Rathite

specimen number:
2262007

location:
Lengenbach Quarry, Fald, Binn, Goms, Valais, Switzerland

description:
Very fine example for this rare species, a metallic prismatic crystal measuring 1.0 cm in length set up on a marble matrix. Minor pyrite is present. Classic material for this locality, in very good condition. The specimen comes with a previous label and data card dating this back to the 1960s. These are shown at the end of the video.

The Lengenbach Quarry, located in the Binn Valley (Binntal) of the Valais Canton, Switzerland, is world-famous as one of the most prolific localities for rare sulfosalt minerals. Geologically, the deposit is unique because it consists of a small, lens-shaped body of Triassic-aged dolomite that underwent high-grade regional metamorphism during the Alpine orogeny. During this metamorphic event, metal-rich fluids containing lead, arsenic, thallium, and copper interacted with the dolomite, precipitating a diverse array of complex minerals within small cavities and along bedding planes. Historically, the site has been known to mineralogists since the early 19th century, with formal quarrying for specimens beginning in earnest in the late 1800s. Unlike most industrial mines, Lengenbach has been operated almost exclusively for the recovery of mineral specimens for scientific research and collectors. Organized specimen mining has been conducted by various syndicates and cooperatives from 1958 through the present day, making it a legendary site for the discovery of species that are found nowhere else on Earth.

Rathite is a rare and complex lead arsenic sulfosalt mineral. It typically occurs as small, lead-gray to iron-black metallic crystals that are often striated and found embedded in the sugary white dolomite matrix characteristic of the Lengenbach Quarry. The mineral was first described in the late 19th century and named in honor of the German mineralogist Gerhard von Rath. Geologically, it is a primary mineral formed during the hydrothermal alteration of the host dolomite under specific pressure and temperature conditions. Because of its structural complexity and its relationship to other rare sulfosalts like baumhauerite and sartorite, rathite is a subject of significant interest in the field of crystallography. Specimens are highly prized by collectors for their sharp metallic luster and their historical association with the alpine mineralogy of the Binn Valley.

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