| Uraninite | |
|---|---|
 Pitchblende from Niederschlema-Alberoda deposit,Germany | |
| General | |
| Category | Oxide minerals |
| Formula (repeating unit) | Uranium dioxide oruranium(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 |
Pitchblende is aradioactive, uranium-richmineral andore. It has achemical composition that is largelyUO2, but also containsUO3 andoxides oflead,thorium, andrare earth elements. It is known as pitchblende due to its black color and highdensity. It is also commonly referred to asUraninite.
The mineral has been known at least since the 15th century from silver mines in theOre Mountains, on theGerman/Czech border. Pitchblende found inGermany was used byM. Klaproth in 1789 to discover the elementuranium.[5]
Pitchblende contains a small amount ofradium as aradioactive decay product of uranium. Because the uranium isotopes238U and235U will decay to form theleadisotopes206Pb and207Pb, pitchblende also always has small amounts of lead. Small amounts ofhelium are also present in pitchblend as a result ofalpha decay.
Helium was first found on Earth in pitchblende after having been discovered in theSun's atmosphere.
Pitchblende is a majorore ofuranium.
Some of the highest grade uranium ores in the world were found in the Shinkolobwe mine in theDemocratic Republic of the Congo (the initial source for theManhattan Project) and in theAthabasca Basin in northernCanada.
Another important source of pitchblende is atGreat Bear Lake in theNorthwest Territories ofCanada, where it is found in large quantities associated withsilver. It also occurs inAustralia,Germany,England, andSouth Africa. In theUnited States it can be found in the states ofNew Hampshire,Connecticut,North Carolina,Wyoming,Colorado,Arizona andNew Mexico.
Uranium ore is generally processed close to the mine intoyellowcake, which is an intermediate step in the processing of uranium.
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