Chalcomenite - Encyclopedia

    Class : Oxides and hydroxides
    Subclass : Selenites
    Crystal system : Orthorhombic
    Chemistry : CuSeO3 2H2O
    Rarity : Rare


Chalcomenite belongs to the little-represented subclass of selenites. It is a secondary mineral which crystallizes in the oxidation zone of copper and selenium deposits by oxidation of selenides. Its name comes from the Greek khalcos (copper) and mene (contraction of selene, the moon). It forms tiny acicular crystals of a beautiful blue color, with frequently rounded faces.

Main photo : Chalcomenite from Baccu Locci, Sardinia, Italy © Italo Campostrini

Chalcomenite from San Guillermo Mine, Andalusia, Spain © Antonio Pliego
Chalcomenite from Baccu Locci, Sardinia, Italy © Stephan Wolfsried
Chalcomenite from San Guillermo Mine, Andalusia, Spain © Christian Rewitzer
Chalcomenite and malachite from Musonoï, Rep. Start from Congo © Italo Campostrini

Chalcomenite in the World

This rare mineral is known in deposits rich in selenides : Cacheuta, Sierra de Umango and Sierra de Famatina (Argentina), Pacajake and El Dragon (Bolivia). But the most beautiful samples come from the Congolese mine of Musonoï (Katanga) and Baccu Locci in Sardinia (Italy), as well as the San Guillermo mine (Spain).

Chalcomenite in France

In France, chalcomenite is found in the small uranium selenide vein of Liauzun, near Olloix (Puy-de-Dôme).

Twinning and special crystallizations

No twin known for this mineral species.

Fakes and treatments

No fakes identified for this mineral species.



Hardness : 2 to 2.5
Density : 3.35
Fracture : Conchoidal
Streak : Blue



TP : Translucent to transparent
RI : 1.712 to 1.732
Birefringence : 0.020
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None


Solubility : Acids


Magnetism : None
Radioactivity : None

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