put
of argentiferous zinc ores decreased from 177,946 to 141,295 tons in
Colorado. The yield of gold and silver bearing lead-zinc ores decreased
from 229,107 to 203,367 tons in Colorado and from 216,764 to 211,609
tons in Utah, but increased from 480,126 to 646,080 tons in Idaho. The
production of these ores in Montana for the two years is not
comparable, owing to changes in the Survey classification of Montana
ores for 1913; but the output for that State made a large increase for
the year to 307,615 short tons.
The
average extraction value of precious metals per ton of dry or siliceous
ores increased in Alaska from $2.85 in 1912 to $2.99 in 1913, and in
California from $4.95 to $5.61, but decreased in Colorado from $10.53
to $9.57, in Nevada from $14.74 to $12.23, in South Dakota from $4.21
to $3.91, and in Utah from $9.78 to $7.97.
The
average extraction value of gold and silver per ton in copper ores
increased from $0.18 to $0.26 in Nevada, and from $0,105 to $0.11 in
Tennessee, remained at $0.41 in Arizona, and decreased from $1.91 to
$1.84-in California, from $0,211 to $0.10 in Michigan (silver only),
from $1.42 to $1.29 in Montana, from $0,275 to $0.11 in New Mexico, and
from $0.56 to $0.38 in Utah. The value in lead ores increased from
$2.78 to $2.99 in Idaho, but decreased from $8.67 to $7.94 in Utah, a
continuation of like changes for 1912. In lead-zinc ores the average
extraction value of gold and silver per ton increased from $2.17 to
$2.47 in Colorado, and from $0.68 to $1.55 in Idaho, but decreased from
$4.48 to $3.60 in Utah. The average value for Montana ores of this
class was $3.44 in 1913.
AVERAGE TENOR OF SILVER IN ORES, BY MINING DISTRICTS.
In
the general Survey report on gold and silver by the writer for 1911 the
results were given of a brief study of the tenor of silver in ores by
mining districts. A few copies of that report are still available for
distribution.
The
bulk of the silver production, as shown, is from more widely
distributed sources than that of gold, the placers and mixed ores
playing little part, but the dry or siliceous silver, silver-gold, and
gold-silver ores, the copper ores, and the lead ores contributing more
equally in the product. The high tenor of many dry or siliceous and
lead ores (with the notable exception of the lead ores of the Coeur
d'Alene) are shown, as well as the high tenor of silver in the copper
ores in the Chitina region, Alaska, and the Leadville, Tintic, and
Chewelah districts in the United States. The low silver content of the
Clifton, Ray, and Ely copper ores, and especially of the Santa Rita
(Chino) copper ores, is also notable.
DISTRIBUTION OF GOLD PRODUCTION OF 1913, BY SOURCES.
As
shown by the following table the great bulk of the domestic gold output
is from dry or siliceous ores—normally gold-quartz and gold-silver
quartzose ores—and from placers, over 91 per cent of the total gold
production coming from these sources alone. The total contribution of
gold derived from the great copper, lead, and zinc mines of the country
is therefore relatively small, notwithstanding their recent enormous
development and tonnage. The changes in relative output from the
various sources given in the table have been unimportant in the last
four years. It is interesting to note, however,
