Argyrodite - Encyclopedia

    Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal System : Orthorhombic
    Chemistry : Ag8GeS6
    Rarity : Very rare

Argyrodite is an extremely rare silver and germanium sulfide, known in low-temperature silver-bearing hydrothermal veins. Tin can completely replace germanium, creating a complete solid solution with canfieldite. Its name comes from the Greek arguros (silver) in connection with its chemical composition. It forms very rare pseudo-octahedral, cubic or dodecahedral crystals. These are often millimetric (but 18 cm giants have been recorded), and frequently gathered in radiate aggregates, encrustations or botryoidal masses. The tint is dark gray with reddish or bluish undertones, but the mineral is photosensitive and quickly tints with a black tarnish. This light corrosion is an excellent criterion for microscopic determination. It is a very accessory ore of tin and silver.

Main photo : Argyrodite from Colquechaca, Potosi, Bolivia © John R. Montgomery

Argyrodite in the World

The best samples of argyrodite come from the argentiferous veins of Brand-Erbisdorf, near Freiberg (Germany), and above all from the Bolivian silver and tin deposits, notably Aullagas near Colquechaca, and Porco near Potosi, which provided largest known crystals. In these deposits, argyrodite accompanies an important procession of silver minerals.
Right photo : Argyrodite from Colquechaca, Potosi, Bolivia © Van King

Argyrodite in France

In France, there are microscopic beaches in the argentiferous  vein of Fournial (Cantal).

Twinning and special crystallizations

Argyrodite may show twins on {111}

Fakes and treatments

No fake or treatments identified for this mineral species.

Hardness : 2.5 to 3
Density : 6.29
Fracture : Irregular
Trace : Gray, black

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

Solubility : -

Magnetism : None
Radioactivity : None