Cuprosklodowskite - Encyclopedia

    Class : Silicates
    Subclass : Nesosilicates
    Crystal System : Triclinic
    Chemistry : (H3O)Cu(UO2)2(SiO4)2 2H2O
    Rarity : Rare

Cuprosklodowskite (formerly called jachymovite) is a secondary silicate from the superficial oxidation zone of uranium deposits where it accompanies, among others, kasolite and vandenbrandeite. Its name is linked to its chemical composition (copper) and its relationship with sklodowskite. Its crystals are elongated to acicular, they can exceed the centimeter, with a perfect cleavage on {100} ; they are grouped in splendid acicular tufts of a silky appearance, or constitute radiate or fibroradiated hummocky encrustations. Emerald green to blue-green in elongated crystals, color fades to pale green in needle-like crystals. It is a rare mineral, only intended for collection.

Main photo : Cuprosklodowskite de Musonoi Mine, Kolwezi, Lualaba, Democratic Republic of Congo

Cuprosklodowskite de Musonoi Mine, Kolwezi, Lualaba, Democratic Republic of Congo
Cuprosklodowskite de Musonoi Mine, Kolwezi, Lualaba, Democratic Republic of Congo
Cuprosklodowskite de Musonoi Mine, Kolwezi, Lualaba, Democratic Republic of Congo
Cuprosklodowskite du Mas d'Alary, Hérault, France © Stephan Wolsfried

Cuprosklodowskite in the World

All the finest samples come from uranium deposits in Katanga, where centimetric fibers are common, and sometimes grouped into star aggregates (Shinkolobwe, Kalongwe, Kambove). The Musonoi mine, in particular, provided acicular crystals reaching 3 cm, implanted on the wall of pitchblende geodes, or grouped in tufts in geodes which can reach 60 cm in diameter for the largest ones. Outside Katanga, cuprosklodowskite is known only in green inlays (Jachymov in the Czech Republic, Amelal in Morocco, etc...).

Cuprosklodowskite in France

In France, cuprosklodowskite is reported in Rabejac and Mas d'Alary near Lodève (Hérault).

Twinning and special crystallizations

No twin known for this mineral species.

Fakes and treatments

No fake identify for this mineral species.


Hardness : 4
Density : 3.85
Fracture : Irregular
Trace : Green

TP : Translucent to transparent
RI : 1.654 to 1.667
Birefringence : 0.010 to 0.012
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : -

Magnetism : None
Radioactivity : Very strong