Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated arsenates
    Crystal system : Monoclinic
    Chemistry : Ca₅(AsO₄)₂(AsO₃OH)₂ 4H₂O
    Rarity : Very rare

Sainfeldite was described in 1963 on samples from the famous Gabe-Gottes vein, in the old silver, copper and arsenic mine of Ste-Marie-aux-Mines (Haut-Rhin, France). It is one of the newly formed calcium arsenates from the oxidation zone of arsenic veins; these arsenates crystallize in abundance in old mining workings as a result of the air oxidation of primary arsenic sulfides (arsenopyrite, löllingite). It was named in honor of the geologist and mineralogist Paul Sainfeld, Curator of the Mineralogy Museum of the Ecole des Mines de Paris. Sainfeldite forms millimeter-sized rosettes, consisting of assemblages of transparent crystals in elongated prisms according to [001], often associated with picropharmacolite and native arsenic. It is generally colorless but takes on a beautiful pink color when it contains traces of cobalt. In addition to this color, it is distinguished from other arsenates by its absence of efflorescence.

Main photo : Sainfeldite from Bauhaus, Hesse, Germany © Christian Rewitzer

No twinning known for this mineral species.

No fakes listed for this mineral species.