DRY AND SILICEOUS ORES.
The
output of silver from dry and siliceous ores was 25,205,749 fine ounces
in 1911, against 23,125,042 fine ounces in 1910. The most notable gains
were in Utah, from 548,498 ounces in 1910 to 2,569,157 ounces in 1911,
and in Nevada, from 11,763,012 ounces in 1910 to 12,830,194 ounces in
1911. Other increases in output of silver from this source were in
California, from 257,355 to 291,896 ounces; in New Mexico, from 708,762
to 1,183,265 ounces; in South Dakota, from 117,333 to 183,317 ounces;
in Texas, from 379,402 to 422,870 ounces; and in Washington, from
194,078 to 202,768 ounces. Decreased production was notable in
Colorado, from 6,117,719 ounces in 1910 to 5,096,026 ounces in 1911;
and in Montana, from 2,139,405 to 1,613,253 ounces.
In
order of production from this source the first five States ranked as
follows in 1911: Nevada, Colorado, Utah, Montana, and New Mexico.
With
a few notable exceptions, where there are mines producing true silver
ores, as in San Bernardino County, Cal., the dry or siliceous ores are
gold-silver or silver-gold ores (the latter notable at 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 the Tonopah district, and the Colorado
production is chiefly from the Leadville, Upper San Miguel, and
Sneffels districts. As shown already, 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 16,759,638 fine ounces in
1911, against 16,024,543 ounces in 1910, corresponding to an increased
copper output 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 amvgdaloid or conglomerate matrix), and a
greater tonnage contains chalcocitc, 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 deposits of Santa Rita, in New Mexico, however, are notably low
in silver, as is shown in another table. 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 with 9,597,752 fine
ounces in 1911, against 9,153,590 ounces in 1910; Utah followed
