Uraninite

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 also known as Joachimsthal) in Czechoslovakia 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.
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Noun
1. a mineral consisting of uranium oxide and trace amounts of radium and thorium and polonium and lead and helium; uraninite in massive form is called pitchblende which is the chief uranium ore
(synonym) pitchblende
(hypernym) mineral
(substance-meronym) uranium, U, atomic number 92

n. uraninite, mineral consisting mostly of uranium oxide (Mineralogy)

(n.)
A mineral consisting chiefly of uranium oxide with some lead, thorium, etc., occurring in black octahedrons, also in masses with a pitchlike luster; pitchblende.
  

General Information:
 Chemical Formula:
UO2
 Composition:
(Molecular Weight = 270.03 gm)
Uranium 88.15 % U 
Oxygen 11.85 % O 
 Empirical Formula:
UO2
 Environment:
Granite and syenite pegmatites. Colloform crusts in high temperature hydrothermal veins. In quartz-pebble conglomerates.
 IMA Status:
Approved IMA 1962
 Locality:
Southern parts of the Canadian Precambrian Shield, Bancroft, Ontario. New Hampshire, USA. Transvaal gold-bearing conglomerates.
 Name Origin:
From its elemental composition containing uranium.
Physical Properties:
 Cleavage:
[???] Good
 Color:
brownish black, gray, grayish black, or black.
 Density:
6.5 - 10.95, Average = 8.72
 Diaphaniety:
Nearly opaque
 Habits:
Crystalline - Coarse - Occurs as well-formed coarse sized crystals., Botryoidal - "Grape-like" rounded forms (e.g.. malachite)., Dendritic - Branching "tree-like" growths of great com plexity (e.g. pyrolusite).
 Hardness:
5-6 - Between Apatite and Orthoclase
 Luminescence:
Non-fluorescent.
 Luster:
Sub Metallic
 Streak:
brownish black
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