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Pitchblende schlema-alberoda.JPG
Pitchblende from Niederschlema-Alberoda deposit, Germany
Category Oxide minerals
(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
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
Major varieties
Pitchblende Massive

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. 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.

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 contains 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.


Uraninite crystals from Topsham, Maine (size: 2.7×2.4×1.4 cm)

Pitchblende 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 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.

Uranium ore is generally processed close to the mine into yellowcake, which is an intermediate step in the processing of uranium.

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