Uraninite

"Pitchblende" redirects here. For other uses, see Pitchblende (disambiguation).

Uraninite
Pitchblende form Niederschlema-Alberoda deposit, Germany
General
Category	Oxide minerals
Chemical formula	Uranium dioxide or uranium(IV) oxide (UO2)
Strunz classification	04.DL.05
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
Streak	Same as colour, black or brownish
Specific gravity	7.8 - 10
Refractive index	Opaque
Pleochroism	None
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). The mineral has been known at least since the 15th century from silver mines in the Erzgebirge Mountains, Germany. However, the type locality is Jáchymov in the Czech Republic, from where F.E.Brückmann described the mineral in 1727.^[1] Pitchblende from the Johanngeorgenstadt deposit in Germany was used by M. Klaproth in 1789 to discover the element uranium.^[2]

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 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 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.

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.

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

See also

• Thorianite
• Uranium ore deposits
• List of minerals
• List of uranium mines

References

1. ^ Veselovsky, F., Ondrus, P., Gabsová, A., Hlousek, J., Vlasimsky, P., Chernyshew, I.V. (2003). "Who was who in Jáchymov mineralogy II". Journal of the Czech Geological Society 48: 93–205. 
2. ^ Schüttmann, W. (1998). "Das Erzgebirge und sein Uran". RADIZ-Information 16: 13–34. 

Notes

• Dana's Manual of Mineralogy ISBN 0-471-03288-3
• Uraninite, Webmineral.com
• Uraninite, MinDat.org, http://www.mindat.org/show.php?id=4102 

External links

Media related to Uraninite at Wikimedia Commons