Franckeite, chemical formula Pb5Sn3Sb2S14, belongs to a family of complex sulfide minerals. It is closely related to cylindrite.
It was first described in 1893 for an occurrence in Chocaya, Potosí Department. 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.
It occurs in hydrothermal silver-tin deposits in Bolivia and in contact metamorphosed deposit in the Kalkar quarry in California. It occurs with cylindrite, teallite , cassiterite , marcasite , pyrite and stannite