The
table shows the number of gold and silver producing mines in the United
States. In the States of the Rocky Mountain region and the Pacific
slope practically every mine producing lead, copper, or zinc also
yields the precious metals. The table, therefore, actually records the
number of producers of gold, silver, copper, lead, and zinc in these
Cordilleran States. It also records the gold and silver
preducing
mines in Michigan and in the Eastern States. It has not een possible to
trace the production of Illinois, Kentucky, and Missouri to individual
mines.
Compared
with the corresponding table for 1906 notable additions are found. The
placer mines operated in 1907 are 2,586 in number, against 2,316 in
1906. The deep mines number 2,604 in 1907, against 2,114 in 1906. In
Alaska 150 more placer mines were worked in 1907 than in 1906. In this
Territory it has proved difficult to record all the small operations
and the number is therefore, in part, an estimate. The number of deep
mines which yielded production in Arizona more than doubled in 1907.
Notable additions are also recorded to the producing deep mines in
California and Colorado, as well as to the placers and deep mines in
Idaho and Montana. The producing deep mines in Nevada increased from
143 to 216. In Oregon the number of placer mines and deep mines
decreased. Thirty-nine deep mines were added to the producing list in
Utah. In total number of mines Alaska ranks first, with 1,276, followed
by California with 1,061, Colorado with 642, Arizona with 437, and
Montana with 436. Idaho has 359 mines, while Utah and South Dakota,
which both stand higher in production than Idaho, have only 179 and 36
mines, respectively.
The
best guide to the development of deep mines is, however, found in the
record of tonnage of ores mined, which is given in a subsequent table.
A
proper classification of the western ores is very difficult on account
of their complex nature and the transitions between the various
classes, however they may be defined. The classification in the
following table is based on the quality of the ore as mined. The ores
are divided into dry or siliceous ores, which comprise the gold and
silver ores proper; further into copper ores, lead ores, zinc ores,
copper-lead-zinc ores, and lead-zinc ores. It is not possible to divide
the dry or siliceous ores into gold ores and silver ores, for the two
metals are present in them in all proportions. However, the silver ores
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