Franckeite (Var: Potosiite), Franckeite - image 1

Franckeite (Var: Potosiite), Franckeite

Unknown Owner
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Sharp crystals of several habits, to 6mm! This is a relatively new occurrence for the species. So far as I am aware from my sources, there were only a handful of these extracted (though it is possible many were simply thrown in the garbage and not recognized for what they were!), and none have been found since the indentity was reported to the Bolivian miners working the San Jose. From what I can gather, previously reported samples were under 2 mm and somewhat granular, indistinct crystals. These occur as both straight crystals to 6 mm on this specimen and as very large, distinct, highly lustrous, curved crystals (in appearance as if one were to curl their finger). I am told that there is only one group of minerals in the world that exhibit a non-commensurate layered crystalline structure and are found with curved crystals, and this is a textbook example of such crystals. 4 x 3.5 x 3 cm

Product details

SpeciesFranckeite
SizeMiniature
Dimensions4.0 x 3.5 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.