Lengenbachite - Encyclopedia
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
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