Ch. 1: Gold and Silver in 1912

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266                                    MINERAL RESOURCES, 1912.
Tonopah, Nev.). The rich surface outcrops, mainly of chloride silver ores, found and worked in the arid West in the early days, have long since been exhausted in explored territory, and there appears little likelihood of further extensive supply from new finds. Deeper sil­ver deposits may of course at any time be found. With high prices of silver, old silver producers closed down 20 years ago in the West may be reopened and prove productive again.
The Nevada output is mainly from tha Tonopah district, and the Colorado production is chiefly from the Leadville, Upper San Miguel, and Sneffels districts. As shown later, a large part of the output of silver from the gold-silver siliceous ores is with the gold by amal­gamation and cyanidation and the metals are separated in refining the gold. The remainder is produced by smelting the richer ores, and the silver is then recovered in the refining of the copper or lead bullion.
COPPER ORES.
The production of silver from copper ores was 18,744,661 fine ounces in 1912, against 16,759,638 ounces in 1911, corresponding to a similar increase in 1911.
The silver production from copper ores is from electrolytic refin­ing of Lake and blister copper produced by smelting. The copper ores are mainly sulphides (except the Lake ores of Michigan, which are native metal in amygdaloid or conglomerate matrix), and a greater tonnage contains chaicocite, chiefly secondary, than primary chalcopyrite, or cupriferous pyrite. The great disseminated copper deposits of Utah, Arizona, Nevada, and New Mexico are of constantly increasing importance. The silver content per ton of the extensive Chino copper deposits of Santa Rita, in New Mexico, however, is notably low. Copper ores are mainly concentrated before smelting. Oxidized copper ores of decreasing relative importance, which are sought for largely as fluxing ores and commonly smelted crude, still come from the Bisbee and Tintic districts.
In output of silver from copper ores Montana led, as in 1911, with 10,655,055 ounces, against 9,597,752 ounces in 1911 and 9,153,590 ounces in 1910; Utah followed with 2,542,381 ounces in 1912, against 2,377,946 ounces in 1911; and Arizona ranked third, with 2,378,593 ounces, against 2,136,121 ounces in 1911. As seen, all of these States showed increased silver output from copper ores. The output from this source has fallen off in recent years in California and Colorado. In Idaho, Nevada, Michigan, and New Mexico, increased yields were recorded for 1912. The production from Montana is mainly from Butte, that of Utah from Tintic and Bingham, that of California from Shasta County, and that of Arizona from Bisbee and Jerome. Of these districts Bisbee alone represents the disseminated type, and output from these ores is still chiefly from deep lodes.
LEAD ORES.
The silver production from argentiferous lead ores in 1912 was 16,632,377 fine ounces, against 15,596,638 ounces in 1911. The output from Idaho increased from 7,059,990 fine ounces in 1911 (an
Ch. 1: Gold and Silver in 1912 Page of 93 Ch. 1: Gold and Silver in 1912
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US Geol. Surv. 1912. Gemstones, Metals.
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