| Uraninite | |
|---|---|
Pitchblende from Niederschlema-Alberoda deposit, Germany |
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| General | |
| Category | Oxide minerals |
| Chemical formula | Uranium dioxide or uranium(IV) oxide (UO2) |
| Strunz classification | 04.DL.05 |
| Crystal symmetry | Isometric, hexoctahedral H-M symbol: (4/m32/m) Space group: F m3m |
| Unit cell | a = 5.4682 Å; Z = 4 |
| Identification | |
| Color | Steel-black to velvet-black, brownish black, pale gray to pale green; in transmitted light, pale green, pale yellow to deep brown |
| Crystal habit | Massive, botryoidal, granular. Octahedral crystals uncommon. |
| Crystal system | Isometric |
| Cleavage | Indistinct |
| Fracture | Conchoidal to uneven |
| Mohs scale hardness | 5–6 |
| Luster | Submetallic, greasy, dull |
| Streak | Brownish black, gray, olive-green |
| Diaphaneity | Opaque; transparent in thin fragments |
| Specific gravity | 10.63–10.95; decreases on oxidation |
| Optical properties | Isotropic |
| Other characteristics | Radioactive: greater than 70 Bq/g |
| References | [1][2][3][4] |
| Major varieties | |
| Pitchblende | Massive |
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 has been known at least since the 15th century from silver mines in the Ore Mountains, on the German/Czech border. The type locality is the town of Jáchymov, on the Czech side of the mountains, where F.E.Brückmann described the mineral in 1727.[5] Pitchblende from the Johanngeorgenstadt deposit in Germany was used by M. Klaproth in 1789 to discover the element uranium.[6]
All uraninite minerals contain a small amount of radium as a radioactive decay product of uranium. Uraninite also always contains small amounts of the lead isotopes 206Pb and 207Pb, the end products of the decay series of the uranium isotopes 238U and 235U 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.
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Uraninite is a major ore of uranium. Some of the highest grade uranium ores in the world were found in the Shinkolobwe mine in the Democratic Republic of the Congo (the initial source for the Manhattan Project) and in the Athabasca Basin in northern Saskatchewan, Canada. Another important source of pitchblende is at Great Bear Lake in the Northwest Territories of Canada, where it is found in large quantities associated with silver. 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. The geologist Charles Steen made a fortune on the production of Uraninite in his Mi Vida mine in Moab, Utah.
Uranium ore is generally processed close to the mine into yellowcake, which is an intermediate step in the processing of uranium.
Media related to [//commons.wikimedia.org/wiki/Category:Uraninite Uraninite] at Wikimedia Commons
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