TRECHMANNITE

    Class : Sulfides and Sulfosalts
    Subclass : Sulfosalts
    Crystal system : Trigonal
    Chemistry : AgAsS2
    Rarity : Very rare

Trechmannite is a very rare silver sulfoarsenide, dimorphic of smithite. It is a mineral of hydrothermal origin known from a handful of deposits. It was named in honor of the English crystallographer Charles Otto Trechmann. Trechmannite forms small, short, equant or prismatic crystals, of a cinnabar red color, in hydrothermalized dolomites, associated with pyrite, tennantite and seligmannite.

Main photo : Trechmannite from Lengenbach quarry, Binn, Valais, Switzerland © Stephan Wolfsried

Trechmannite in the World

The most beautiful crystals of trechmannite are millimetric and come from the Lengenbach quarry near Binn (Valais, Switzerland). It is also reported at the St-Anna mine (Austria) and at Niederbeerbach (Germany).

Right photo : Trechmannite from Lengenbach quarry, Binn, Valais, Switzerland © Mischa Crumbach


Trechmannite in France

Trechmannite is not known in the French underground.

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 1.5 to 2
Density : 4,77
Fracture : Conchoidal
Streak : Red

TP : Translucent to transparent
RI : 2.400 to 2.600
Birefringence : 0.200
Optical character : Uniaxial -
Pleochroism : Low
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None

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