Erythrite - Encyclopedia
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 in the World
Erythrite in France
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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.
Twinning and special crystallizations
Fakes and scams
No fakes reported for this mineral species.
Hardness : 1.5 to 2.5
Density : 3.06 to 3.18
Fracture : Sectible
Trace : Pink
TP : Translucent to transparent
IR : 1.626 to 1.701
Birefringence : 0.071
Optical character : Biaxe +
Pleochroism : Strong
Fluorescence : Sometimes orange
Solubility : Acids
Magnetism : None
Radioactivity : None