Sphalerite with Pyrite

specimen number:
2282088

location:
Fald, Binntal, Valais, Switzerland

description:
A sharp slightly translucent crystal of sphalerite 0.6 cm in size on a marble matrix with pyrite. In great condition. Classic material for this locality. The specimen comes with an antique label as shown at the end of the video.

The hamlet of Fald, situated in the Binntal within the Valais canton of Switzerland, is the access point for the historic Lengenbach quarry, a mineral locality known for its complex sulfosalt chemistry. Geologically, the deposit is hosted within Triassic meta-dolomites belonging to the Penninic Monte Leone nappe of the Swiss Alps, which underwent upper greenschist to lower amphibolite facies metamorphism during the Alpine orogeny. This metamorphic overprinting transformed synsedimentary base-metal sulfides into a highly specialized mineral assemblage dominated by rare thallium, lead, silver, and copper-bearing arsenic sulfosalts embedded within a sugary white dolomite matrix. The site first attracted industrial attention in 1728 when local authorities commissioned the evaluation of its iron deposits, leading to an initial mining concession in 1730 for the extraction of pyrite. Because commercial metal extraction proved economically unviable, operations shifted entirely toward scientific and collector specimen recovery by the nineteenth century. Systematic, organized seasonal specimen mining has been conducted continuously at the quarry since 1958 under local community syndicates and the Lengenbach Research Association, maintaining active research and educational operations into the twenty-first century.

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