- Franckeite (Var: Potosiite), Franckeite
- Small Cabinet, 7.1 x 5.8 x 3.0 cm
- San Jose Mine, Oruro City, Cercado Province, Oruro Department, Bolivia
From the find of 2004, this specimen hosts two of the rarest sulfosalts in the world. This specimen is a very attractive, very rare, superb, crystallized specimen of the triclinic lead, antimony, iron, tin sulfosalt Potosiite consisting of several, very rare, highly lustrous, heavily striated, tabular blades (some are twinned) of Potosiite measuring up to 10.5 mm sitting atop crystallized and the equally rare triclinic lead, tin, iron, antimony sulfosalt Franckeite. The crystals of Potosiite on this specimen are exceptionally large. Before these new specimens were discovered, some of the largest known crystals of Potosiite were massive, uncrystallized, granules less than 1 mm. in most cases. The crystals on this specimen are not micros, you can clearly see them with the naked eye and they are very distinct. Ex. Brian Kosnar Collection.