PLACERS.
The
output of silver from the refining of placer gold was 154,968 fine
ounces in 1915, against 152,128 ounces in 1914. Seventy-eight per cent
of the production was from Alaska and California.
DRY AND SILICEOUS ORES.
The
mine production of silver from dry and siliceous ores in 1915 was
25,709,505 fine ounces, against 27,812,235 ounces in 1914. About 54
]x>r cent of this was from Nevada (chiefly from the Tonopah
district) and 20 per cent was from Colorado (mainly from the
Leadville, Upper San Miguel, and Sneffels districts). New Mexico,
Montana, and Utah also each produced more than 1,000,000 ounces of
silver from this source. Texas was one of the largest producers of
silver from siliceous silver ores.
A
large part of the silver from gold-silver siliceous ores is obtained
with the gold by amalgamation and cyanidation in the mills, and the
silver is recovered by refining the mill bullion. The remainder is
p
roduced by smelting the richer ores and refining the copper or lead bullion produced.
COPPER ORES.
The
mine production of silver from domestic copper ores in 1915 was
18,781,365 fine ounces, against 14,829,828 ounces in 1914. The
increased production of silver from copper ores mined in Alaska,
Arizona, Utah, Montana, and New Mexico amounted to 4,375,154 ounces.
The
production of silver from copper ores is from the 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 and conglomerate matrix), and a greater tonnage
contains chalcocite than chalcopyrite or cupriferous
S
pyrite. The great
disseminated copper deposits of Utah, Arizona, Nevada, and New Mexico
are of increasing importance, and the lode deposits of Butte, Mont.,
have long been famous. The sdver tenor of the extensive Chino
disseminated deposits of the Santa Rita district, N. Mex., is notably
low, but similar deposits elsewhere add largo quantities of silver.
Deducting
the copper ore from Michigan and the silver recovered in refining the
metal derived therefrom it is shown that 30,973,166 tons of copper ore
yielded 18,195,432 ounces of silver, or slightly less than 0.6 ounce
per ton.
In
output of silver from copper ores Montana continued to lead with
8,819,772 ounces in 1915, against 8,015,694 ounces in 1914; Arizona
followed with 4,010,510 ounces in 1915, against 2,604,371 ounces in
1914; Utah ranked third with 2,065,661 ounces in 1915, against
1,726,230 ounces in 1914; and California produced 1,056,895 ounces in
1915, against 703,042 ounces in 1914. The production of Montana : is
mainly from Butte, that of Arizona has been chiefly from Bisbee and
Jerome, that of Utah from Tintic and Bingham, and that of California
from Shasta County. Of these districts Bisbee well represents the
