silver as a by-product from refining copper produced from magnetic separation of the iron ores.
The silver output of Maryland and Pennsylvania combined in 1912 was 502 fine ounces against 87 ounces in 1911.
IDAHO.
Gold.—The
gold production of Idaho was $1,381,214 in 1912, against $1,372,387 in
1911. The deep mines produced $749,185 in gold, chiefly from gold and
gold-silver siliceous ores but also as a byproduct from lead and
copper ores. The placers produced $632,029, of which about 76 per cent
was won by dredging, and the remainder chiefly by sluicing. At gold and
silver mills 12,852.03 fine ounces of gold were produced by
amalgamation and 14,163.86 ounces by cyanidation. Crude ore shipped to
smelters contained 5,143.40 ounces of gold in 1912, and concentrates
4,004.26 ounces. Boise County led in gold output with $502,277, of
which $453,309 was produced chiefly by dredges in the Boise Basin, and
was followed by Owyhee County with $289,255, of which $288,465 was
produced by deep mines, and by Lemhi County with $225,473, of which
$144,379 was produced by deep mines. Dredging has been active in Boise,
Lemhi, and Clearwater counties, and production has offset decrease from
other sources of gold mining.
Silver.—The
production of silver in Idaho in 1912 increased to 8,294,745 fine
ounces from 8,196,136 ounces in 1911. A considerable increase was made
in output from copper ore, and a large decrease from siliceous ore. The
bulk of the output of silver in Idaho is from the lead ore of the great
Ccsur dAlene mines in Shoshone County, which produced over 6,650,000
ounces in 1912. Lemhi County also produced nearly 350,000 ounces,
almost entirely from lead ores, and ranked second in county output of
silver. Shoshone County produced in all 7,558,314 ounces of silver in
1912, of which 378,764 ounces were from copper ores of the Coeur
d'Alenes. Of siliceous ores the output was 232,583 ounces, of which
207,835 ounces came from Owyhee County. Crude ore shipped to smelters
from Idaho contained 2,679,943 ounces of silver in 1912, and
concentrates shipped contained 5,402,543 ounces, of which 4,857,676
ounces were from lead concentrates.
MICHIGAN.
Silver.—The
Michigan copper mines produced 528,453 fine ounces of silver in 1912,
against 497,281 ounces in 1911. The silver output is mainly -from the
electrolytic refining of he copper produced, and as this refining may
proceed at a different rate from the mining there is no direct relation
between the silver production and the mining industry. The average
recovery of silver per ton of "rock" treated in 1912 (both conglomerate
and amygdaloid) was 0.05 ounce, against 0.04 ounce in 1911 and 0.03
ounce in 1910. Of the total output, Houghton County produced 475,453
ounces in 1912, against 459,715 ounces in 1911; and Keweenaw County,
53,000 ounces in 1912, against 37,053 ounces in 1911.
MISSOURI, ILLINOIS, AND KENTUCKY.
Silver.—The
lead and zinc mines of the Central States contribute no gold and but
little silver. This last is a by-product, mainly from
