Shoshone
County produced more than 87 per cent of the total quantity in 1920, 86
per cent in 1919, 92 per cent in 1918, 93.4 per cent in 1917. Lead ores
contained 83 per cent of the output of silver and lead-zinc ores nearly
12 per cent. Crude ore shipped, which averaged 18.28 ounces of silver a
ton, supplied more than 25 per cent of the silver, and concentrates,
which averaged 19.70 ounces of silver a ton, contained more than 74 per
cent of the total silver.
MASSACHUSETTS AND PENNSYLVANIA.
A
small quantity of ore was shipped in 1920 from the Chipman mine at
Newburyport, in Massachusetts, and from a prospect near Phoenixville,
in Pennsylvania. These ores contained $178 in gold and 1,250 ounces of
silver.
MICHIGAN.
Silver.—The copper
mines of Michigan produced 470,189 fine ounces of silver in 1920,
against 441,430 fine ounces in 1919. The silver was derived mainly from
the electrolytic treatment of 38,907,000 pounds of copper. The average
recovery of silver per ton of "rock" treated was 0.289 ounce.
MISSOURI, OKLAHOMA, ILLINOIS, AND KENTUCKY.
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 1920 was 111,128 fine ounces, which, with the exception of 28,664
ounces recovered from cobalt-nickel-copper ore and copper concentrates,
was derived from lead recovered from 90,000 tons of galena
concentrates. The average recovery was slightly more than 0.91 ounce of
silver per ton of concentrate smelted.
The
lead-zinc fluorspar deposits of the Kentucky-Illinois field carry
silver, and from the lead concentrates shipped from Illinois in 1920 a
recovery of 8,193 ounces of silver was obtained, against 4,440 ounces
in 1919. The average silver content per ton recovered from lead
concentrates from Illinois in 1920 was 6.55 ounces. No silver ore was
shipped from the Criswell mine, near Byars, McClain County, Okla., in
1920.
MONTANA.
Gold.—The
mine production of gold in Montana decreased from $2,229,588 in 1919 to
$1,851,165 in 1920, and the placer output was $288,946—a decrease of
$2,484. Silver Bow County had the largest total output, $647,013. Most
of the placer gold was recovered by one company, which operated a
dredge in Alder Gulch, in Madison County. Lewis and Clark County
produced $335,036 and Deer Lodge County $121,512, chiefly from
siliceous ores. At amalgamation and cyanidation plants $533,798 in
gold was recovered, an average of $6.45 per ton of ore and tailings
treated. Ore treated at concentration mills yielded concentrates
containing $575,479, or 55 cents a ton, and crude ore shipped to
smelters contained $402,339 in gold, an average of $2.21 a ton.
