750 MINERAL RESOURCES, 1918----PART I.
During
1918 the Roosevelt tunnel was completed and connected with the Portland
No. 2 shaft at a depth of 2,131 feet from the surface. The main
drainage tunnel, work on which was commenced 11 years ago, is 24,255
feet in length from its portal to heading.
The
San Juan region, in Dolores, La Plata, Ouray, San Juan, and San Miguel
counties, produced $2,502,804; Lake County yielded $843,239, a decrease
of $331,980; and there were also decreases in Boulder, Clear Creek,
Gunnison, Gilpin, La Plata, Park, Chaffee, San Juan, and Summit
counties. Siliceous and dry ores, which amounted to 76 per cent of all
the ore sold or treated, yielded 92 per cent of the total output of
gold. Slightly less than 3 per cent came from lead ore, 4 per cent from
placers, about 1 per cent from lead-zinc ore, and the remainder from
other classes of ore. The placer production in 1918 was $526,202, a
decrease of $134,826. Summit County produced 82 per cent and Lake
County nearly 18 per cent of the placer gold. Dredges in these two
counties recovered more than 99 per cent of the placer gold.
Silver.—The
mine production of silver in Colorado in 1918 was 7,063,554 fine
ounces, a decrease of 240,799 ounces. Lake County, principally
Leadville, produced 2,290,121 ounces, an increase of 106,121 ounces.
San Miguel County produced 836,570 ounces, an increase of 57,200
ounces. There was larger production of silver from Custer, Eagle,
Gilpin, Hinsdale, Mineral, and San Miguel counties, and decreased
output from Boulder, Chaffee, Clear Creek, Gunnison, Pitkin, and San
Juan counties. Siliceous and dry ores yielded 67.3 per cent of the
silver recovered, lead ores 20.6 per cent, lead-zinc ores 8 per cent,
and copper ores 2.4 per cent. The remainder came from placers, zinc
ores, and copper-lead ores.
IDAHO.
Gold.—The
mine production of gold in Idaho in 1918 was $702,816, a decrease of
$101,993. The total production of gold from Idaho from the discovery of
placer gold in 1863 to the end of 1918 is estimated at $131,613,785 by
C.N. Gerry.1
Boise
and Shoshone counties were the largest producers of gold in 1918 and
yielded about 67 per cent of the total output. The lode mines produced
gold valued at $426,406. The placer mines produced $276,410 in gold in
1918, of which $239,762 was won by dredging. The total output of gold
recovered by dredges from 1897 to the end of 1918 has been $4,021,265.
Of the total gold in 1918 about 39 per per cent came from placers, 42
per cent from siliceous ores, 10 per cent from copper ores, and the
remainder from lead and lead-zinc ores.
Silver.—The
mine production of silver in Idaho in 1918 was 9,172,-340 fine ounces,
or 2,856,998 ounces less than in 1917. The total yield of silver from
Idaho for the period 1863 to 1918, inclusive, is 233,878.-295 fine
ounces.1
There
was a decrease of 26 per cent in the output of silver from Shoshone
County, which yielded 92.1 per cent of the total quantity of silver in
1918, 93.4 per cent in 1917, 95 per cent in 1916 and 1915, and 98 per
cent in 1914. Lead ores contained 88 per cent of the output of of
silver and lead-zinc ores 9 per cent. Crude ore shipped, which
i U. S. Geo]. Survey Mineral Resources, 1918, pt. 1, p. 461.
