- Franckeite (Var: Potosiite), Franckeite
- Cabinet, 9.8 x 6.3 x 3.4 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, fine quality, crystallized specimen of the triclinic lead, antimony, iron, tin sulfosalt Potosiite consisting of several extremely rare, highly lustrous, heavily striated, tabular blades (some are twinned) of Potosiite measuring up to 9 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 for the species. 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 Potosiite has been positively identified through X-ray Diffraction. This specimen is from a newly opened vein in this historic mine in 2004.