LENGENBACHITE (extremely rare)

A very rare and older specimen from the Lengenbach Quarry.

Lengenbachite is a recognized mineral species that was first identified in 1904 by R. H. Solly. Named after its type locality, the renowned Lengenbach Quarry in the Binntal region of Switzerland, this mineral is notable for its unique sulfosalt composition. Lengenbachite features a complex chemical formula: Ag₄Cu₂Pb₁₈As₁₂S₃₉, indicating a significant presence of lead (Pb), along with silver (Ag), copper (Cu), arsenic (As), and sulfur (S). Characterized by its relatively low hardness and high specific gravity—primarily due to its lead content—Lengenbachite exemplifies many sulfosalts. Its triclinic crystal system highlights the intricate nature of its crystal structure and formation conditions. As a member of the sulfosalt category, Lengenbachite shares structural similarities with other minerals formed from complex sulfide frameworks. In the Lengenbach Quarry, it is frequently found alongside minerals such as pyrite, dolomite, and various tennantite subgroup members, which are essential for understanding the hydrothermal and metamorphic processes that lead to these mineral formations.