The Black Rock Desert is a semi-arid region of lava beds and playa, or alkali flats. The silt playa 100 miles (160 km) north of Reno encompasses more than 300,000 acres of land and contains more than 120 miles of historic trails. Agate, Arsenopyrite, Azurite, Barite, Cinnabar, Epidote, Fire Opal, Geodes, Gypsum, Magnetite, Malachite, Marcasite, Miargyrite, Obsidian, Petrified Wood, Stibnite, Topaz, Rhyolite, Tourmaline can all be found in the Black Rock-High Rock country.