Through laboratory research

Through laboratory research, the U.S. Geological
Survey has developed new methods for determining
the gold content of rocks and soils of the Earth’s
crust. These methods, which detect and measure the
amounts of other elements as well as gold, include
atomic absorption spectrometry, neutron activation,
and inductively coupled plasma-atomic emission
spectrometry. These methods enable rapid and
extremely sensitive analyses to be made of large
numbers of samples.
Gold was produced in the southern Appalachian
region as early as 1792 and perhaps as early as 1775
in southern California. The discovery of gold at
Sutter’s Mill in California sparked the gold rush of
1849-50, and hundreds of mining camps sprang to life
as new deposits were discovered. Gold production
increased rapdly. Deposits in the Mother Lode and
Grass Valley districts in California and the Comstock
Lode in Nevada were discovered during the 1860’s,
and the Cripple Creek deposits in Colorado began to
produce gold in 1892. By1905 the Tonopah and
Goldfield deposits in Nevada and the Alaskan placer
deposits had been discovered, and United States gold
production for the first time exceeded 4 million troy
ounces a year—a level maintained until 1917.