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| Uraninite | |
|---|---|
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| General | |
| Chemical formula | Uranium dioxide or uranium(IV) oxide (UO2) |
| Identification | |
| Color | Black or brownish |
| Crystal habit | Massive, botryoidal, granular. Crystals uncommon. |
| Crystal system | Isometric |
| Cleavage | Indistinct |
| Fracture | Conchoidal to uneven |
| Mohs Scale hardness | 5 - 6 |
| Luster | Submetallic, greasy |
| Refractive index | Opaque |
| Pleochroism | None |
| Streak | Same as colour, black or brownish |
| Specific gravity | 7.8 - 10 |
| Solubility | Soluble in sulfuric, nitric, and hydrofluoric acids. |
| 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). 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. 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 previously being 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 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.
References
See also
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- This page was last modified on 3 December 2008, at 17:25.
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