Chalcostibite - Encyclopedia

    Class : Sulfides and sulfosalts
    Subclass : Sulfosalts
    Crystal system : Orthorhombic
    Chemistry : CuSbS2
    Rarity : Uncommon to rare

Chalcostibite is a fairly rare sulfosalt from copper and antimony veins, associated with many other copper or antimony minerals, including chalcopyrite and tetrahedrite. Its name is linked to its chemical composition and comes from the Greek khalcos (copper) and the Latin stibium (antimony). It occurs in prismatic crystals, often elongated and striated in parallel, sometimes lamellar flattened according to {010}, as well as in lamellar to grained masses. Its color is iron gray to lead gray but chalcostibite is frequently covered with an alteration film of azurite or malachite.

Main photo : Chalcostibite from St-Pons, Alpes-de-Haute-Provence, France © Pascal Chollet

Azurite pseudomorph after chalcostibite from Rar-el-Anz, Morocco © J.-F. Carpentier
Chalcostibite from St-Pons, Alpes-de-Haute-Provence, France © Simon Philippo
Chalcostibite from Boldut Mine, Cavnic, Romania © Christian Rewitzer
Chalcostibite from Boldut Mine, Cavnic, Romania © Gianfranco Ciccolini

Chalcostibite in the World

Exceptional crystals, the largest known, measuring 10 cm, are embedded in the white dolomite of Rar-el-Anz (Morocco), magnificent centimeter-sized crystals have also been discovered in Bolivia, notably in Oruro, and in Spain, near Grenade.

Chalcostibite in France

In France, chalcostibite is present in good crystallized samples on the St-Pons deposit (Alpes-de-Haute-Provence).

Twinning and special crystallizations

A twin is known on {104}.

The crystals can be partially to completely transformed into blue azurite or malachite (pseudomorph), notably on the Moroccan deposit of Rar-el-Anz.

Fakes and treatments

No fakes recorded for this mineral species.

Hardness : 3 to 4
Density : 4.9 to 5.0
Fracture : Sub-conchoidal
Streak : Black

TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None

Solubility : Nitric acid

Magnetism : None
Radioactivity : None


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