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MINERAL RESOURCES.
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Source
of silver in 1907 in States and Territories, as reported from the mines
to the United States Geological Survey, by kinds of ore and by States,
in fine ounces—Continued.
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General statement.—The
total silver product for 1907 was, as usual, divided chiefly between
siliceous ores, copper ores, and lead ores. The proportion is, however,
somewhat different from 1906. Only a small quantity is recovered from
placers, most of which is credited to Alaska. In percentages of the
total the division is as follows: Siliceous ores, 36.4 per cent; copper
ores, 26.8 per cent; lead ores, 32.5 per cent; copper-lead ores, 1 per
cent; lead-zinc ores, 3 per cent; zinc ores, 0.2 per cent; placers, 0.2
per cent.
Dry and siliceous ores.—The
total quantity from this source was 19,038,042 ounces, compared with
16,792,799 ounces in 1906. The important States rank as follows:
Colorado, Nevada, Montana, Arizona, Idaho, New Mexico, and California.
The larger part of these ores are not silver ores proper, but
gold-silver ores. Only about 1,500,000 ounces were recovered from ores
carrying exclusively silver values. Silver is practically a by-product
of smelting ores and gold-silver milling ores. The production of
Colorado was obtained from the gold-silver ores, partly free milling,
from the Gilpin and San Juan regions, also from mixed ores, either
pyritic or siliceous, which are concentrated and smelted and which also
contain copper, lead, or gold. The silver from siliceous ores in Nevada
remained at about the same figure as in 1906; most of it is derived
from the siliceous gold-silver ores of Tonopah. The production of
Montana, which showed a notable decrease, is largely derived from the
pure silver ores from Granite County and mixed siliceous ores from
other counties. In no other State does the quantity of silver reach
1,000,000 ounces.
The
silver is recovered from siliceous ores by amalgamation or cyanide
processes; some rich siliceous ores are smelted and the silver obtained
by desilverization of lead bullion or by electrolytic refining of
copper.
Copper ores.—From
copper ores 13,955,436 ounces were recovered; a decrease of somewhat
less than 2,000,000 ounces is shown compared with 1906. The States rank
as follows: Montana, Utah, Arizona, California, and Idaho; none of the
other States produce over 500,000
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