Uranium mining in the United States 1954 in the Sierra Nevada of Kern County, along the Kern River about northeast of Bakersfield. Two mines, the Kergon mine and the Miracle mine, made small shipments in 1954 and 1955. Uranium occurs as uraninite and autunite in shear zones in granodiorite. Accessory minerals include fluorite and the molybdenum minerals ilsemanite and jordisite. The first uranium identified in the US was pitchblende from the Wood gold mine at Central City, Colorado in 1871. Uranium mining in southwest Colorado goes back to 1898. The Uravan district of Colorado and Utah supplied about half the world's radium from 1910 to 1922,
Uranium ore Mineralization may be primary, that is magmatic-related or as secondary mineralization due to leaching, remobilization and re-precipitation. The principal uranium mineral in volcanic deposits is pitchblende, which is usually associated with molybdenite and minor amounts of lead, tin and tungsten mineralization. Volcanic hosted uranium deposits occur in host rocks spanning the Precambrian to the Cenozoic but because of the shallow levels at which they form, preservation favors younger age deposits. Some of the more important deposits or districts are Streltsovskoye, Russia; Dornod, Mongolia; and McDermitt, Nevada. The average deposit size is rather small with grades of 0.02% to 0.2% UO.