New Idria is an unincorporated town in San Benito County, California, which was named for a quicksilver (cinnabar) mine of the same name. The mine itself was named in honor of the world's second largest quicksilver mine in Idrija, Slovenia.
The history of mercury mining at the location begins in 1854. At one time, the New Idria mines were America's second most productive. The discovery of mercury ore at New Idria came soon after the start of the California gold rush. At that time, mercury was a key component in extracting gold from gold ore. Before New Idria and New Almaden, the mercury came almost exclusively from Europe.
The New Idria Mining Company was formed soon after the discovery of cinnabar (quicksilver ore) in the southern Diablo Range of central California in 1854. The town of New Idria began around 1857 and about 300 men were employed at the mine by 1861. The New Idria Quicksilver Mining Company closed in 1974 and the town has since become a ghost town. New Idria is a California Historical Landmark (#324) and home of the world's first Gould Rotary Furnace. The Gould Rotary Furnace revolutionized ore processing technology worldwide.