tana,
California, Colorado, and Idaho. It will be observed that the Utah
copper ores are by far richer in gold than those of any other State. In
spite of its immense tonnage Arizona yielded only about one-fourth or
the production of Utah from this source. Most of this came, moreover,
from a single camp, the United Verde. The gold from the Butte ores
declined very materially. Compared with 1906 a remarkable increase is
shown by Utah, due largely to an increased amount of rich ores from
Tintic. Idaho, New Mexico, and California added materially to their
output from this source. The decreases are in Montana and Arizona.
The
copper ores which contain gold are chiefly of sulphide class.
Chalcocite is the most abundant mineral, though in some districts
chalcopyrite prevails. Oxidized ores are still extensively mined at
Bisbee, Ariz., and Tintic, Utah; also at the Snowstorm mine in Idaho,
and at some other places. The sulphide ores are ordinarily concentrated
and smelted; the oxidized ores are smelted without concentration. The
gold is recovered by electrolytic refining of the copper.
Lead ores.—From
lead ores and mixed copper and lead ores approximately 129,000 ounces
were recovered, which represents a considerable increase over 1906,
most of which was due to the mining of rich lead ores at Tintic.
Colorado decreased its output very materially, and losses were also
shown in Arizona and Idaho. A somewhat increased production is recorded
from Montana and Nevada. The States producing gold from lead ores rank
as follows: Utah, Colorado, Nevada, Montana, Idaho, and Arizona. The
first two States are far ahead of the others. The lead ores are chiefly
of the sulphide class. Large quantities of oxidized ores are, however,
still furnished by the Tintic district.
Zinc ores and zinc-lead ores.—Only
small amounts of gold are recovered from zinc ores. A total of 5,738
ounces was recovered from pure zinc ores; nearly the whole of this was
derived from Montana, Colorado contributing only a fraction. The zinc
ores of Leadville contain very little gold. The zinc-lead ores yielded
only 2,039 ounces, against 11,691 ounces in 1906. This decrease is due
to the cessation of mining of zinc ores at Leadville because of the
low price of spelter.
DISTRIBUTION OF SILVER PRODUCT IN 1907.
The following table shows the source of silver in the United States in 1907, by kinds of ore and by States:
Source
of silver in 1907 in States and Territories, as reported from the mines
to the United Slates Geological Survey, by kinds of ore and by States,
in fine ounces.«
