Potosiite on Franckeite (very rare) (superb crystals) (ex Brian Kosnar Collection)

Item Description

From the great find of 2004. This specimen is a very attractive, incredibly rare, superb quality, crystallized specimen of Potosiite consisting of many extremely rare, lustrous, heavily striated, silvery, tabular blades and unusually "bent" crystals measuring up to 10 mm sitting atop crystallized triclinic crystals of the lead, tin, iron, antimony sulfosalt, Franckeite plus some minor associated acicular Jamesonite. It must be noted that Potosiite was at one point a valied species, but is now defined as a variety of Franckeite. It does not take away from the great rarity and value of the specimen whatsoever. For those of you who are unaware, the Potosiite crystals on this specimen are EXCEPTIONALLY LARGE for the material. 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; they are distinct, and you can clearly see them with the naked eye. Despite their larger size, I did photograph them under the microscope to better illustrate their quality. These are undoubtedly some of the LARGEST KNOWN POTOSIITE CRYSTALS IN EXISTENCE, and this particular specimen is one of the finest known examples of this material extant. Directly from the private collection of Brian Kosnar who stashed this one away when it came out. It's completley irreplaceable now as, I have been told that the part of the mine that produced these specimens is now mined out and will most likely never produce these impressive specimens again. Valued at $3500 for crystal size / specimen size, quality and immense rarity. It's not a black rock, but rather a superb rarity from one of the more impressive rare mineral discoveries in South America in the last 30 years. If you care about collecting superb examples of crystallized mineral species, do not miss out on this one.