778 MINERAL RESOURCES, 1915----PART I.
Eight
of the 30 counties in California which reported mine production of
gold had a vield of more than $1,000,000 in 1915, as follows: Amador,
$3,894,125; Nevada, $3,466,722; Yuba, $2,703,710; Sacramento,
$2,131,813; Butte, $1,545,976; Calaveras, $1,391,134; Shasta,
$1,120,848; and Tuolumne, $1,058,103. Of these, Yuba, Sacramento, and
Butte counties obtained most of their yield by dredging; Amador,
Calaveras, and Tuolumne counties are on the Mother Lode; Shasta Cotmty
produced both siliceous and copper ores; and the Nevada County
production was mainly from siliceous ores of the Grass Valley district.
The five Mother Lode counties—Amador, Calaveras, Eldorado, Mariposa,
and Tuolumne—whose output is mainly gold milling ores, produced
$4,059,435 in gold from mill bullion and $2,-249,989 from concentrates
in 1915, against a recovery of $3,235,116 from mill bullion and
$1,809,682 from concentrates in 1914.
Silver.—The
mine production of silver in California in 1915 was 1,678,756 fine
ounces, an increase of 206,897 ounces. More than half the output, or
860,057 ounces, came from the copper ores of Shasta County. Copper ores
from Calaveras, Placer, Plumas, and other counties yielded 196,838
ounces. Zinc ores yielded 114,682 ounces, siliceous ores 272,849
ounces, lead ores 127,958 ounces, and silver ores, silver-lead ores,
and placers the remainder. The only counties producing more than
100,000 ounces of silver in 1915 were Shasta, Inyo, San Bernardino, and
Calaveras. More than 86 per cent of all "the silver was recovered from
crude ores sent to smelters.
COLORADO.
Gold.—The
total mine production of gold in Colorado in 1915 was $22,414,944, an
increase of $2,531,839. This yield was the largest since 1908. The
Cripple Creek district, with an increase of $1,-687,378, produced
$13,683,494 in gold, which was 61 per cent of the State output of gold
from all sources. During 1915 the Roosevelt tunnel was driven 1,920
feet. The total recession of water was 149 feet, and the water
discharged was equal to about 37,000,000 gallons per vertical foot.
The
San Juan region, in Dolores, La Plata, Ouray, San Juan, and San Miguel
counties produced $3,854,521, a decrease of $115,336. Lake County
yielded $2,246,152, an increase of $674,701, and there were also good
increases in Boulder, Clear Creek, Eagle, Park, Gunnison, and San Juan
counties. There was areduced output of gold from La Plata, Ouray, San
Miguel, Chaffee, and Gilpin counties. Siliceous and dry ores, which
amounted to 80 per cent of all the ore sold or treated, yielded 94 per
cent of the total output of gold. Only 2 per cent came from lead ores,
3 per cent from placers, and about 1 per cent from other classes of
ore. The placer production in 1915 was $693,310, an increase of
$50,950. Summit County produced nearly 88 per cent and Lake County 10
per cent of the placer gold. More than 99 per cent of the placer gold
from these two counties was recovered by dredges.
Silver.—The
mine production of silver in Colorado in 1915 was 7,027,972 fine
ounces, a decrease of 1,768,093 ounces. Lake County, principally
Leadville, produced 2,571,002 ounces, a decrease of 1,239,828 ounces.
San Miguel County produced 1,096,641 ounces, a
