SAINFELDITE

    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

Sainfeldite from Wilhelm Mine, Hesse, Germany © Gianfranco Ciccolini
Sainfeldite & picropharmacolite from Bou Azzer, Morocco © Jean-Pierre Barral
Sainfeldite from Neuenberg, Sainte-Marie-aux-Mines, Haut-Rhin, France © Cédric Lheur
Sainfeldite from Duranus, Alpes-Maritimes, France © Pascal Chollet

Sainfeldite in the World

Sainfeldite is reported in Jachymov (Czech Republic), in Germany in Richelsdorf (Thuringia), at the Sophia mine (Wittichen), the Anton mine (Heubachtal) and Schiltach (Black Forest), as well as at Bou Azzer in Morocco.

Sainfeldite in France

The best samples of sainfeldite are French and come from the Gabe-Gottes vein (level -40) in Ste-Marie-aux-Mines (Haut-Rhin). It has also been described in Duranus (Alpes-Maritimes) and Salsigne (Aude).

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 4
Density : 3.04
Fracture : Irregular
Streak : White

TP : Translucent to transparent
RI : 1.600 to 1.616
Birefringence : 0.016
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None

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