Class : Sulfates, chromates, molybdates
    Subclass : Hydrated sulfates
    Crystal system : Monoclinic
    Chemistry : FeSO₄ 7H₂O
    Rarity : Common

Pisanite is the copper-bearing (up to 19% CuO) variety of melanterite, a hydrated iron sulfate that forms by weathering pyrite or marcasite under very acidic pH conditions. It is a very fragile secondary mineral, difficult to preserve outside the acidic humidity of the mine galleries where it was born, due to its great solubility and its ability to dehydrate in a dry atmosphere. It was named in honor of the French chemist Félix Pisani. Pisanite most often forms fibers, sometimes capillary, assembled into mats, encrustations or efflorescences. The concretions or stalactites, as well as the rare isometric or short prismatic crystals display a magnificent greenish blue color, passing to clear blue and sometimes purplish blue for the terms richest in copper.

Main photo : Pisanite des Malines, St-Laurent-le-Minier, Gard, France © Pascal Chollet

No twin known for this mineral species.

No fakes recorded for this mineral species.