31.6
per cent in 1913, and 29 per cent in 1912, indicating an accelerating
transition from placer to lode mining. The 650 placers operated in 1916
yielded approximately 7,100,000 cubic yards of auriferous gravel, of
which the dredges handled about 3,900,000 cubic yards and made an
average recovery of 69 cents a yard in 1916, against 51 cents a yard in
1915, and 52 cents a yard in 1914. The estimated total recovery of gold
by dredging for the period 1903-1916, inclusive, is $15,109,894.
The only new placer-bearing area discovered in 1916 was in the Tolstoi Creek basin in the southern part of the Innoko district.
Silver.—The
mine production of silver in Alaska in 1916 was 1,379,171 fine ounces,
against 1,071,782 ounces in 1915. The copper mines produced 1,207,121
ounces, an increase of 309,282 ounces. The siliceous ores yielded
110,050 ounces in 1916, against 91,341 ounces in 1915, 28,254 ounces in
1914, and the placers 62.000 ounces in 1916, against 82,602 ounces in
1915.
ARIZONA.
Gold.—The
mine production of gold in Arizona in 1916 was $3,985,559, which was
$180,466 less than in 1915. Placers contributed only $14,281, most of
which came from small mines in Yuma and Yavapai counties. The deep
mines produced $3,971,278, of which 38 per cent came from dry or
siliceous ores mined chiefly in Mohave, Yavapai, and Cochise counties,
and 55 per cent was contained in copper ores mined chiefly in Cochise
and Yavapai counties. Mohave County had a gold output of $1,038,814,
Cochise County $1,512,878, and Yavapai County $1,035,351. The gold
recovered from ores treated at gold and silver mills represented 36 per
cent of the total output and crude ores shipped to smelters contained
nearly 53 per cent. The crude copper ores mined and smelted directly
(without previous concentration) contained an average gold content of
53 cents a ton.
Silver.—The
mine production of silver increased from 5,649,020 fine ounces in 1915
to 7,212,039 ounces in 1916. Of this production 5,347,893 ounces came
from copper ores, 997,372 ounces from dry or siliceous ores, 539,108
ounces from lead ores, 159,247 ounces from lead-zinc ores, and smaller
quantities from zinc, copper-zinc, and copper-lead ores. Cochise County
produced 3,709,225 ounces in 1916, of which 2,478,568 ounces came from
copper ores and 776,279 ounces from siliceous ores. The silver output
of Yavapai County, which increased from 1,343,363 ounces in 1915 to
1,735,302 ounces in 1916, was mainly derived from copper ores. Bullion
recovered from gold and silver ores, almost all by cyanidation, yielded
658,830 ounces of silver. Concentrates contained 1,179,552 ounces and
crude ore shipped to smelters contained 5,305,608 ounces, or more than
73 per cent of the total output of silver.
CALIFORNIA.
Gold.—The mine production of gold in California in 1916 was $21,410,741. The decreased yield of $1,031,555 was due to a smaller production from deep-mining operations.
In
1916 the deep mines produced $12,835,084 (a decrease of | $998,595), of
which gold-quartz ores yielded 92.5 per cent and copper
