The Basin Ranges occupy most of Mono and Inyo Counties and small portions of several other counties, including Modoc County in the northeast corner of the state (see fig. 3). These mountain ranges lie east of the Sierra Nevada and north of the Garlock fault, which separates them from the Mojave Desert. The Basin Ranges province is a region of roughly parallel mountain ranges alternating with basins or troughs and controlled by fault block structure. The region is underlain by granitic, sedimentary and metamorphic rocks of Precambrian, Paleozoic and Mesozoic ages, which in places are overlain by Cenozoic sedimentary and volcanic rocks. As in the Mojave Desert province, the gold occurs either as epithermal deposits in silicified and brecciated zones in volcanic rocks or as mesothermal gold-quarrz veins in older metamorphic or granitic rocks. The largest source of gold in the Basin Ranges province has been the Bodie district in Mono County. Appreciable amounts of gold also have been mined in the Argus, Chloride Cliff, Russ, Skiddoo, and Ballarat districts.