Weilite

weilite

haidingerite

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Formula: Ca(AsO3OH)
Arsenate
Crystal System: Triclinic
Specific gravity: 3.48 measured, 3.45 calculated
Streak: White
Colour: White
Luminescence: Not fluorescent under UV
Environments

Hydrothermal environments

Weilite is a rare secondary mineral in the oxidised zone of arsenic-bearing hydrothermal mineral deposits. Associated minerals include pharmacolite, haidingerite and picropharmacolite (HOM).

Localities

There are three co-type Localities:
Gabe Gottes Mine, Sankt Jakob vein, Neuenberg, Sainte-Marie-aux-Mines, Colmar-Ribeauvillé, Haut-Rhin, Grand Est, France
Wittichen, Schenkenzell, Rottweil, Freiburg Region, Baden-Württemberg, Germany
Schneeberg, Erzgebirgskreis, Saxony, Germany

Weilite occurs as a secondary mineral in the oxidised zone of arsenic-rich veins; it is often an alteration product of pharmacolite and haidingerite. The implied dehydration takes place in 3 months at 120oC, but does not proceed in the same time at ordinary temperatures, even in the presence of P2O5 or H2SO4.
Weilite occurs as powdery incrustacions or pseudomorphs after pharmacolite or haidingerite (AM 49.2.816).

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