Franckeite (Var: Potosiite), Franckeite - image 1
Franckeite (Var: Potosiite), Franckeite - image 2

Franckeite (Var: Potosiite), Franckeite

Unknown Owner
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From the find of 2004, this specimen hosts two of the rarest sulfosalts in the world. This specimen is a very attractive, very rare, superb, crystallized specimen of the triclinic lead, antimony, iron, tin sulfosalt Potosiite consisting of several, very rare, highly lustrous, heavily striated, tabular blades (some are twinned) of Potosiite measuring up to 10.5 mm sitting atop crystallized and the equally rare triclinic lead, tin, iron, antimony sulfosalt Franckeite. The crystals of Potosiite on this specimen are exceptionally large. Before these new specimens were discovered, some of the largest known crystals of Potosiite were massive, uncrystallized, granules less than 1 mm. in most cases. The crystals on this specimen are not micros, you can clearly see them with the naked eye and they are very distinct. Ex. Brian Kosnar Collection.

Product details

SpeciesFranckeite
SizeSmall Cabinet
Dimensions7.1 x 5.8 x 3.0 cm
Added on10/23/2024
LocalityBolivia, Potosí, San Jose Mine

Known provenance

DateCollectorAcquisition price
08/2024Unknown OwnerNot disclosed
—The ArkenstoneNot disclosed

Learn more

Mineral guide
Learn about Franckeite
, a rare micaceous lead-tin-antimony sulfosalt, forms layered rosettes and curved plates; Bolivian origin and texture make it collectible.
Franckeite
Regional guide
Franckeite from San José Mine, Bolivia
from the San José Mine is one of the classic Bolivian sulfosalt specimens: black to steel-gray, metallic, soft, heavy, and often built from curving blades and radiating rosettes rather than simple textbook crystals. The best pieces have a lively sheen that moves across the bent plates as the specimen is turned, giving an otherwise dark mineral a surprisingly sculptural presence. Collectors prize San José franckeite because it shows the species in displayable form—not merely as a massive ore constituent, but as rosettes, foliated aggregates, compact sprays, and curved, bladed crystals that express the mineral’s layered structure in the hand.