Franckeite - Encyclopedia
Class : Sulfides and sulfosalts
Subclass : Sulphides
Crystal system : Triclinic
Chemistry : FePb5Sn3Sb2S14
Rarity : Rare
Franckeite is a very rare lead and tin sulfide present in certain tin-bearing hydrothermal veins, mainly in Bolivia. It was named in honor of the two German mining engineers Carl and Ernest Francke, pioneers of Bolivian geology in the 19th century. Franckeite occurs in fine, lamellar crystals, more rarely elongated and grooved on {010}, often curved, but more commonly in masses, with a foliated or radiated appearance, in multicentimetric spherical aggregates, in rosettes or cauliflowers reaching 1 cm in diameter. Franckeite is lead gray to gray-black in color. It is a very minor ore of tin.
Main photo : Franckeite de San José Mine, Oruro, Cercado Province, Oruro, Bolivia © Oleg Lopatkin
Franckeite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 2.5 to 3
Density : 5.90
Fracture : Irregular
Streak : Grey-Black
TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None
Solubility : Nitric acid
Magnetism : None
Radioactivity : None