Cassia County (formed from Lincoln County), on the south side of the Snake River forms much of Idaho’s southern boundary with Utah and Nevada on the west. It contains a diverse assemblage of rocks, including the oldest rocks in Idaho. Most of the people in Cassia County live in irrigated agricultural areas near Burley, Declo and Oakley. This area, on the southern edge of the Snake River Plain, is underlain by Quaternary basalt, including shield volcanoes visible today. Thick cobble gravel derived from the Albion Range in Pleistocene time underlies the Oakley valley.
Along the gravel bars of the Snake River of Cassia County roughly 20,000 reported ounces of gold were taken from the gravel bars. Most of the placer gold here is flour gold deposited from flooding, however there is coarser and bigger placer gold to be found here as well when digging in hard packed rocky soil.
There was also a large dredge in operation on the Snake River known as the Sweetser & Burroughs Gold Mining Dredge. (pictured below)
A number of lode gold mines are found in the Black Pine Mountain area in southeastern Cassia County. The largest is the Black Pine Mine, a open-pit gold mine, no longer in production. Both gold and silver were found here.
Burley is where placer deposits were worked along the snake River in Township 9 and 10 South, Range 24 and 25 East. The Lead and silver mines in Township 15 and 16 south and Range 21 east has gold showings on the ore dumps. There were miners in the old days along the banks of the Snake River using pans or rockers to extract the fine gold dust.