The deposits of the useful minerals & rocks; their origin, form, and content . rrite, bismuthinite,famatinite,^ and small amounts of enargite, goldfieldite ^ with 17 per centtellurium, chalcop^Tite, galena, sphalerite, pyrargyrite, proustite, etc. Atleast 95 per cent of the gold is native, only a small portion being in com-bination. Silver is very subordinate, but 1 part occurring for every 7-5parts of gold. The most important gangue-mineral is quartz, this beingaccompanied by kaoUn, akmite, barite, selenite, and other secondarysulphates. Calcite does not occur in the lode material. After trem
The deposits of the useful minerals & rocks; their origin, form, and content . rrite, bismuthinite,famatinite,^ and small amounts of enargite, goldfieldite ^ with 17 per centtellurium, chalcop^Tite, galena, sphalerite, pyrargyrite, proustite, etc. Atleast 95 per cent of the gold is native, only a small portion being in com-bination. Silver is very subordinate, but 1 part occurring for every 7-5parts of gold. The most important gangue-mineral is quartz, this beingaccompanied by kaoUn, akmite, barite, selenite, and other secondarysulphates. Calcite does not occur in the lode material. After tremendous eruptive activity followed undoubtedly an extensive ,^^//M^^^im^ Diajnondfield Goldfie^ (Town. Alunitized area. Productive auriferous area. Fig. 305.—Plau of the C4oldfield district. The white areas are chiefly andesite,dacite, and vitrophyre. Ransonie, 1909. period of thermal activity, from which the alunitization resulted. Laterstill, probably in late Miocene or early PUocene time, a second more Umitedthermal period began, to which the introduction of the gold was the period of ore-deposition the surface has at the most been loweredabout 300 m. by erosion. The ore now occurs in irregular fissures, which,being limited along the strike, Ransome did not regard as lodes ^ but asveins.* The production, which in 1903 was small, rose in 1904-1905, and ^ Copper-antimony-arsenic sulphosalt. a 5CuS (Sb, Bi, As)2 (S, Te)3. 3 Ransome, lodes or veins. * Ransome, ledges, see Preface to Vol. I. THE YOUNG GOLD-SILVER LODES 569 still more rapidly in 1906-1907, amounting in the latter year to406,756 oz. or 12,876 kg. of gold, equivalent to $8,455,725 or £1,750,000when the small am
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
