Mineral description : Uraninite

Uraninite (pitchblende) from Vall Fosca.
Uraninite crystals from Varuträsk.

Mineral class Oxides : uraninite - ianthinite group
Chemical formula UO2
Crystal system Cubic.
Habitus Cubical crystals in different modifications. As unregular grains or masses (pitchblende).
Cleavage Indistinct, fracture conchoidal to uneven.
Hardness 5-6
Density 7.5-9.7
Color Black
Streak Black to brownish black.
Luster Submetallic.
Description Uraninite is the main ore of uranium.
Occurance In pegmatites and hydrothermal veins. Also in sedimentary rocks.
Associates Gummite, uranophane.
Notes Strongly radioactive.
Insoluble in hydrocloric acid, but dissolves slowly in nitric acid.
If a drop of nitric acid is placed on top of uranite it becomes strongly flourescent.
Locations A very widespread mineral.
  • Billingen, Västergötland.
  • Västervik area.
  • Tåsjö, Västernorrland.
  • Varuträsk, Västerbotten. As cubes up to 5mm surrounded by yellow oxidation products.
  • Derome feldspar quarry, Varberg. As a rarity.
  • Digelskär, Gräsö, Roslagen. As pitchblende.
  • Håkanstorp iron mine, Åmmeberg. In veins and cracks.
  • Stripa and Blanka iron mines, Västmanland. In veins and cracks.

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Mineral group index.
Main index.

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Last changed : 1998-03-07