Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/488

Rh 470 [MINERAL PRODUCE OF but it went as low as 10,000 flasks in 1850, and rose to 53,000 flasks five years later; from this it declined to 15,000 flasks in 1875, though in the following year it grew to 75,000 flasks. Last year we produced 59,000 flasks. &quot; Gold is the only metal in which our production has been declining. In 1852 it amounted to $60,000,000 ; but, with some fluctuations, it lias now declined to less than $32,000,000 annually. &quot; The production of silver, on the contrary, has largely increased. Commenc ing in 1859 with $100,000, it has now attained $45,000,000. In 1877 only were these figures exceeded, and then only by about $1,000,000. &quot; The production of petroleum, that great American industry, has grown with wonderful rapidity. In 1859 it commenced with only 3000 barrels, and, after an almost uniform increase, it attained last year the enormous figures of 27,000,000 barrels. Scientific investigation has recently raised a note of warning in this Industry, asserting the limited area of oil-producing territory and its approaching exhaustion.&quot; Some valuable statistics concerning the production of the precious metals in the. United States are contained in a report issued by the Census Bureau. 1 The output for the year ended 31st May 1880 is summed up as follows : Gold. Silver. Total. Ounces. Value. Ounces. Value. Value. Deep mines.... Placers 1,033,974 580,767 $21,374,152 12,005,511 31,717,297 80,177 $41,007,296 103,661 62,381,448 12,109,172 All mines 1,614,741 33,379,603 31,797,474 41,110,957 74,490,620 The State producing the greatest value is Colorado, viz., $19,249,172, or gold 130,607 oz. and silver 12,800,119 oz. ; Cali fornia comes next, having produced $18, 301, 828 of bullion, and then Nevada, with $17,318,909 of bullion. The greatest gold producer among the States and Territories is California, with 829,676 oz. of gold, half from deep mines and half from placers. Next follows Nevada, with 236,468 oz. of gold, of which only about 1 per cent, came from placer mines ; then Dakota, 159,920 oz. of gold, nearly entirely produced by deep mines ; and in the fourth rank Colorado, 130,607 oz., with a placer production of less than 5000 oz. The greatest silver producer is Colorado, with 12,800,119 oz. ; then Nevada, 9,614,561 oz. ; then Utah, 3,668,365 oz.; Montana, 2,246,938 oz. ; and fifthly Arizona, 1,798,920 oz. It is useless within the limits of this article to attempt to convey hn adequate idea of the enormous mineral resources of the United States. We can merely very briefly allud-e to some of the principal deposits, which are of commercial value on account of their magni tude, of scientific interest owing to their mode of occurrence, and of technical importance as having led to the introduction of consider able improvements in the arts of mining, milling, and dressing. Among these may be mentioned the coal and anthracite mines and oil wells of Pennsylvania, the gold and quicksilver mines of California, the silver mines of Nevada, the lead and silver mines of Colorado, and the copper mines of Lake Superior. The articles COAL (vol. vi. p. 60) and GOLD (vol. x. p. 743) may be referred to for information concerning the occurrence of these minerals and the method of extracting gold by hydraulic mining and improved stamping machinery. Quicksilver in the form of native mercury and cinnabar occurs in considerable abundance in California, and much of it is found in connexion with serpentine, either in the serpentine itself or in sand stone near its junction with serpentine. The most important mines are those of New Almaden in the southern part of the State near San Jose. The deposit at Sulphur Bank in Lake County is of much geological interest. It consists of native sulphur, gypsum, and cinnabar in a decomposed andesitic lava close to an extinct geyser from which boiling water still issues. The top of the bank was worked open-cast for sulphur, and then for sulphur and cinnabar, and now underground mining is carried on in stratified sandstone and shale impregnated with cinnabar and underlying the lava. Some of the most marvellous silver mines in the world are those upon the Comstock lode in Nevada. A horizontal section of part of this great vein is shown on Plate IV., copied from the excellent and well-known report of Mr J. D. Hague. 2 The strike is nearly north and south, and the dip about 43 to the east. &quot; The vein matter of the Comstock consists of crushed and decomposed country rock, clay, and quartz.&quot; &quot;Up to January 1, 1880, the Comstock had yielded in twenty years about $325,000,000 worth of bullion. The total length of shafts and galleries is about 250 miles. The number of men employed in the mines in January 1880 was 2800, earning average wages* of $4 a day. At the same date 340 men were at work in the amalgamating mills.&quot; 3 The heat of the Comstock lode is remarkable. On the 2700 feet level of the Yellow Jacket mine Mr Becker found the temperature of the water to be 153, that of the air 126 ; whilst the water in the Yellow Jacket shaft at a depth of 3065 feet has a temperature of 170 Fahr. 4 1 Clarence King, special agent of the Census, Statistics of the f reduction of the Precious Metals in the United Stales, Washington, 1881, p. 69. 2 United States Geological Exploration of the Fortieth Parallel, vol. in., Mining Industry, Atlas, plate 11. 3 Clarence King, First Annual Report of the U.S. Geological Survey P 39 During the last few years the Comstock lode has been falling off in productiveness. In 1876 the total yield of the Comstock lode was $38,572,984 (gold, $18,002,906; silver, $20,570,078). During the census year ending May 31, 1880, the product of the whole Comstock district, including outlying veins, was $6,922,330 (gold, $3,109,156; silver, $3,813,174), showing a decline of $31,650,654, or 82-06 per cent., since 1876. B Though the extraction of silver from its ores may be regarded as the business of the metallurgist rather than of the miner, we must not forget to mention that it is to the necessities of the treat ment of the Nevada ores that we owe the system of pan amalgama tion first developed in that State and practised since in Colorado. Another district in Nevada which cannot be passed over in silence is that which contains the Eureka and Richmond mines, which are celebrated, not only for the silver they have produced, but also for the important trial in which the issue hinged upon the defini tion of the term vein or lode (p. 441). The bullion produced in the Eureka district from ore raised and treated during the census year ended May 31, 1880, was gold, 62,893 oz. ; and silver, 2,037,666 oz. ; worth altogether $3,934,621. 6 The history of Leadville in Colorado seems like a romance when we read of the rapid development of the mines, the creation of a large and important town, the erection of smelting works and the building of railways, under very adverse conditions, in the heart of the Rocky Mountains, all within the space of four or five years. It affords additional proof that the miner is the true pioneer of civilization. The main facts concerning the Leadville deposits are admirably summed up by Mr S. F. Emmons, from whose report 7 we borrow, not only the following facts, but also the geological section across the district (Plate IV.). The principal deposits of the region are found at or near the junction of the porphyry with the Blue limestone, which is the lowest member of the Carboniferous formation. This bed is about 150 or 200 feet thick, and consists of dark blue dolomitic limestone. At the top there are concretions of black chert. The porphyry occurs in intrusive sheets which generally follow the bedding, and almost invariably a white porphyry is found overlying the Blue limestone. This porphyry is of Secondary age ; it is a white homo geneous-looking rock, composed of quartz and felspar of even granular texture, in which the porphyritic ingredients, which are accidental rather than essential, are small rectangular crystals of white felspar, occasional double pyramids of quartz, and fresh hexa gonal plates of biotite or black mica. Along the plane of contact with the porphyry the limestone has been transformed, by a process of gradual replacement, into a vein consisting of argentiferous galena, cerussite, and cerargyrite mixed with the hydrous oxides of iron and manganese, chert, granular cavernous quartz, clay, heavy spar, and &quot;Chinese talc,&quot; a silicate and sulphate of alumina. The vein seems to have been formed by aqueous solutions, which took up their contents from the neighbouring eruptive rocks and brought about the alteration of the limestone as they percolated downwards through it. In Carbonate Hill, a gradual passage may be observed from dolomite into earthy oxides of iron and manganese. The masses of workable ore are extremely irregular in shape, size, and distribu tion. They are often 30 to 40 feet thick vertically, and occasionally 80 feet, but only over a small area. The rich ore bodies are common est in the upper part of the ore-bearing stratum. At Fryer Hill the Blue limestone is almost entirely replaced by vein material. In the census year ended May 31, 1880, Lake County, Colorado, which includes the Leadville district, produced 28, 226 gross tons of lead, with 3830 oz. of gold and 8,853,946 oz. of silver, of a total value of $13, 032,464. 8 The most important copper mines of the United States are those on Lake Superior, where the native metal occurs &quot;in veins, in large masses, or scattered more or less uniformly in certain beds which are either amygdaloid or conglomerates.&quot; 9 The copper-producing districts are those of Ontonagon, Keweenaw County, and Portage Lake. The last-named contains the famous Calumet and Hecla mine, which alone produced 15,837 tons of copper in 1880, or about half the entire output of the United States. The deposit from whence this vast amount of copper was obtained is a bed of conglomerate, generally called a vein, dipping about 38 north west. It has been worked for a depth of 2250 feet on the incline. In 1875 the stuff stamped yielded 4i per cent, of copper. In conclusion, we will point out that the value of the mining industry in the United States exceeds that of any other country in the world, Mr Porter estimating it for 1879-1880 at 360 million dollars, and that of Great Britain at 325 millions. 10 Germany holds s Clarence King, Statistics of the Production of the Precious Metals in the United States, Washington, 1881, p. 19. 8 Op. cit., p. 21. 7 Abstract of a Report upon the Geology and Mining Industry of Leadcille, Colorado, Washington, 1882. 8 Clarence King, op. cit., p. 47. 9 Charles E. Wright, commissioner, Annual Report oj the Commissioner of Mineral Statistics for the State of Michigan for 1880, Lensing, Michigan, 1881. 10 Robert P. Porter, The West from the Census of 1880, Chicago and Londcn 1882, p. 19.
 * Op. tit., pp. 44. 4, r &amp;gt;.