Franckeite (Var: Potosiite), Franckeite
San Jose Mine, Oruro City, Cercado Province, Oruro Department, Bolivia
Miniature, 4.0 x 3.5 x 3.0 cm
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