ethod
of taking gold from the rock is first by blasting, and afterward
grinding the rock in a stamp mill, which reduces it to powder, after
which the gold is separated by refining processes. The gold which occurs
in the sand, gravel, or clay soil, is washed out. When done on a small
scale this is called "panning." The larger operations of this kind are
called "placer" and "dredge" mining. There is also a considerable amount
of gold obtained as a by-product from copper mining.

Generally speaking, quartz mines are in the mountains and placer mines
in the river valleys. Placer mining by powerful water pressure, called
hydraulic mining, destroys the banks, and also fills up the river beds
with masses of rock and gravel. Some of the large rivers of California
have been made unfit for steamboat traffic, and serious damage has been
done to the harbor of San Francisco. For this reason hydraulic placer
mining has been stopped by law. This has greatly lessened the gold
production of California.

In 1907, the United States produced $94,000,000 worth of gold. Of this,
Colorado produced more than any other state. Next in their order come
Alaska, California and Nevada. Each produced from $15,000,000 to
$20,000,000 worth. Together they furnished nearly four-fifths of the
entire supply. The remaining one-fifth comes from Utah, South Dakota,
Montana, Arizona, Idaho, and Oregon, with very small amounts from the
southeastern states, the two Carolinas and Georgia, New Mexico,
Washington, and Wyoming. South Dakota has the most profitable single
gold mine in the United States. It has produced nearly $60,000,000 in
gold, and is now turning out about $5,000,000 worth a year.

The United States has many unworked gold mines, "gold reserves" they are
called, whose value can not in any way be exactly estimated. The value
of the placer mines can be better judged than that of the lode or quartz
mines. The placer mines are chiefly in Alaska and California. These
mines may yield gold to the amount of a billion dollars. There are
lesser, but important resources of placer gold in Montana, Idaho, and
Oregon.

The placer gold mined in 1907 was valued at $24,000,000, and it is
thought that about this quantity can be supplied for a long time.

The amount of gold yielded in the reduction of copper ores was about
$5,500,000. It is probable that this amount will be gradually increased,
and can be relied on to last many years. From the lead ores a little