was
mainly derived from copper ores. Bullion recovered from gold and silver
ores, almost all by cyanidation, yielded 254,353 ounces of silver.
Concentrates contained 1,271,890 ounces and crude ore shipped to
smelters contained 5,312,292 ounces, or 76 per cent of the total output
of silver.
CALIFORNIA.
Gold.—The
mine production of gold in California in 1917 was $20,087,504. The
decrease of $1,082,634 was due to a smaller production from deep-mine
operations.
In
1917 the deep mines produced $11,013,474 (a decrease of $1,821,610), of
which gold-quartz ores yielded 93 per cent and copper ores 6.1 per
cent. California placers in 1917 produced $9,074,030 in gold, or
$498,373 more than in 1916. Of the placer production $8,313,527 was
recovered by dredging. The total dredge production from 1896 to the end
of 1917 has been $95,193,985 and the yield of gold by dredges was equal
to 41 per cent of the total yield of gold for 1917. The Yuba County
dredges, 12 in number, made the largest output of gold, the value being
$3,659,211, an increase of $519,061. Sacramento County, with 12 dredges
working, made an output of $1,913,504, an increase of $84,026. In Butte
County (including Oroville and other districts) 11 dredges produced
$898,141 in gold, or $312,733 less than in 1916. Dredges were also
operated in Calaveras, Eldorado, Merced, Stanislaus, Placer, Shasta,
Siskiyou, and Trinity counties.
Five
of the 26 counties in California which reported mine production of
gold had a yield of more than $1,000,000 in 1917, as follows: Nevada,
$3,682,947: Amador, $3,664,164; Yuba, $3,677,673; Sacramento,
$1,919,581; Calaveras, $1,471,442. Of these Yuba and Sacramento
counties obtained most of their yield by dredging, Amador and Calaveras
are on the Mother Lode, and Nevada County produced 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 $3,202,212 in gold from
mill bullion and $1,888,961 from concentrates in 1917, against a
recovery of $3,719,649 from mill bullion and $2,092,169 from
concentrates in 1916.
Silver.—The
mine production of silver in California in 1917 was 1,775,431 fine
ounces, a decrease of 788,923 ounces. More than 36 per cent of the
output, or 625,000 ounces, came from the copper ores of Shasta County.
Copper ores yielded 882,480 ounces. Siliceous ores yielded 139,492
ounces, silver-lead ores, silver ores, and lead ores 726,174 ounces,
and placers the remainder. The only counties producing more than
100,000 ounces of silver in 1917 were Shasta, Inyo, Calaveras, and San
Bernardino. About 85 per cent of all the silrer was recovered from
crude ores sent to smelters.
COLORADO.
Gold.—The
total mine production of gold in Colorado in 1917 was $15,729,224, a
decrease of $3,424,597. The Cripple Creek district, with a decrease of
$1,724,703, produced $10,394,847 in gold, which was 66 per cent of the
State output of gold from all sources. During
