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–uranium dating between the ranges of Th/U (accurate up to ca. 450,000 years) and U–Pb dating (accurate up to the age of the solar system, but problematic on samples younger than about 2 million years). Uranium–uranium dating Uranium–uranium dating is a radiometric dating technique which compares two isotopes of uranium (U) in a sample: uranium-234 (U) and uranium-238 (U). It is one of several radiometric dating techniques exploiting the uranium radioactive decay series, in which U undergoes 14 alpha and beta decay events on the way to the stable isotope Pb. Other dating techniques using this decay series include uranium–thorium dating and