MICHIGAN.
Silver.—The
copper mines of Michigan produced 585,933 fine ounces of silver in
1915, against 413,500 ounces in 1914. The silver was mainly derived
from the electrolytic treatment of 52,509,000 pounds of copper. The
average recovery of silver per ton of "rock" treated was 0.29 ounce a
ton. Of the total output of silver 511,224 ounces came from mines in
Houghton County.
MISSOURI, OKLAHOMA, ILLINOIS, KENTUCKY, AND WISCONSIN.
Silver.—The
lead and zinc mines of the Central States produce no gold and only a
comparatively small quantity of silver. Nearly all the silver is a
by-product from the refining of lead from concentrates of lead ores
mined in southeastern Missouri. The total yield of silver from Missouri
in 1915 was 57,756 fine ounces, which, with the exception of a few
ounces recovered from copper matte shipped from the Missouri Copper
Mountain mine, was derived from lead recovered from 64,377 tons of
galena concentrates. The average recovery was slightly less than an
ounce of silver per ton of concentrates smelted.
The
lead-zinc fluorspar deposits of the Kentucky-Illinois field carry
silver and from the lead concentrates shipped from Illinois in 1915 a
recovery of 3,864 ounces was recorded, against 2,112 ounces in 1914.
The average silver content per ton recovered from lead concentrates
from Illinois in 1915 was 6.03 ounces.
MONTANA.
Gold.—The
mine production of gold in Montana increased from $4,117,911 in 1914 to
$5,004,195 in 1915. The placer yield was $949,248, or about the same as
in 1914, so that the increased output was due to the lode mines.
Madison County had the largest output, $1,137,012, of which $862,719
came from placer mines. Most of the placer gold was recovered by one
company which operated 4 dredges in Alder Gulch and handled about
6,000,000 cubic yards of gravel. Deer Lodge County produced $871,864
chiefly from siliceous ores and Silver Bow County $809,314 mainly from
the smelting of concentrates from the Butte copper mines. At
amalgamation and cyani-dation plants $1,190,934 m gold was produced, or
an average recovery of $3.32 per ton of ore and tailings treated. Ore
treated at concentration mills yielded concentrates containing
$687,630, or 41 cents a ton, and crude ore shipped to smelters
contained $2,173,743 in gold, or an average of $3 a ton.
Silver.—Montana
mines produced 14,378,437 fine ounces of silver in 1915, a production
nearly 20 per cent larger than that of 1914. The copper ores yielded
8,819,772 ounces (an average of 1.81 ounces per ton), of which Silver
Bow County (Butte) supplied 8,809,600 ounces. The lead-zinc ores
produced 2,768,976 ounces, of which Silver Bow County supplied
2,649,388 ounces and Mineral County 114,265 ounces. The dry or
siliceous ores produced 1,635,221 ounces, of which Granite County
supplied 802,763 ounces. All of the silver from zinc ore, 734,798
ounces, came from Silver Bow County.
