California State Mining and Mineral Museum is 1.8 mi. s. on SR 49, at the main entrance to the county fairgrounds. It contains a collection of minerals, gold, diamonds and other gems, including examples of benitoite, the California state gemstone. A highlight is the Fricot Nugget, a nearly 14-pound chunk of crystalline gold discovered in the American River in 1864. Other exhibits include models of an assay office and stamp mill (a machine that crushed quartz) and a full-scale replica of a mine. The museum also presents rotating exhibitions of gem and mineral specimens from other institutions and private collections.