Franckeite with Zinkenite, Stannite

specimen number:
2262006

location:
Itos Mine, Oruro, Bolivia

description:
Very fine metallic crystallized franckeite in a cluster with zinkenite and stannite crystals. This is in very good condition all around.

The Itos Mine, situated in the historic Oruro mining district of the Altiplano in Bolivia, is a classic high-altitude Andean tin and silver operation. Geologically, the deposit consists of complex hydrothermal vein systems associated with the San Jose-Itos mineralized zone, which is hosted within a sequence of Paleozoic sedimentary rocks and fractured volcanic domes. These veins are renowned for their unique mineral chemistry, containing high concentrations of tin, lead, silver, and antimony, which precipitated from hot, metal-rich fluids during the Neogene period. Historically, the mine has been active since the colonial era, though its primary industrial expansion occurred in the late 19th and early 20th centuries during the Bolivian tin boom. The Itos Mine was a significant producer for many decades under various owners, eventually becoming part of the state-owned COMIBOL operations. While large-scale commercial extraction has fluctuated with global metal prices, the site remains a legendary locality for specialized mineral collectors due to the rare and complex sulfosalts found within its deep underground workings.

Franckeite is an extraordinary sulfosalt mineral that is famous for its unusual physical structure, which consists of alternating layers of different atomic arrangements. These layers cause the crystals to naturally curve, often forming rounded, thin plates or "rosettes" with a metallic, lead-gray luster. Geologically, it occurs in hydrothermal tin-silver veins, typically as a late-stage mineral in association with other rare species like cylindrite and zinkenite. The Itos Mine is one of the world's most significant localities for this species, producing some of the largest and most distinct specimens ever recorded. Because of its complex composition and the mathematical precision of its layered curvature, franckeite is of great interest to crystallographers and mineral collectors who value it for both its aesthetic uniqueness and its remarkable geological origin.

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