Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal system : Cubic
    Chemistry : (Ag,Cu,Fe)₁₂(Sb,As)₄S₁₃
    Rarity : Common

Freibergite is the least common mineral of the gray copper group. It forms a series (continuous solid solution) with tetrahedrite, the antimoniferous pole, and some authors still consider it as an argentiferous variety of this mineral. Freibergite remains much rarer than the latter, but is frequently associated with it in deposits rich in silver. It is known in polymetallic veins and gold-bearing epithermal veins, as well as in massive sulfide masses where its easy alteration into blue and green carbonates (azurite, malachite) makes it easily detectable. It was named after its location of discovery : Freiberg (Saxony, Germany). Freibergite has a metallic luster and an iron gray to black color, with a sub-conchoidal fracture and a generally tetrahedral appearance. It is an accessory ore of copper and silver. It is likely that it was confused with tetrahedrite in many deposits.

Main photo : Freibergite on rhodochrosite from Freiberg, Saxony, Germany © Jordi Fabre

Twins are known on {111}.

No fakes recorded for this mineral species.