions. Selen-tellurium, SeTe, a blackish-gray mineral with metallic luster, consisting of selenium and tellurium in the ratio of 2: 3. Clausthalite, PbSe, a selenide of lead. Naumannite, PbSe, 13Ag' 2 Se. Another variety gives 5PbSe, Ag 2 Se; a third variety is Ag 2 Se, with 73.15 per cent, of Ag. Guanajuatite, Bi 2 Se 3 , a selenide of bismuth. Berzelianite, Cu 2 Se, a selenide of copper. Lehrbachite, (PbHg 2 ) Se, a selenide of lead and mercury. Eucairite, Cu 2 Se, Ag 2 Se, a selenide of copper and silver. Crookesite, (Cu, Ag, Tl) 2 Se, a selenide of copper, silver, and thallium. Zorgite, a mixture of the selenides of silver, lead, and copper. Origin of the Ores. The majority of the selenides are primary minerals; only a few are of secondary origin. Native selenium may be a product of volcanic emanation, like its associate sulphur. Selen-sulphur occurs in crusts with sal-ammoniac on 284 ECONOMIC GEOLOGY the Vulcano and Lipari Islands, also at Kilauea in the Hawaiian Islands. Selen-tellurium occurs with a gangue of quartz and barite in the silver veins of El Plomo, Honduras. Zorgite occurs in argillaceous schist with galenite and various copper minerals in Thuringia. Character of Ore Bodies. Selenium minerals appear in metal- liferous veins with the commoner gangue minerals, and as crusts from volcanic emanation. Geographical Distribution. Selenium minerals are rare and not widely distributed. In America they are largely confined to the Cordilleran section. Selenides appear in association with the gold ores of the Camp Bird mine near Ouray, Colorado; in the Tonopah gold ores, Nevada; near Marysville, Utah; and at Clear Lake, California; in the New Zealand gold fields; in Japan ; and in the Lipari Islands. Geological Horizon. The selenium minerals are more abun- dant in the terranes associated with the later intrusives of the Cretaceous and Tertiary ages than in the older rocks. Method of Extraction. Pyrite containing small quantities of selenium is often used in the manufacture of H 2 S0 4 . In the roasting of the pyrite, the selenium is oxidized to Se0 2 , and is carried off with the sulphur, which is oxidized to SO 2 . The selen- ium dioxide is deposited as a solid partly in the flues and partly in the chambers. These deposits are gathered and boiled with dilute H 2 S0 4 and HN0 3 or KC1O 3 to oxidize the substance completely to H 2 Se0 4 . Strong HC1 reduces the selenic acid to selenous acid, H 2 Se0 3 . Then SO 2 passed through the selenous acid precipitates the selenium as a red powder, and the SO 2 is oxidized to H 2 S0 4 . Uses. In the light, selenium is a good conductor of electricity, and on account of this peculiarity, it is used in a number of electrical devices. It has been used in telephoning along a ray of light, and in transmitting pictures, photographs, or even sounds to a considerable distance by means of a telephone or telegraph wire. It is used to light and extinguish gas-buoys automatically. This use is dependent upon the fact that selenium is a non-conductor of electricity in the dark and a good conductor in the light. Selenium is used also in measuring the quantity of Rontgen rays in therapeutiapc plications. Economics. The production of selenium from year to year is very small. It is sometimes recovered from the anode THE RARE METALS 285 slimes or mud where it is left with the gold, silver, etc., in the electrolytic refining of copper. The price per ounce is approxi- mately $2. Tellurium Properties. Tellurium, symbol Te, is a semi-metallic element, the least abundant of the sulphur group. It is brittle and possesses a metallic luster. The color is tin-white or bluish- white. It is a poor conductor of both heat and electricity. It burns with a blue flame to Te0 2 , its melting point is 446 C., its hardness is 2.2; its specific gravity is 6.25, and its atomic weight is 127.5. Ores of Tellurium. Native tellurium, Te, often with traces of selenium and gold. It occurs in hexagonal crystals, also massive. Selen-tellurium, SeTe, with the ratio of tellurium to selenium nearly that of 2 to 3. Stutzite, Ag 4 Te, is a telluride of silver with metallic luster, containing 22.5 per cent, of Te and 75 . 5 per cent, of Ag. Hessite, Ag 2 Te, is another telluride of silver, with 36.7 per cent, of Te and 63 . 3 per cent, of Ag. Petzite, (AgAu) 2 Te, is a telluride of both silver and gold. If the ratio of the silver to the gold be 3:1, the analysis would give 32.5 per cent. Te, 42 per cent. Ag, and 25.5 per cent. Au. Sylvanite, (AuAg)Te 2 , is a telluride of gold and silver. With a ratio of 1:1, the analysis would give 62.1 per cent. Te, 24.5 per cent. Au, and 13.4 per cent. Ag. Krennerite, Ag 2 Te, Au 2 Te 3 , appears to be an admixture of the tellurides of gold and silver. Calaverite, AuTe 2 , is a telluride of gold, although a part of the gold is often displaced by silver. These tellurides appear in the nature of alloys rather than definite compounds, for both tellurium and the tellurides of gold serve as a precipitant for gold. Altaite, PbTe, is a telluride of lead, with 37.7 per cent. Te and 62.3 per cent. Pb. Coloradoite, HgTe, is a telluride of mercury, with 38 . 5 per cent. Te and 61 . 5 per cent. Hg. Melonite, Ni 2 Te 3 , is a telluride of nickel, with 76.2 per cent. Te, and 23.8 per cent. Ni. Rickardite, Cu 4 Te 3 , is the telluride of copper. 286 ECONOMIC GEOLOGY There are also three well-known tellurides of bismuth: Tetradymite, Bi 2 Te 3 ; Joseite, Bi 2 Te; Wehrlite, Bi 3 Te 2 , and a sulphotelluride of bismuth, Grunlingite, Bi 4 TeS 3 . Tellurite, TeO 2 , the dioxide, is an oxidation-product of tellurium. There are complex tellurides and sulphotellurides of the precious metals that need not be mentioned here. Origin of the Ores. The most of the tellurium minerals are of primary origin. The oxide, the tellurates and the tellurites are alteration-products. Character of the Ore Bodies. The tellurides of the precious metals occur in large fissure-veins, often in pockets of immense richness. The intrusive granites are traversed by younger irruptives, with which the tellurides are connected. H. Ries states that they are not found in contact deposits. (Calaverite occurs as a coating on the walls of fissures at Cripple Creek, Colo.) Geographical Distribution. The tellurides of the metals in the United States are largely confined to the Cordilleran and Pacific Coast belts. Altaite has been found in Gaston County, North Carolina. The tellurides are found abundantly at the Red Cloud mine, Boulder County, Colorado; the Camp Bird and Torpedo-Eclipse mines in Ouray County; in many mines at Telluride and Cripple Creek, Colorado; and in the Stanislaus and Golden Rule mines in Calaveras County, California. The tellurides occur abundantly in western Australia. Geological Horizon. A little tellurium may be found in the mineral deposits of the older geological formations; but it is far more abundant in association with the Cretaceous and Tertiary formations of the west. Uses. The aluminum alloy, Al 2 Te 3 is made by melting aluminum and throwing in from time to time small pieces of tellurium. When the powdered metals are heated together, they unite with great violence. The uses of the semi-metal tellurium are few. Economics. The output is small, like that of selenium. A small amount of tellurium may be obtained in the electrolytic refining of copper, where the tellurium is deposited in the anode slime or mud, with its associates, selenium, gold, and silver. CHAPTER X i ECONOMICS The statistical portion of this book has been left for the final chapter on economics. The author refrains from giving in detail the output of the different metals by states and countries, and would refer the reader for such data to the carefully compiled statistics in the Mineral Resources of the United States and in the Mineral Industry. The order followed in this chapter in the discussion of the economic conditions surrounding the different industries and the output of the different metals is the same as that given in the main body of the work. GOLD Production in the United States. The output of gold in the United States during the present century has been fairly steady. A decrease of about $4,000,000 was suffered in 1903. A similar decrease was experienced in 1907. This was followed by a third decrease in 1910, and by a large decrease in 1912. The banner year was reached in 1909 when the production was $99,673,400. This large production was due to several causes: (1) The tendency to increased production which began in 1907. (2) To a small degree to the closing of many mines in the base metal camps which curtailed the output of lead, copper and zinc, and increased the output of gold by the shifting of labor to the placer deposits. (3) The fundamental cause of the large prosperity in the gold mining industry is the fixed and limitless demand for the yellow metal. According to H. D. McCasky of the U. S. Geological Survey, the output of gold for 1912 was $91,685,168. In 1911 it was $96,890,000. The decrease is ascribed mainly to Nevada where there was a falling off in the annual production of nearly $4,000,000, chiefly from Goldfield, but to a smaller degree also to Nation and Seven Troughs camps. The Goldfield mines pro- duced a larger tonnage of ore, but of lower grade than in the 287 288 ECONOMIC GEOLOGY preceding year. The production was delayed at Seven Troughs by a cloudburst in July and the mill at National was burned in September. On the other hand there was an increased production in the Manhattan, Fairview, and Round Mountain districts. In Colorado also there were several fluctuations in the gold mining camps. The San Juan district, which includes the counties of Dolores, La Plata, Ouray, San Juan, and San Miguel, showed a decrease of about $1,000,000. This came largely from the Camp Bird mine on Sneffels creek. The Cripple Creek district increased its output by nearly $400,000, due in part to the successful drainage by the Roosevelt tunnel. Montana, Utah and Washington each showed a decreased production. The gold mining industry in South Dakota gave the largest output in the history of the state, the increase being about $400,000 over the output of 1911, due largely to activities in the Homestake mines. The large hydroelectric plant of the company owning these mines was completed and put into operation in 1912. California retains the rank of the first producer which position she wrested from Colorado in 1911. Nevada, Alaska and South Dakota are also large producers. Gold dredging was especially active in California and Alaska where increased dredging capacity was added. The 120 dredges in operation in 10 states including Alaska produced more than $10,000,000 of gold. According to the Geological Survey, in 1911, the gold and silver mills produced 53.8 per cent, of the output, the placers 24 per cent., and the large smelting plants 22 per cent. Of the product from the gold and silver mills 26 . 1 per cent, was produced by cyanidation, 23.9 per cent, by amalgamation, and 3.8 per cent, by chlorination. Dredging alone gave 10.9 per cent. During the past few years there has been a general decline in the prospecting, and no notable discoveries of new ore bodies or deposits that seem likely to give immediate material increase to the annual output of gold have been effected. The ore bodies in some of the large camps, as at Goldfield, already show a diminu- tion in the value per ton of ore mined. Imports and Exports. According to estimates made for the Survey by the Bureau of Foreign and Domestic Commerce, the imports of gold for 1912 were valued at $61,400,000. The exports for the same year were valued at $48,600,000, The ECONOMICS 289 excess of the imports over the exports for 1912 was $12,800,000 which forms a striking contrast with the conditions in 1909 when the exports exceeded the imports by $88,793,855. The imported gold in both ore and bullion came from Mexico, Canada, England, France, Central and South America. The exports consisted of refined bullion and coin and went largely to France, South America, Canada, and Japan with smaller ship- ments to the West Indies. World's Production. According to Frederick Hobart, the gold production of the world for 1912 exceeded that of any previous year. It was an increase of $10,000,000 or 2.2 per cent, over the output of 1911. The gain in the Transvaal alone was approximately $18,225,000. The mines of Rhodesia and West Africa also showed notable gains. The total African production was $21 1 ,789,000 while the Transvaal alone produced $ 188,285,000. The Asiatic mines, especially those in the Kolar district in British India, increased their annual output. Australasia, which at one time produced nearly one-third of the world's total output of gold, now produces only 12.1 per cent, of the total. Western Australia is the largest producer in Australasia, The steady decrease in the value of the ore mined and the fact that no new gold-bearing ore bodies are being discovered are matters of moment in the consideration of the future of the industry. New Zealand also records a lessened production due to labor difficulties which it is expected will not materially affect the output of 1913. The decline in Russia was due also to labor difficulties and to the shortage of water in many of the important places, notably the Lena Gold Mining Company which in recent years has been the largest producer of Siberia. A decline was recorded also for Mexico which is attributed to the disturbed political condition of the country. The total output of gold for 1912 was $469,618,083. There has been a steady annual increase in the production of gold for the last 14 years, save in 1910 when there was a decrease of approximately $5,000,000. Since 1893 the world's annual production of the yellow metal has increased $311,180,532. SILVER Price and Production. The conditions surrounding the silver mining industry from 1908 to 1912 were not altogether satis- factory. The average price for silver in 1908 was 53 cents per 19 290 ECONOMIC GEOLOGY Troy ounce; in 1909 it was 52 cents; in 1910, 54 cents; in 1911, 53 cents; in 1912, it was 60.9 cents. While the lower prices for silver obtained, several large smelters in Utah and Colorado were partly closed or operated on a reduced capacity. This held especially true at Leadville where the ores are low grade. The conditions operating against a large output of silver from 1908 to 1911 were: (1) The low price of silver for commercial purposes. (2) The low price of copper, lead and zinc with which silver ores are so often associated. (3) The failure of India to buy as much silver as usual, a condition that was partly offset by a larger purchase on the part of China. (4) The increased production in Canada due to the more recently discovered districts of Cobalt, South Lorrain and Gowganda. The estimates of the United States Geological Survey and the Bureau of the Mint indicate a domestic silver production for 1912 of 62,369,974 fine ounces, valued at $37,982^414. This represents the largest annual output of silver for the last twenty years, although it does not represent the largest value of the period. The reports from the west indicate that when the statistics are finally completed the output will approximate 64,000,000 oz. If it reaches that figure it will represent the largest output in the history of the industry. The conditions favoring this increase for 1912 were: (1) A higher price for the metal for commercial purposes; (2) a year of general business prosperity; (3) a liberal buying in all metals during the year; (4) large purchases of silver on the part of India and (5) a notable increase in the output of copper ores, especially those of Butte, Montana, which contain considerable silver, and of argentiferous lead ores, especially of the Tintic and Park City districts of Utah; the Pioche district of Nevada; the San Juan, Leadville and Aspen districts of Colorado. There was a small decrease in the output of the Coeur d'Alene mining district in Idaho due to lower grade of ore than formerly mined. According to the Mineral Resources of the United States for 1911, Nevada was the first producer of silver with a value of $6,987,839 followed by Utah with a value of $6,611,107 and Mon- tana with $6,352,154 . In 1912 the outputs in Troy ounces were as follows: Nevada, 13,042,118; Utah, 12,795,072; Montana, 12,338,589. Imports and Exports. According to estimates made by the Bureau of Foreign and Domestic Commerce the imports of silver ECONOMICS 291 for 1912 were valued at $47,800,000. The exports for the same year were valued at $70,272,000, or $22,472,000 in excess of the imports. The imports were largely silver ore and bullion from Mexico and Canada. The exports were almost wholly in refined bullion and coin and went chiefly to the United Kingdom, although large amounts were shipped to France and China, with smaller amounts to British India. World's Silver Production. The silver production of the world in fine ounces for 1912 as given by the Engineering and Mining Journal is as follows: Mexico 76,500,000 United States 62,369,903 Canada 35,250,000 Australasia 17,950,000 Other countries 37,500,000 Total 229,569,903 As will be seen in the table given above Mexico still holds the position of the first producer and the United States the second. By a comparison of these figures with those of 1911 it will be seen that the production of Mexico decreased approximately 3,000,000 oz., while that of the United States increased approxi- mately 2,000,000. The remarkable increase during the past three years is in Canada where the production was more than 13,000,000 oz. greater in 1912 than in 1909. The one field giving rise to this condition is Cobalt where large supplies of silver ore have been opened in recent years. This field is somewhat augmented by outputs from the South Lorrain and Gowganda districts. PLATINUM Production. Some platinum of recent years has been pro- duced at the placer mines in Butte, Humboldt, Siskiyou, Trinity, Calaveras, Sacramento and Del Norte Counties, California, together with a small amount from western Oregon. Three- fourths of all the domestic platinum comes from Butte County. The most noteworthy event in the platinum industry during the present century is the discovery of the comparatively new mineral sperrylite, the arsenide of platinum, PtAs 2 , which occurs in the nickel-bearing ores of Sudbury, Ontario, and in the Rambler mine of Wyoming. 292 ECONOMIC GEOLOGY Importance is also attached to the discovery of platinum in association with several copper minerals, as covellite, the sulphide of copper, CuS. This result may lead to the discovery of platinum in other members of the copper group. The average price paid for platinum in 1912 was $45.55 per Troy ounce as compared with $43.12 in 1911 and $32.70 in 1910. With this higher price for platinum it is rational to expect a persistent search for platinum ores in the placer gravels of serpentine rocks; in the members of the copper group, and in the nickeliferous pyrrhotites. The demand for platinum is increasing faster than the supply. The newer requirements in the electrical and automobile-engine industries absorb the metal and remove it from the market entirely. The same is largely the case in the jewelry industry, while the metal used in making chemical ware is largely returned in the form of scrap platinum for manufacture. The imports of platinum for 1912 were valued at $3,634,738. No platinum seems to have been re-exported. Russia is the world's chief producer of platinum. The metal comes from the Siberian side of the Urals. The production for 1912 is estimated at 310,000 ounces. Colombia is the second producer with an output estimated at 12,000 ounces. A small amount of platinum is derived also from Canada, New South Wales, Borneo and Sumatra. LEAD Production. The value of the output in the lead industry has risen from $23,280,200 in 1901 to $43,280,460 in 1912. The increment of increase has not been steady. In 1908 the produc- tion fell 32. 56 per cent, below that of 1907. The lead produced in the United States is derived from various sources and receives different names, dependent upon its source. Primary lead signifies lead that has been produced directly from its ores. Secondary lead is derived from scimmings, drosses, old metal, alloys, as babbitt, solder, and type metal. The recovery of lead by refining these materials constitutes an integral portion of the lead industry. The business is mostly carried on by the small refineries scattered over the United States, but the large smelters and refineries working primary lead frequently incorporate material from secondary sources. ECONOMICS 293 Soft lead represents the production of the smelters in the Mississippi Valley where the ores are almost free from silver. Only one of the smelters in this district desilverizes its lead. However, a considerable quantity of soft lead ores have been annually smelted by various silver-lead smelters. A little soft lead ore is annually derived from Washington and other western states. Refined lead embraces all of the desilverized lead produced in this country and the pig lead recovered from the Mississippi Valley lead industry. Antimonial lead, or hard lead, is derived from the treatment of the gold and silver ores bearing antimony. The antimony combines with the lead as antimonial lead. The two metals are never separated, and there is a large demand for this product. There are two lead pigments produced directly from various plumbiferous ores, namely, sublimed white lead and sublimed blue lead. The former consists of lead sulphate 75 per cent., lead oxide 20 per cent., and zinc oxide 15 per cent. The latter consists of lead sulphate varying from 50 to 53 per cent., lead oxide 41 to 38 per cent., together with small proportions of lead sulphide, lead sulphite, and zinc oxide. Zinc-lead oxide con- tains from 46 to 50 per cent, of lead sulphate, frem 32 to 46 per cent, of zinc oxide, and a small amount of zinc sulphate. Leaded zinc oxide varies from 4 to 20 per cent, in its lead sulphate content, while the remainder is zinc oxide together with a small proportion of zinc sulphate. The total lead content from domestic ores averages between 7000 and 8000 short tons. Missouri is the first producer of lead followed by Idaho, Utah, and Colorado in the order of their importance. The United States produced approximately twice as much lead as any other country, followed by Spain, Germany and Mexico each of which produces more than 100,000 metric tons. MERCURY Production. The unit of measure for mercury is different from that of the other metals^ The liquid metal is put up in flasks. Each flask contains 75 Ib. The market at San Francisco determines the price. The average price per flask for 1912 was $42.04. This represents a total value of $1,057,180 for the 1912 production. 294 ECONOMIC GEOLOGY According to H. D. McCaskey the gain of 3891 flasks over 1911 shows a larger increase than was generally expected, but he does not think it implies a corresponding increase in the output of 1913. A gradual decline in the output of some of the larger ore bodies and possibly unfavorable market conditions and prospects tend toward a reduction of the output. The output of 1912 was the largest in California since 1905. The increase was due to two factors: (1) The satisfactory product of the New Guadalupe mine in Santa Clara county. (2) To increased output from several other mines. The New Idria mines in San Benito County are the largest producers in America and in fact produce nearly one-half of the California mercury. The output of these mines for 1912 was slightly less than in 1911 because attention was paid to development work rather than to increased production on account of low prices. Ore reserved for treatment when prices were at a higher level seemed preferable. Sixteen mines were producers for the year 1912 in California. Texas is also a producer of mercury. According to W. B. Phillips there were no material changes in the industry during the year 1912. The Chisos Mining Company carried their explorations into the Buda limestone that underlies the Eagle Ford shales and found about the same quality of ore as in the overlying bituminous shales. A furnace has been constructed on the property to handle a larger tonnage of lower grade ore rather than a smaller tonnage of high grade ore. In the Terlingua district the larger percentage of the ore has come from the hard, dense limestone of the Edwards formation which has yielded ore of extreme richness at comparatively shallow depths. It is Phillips' belief that the future of the mercury industry in Texas will be more intimately connected with the bituminous shales than with the associated limestones. BISMUTH Production. The production of metallic bismuth in the United States is very small. The years 1902, 1903, 1907, report no out- put whatever. The United States Metals Refining Company produces a small amount of bismuth as a by-product at its electrolytic lead refinery at Grasselli, Indiana. The bismuth is obtained in the anode muds of lead bullion. The most of the ECONOMICS 295 bismuth-bearing ores come from the Tintic district, Utah, and are smelted at Bingham Junction. Many tungsten ores are bismuth bearing. The latter metal may be recovered as a by-product when reducing the tungsten. Some bismuth is recoverable in the electrolytic copper refineries. According to F. L. Hess in 1911 one lot of bismuth-bearing ore was produced at the Comstock mine, La Plata, La Plata County, Colorado. This ore contains from 6 to 8 per cent, of bismuth but was sold for its gold and silver content. A smaller amount of higher grade bismuth ore was mined near Tularosa, New Mexico. The average price for metallic bismuth for the year was $1 . 72 per pound. The value of imported bismuth for several years has been between $300,000 and $400,000. The larger part of the supply of the crude metal comes from Bolivia, where the Aramayo Francke Mines, Ltd., is one of the large producers. The crude metal is shipped to Europe for subsequent refining. According to the Engineering and Mining Journal there will be one new producer of bismuth in 1913, viz., The American Smelting and Refining Company which has completed its plant at Omaha, Nebraska. COPPER Production. The production of copper in the United States shows a steady increase. The only large reduction in any single year came in 1907 as a result of the general financial de- pression. The output of copper for 1912 is the largest ever recorded. The copper-producing states, Arizona, Michigan, Utah, Colorado, New Mexico, and Alaska, each exceeded all former records. Montana and Tennessee nearly equalled their banner output. There is no close competitor to the United States in the produc- tion of the red metal. In fact the United States produces more than 50 per cent, of the world's supply of copper. The increased output is due to several causes. (1) The discovery and the opening of many new mines. (2) The working of old mines to their full capacity. (3) The extension of electrical works of all kinds. (4) The construction of new electrical roads. (5) The substitution of electricity on existing roads. (6) The present period of high and profitable prices. 296 ECONOMIC GEOLOGY According to B. S. Butler of the U. S. Geological Survey the output of blister and Lake copper for 1912 was 1,249,000,000 lb., which at an average price of 16 cents per pound amounts to approximately $200,000,000. The figures of the Copper Pro- ducers' Association indicate a production of refined copper from all sources, domestic and foreign, of approximately 1,500,000,000 lb. for 1912. The average price for electrolytic copper for 1912 was highly satisfactory, averaging about 16 cents as compared with 12.5 cents per pound in 1911. According to the Bureau of Statistics the imports of copper for 1912 approximated to 404,721,323 lb., which is 70,000,000 lb. in excess of the importation of 1911. The metal is imported in the forms of old copper, pigs, bars, ingots, plates, etc. The exports for 1912 were approximately 750,000,000 lb. Arizona holds the rank of the first producer. The state also holds the enviable record of furnishing a larger production than that ever recorded by any state for a single year. The output approximated 350,000,000 lb., and came largely from the Bisbee, Morenci-Metcalf, and Globe-Miami districts. Montana was the second producer with an output exceeding 300,000,000 lb. As in previous years the output came largely from the Butte district. Michigan ranks third as a copper producer. The product came largely from the old producers stimulated by the high prices for the metal. Utah, Nevada, California, New Mexico and Alaska are noteworthy producers. The output in Alaska came largely from the Copper River and Prince William Sound districts although southeastern Alaska contributed somewhat to the supply. The total output of copper for the world for 1912, as estimated by the Engineering and Mining Journal, was 1,004,844 metric tons. Of this amount the United States produced 536,747 tons, Mexico 71,982 tons, Spain and Portugal 58,000 and Japan 54,000. CADMIUM Production. The output of cadmium in the United States is small, due to the fact that its chief ore is limited in quantity and distribution, and also to the limited demand for the metal. According to C. E. Siebenthal, metallic cadmium has been ECONOMICS 297 recovered in the United States since 1907 by only one company until the latter part of 1910. Since that time there have been two producers. A small quantity of the pigment, cadmium sulphide, is also produced. The metal may be derived: (1) From the fractional distillation of zinc ores; (2) recovered as a by-product in the manufacture of lithopone; and (3) by the dry distillation or electrolysis of the slimes formed in the manufacture of zinc chloride. The chief output of cadmium comes from the zinc-producing districts of Silesia, where the metal is recovered as a by-product in the manufacture of zinc. In England a small amount of cadmium has been recovered in the purification of the solution of zinc sulphate in the manufacture of lithopone. A small amount of metallic cadmium is annually imported in the form of sticks. Also a small amount of the sulphide under the name of cadmium yellow. The total average value of these products is less than $5000 per annum. ARSENIC There was no production of white arsenic in the United States prior to 1901. Among the new industries that have been devel- oped recently is the manufacture of white arsenic as a by- product in the treatment of other ores. A pioneer in this industry was the Puget Sound Reduction Company which recov- ered arsenic from the Monte Cristo, Washington, ores. The Everett smeltery at Everett, Washington, the Washoe plant at Anaconda, Montana, and the United Smelting Company at Midvale, Utah, are among the producers of this commodity. The production suffered a decline in 1904, 1909, and in 1912. The output for 1912 was 5,852,000 Ib. in comparison with 6,162,000 Ib. in 1911. The imports of arsenic are not heavy. About 150 tons of red arsenic, As 2 S 2 , and from 50 to 75 tons of metallic arsenic and lead- arsenic alloys meet the demand for these products. Germany, France, United Kingdom, Spain, in the order of their output, produce a total of between 2000 and 3000 metric tons of white arsenic per annum. ANTIMONY Antimony for consumption in the United States is largely derived from four sources: (1) Hard lead obtained in the 298 ECONOMIC GEOLOGY smelting of foreign and domestic ores; (2) imported regulus or metal; (3) imported antimony ores; and (4) domestic ores. According to the Engineering and Mining Journal several carloads of ore were mined in 1912 in Utah, and successfully treated to recover the antimony content, but even at the present price of the metal, the mines are burdened with too expensive transporta- tion to be profitable, and they have suspended production. The bulk of antimony used in the United States must therefore be imported. The duty on the crude metal is 1J cents per pound and 1 cent per pound on the metal in ore. The average price for metallic antimony in 1912 was 8.26 cents per pound. The imports of antimony in all forms for the first 10 months of the year were 8,848,874 lb., which was an increase of 355,370 lb. over 1911. The antimony oxide produced during the year was practically all manufactured from Chinese needle antimony. TIN The production of tin in the United States is a matter of perennial interest because of the peculiar deficiency of tin deposits and the large domestic consumption. The chief interest sur- rounding the tin industry during the present century lies in the construction of a mill and smelter for the production of the metal by the El Paso Tin Mining and Smelting Company in Texas. (2) The Pahasa Mining Company has opened the old shaft of the Harney Peak Tin Company of the Southern Black Hills in South Dakota, and sampled the ore bodies to ascertain their value. (3) The increasing output of tin in Alaska. The tin for domestic consumption comes from three sources: (1) domestic primary tin, (2) secondary tin, (3) imports. According to F. L. Hess the output of tin in Alaska for 1911 was 61 tons of metallic tin valued at $52,409. The vast majority of this came from the placers on Buck Creek. A small amount came from the placers of Tofty Gulch, on Sullivan Creek, between Fairbanks and the mouth of Tanana River. The tin mine near El Paso, Texas, produced 5 tons of metallic tin. The entire output of the United States for 1911 was values at $56,635. According to J. P. Dunlop the secondary recoveries of tin form the most important domestic source of supply. Tin is recovered from the various alloys containing the metal as ECONOMICS 299 babbitt, bronze, solder, etc. It includes the tin content of products made by several plants from tin scrap as tin oxide, putty powders, but mainly tin chloride. The largest recovery of tin is made from the scruff and drosses that are formed in the manufacture of tiii and terne plate. Practically no clean scrap tin plate is wasted. A large quantity of tin is recovered in the form of tin powder by electrolytic treatment. Lesser sources of tin are tin foil, block-tin pipe, and old tin cans. The amount of secondary tin recovered from all sources in 1911 was valued at $12,353,040. The total value of the imports of tin for 1911 amounted to $43,584,219, which exceeds the value of the importation for any other year. The Federated Malay States produces more tin than all the other countries of the world combined. The order of the states in the production is as follows : Perak, Selangor, Negri Sembilan, and Pahang. Bolivia is the second producer and Banka the third. The shipments from Banka are to Holland. The output of Cornwall, England, is about 5000 short tons per annum. IRON According to E. F. Burchard of the United States Geological Survey the production of iron ores for 1912 was between 54,500,- 000 and 57,500,000 tons. The quantity represents an increase of approximately 30 per cent, over the output of 1911 which was 43,550,633 tons. A high record in the output of iron ores was established in 1910. When it aggregated 56,889,734 long tons. The percentage of red and specular hematite mined year after year is increasing. More than 90 per cent, of the iron ore mined for 1912 came from these two varieties of hematite. Limonite and magnetite in about equal proportions contributed the remainder save for a very small percentage of siderite. This mineral ordinarily contributes in America about 0.1 per cent. The Lake Superior district produces more than 80 per cent, iron ore. These ores not only supply the furnaces of the Central West but also find their way east of the Atlantic Coast. The production of the Birmingham district in Alabama was also largely increased in 1912. For this increase the Clinton hematite of the Red Mountain group was largely responsible. 300 ECONOMIC GEOLOGY The production of Tennesee, North Carolina and Virginia remained about the same as in 1911. The heavy demand for iron ores in 1912 increased mining activities in New York, New Jersey, and Pennsylvania. In these states several new mines were opened, some old mines were reopened, and some improvements were made in the con- centration of the ore to make it more available for the furnaces. The largest activity was in the Champlain district in the vicinity of Port Henry, Mineville and Dannemora. Imports and Exports. The imports of iron ore for the first ten months of 1912 were 1,741,607 tons. Of this amount more than 1,000,000 tons came from Cuba. Other contributors in the order of their importance are Sweden, Newfoundland, Canada, Spain, and Venezuela. The exports of iron ore for the same period exceeded 1,000,000 tons. The ores were mainly derived from the Lake Superior district and were shipped to Canadian furnaces. The Bureau of Statistics gives the value of the exports of iron ore for the 10 months ending Oct. 31 as $238,972,631 as compared with imports for the same period of $23,885,776. Pig Iron. According to the Engineering and Mining Journal the production the pig iron in 1912 aggregated 29,647,274 tons, thereby surpassing the production of 1910, and nearly equalling that of 1909. The production is classified as follows : Bessemer 11,740,055 Basic 11,386,176 Foundry and forge 5,965,591 Charcoal 353,266 Spiegel and ferro 202,186 Total 29,647,274 The pig iron industry in the United States during the present century has suffered three reverses due to disturbed financial conditions. The first came in 1904 in which the reduction was approximately 2,000,000 tons. The second came in 1908 with a reduction of approximately 10,000,000 tons. The third came in 1911 with a reduction of approximately 3,500,000 tons. Germany stands next to the United States in the production of both pig iron and steel. The amount approximates 13,000,000 tons of each commodity. The United Kingdom ranks third ECONOMICS 301 in the list. The output of pig iron approximates 10,000,000 metric tons, and of steel 6,000,000 tons. The United States produces nearly one-half of both the pig iron and steel of the world. The three great nations, the United States, Germany, and the United Kingdom produce approxi- mately four-fifths of the world's supply of these two most important commodities. ALUMINUM The increase in the magnitude of the aluminum industry in the United States is reflected by the fact that in 1883 the produc- tion was only 83 Ib. and in 1911 it was 46,125,000 Ib. In 1912 there was no substantial increase in the production of the metal nor any substantial change in the general manufacturing conditions. The Aluminum Company of America is at present the chief manufacturer of the metal in the United States. There were no radically new uses for the metal developed during the year. There was marketed a new electrical conductor composed of seven wires. The center wire was steel of high tensile strength. This type of cable supplies a conductor that is both light and strong for long distance transmission work. A minor new use for the metal lies in the manufacture of aluminum foil which is displacing tin foil as a wrapper for candy and tobacco. CHROME IRON ORE According to W. C. Phalen the production of chrome iron ore in 1911 was only 120 long tons valued at $1629. This, however, represents the amount actually sold. It is a reduction of almost 50 per cent, in both tonnage and value from that of 1910. The chrome iron industry has been fluctuating and is declin- ing. Prices have had a downward trend. This fact seems a little strange in the light of the quotations for tungsten and vanadium ores as ingredients in special steel alloys, one of the most impor- tant uses of a chromium. One reason for the decline lies in the wide distribution of chromite and the pockety character of known deposits free from impurities. The chrome iron ore of recent years has been produced mainly in New Caledonia, Asia Minor, Greece, Canada, India, Rhodesia 302 ECONOMIC GEOLOGY and Japan. The supply in New Caledonia is the best known but this also fluctuates in the amount and value of its production. In 1906 the production of this single field was 84,241 metric tons, but in 1907 it fell to 3800 metric tons. The output of Rus- sia where the industry centers in the Urals, and in India in Balu- chistan and Mysore, the industry is subject to the same fluctua- tions. The output of Rhodesia which is the foremost producer at present is increasing. The mines are not far from Selukwe, about 560 miles from the port of Beira. The production from Rhodesia shows that ores from deposits in a comparatively inaccessible part of the world may be placed upon the European market under conditions which enable them to compete with more favorably situated supplies. COBALT According to F. L. Hess there was no production of cobalt in the United States in 1911. A possible source of cobalt lies in the concentrates saved in extracting lead ores at Fredericktown and Mine La Motte, Missouri. A second possible source when transportation facilities are improved is near Blackbird, Idaho. The supply of cobalt for domestic consumption is said to come wholly from Cobalt, Ontario. The ores are shipped to England and the oxide imported. Cobaltiferous ores from which the oxide is also manufactured are treated by the Orford Copper Company, Constable Hook, N. Y. The interesting alloy stellite, composed of cobalt and chromium, is manufactured on a small scale for knives with stellite blades. This use appears to hold the most promising outlook for the metal. NICKEL A small amount of nickel, amounting approximately to $125,000 is saved as a by-product from the electrolytes of the copper refineries. Much of the copper refined electrolytically contains small percentages of nickel which during the process of refining the copper passes into the electrolyte. If the accumu- lation exceeds 1 per cent, it is said to be harmful to the perfect deposition of the copper. The copper thus treated comes from domestic and foreign sources, but the amount derived from ECONOMICS 303 each source is unknown. All other nickel used for domestic consumption comes from Sudbury, Ontario. In the Sudbury district nickel mining was active during 1912 and the production, the largest on record, approximately 21,000 tons. The Canadian Copper Company by a series of testing in the Frood mine is said to have proven in this mine alone the existence of 10,000,000 tons of ore. The Mond Nickel Company carried on development work on an extension of the Frood ore body. The Alexo mine in Dun- donald township shipped several thousand tons of good ore during the latter part of 1912 to the Mond Nickel Company's smeltery at Victoria Mines. The Dominion Nickel-Copper Company by a similar series of drill testings has proven the existence of about 6,000,000 tons of ore about one-fourth mile west of the old Murray mine. The imports of nickel average about $4,000,000 while the exports of nickel, nickel oxide, and matte surpass $8,000,000. MANGANESE The managanese industry in the United States depends largely upon the activities in the pig iron and steel industries. With the increased production of pig iron during the last two years there has been a greater demand for managnese ores. The production, however, has been small, averaging about 2,500 tons per year valued approximately at $25,000. Virginia and California are the principal producers. The value of the imports of managnese ores for domestic consumption exceeds $1,000,000. The annual domestic production of manganiferous ores exceeds 500,000 long tons. The Lake Superior region produced over 91 per cent, of the tonnage. The ore averages less than 6 per cent, of manganese and is used a source of high-manganese pig iron. The manganese ores of Colorado, which is the second state in rank in this industry, are used for fluxing. These ores are also argentiferous. The manganiferous ores of Batesville, Arkansas, are utilized in the manufacture of high-manganese pig iron in the blast furnaces at St. Louis, Missouri. The production of manganese- zinc residuum from New Jersey zinc ores has averaged more than 100,000 long tons per annum. These ores consist of franklinite, zincite, and willemite. In 304 ECONOMIC GEOLOGY the roasting process most of the zinc is removed, and the residuum consists largely of manganese and iron oxides. These are .used for the manufacture of ferromanganese and spiegeleisen. The largest value for this product was recorded in 1908, viz., $423,792. The manganese deposits of the Caucasus are among the richest in the world. The principal mines are at Tchiatouri in the Government of Kotais, about 126 miles from the ports of Batum and Poti on the Black Sea. England, Germany, and the United States are the largest purchasers. Smaller quantities are shipped to France and Belgium. The total exports from these shipping points during the last few years has averaged approxi- mately 500,000 tons. Manganese ores are mined in widely separated districts in India. The production now approximates 1,000,000 metric tons per annum. Some of the manganese mines in the State of Minas Geraes, Brazil, have been worked since 1894, with an annual production of about 60,000 tons. In the States of Bahia and Matto Grosso manganese ores are also mined. The Brazillian ores are estimated as sufficient to supply the world's requirements for several centuries. ZINC The principal source of zinc ores for 1912 came from the Joplin district in Missouri, the Wisconsin district, Leadville, Colorado, and Butte, Montana. According to C. E. Siebenthal of the United States Geological Survey the zinc industry for 1912, stimulated by the prevailing high price of spelter, went far beyond all preceding records in the production of spelter. The production of primary spelter from domestic ores was 323,961 short tons and from foreign ores 14,669 tons making a total aggregate of 338,630 tons. The value of this banner pro- duction is estimated at $46,731,000 which is an increase of more than $12,000,000 over the value of the production for 1911. The imports of zinc ore for 1912 were approximately 78,000 short tons, containing about 31,500 tons of zinc. This excludes 18,245 tons of lead ore from South America which contained 2,431 tons of zinc. This amount was not recovered in the smelting of the lead. The imports of spelter for 1912 were the largest for many years. The amount is estimated at 10,700 short tons and the value at $1,202,000. ECONOMICS 305 The exports of domestic zinc ores were 19,953 short tons and the export of zinc dross for the same year amounted to 203 short tons. The average price of spelter at St. Louis, Missouri, was 6.9 cents per pound as compared with 5.7 cents for 1911. The United States ranks first as a producer of spelter and is closely followed by Germany and Belgium. The world's production of spelter in 1912 was 956,335 metric tons. MOLYBDENUM There is annually a small production of molybdenum ore in the United States. The Primos Chemical Company of Primos, Pennsylvania, is the chief manufacturer of molydenum and ferro-molybdenum in this country. The price of the metal in 1912 was $1.40 per pound and of the alloy about $1 .60 per pound of its molybdenum content. The metallurgical requirement for molybdenite is 92 per cent, molybdenum sulphide. The value of such ore is approxi- mately $400 per ton. To maintain this value the ore must be reasonably free from copper as the latter is an objectionable impurity. Lower grade molybdenite ores are valued at about $1 per unit. This holds especially true if the ore concentrates to 25 per cent, molybdenum sulphide. Wulfenite which contains 25 per cent, of molybdic trioxide, MoOa, is worth about $100 per ton. TUNGSTEN According to F. L. Hess of the United States Geological Survey the amount of tungsten ores mined and marketed in the United States in 1912 was 1290 tons carrying 60 per cent, tungsten trioxide, WOs. The value of this product was estimated at $492,000. It was a substantial increase over the output of 1911. The average price per unit was $6.35. The unit is 1 per cent, of a short ton of tungsten trioxide. The largest production of any single district came from the unique ferberite deposits of Boulder County, Colorado. About 1200 tons of ore was shipped from this district. The Primos Mining and Milling Company and the Wolf Tongue Mining Company are the largest producers. 20 306 ECONOMIC GEOLOGY In California the Atolia Mining Company, which controls the Atolia field at the north edge of San Bernadino County, increased its production ofscheelite. This company is the largest indi- vidual producer of tungsten ores in the United States. A new discovery of scheelite was reported from the west side of Rand Mountains but no ore was sold during 1912. A few tons of mixed scheelite and wolframite were shipped from the vicinity of Nipton in the east end of San Bernadino County. In Arizona a few tons of hubnerite were shipped from the dry placers and some ore from the veins near Dragoon. Hubnerite was shipped also from Arivaca and scheelite from Oracle. Other small shipments were made from Nevada, Idaho, Washington, and New Mexico. URANIUM The production of uranium oxide for 1912 has been estimated by F. L. Hess as 26 short tons. This would represent approxi- mately 20 tons of metallic uranium. This was a slight increase over the production of 1911. The uraniferous ores were all carnotite, a variable compound of uranium and vanadium, from the Jura-Trias formations of the high plateau region of Colorado and Utah. The largest and richest deposits are found in Montrose County, Colorado, in Paradox Valley, Long Park, and the Mclntyre districts. In Utah the carnotite came from Emery and Grand Counties. A small amount of uraninite was mined near Central City, Gilpin county, Colorado, and sold as laboratory material. A few pounds partly altered to gummite were mined near Penland, North Carolina. VANADIUM The larger part of the vanadium ore mined in the United States in 1912 was a sage-green vanadiferous sandstone which contains the vanadium mica, roscoelite. It was mined near Newmire, San Miguel County, Colorado. The vanadium was obtained in the form of an iron vanadate at the local reduction plant of the Primos Chemical Company. The iron vanadate was shipped east to be smelted into ferro-vanadium. The price of metallic vanadium in former years has been from $4 to $5 per pound ECONOMICS 307 but in 1912 it fell to $2.50 and $2 for the vanadium contained in ferro-vanadium. The imports of roasted patronite, a vanadium sulphide, from Peru, were large and the production of ferro-vanadium probably the largest in the history of the industry. TITANIUM According to F. L. Hess there was only one American producer of rutile in 1912. This was the American Rutile Company whose mine and mill are located at Roseland, Nelson County, Virginia. This company produced in 1912, 275 tons of concentrates carry- ing from 80 to 85 per cent. Ti0 2 . The principal impurity is an iron oxide in ilmenite. The ilmenite is separated from the rutile by an electro magnet. About 100 tons of concentrates were produced in 1912, containing 94 per cent, of Ti(>2. The separated material carries from 50 to 60 per cent, of titanic oxide and 42.3 per cent, of iron oxide. The prices ranged from $30 to $100 per ton according to percentages of Ti(>2 and the quantity of the concentrates placed at one time. ZIRCONIUM The production of zirconium in the United States is limited to a few thousand pounds per annum. In 1910 there was no output recorded. The product is generally derived from the monazite sands of North Carolina. Another interesting locality is Barin- ger Hill, Texas. This locality is 12 miles north of Kingsland, the nearest railroad station. The economic interest in the rare earth minerals centers in their incandescence when heated. Thoria, beryllia, yttria, and zirconia show this property in the largest degree. Thoria and beryllia form the bulk of the incandescent oxides used in gas man- tles. They are too easily volatilized to be used in an electric glower, such as the Nernst lamp. Zirconia and yttria will stand the necessary high temperature. According to the January-March, 1913, Bulletin of the Impe- rial Institute the largest use of zirconia lies in its employment as a refractory material. Crucibles moulded from a mixture of 90 parts of zirconia and 10 parts of magnesia made into a paste with 10 per cent, of phosphoric acid are extremely resistant to 308 ECONOMIC GEOLOGY heat and practically unaffected by molten alkalis and strong acids. Starch is sometimes used as a binder. The crucibles are dried for several days and fired in a Hempel electric furnace at a temperature of 2000 to 3000 C. Owing to the low coefficient of expansion of zirconia these wares can be plunged red-hot into water without risk of fracture. A small amount of zirconium is manufactured into ferro-zircon- ium which is used in the refining of steel. COLUMBIUM The production of columbite in the United States is limited to the mining of a few hundred pounds annually for museum and laboratory material. Such a production was produced in 1911 by E. E. Hesnard, Custer, South Dakota. TANTALUM The production of tantalum in the United States is likewise small. It is derived largely for domestic consumption from the mineral tantalite. The one use which has brought tantalum into prominence has been the making of filaments for incandes- cent electric lamps. The toughness of the metal made its use popular. Within the last few years the process by which tungsten wires can be drawn has been so far improved that tantalum lamps can show little advantage in toughness over tungsten lamps. As wire for incandescent electric lamps tantalum is valued at approximately $500 per avoirdupois pound. A small quantity of tantalum is annually imported. SELENIUM The production of selenium in the United States is not large. It now averages about 10,000 Ib. The product is obtained as a by-product in the electrolytic refining of copper. The price ranges from $3 to $5 per pound. Selenium is used in the manufac- ture of enamels, glazes and red glass. TELLURIUM The actual production of tellurium in the United States is small. It can be recovered in considerable quantities in the elec- ECONOMICS 309 trolytic refining of copper. It is abundant in the Cripple Creek, Colorado, district as the mineral calaverite. It occurs also in the gold ores of the Camp Bird and Torpedo-Eclipse Mining Compa- nies in the San Juan district. In the Cripple Creek district alone more than 500 tons of tellurium has become a waste prod- uct. No practical use is known for the element and therefore there is no market. It is known however that in certain experi- ments the element has shown a peculiar behavior toward elec- tricity which seems to indicate that electrical uses may yet be found for tellurium. INDEX Alabandite, 246 Alaska, 77, 78, 155 Allemontite, 164 Altaite, 285 Aluminite, 228 Aluminum, 218 character of ore bodies, 221 extraction of, 225 geographical distribution, 222 geological horizon, 225 ores of, 218 origin of ores, 219 production of, 301 properties of, 218 uses of, 225 Alunite, 218 Alunogen, 218 Amalgam, 126 Amalgamation, 86, 98 Amonal, 227 Andrews, T., 190 Anglesite, 110, 111 Annabergite, 238 Antimonial lead, 175 Antimony, 171 character of ore bodies, 172 extraction of, 173 for domestic consumption, 176 geographical distribution, 172 geological horizon, 173 ores of, 171 origin of ores, 171 production of, 298 properties of, 171 uses of, 174 Argentite, 90 Arsenic, 164 character of ore bodies, 165 extraction of, 167 geographical distribution, 165 Arsenic, geological horizon, 167 in alloys, 170 ores of, 164 origin of ores, 164 production of, 297 properties of, 164 sources of, 167 uses of, 297 Arsenolite, 164 Arsenopyrite, 164 Arsenuretted hydrogen, 167 Asbolite, 235 Ashcroft and Swinburne, 265 Aspen, Colorado, 95 Atacamite, 135 t Awaruite, 238 Azurite, 135 B Babbitt, 174 Bahia, Brazil, 252, 252 Barlow, A. E., 239 Batesville, Arkansas, 251 Baux, France, 224 Bauxite, 218, 224, 229 metasomatic, 40 Bayley, W. S., 207, 209 Beccarite, 275 Beck, R., 136 Becker, G. F., 165 Bell, R., 39 metal, 185 Belonesite, 268 Berzelianite, 283 Beyrichtite, 238 Bingham, Utah, 154 Birmingham, Alabama, 200 Bisbee, Arizona, 150 Bischof, G., 2 Bismite, 131 Bismuth, 131 311 312 INDEX Bismuth, character of ore bodies, 132 extraction of, 133 geographical distribution, 132 geological horizon, 132 native, 131 ores of, 131 origin of ores, 131 production of, 294 properties of, 131 uses of, 133 Bismuthinite, 131 Bismutite, 131 Bismutosphaerite, 131 Black Hills, South Dakota, 62, 180 Blue lead, 125 Bolivia, 183 Bornite, 135 Boussingault, J. B., 247 Boutwell, J. M., 155 Braddelyite, 275 Branner, J. C., 224 Braunite, 246 Brochantite, 135 Broggerite, 279 Bromyrite, 90 Brookite, 273 Browne, D. H., 239 Burchard, E. F., 299 Butler, B. S., 296 Butte, Montana, 91, 146 Cadmium, 161 character of ores, 162 extraction of, 162 geographical distribution, 162 geological horizon, 162 ores of, 162 origin of ores, 162 production of, 296 properties of, 161 uses of, 162 Calamine, 257 Calaverite, 52, 285 Calomel, 126 Campbell, Wm., 97, 192, 239 Carnelly, T., 136 Carnotite, 276, 279 Cassiterite, 31, 177 Cavities, origin of, 7, 8, 9 Ceboela district, Colorado, 210 Cerargyrite, 90 Cerussite, 110 Cervantite, 171 Chalcanthite, 135 Chalcocite, 135 Chalcopyrite, 135, 136 Challenger expedition, 24 Chamberlain, T. C., 24 Chloanthite, 238 Chrome ocher, 230 Chromite, 232, 236 Chromium, 230 character of ore bodies, 231 extraction of, 231 geographical distribution, 231 ores of, 230 origin of ores, 230 production of, 301 properties of, 230 uses of, 231 Chrysocolla, 135 Cinnabar, 126, 127 Clarke, F. W., 43, 91, 132, 138, 164, 171, 177, 178, 190, 191, 194, 219, 236, 238, 246, 247, 257, 272, 275 Clarke, J. M., 198 Clausthalite, 283 Clements, J. M., 206, 209 Cleveite, 279 Clifton-Morenci district, 152 Clinton, New York, 190, 200 Cobalt, 235 character of ore bodies, 235 extraction of, 237 geographical distribution, 236 geological horizon, 237 ores of, 235 origin of ore bodies, 235 production of, 302 properties of, 235 uses of, 237 Cobaltite, 237 Cobalt, Ontario, 97, 237 Coeur d'Alene, Idaho, 95 Coleman, A. P., 192, 239 INDEX 313 Collins, J. H., 177 Coloradoite, 285 Columbite, 281 Columbium, 281 character of ore bodies, 281 extraction of, 281 geographical distribution, 281 geological horizon, 281 production of, 308 properties of, 281 uses of, 281 Comstock Lode, Nevada, 72, 95 Cook, G. H., 190 Coolgardite, 53 Copper, 135 character of ore bodies, 139 chlorination process, 158 electrolytic process, 158 extraction of, 157 geographical distribution, 140 geological horizon, 157 in Vermont, 141 native, 135 ores of, 135 metasomatic, 40 primary, 35 origin of ores, 136 oxidation process, 158 production of, 295 properties of, 135 reduction process, 157 scrap iron process, 158 uses of, 159 Copperfield, Vermont, 142, 143 Copper River district, 157 Coquimbite, 189. Coracite, 279 Cornwall, England, 32, 177, 181 Corundum, 218, 221 Cotunnite, 110 Covellite, 135 Cripple Creek, Colorado, 66 Crocoite, 110, 230 Crook, A. R., 268 Crookesite, 283 Cryolite, 218, 222, 229 Crystal Falls district, 209 Cuprite, 135 Cuprodescloizite, 276 Cuprotungstite, 269 Cuyuna district, 207 Cyanide process for gold, 87 for silver, 101 Dana, J. D., 138, 172 DaubrSe, A., 165, 190, 191 DaubrSelite, 230 Deep Creek, Utah, 46 Derby, O. A., 248 Descloizite, 276 Detrital deposits, 47 Diaspore, 218 Dieulafait, L., 246, 257 Dioptase, 135 Dip, 9 Doelter, C., 177 Doherty, W. M., 248 Dolomitization, 7 E Eckel, E. C., 201 Elba, Island of, 214 Embolite, 90 Emery, 218 Emmons, S. F., 94, 117, 118 Enargite, 135 Erythrite, 235 Eucairite, 283 Euxenite, 281 Fay, A. H., 181 Faults, 9 Federated Malay States, 181 Fergusonite, 281 Ferrochrome alloy, 233 Ferromanganese, 255 Foot wall, 12 Forschammer, G., 246 Franklin Furnace, New Jersey, 250, 259 Franklinite, 190, 257 Freiberg district, 97 314 INDEX G Gangue, 1 Garnierite, 238 Gautier, A., 165 Geikie, A., 194 Genth, F. A., 178 Genthite, 238 Georgia-Alabama district, 223 Georgetown district, Colorado, 70 Gersdorffite, 238 Gibbsite, 212, 222 Globe, Arizona, 152 Gold, 33 chlorination process, 88 cyanide process, 87 deposits, classification of, 58, 59,60 metasomatic, 40 detrital, 49 electrolytic process, 88 extraction of, 86, 87, 88 geographical distribution, 60 geological horizon, 83 occurrence of, 52 ores of, 52 origin of ores, 53 placer mining, 84 primary veins, 34 production of, 287 properties of, 52 sodium thiosulphate process, 88 uses of, 89 Goldfield, Nevada, 72 Goslarite, 257 Gossan, 4, 5 Gothite, 190, 193 Gowganda, Ontario, 97 Graton, L. C., 179 Greenockite, 162 Greisenization, 170 Griilingite, 286 Guanajuatite, 131, 283 Gumbel, C. W., 247 Gummite, 259 H Hade, 9 Hague, A., 72 Hall, James, 201 Hancock, E. T., 62, 117, 154, 208, 261 Hanging wall, 12 Hanover, New Mexico, 212 Hausmannite, 246 Hawes, G. W., 190 Haworth, E., 136 Hayes, C. W., 219, 223, 224 Hematite, 190, 195 Hess, F. L., 181, 270, 273, 282, 295 Hessite, 52, 90, 285 Hobart, F., 289 Homestake district, 62, 63, 64 Hornstein, F. F., 190 Horse, 15, 16 Hiibnerite, 269 Hussak, E., 190 Hydatogenesis, 33 Hydrozincite, 257 Iddings, J. P., 72 Igneous rocks, composition of, 3 Ilmenite, 273 Ilmenorutile, 273 lodyrite, 90 lola, Kansas, 265 Iridium, 106 Iridosmine, 107 Iron, 188 Appalachian belt, 197 character of ore bodies, 195 classes of minerals, 189 extraction of, 215 geographical distribution, 196 geological horizon, 205 impurities in, 196 metasomatic deposits, 38, 201 native, 189 ores and minerals, 189 origin of ores, 190 precipitated deposits, 41 production of, 300 properties of, 188 residual enrichment, 201 sedimentary origin, 201 uses of, 216 INDEX 315 Iron Mountain, Wyoming, 212 Irving, J. D., 64, 270 Irving, R. D., 209 Jaipurite, 235 Jenney, W. P., 258 Jerome district, Arizona, 152 Joplin, Missouri, 260, 267 Joseite, 285 Josephinite, 238 K Kalgoorlite, 53 Kemp, J. F., 190, 260 Kermesite, 171 Keyes, C. R., 1, 24, 240, 258 King, Clarence, 72 Klondike, Yukon Territory, 80, 81, 84 Knight, C. W., 239 Kotsina district, Alaska, 157 Krennerite, 52, 285 Lake Superior region, 142 Lane, A. C., 136, 142, 144, 145 Laterite, 49 Laurite, 103 Lead, 110 character of ore bodies, 111 extraction of, 122 geographical distribution, 114 geological horizon, 122 lime-roasting process, 123 metasomatic deposits, 40 ores of, 110 origin of ores, 111 precipitation process, 127 primary ores, 35 production of, 292 properties of, 110 reduction process, 122 roast-reaction process, 122 uses of, 123 Leadville, Colorado, 91, 117 Leadville minerals, 94 Le Conte, Joseph, 35 Lehrbachite, 283 Leucopyrite, 164 Leucoxane, 272 Lieth, C. K., 192, 204 Limonite, 190, 193 gossan, 204 residual, 202 Lindgren, W., 77, 136 Linnaeite, 235 Lithopone, 267 Livingstonite, 267 Lixiviation, 100 Lollingite, 164 Losses of precious metals, 108, 109 Lotti, B., 137 M MacAlister. See Thomas and Mac- Alister, 30, etc. Magnalium, 228 Magnetite, 190, 192, 195 Malachite, 135 Mallet, F. R., 248 Manganese, 245 character of ore bodies, 248 extraction of, 254 geographical distribution, 250 geological horizon, 254 precipitated ores, 41 production of, 303 properties of, 245 ores of, 246 origin of, 246 uses of, 254 Manganite, 246 Manganocolumbite, 281 Manganosite, 281 Marcasite, 189 Marquette district, 207 Massicot, 110 Maumene 1 , E., 246 McCallie, S. W., 201 McCasky, D. EL, 287 Menominee district, 209 Mercur, Utah, 26 Mercury, 126 character of ore bodies, 127 distillation of, 129 316 INDEX Mercury, extraction of, 129 geographical distribution, 128 geological horizon, 130 native, 126, 127 ores of, 126 origin of ores, 126, 127 production of, 293 properties of, 126 roasting process, 129 sublimation of, 129 uses of, 130 Mesabi Range, 204 Metamorphism, 42 Metasamosis, 35 Meteorites, content of, 25 number of, 24 Meunier, S., 177, 190, 230 Michel, L., 138 Miller, W. G., 236, 240 Minckin, 244 Mine, definition of, 20 Mineralizers, 30, 33, 40 Mineral springs, 6 Mineville, New York, 198 Minium, 110 Mississippi River belt, 115 Molybdenum, 268 character of ore bodies, 268 extraction of, 269 geographical distribution, 269 geological horizon, 269 ores of, 268 origin of ores, 268 production of, 305 properties of, 268 uses of, 269 Molybdic ocher, 268 Morenosite, 241 Morozewicz, J., 219 Mother Lode, California, 75 Mottramite, 276 Murray, J., 247 N Nagyagite, 52 Nantokite, 135 Naumannite, 283 Navarro, F., 190 Newberry and Le Conte, 119 Niccolite, 164 Nickel, 238 character of ore bodies, 241 extraction of, 244 geographical distribution, 242 geological horizon, 243 ores of, 238 origin of ores, 238 production of, 302 properties of, 238 uses of, 244 Nickeloid, 244 Nigrine, 273 Nivenite, 279 Nordenskiold, A. E., 24, 190 Nordenskioldine, 177 Noumea, New Caledonia, 241 O Octahedrite, 273 Omichen, H., 137 Orange mineral, 125 Ore bodies, enrichment of, 3, 6 Ore deposits, 1 classification of, 18 of Crosby, 18 of Kemp, 18 of Prosepny, 18 of Weed, 18, 19, 20 meteoric origin, 24 Ores, primary source of, 1, 2 Orpiment, 164, 168 Osmiridium, 102 Osmium, 106 Ouray district, Colorado, 69 Pacific Coast region, 75, 153 Palladium, 106 Paris green, 169 Pateraite, 269 Pattinson process, lead and silver, 99 Peary, R. E., 190 Penokee-Gogebic district, 209 Penrose, R. A. F., 194, 250 Pentlandite, 238 INDEX 317 Perovskite, 273 Peters, E. D., 159 Petzite, 52, 90, 285 Pewter ware, 185 Pirsson, L. V., 165 Pitchblende, 279 Placer mining, 84, 85, 86, 101 Placers, 79, 80, 81 ancient beach, 81 associated minerals, 50, 57 bench, 81 creek, 80, 81 deep lead, 50 gravel-plain, 81 gulch, 80 hillside, 81 residual, 80 river-bar, 81 sea-beach, 81 shoad, 50 sorted, 80 Platinum, 102 alloys of, 105 character of ore bodies, 102 detrital, 50 extraction of, 104 geographical distribution, 103 geological horizon, 103 native, 102 ores of, 102 origin of ores, 102 production of, 291 properties of, 102 uses of, 104 Platiniridium, 102 Pneumatolysis, 29, 30 Polianite, 246 Polybasite, 90 Polydimite, 238 Porcupine, Ontario, 83 Powellite, 269 Pratt, J. H., 219, 231 Precipitation, 41 causes of, 4 Proustite, 90 Psilomelane, 246 Pucherite, 276 | Pyrargyrite, 90 Pyrite, 189 Pyrochlore, 281 Pyrochroite, 246 Pyrolusite, 246 Pyromorphite, 110 Pyrrhotite, 189, 238 Quartz, as gangue, 1 Quebec, Canada, 199, 230 Queluz, Brazil, 248 R Rammelsbergite, 238 Ransome, F. L., 69, 122 Realgar, 164, 168 Red lead, 125 Reinite, 269 Rhodium, 107 Rhodochrosite, 246 Rhodonite, 246 Richthofen, F., 75 Rickard, T. A., 80 Rickardite, 285 Ries, Heinrich, 69, 119, 128, 132, 142, 148, 152, 165, 179, 200,224,231,242,248,250 Robertson, J. D., 258 Roscoelite, 276 Ruby, 218, 222 Russell, I. C., 201 Ruthenium, 107 Rutile, 272 S Safflorite, 235 Samarskite, 281 San Juan district, Colorado, 68 Sapphire, 218 Saucon Valley, Pennsylvania, 259 Scheelite, 269 Schmidt's law, 11 Schrivenor, J. B., 183 Secondary changes, 46 Segregation, 25 causes of, 26 order of, 26 Selenium, 283 character of ore bodies, 284 318 INDEX Selenium, extraction of, 284 geographical distribution, 284 geological horizon, 284 ores of, 283 origin of ores, 283 production of, 308 properties of, 283 uses of, 284 Selen-sulphur, 283 Selen-tellurium, 283 Selvage, 12 Semmons, W., 178 Senarmontite, 171 Shaler, N. S., 194 Siderite, 189, 196 Siebenthal, C. E., 296 Sierra region, 72 Silver, 89 character of ore bodies, 91 cyanide process, 101 electrolytic process, 101 extraction of, 98 geographical distribution, 97 geological horizon, 98 lixiviation process, 100 native, 89 ores of, 90 origin of ores, 91 primary ores, 35 production of, 290 properties of, 89 smelting process, 99 uses of, 102 Silverton district, Colorado, 69 Singewald, J. T., 210 Sippylite, 281 Skutterudite, 235 Smaltite, 164, 235 Smith, G. O., 268 Smith, W. S. T., 262 Smithsonite, 257 Smyth, C. H., 183, 201 Smyth, H. L., 207, 209 Solder, 185 Solfataras, 7 Solutions, ascending, 2 descending, 2 lateral secreting, 2 trend of, 2 South Lorrain, Ontario, 97 Spencer, A. C., 79, 259, 260 Sperrylite, 102 Sphalerite, 257 Spiegeleisen, 255 Spurr, J. E., 54, 70, 120 Stannite, 177 Steel, Bessemer, 216 Stephanite, 90 Stibnite, 170 Strike, 9 Stolzite, 110, 269 Sudbury, Ontario, 239 Swinburne. See Ashcroft and Swin- burne, 265 Tantalum, 282 character of ore bodies, 282 extraction of, 282 geographical distribution, 282 geological horizon, 282 ores of, 282 origin of ores, 282 production of, 308 properties of, 282 uses of, 282 Tellurium, 285 character of ore bodies, 286 extraction of, 286 geographical distribution, 286 geological horizon, 286 ores of, 285 origin of ores, 285 production of, 308 properties of, 285 uses of, 286 Telluride district, Colorado, 69 Tellurite, 286 Tennantite, 135 Tenorite, 135 Tetradymite, 131, 286 Tetrahedrite, 135 Thames district, 95 Thermit, 227 Thomas and MacAlister, 30, 32, 39, 112, 137, 140, 167, 172, 178, 181, 214, 225, 232, 264 INDEX 319 Thresh, M., 248 Throw, 9 Tiemannite, 126 Tin, 176 character of ore bodies, 178 extraction of, 184 geographical distribution, 178 geological horizon, 184 in Alaska, 181 in canned goods, 186 in foreign countries, 181 ores of, 177 origin of ores, 177 production of, 298 properties of, 176 uses of, 185 Titanite, 273 Titanium, 271 character of ore bodies, 273 extraction of, 274 geographical distribution, 274 geological horizon, 274 ores of, 272, 273 origin of ores, 273 production of, 307 properties of, 271 uses of, 274 Travertine, 6 Troy, Vermont, 199 Tungsten, 269 character of ore bodies, 270 extraction of, 270 geographical distribution, 270 geological horizon, 270 production of, 307 properties of, 269 uses of, 270 Tungstite, 269 Turgite, 190 Turquoise, 218 Type metal, 174 U Ural Mountains, 214 Uraninite, 278 Uranium, 278 character of ore bodies, 279 extraction of, 280 Uranium, geographical distribution, 280 geological horizon, 280 ores of, 279 origin of ores, 279 production of, 306 properties of, 278 uses of, 280 Utah, silver in, 95 Valentinite, 171 Vanadium, 276 character of ore bodies, 277 geographical distribution, 277 geological horizon, 277 ores of, 276 origin of ores, 276 production of, 306 properties of, 276 uses of, 277 Van Hise, C. R., 55, 207, 209 Veatch, A. C., 222 Veins, 11 age of, 18 fissure, 12 gash, 12 irregularities in, 15, 17 occurrence of, 13 parallel, 13 ribbon structure in, 17 richness of, 14 segregated, 12 Vermillion, district, 206 Vogt, J. H. L., 28, 46, 191, 239 Voit, F. W., 240 Voltzite, 257 W Wad, 246 Walker, T. L., 239 Waters, acidulated, 6 carbonated, 6 sulphur bearing, 7 thermal, 7, 30 Watson, T. L., 250 Weed, W. H., 18, 95, 120, 150, 165 320 INDEX Wehrlite, 286 Wells, J. W., 269 Wheeler, H. A., 258 White lead, 124 Willemite, 257, 258 Williams, J. F., 224 Wirthle, F,. 186 Wohler, F,. 225 Wolff, J. E., 260 Wolframite, 110, 268 Wurtzite, 257 X Xanthosiderite, 190 Y Yamada, K, 173 Yeats, W. S., 136 Young, C. A., 24, 191 Zinc, 256 character of ore bodies, 259 Zinc, extraction of, 265 geographical distribution, 259 geological horizon, 264 metasomatic deposits, 40 ores of, 257 origin of ores, 257 primary ores, 35 production of, 304 properties of, 256 uses of, 266 Zincite, 257 Zircon, 275 Zirconia, North Carolina, 276 Zirconium, 274 character of ore bodies, 275 extraction of, 275 geographical distribution, 275 geological horizon, 275 ores of, 275 origin of ores, 275 production of, 307 uses of, 276 Zorgite, 283 UNIVERSITY OF CALIFORNIA LIBRARY