LENGENBACHITE

    Class : Sulfides and sulfosalts
    Subclass : Sulfosalts
    Crystal system : Triclinic
    Chemistry : Pb6(Ag,Cu)2As4S13
    Rarity : Very rare

Lengenbachite is a very rare lead sulfoarsenide of hydrothermal origin. It bears the name of its discovery location : the Lengenbach quarry near Binn (Switzerland). Lengenbachite forms very fine, frequently curved lamellar crystals reaching 4 mm, within hydrothermalized dolomite. It is associated with pyrite and jordanite. It is a dark gray mineral that tarnishes in the air ; it is very difficult to distinguish from other lead sulfoarsenides without extensive analytical means.

Main photo : Leifite de Poudrette quarry, Mont St-Hilaire, Quebec, Canada © Joachim Esche

Lengenbachite in the World

Lengenbachite is known from the Lengenbach quarry (Switzerland), it has also been reported in Yellowknife (Canada) as well as on the Kochkovskoe gold deposit (Russia).

Right photo : Lengenbachite curve from Lengenbach quarry, Binn, Valais, Switzerland © Joan Rosell


Lengenbachite in France

Lengenbachite is not present in the French underground.

Twinning

Twins are known on {100} but only visible in polished sections.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 1.5 to 2
Density : 5.8 to 5.85
Fracture : Undetermined
Streak : Brown-black

TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None