sentences:  In 2018 California produced of gold from its only operating mine, the Mesquite mine (owned by Equinox Gold Corp.) in Imperial County, which restarted active mining in 2007, having been inactive since 2001.Gold was discovered in 1858 during the Pike's Peak Gold Rush in the vicinity of present-day Denver in 1858, but the deposits were small.The first important gold discoveries in Colorado were in the Central City-Idaho Springs district in January 1859.