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Uraninite



Uraninite

General
CategoryMineral
Chemical formulauranium oxide, UO2
Identification
ColorBlack or brownish
Crystal habitMassive, botryoidal, granular. Crystals uncommon.
Crystal systemIsometric
CleavageIndistinct
FractureConchoidal to uneven
Mohs Scale hardness5 - 6
LusterSubmetallic, greasy
Refractive indexOpaque
PleochroismNone
StreakSame as colour, black or brownish
Specific gravity7.5 - 10
SolubilitySoluble in sulfuric, nitric, and hydrofluoric acids.
Major varieties
PitchblendeMassive

Uraninite is a uranium-rich mineral with a composition that is largely UO2 (uranium dioxide), but which also contains UO3 and oxides of lead, thorium, and rare earths. It is most commonly known in the variety pitchblende (from pitch, because of its black color, and blende, a term used by German miners to denote minerals whose weight 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 the Jáchymov (then Joachimsthal, Austria-Hungary) now in the Czech Republic 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.

Additional recommended knowledge

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.

References

  • Dana's Manual of Mineralogy ISBN 0-471-03288-3

See also

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Uraninite". A list of authors is available in Wikipedia.
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