Pitchblende
oxide mineral / From Wikipedia, the free encyclopedia
Pitchblende is a radioactive, uranium-rich mineral and ore. It has a chemical composition that is largely UO2, but also contains UO3 and oxides of lead, thorium, and rare earth elements. It is known as pitchblende due to its black color and high density. It is also commonly referred to as Uraninite.
Uraninite | |
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Pitchblende from Niederschlema-Alberoda deposit, Germany | |
General | |
Category | Oxide minerals |
Formula (repeating unit) | 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 |
The mineral has been known at least since the 15th century from silver mines in the Ore Mountains, on the German/Czech border. Pitchblende found in Germany was used by M. Klaproth in 1789 to discover the element uranium.[5]
Pitchblende contains a small amount of radium as a radioactive decay product of uranium. Because the uranium isotopes 238U and 235U will decay to form the lead isotopes 206Pb and 207Pb, pitchblende also always has small amounts of lead. Small amounts of helium are also present in pitchblend as a result of alpha decay.
Helium was first found on Earth in pitchblende after having been discovered in the Sun's atmosphere.