franckeite

{{infobox mineral | name = Franckeite | category = Sulfosalt mineral | boxwidth = | boxbgcolor = | image = Franckeite-119411.jpg | imagesize = 260px | alt = | caption = Franckeite var. Potosíite, San José Mine, Cercado Province Bolivia. Field of view about 10mm. | formula = (Pb,Sn2+)6Fe2+Sn2Sb2S14 | IMAsymbol = Fke | molweight = | strunz = 2.HF.25b | dana = 03.01.04.02 | system = Triclinic | class = Pinacoidal () (same H-M symbol) | symmetry = P | color = Grayish black | colour = | habit = Typically in spherical, rosette aggregates of thin plates; commonly massive, radiated, or foliated | twinning = Complex | cleavage = {010}, perfect | fracture = | tenacity = Flexible, inelastic; slightly malleable | mohs = 2.5 – 3 | luster = Metallic | streak = Grayish black | diaphaneity = Opaque | gravity = 5.88 – 5.92 | density = | polish = | opticalprop = | refractive = | birefringence = | pleochroism = Weak | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = }} Franckeite, chemical formula Pb5Sn3Sb2S14, belongs to a family of complex sulfide minerals. Franckeite is a sulfosalt. It is closely related to cylindrite.

It was first described in 1893 for an occurrence in Chocaya, Potosí Department, Bolivia. It is named after the mining engineers, Carl and Ernest Francke. It can be found in Bolivia at Poopó in Oruro and at Las Aminas, southeast of Chocaya, in Potosi. Franckeite has an average density of 5.7 and can be both grayish black, blackish gray in color.