Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated arsenates
    Crystal system : Monoclinic
    Chemistry : Co₃(AsO₄)₂ . 8H₂O
    Rarity : Rare

Erythrite (sometimes referred like erythrine) is a rare secondary mineral of the oxidation zones of cobalt-nickel sulphide deposits (skutterutide, cobaltite, etc...), but it is nevertheless the most common of the cobalt arsenates. It has the same crystalline structure as annabergite (nickeliferous) with which it constitutes a continuous series. Erythrite owes its name to the Greek eruthros (red), in reference to its color. It occurs in very aesthetic flat acicular crystals, flattened according to the perfect cleavage {010}, striated vertically, frequently grouped in rosettes or sheaves. The clear shapes, however, are relatively rare and the mineral is mostly known in radiated fibers, or encrustations with a fibrous to earthy structure. Its color, a beautiful purplish pink among large crystals, fades into carmine pink in small ones and then pale pink in incrustations. It is a rare mineral sought after by collectors that has no special use and whose low hardness (1 to 2 on the Mohs scale) prohibits any use in ornament or jewelery.

Erythrite is known in France in rare millimetric crystals at the Treille Mine near Ste-Marie-aux-Mines (Haut-Rhin) and at the Chalanches mine in Isère the type-locality where it occurs in encrustations. It is also found at the St-Daniel mine near Giromagny, Territoire-de-Belfort (photo on the right © Thierry Brunsperger - Mindat) and Beyrède-Jumet (Hautes-Pyrénées) in millimetric rosettes.

No fakes reported for this mineral species.