The Enrichment of Ore Deposits, Issue 625

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U.S. Government Printing Office, 1917 - Ore-deposits - 530 pages
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Page 386 - Geol. Survey Bull. 9, 1903. Bain. HF, Zinc and lead deposits of the upper Mississippi Valley : US Geol. Survey Bull. 294, 1906. Cox, GH, Lead and zinc deposits of northwestern Illinois : Illinois
Page 231 - replacement of limestone and genetically associated with metamorphism of a kind usually attributed to the contact action of intrusive rock, (2) metasomatic vein deposits in altered limestone, and (3) metasomatic vein deposits in granodiorite. To the first or contact-metamorphic class belong the deposits worked by the Bluestone, Mason Valley, and other mines. In the
Page 482 - Alunite, K 2 O.3A1 2 O 3 .4SO 3 .6H 2 O, is a white or faintly pink mineral which in some of its occurrences closely resembles kaolin and sericite. It is formed from either hot or cold solutions. It is not known to have formed under high temperature and great pressure. The alunitic deposits of Goldfield,
Page 356 - In deposits carrying both metals, especially where chlorides form, secondary silver minerals are likely to be precipitated as bonanzas near the surface, while gold may be carried to greater depths. Examples are deposits of Mohave, Cal. (Exposed Treasure mine), Creede, Colo. (Amethyst lode), and probably the Comstock lode, Nevada, although in the Comstock district
Page 329 - The ores, though uniformly of low grade, are very profitable. Some of the ores at the surface were below the average tenor, while other surface ores were two or three times as rich as the average. The valuable minerals extend downward as far as exploration has gone and are fairly uniform to depths
Page 45 - and by Finch, 4 the lower levels of many deep mines are dry. THE LEVEL OF GROUND WATER. The terms " water table" and "level of ground water" are generally used to describe the upper limit of the zone in which the openings in rocks are filled with water. This upper limit of the zone of
Page 189 - with it. There is no evidence that any of the bornite Is of secondary origin. It is therefore believed that in the Virgilina district the greater part of the chalcocite is a primary mineral contemporaneous with the bornite and in no way
Page 13 - The place of the bed of copper ore marks the limit of the decomposition of the vein ; beneath It the ore exists in its original condition. The depth at which the gossan terminates is nearly coincident with the water level or the point where, In sinking, water is found in considerable quantity. The
Page 249 - The ore minerals are bornite and chalcocite. They are chiefly in quartz, but are not confined to any one of the gangue minerals. Bornite is in slight excess over chalcocite and is apparently of only one period of deposition. Chalcocite is of two
Page 237 - The climate is moist. The prevailing rocks of the district are sandy schists and graywackes. with which are interbedded mica schists. The dominant series is the metamorphosed product of an association of sedimentary beds, including conglomerate, grits, sandstones, and shales. The beds grade into one another along the strike and across the bedding. They contain small bodies of pegmatites

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