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
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