table shows the number of gold and silver producing mines in the United
States. In the States of the Cordilleran mountain system practically
every mine producing lead, copper, or zinc also yields the precious
metals. There are a few exceptions to this rule—for instance, a lead
mine in Washington, a lead-zinc mine in Nevada, and a few small copper
mines in New Mexico—but these exceptions are included in the table for
the sake of completeness, so that it actually records the number of
producers of gold, silver, copper, lead, and zinc in these Cordilleran
States. It also records the gold and silver producing mines in Michigan
and in the Eastern States, but does not include the properties in this
territory which produce only copper, lead, or zinc. It has not been
possible to trace the small silver production of Missouri to individual
with the corresponding table for 1905 the placer mines show little
change, the number for 1905 being 2,287, against 2,316 in 1906. In both
years Alaska shows the greatest number, followed by California, Oregon,
Idaho, and Montana. In no other State is placer mining of great
importance. The number of placers in California and Montana decreased
somewhat, while southwestern Oregon and Idaho added many properties to
the list of producers.
number or deep mines was 1,929 in 1905, and 2,114 were recorded in
1906. California lost nearly 100 producing deep mines, but a fairly
uniformly distributed increase in numbers appears in all of the other
important States. In spite of extremely active prospecting Nevada added
onljr 29 new producers to its record of 1905.
total number of mines Alaska has now assumed the lead, with 1,125
mines, but is closely followed by California, with 1,017 mines.
Colorado is third in rank, having 664 mines.
best guide to the development of deep mining is, however, found in the
tonnage record, which is given in the following table, now for the
first time subdivided into the most important classes of ores and their
average value in gold and silver.