 In addition to gold, major minerals of the area include copper, chromium, tungsten, and manganese.In 1994, mining of gravel and sand surpassed gold, with the Feather, Yuba, American, and Bear rivers providing a large amount of alluvial deposits for aggregate mining.The Yuba River has a high level of sediment supply, with a bed-load composed primarily of mining gravel as a result of intense levels of hydraulic mining that occurred in the area.