- Franckeite (Var: Potosiite)
- San Jose Mine, Oruro City, Cercado Province, Oruro Department, Bolivia
- Miniature, 4.1 x 3.7 x 2.3 cm
From the new find of 2004, this specimen hosts two of the rarest sulfosalts in the world. This specimen is a very attractive, incredibly rare, superb 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 5 mm sitting atop crystallized and the equally rare triclinic lead, tin, iron, antimony sulfosalt Franckeite. For those of you who are unaware, 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. This new find has completely redefined the species of Potosiite. The crystals on this specimen are NOT micros, you can clearly see them with the naked eye and they are very distinct. These are undoubtedly some of the LARGEST KNOWN POTOSIITE CRYSTALS In EXISTENCE. The Potosiite has been positively identified through X-ray Diffraction. This specimen is from a newly opened vein in this historic mine. Ex. Brian Kosnar Collection.