U.S. Borax Boron Mine, California

This mine is the largest open pit mine in California, and is probably the largest borate mine in the world, supplying almost half of the world's borates. The mine and refinery complex was established in the late 1920's, after a large source of borax was discovered here. Prior to this time, borax was mined out of Death Valley and hauled to the railway at Mojave by the famous 20-mule team. This mine consists of a 755 feet deep pit, 2 miles long by 1.75 miles wide. The substances obtained from the borates extracted from this deposit are used in numerous products, including detergents, glass, insulation, and ceramics. Operated for years by the U.S. Borax Campany, it is now owned by Rio Tinto. There is a visitors center, open to the public.