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Uraninite is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2, but also contains UO3 and oxides of lead, thorium, and rare earth elements. It is most commonly known as pitchblende (from pitch, because of its black color, and blende, a term used by German miners to denote minerals whose density suggested metal content, but whose exploitation was, at the time they were named, either impossible or not economically feasible). The mineral is known at least since the 15th century from silver mines in the Erzgebirge Mountains, Germany. However, the type locality is Jáchymov in the Czech Republic, from where F.E.Brückmann described the mineral in 1727. Pitchblende from the Johanngeorgenstadt deposit in Germany was used by M.Klaproth in 1789 to discover the element uranium.
All uraninite minerals contain a small amount of radium as a radioactive decay product of uranium; it was in pitchblende from Jáchymov in the Czech Republic (then Joachimsthal, Austria-Hungary) that Marie Curie discovered radium and polonium. Uraninite also always contains small amounts of the lead isotopes Pb-206 and Pb-207, the end products of the decay series of the uranium isotopes U-238 and U-235 respectively. Small amounts of helium are also present in uraninite as a result of alpha decay. Helium was first found on Earth in uraninite after having been discovered spectroscopically in the Sun's atmosphere. The extremely rare element technetium can be found in uraninite in very small quantities (about 0.2 ng/kg), produced by the spontaneous fission of uranium-238.
Uraninite is a major ore of uranium. An important occurrence of pitchblende is at Great Bear Lake in the Northwest Territories of Canada, where it is found in large quantities associated with silver. Some of the highest grade uranium ores in the world have been found in the Athabasca Basin in northern Saskatchewan. It also occurs in Australia, Germany, England, and South Africa. In the United States it can be found in the states of New Hampshire, Connecticut, North Carolina, Wyoming, Colorado, Arizona and New Mexico.
Uranium ore is generally processed in the area in which it is mined into yellowcake, which is an intermediate step in the processing of uranium.
1. ^ Veselovsky, F., Ondrus, P., Gabsová, A., Hlousek, J., Vlasimsky, P., Chernyshew, I.V. (2003). "Who was who in Jáchymov mineralogy II". Journal of the Czech Geological Society 48: 93–205.