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Download hereGENERAL DESCRIPTION
Franckeite is a lead, iron and tin sulfo-antimonide. It is found in the hydrothermal silver and tin deposits, in particular in the sulfide ore-bodies of Peru and Bolivia.
It can be associated with cylindrite, a related sulfo-antimonide. The crystals are prismatic and striated. They form also radial aggregates of crystals. Twins are common.
The crystals are gray and have a metallic luster. The occurences of franckeite are rather numerous in Peru and in Bolivia. Spectacular samples of franckeite are also found in the silver mines of Wallah Wallah in Australia.
In France, 2 localities are known: Vens-Haut (Brioude-Massiac district, Puy de Dôme) and Huelgoat (Finistère).
The type mineral for franckeite is kept at the Bergwerk Akademie ("School of Mines") ("School of Mines") of Freiberg in Germany. Alfred Stelzner donated it in 1893. Franckeite was first described this same year on a sample coming from the Chocaya mine, Atocha-Quechisla district, in the south of the Chichas province, Potosi department, Bolivia.
HISTORY : Species dedicated to Carl et Ernest Francke, mining engineers
Species first described in 1893 by Alfred Wilhelm Stelzner (1840-1895), German geologist
Type-locality : Las Animas district, Chocaya, Bolivia
CHEMICAL FORMULA : Pb5Sn3Sb2S14
CRYSTAL SYSTEM : Triclinic
COLOR : Black grayish
DIAPHANIETY : Opaque
LUSTER : Metallic
STREAK : Black grayish
MORPHOLOGIE : Fine crystals, striated, tabular, massive
HARDNESS : 2,5-3,0
CHEMICAL CLASS: 5,88
DENSITY : II - Sulfides, arsenides, antimonides and selenides
GROUP : Cylindrite - franckeite series
STRUNZ CLASS BEFORE 2001 : 2/C.17-70
STRUNZ CLASS AFTER 2001 : 2.HB.20
