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

Item Description

This piece is one of the finest examples from the great find of 2004, which produced the most significant crystals of Potosiite ever found. This specimen is a very attractive, superb quality, crystallized specimen of Potosiite featuring extremely rare, heavily striated, tabular blades (some are twinned) measuring up to 1.2 cm (!!) sitting atop crystallized triclinic crystals of the equally rare lead, tin, iron, antimony sulfosalt, Franckeite. The crystals are a marvel for their unique form and intricate beauty which we've illustrated in the photos. It must be noted that Potosiite was at one point a valid 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, especially now that we are more than 15 years past its discovery, and NONE more have been found. 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. These pieces represent undoubtedly some of the LARGEST KNOWN POTOSIITE CRYSTALS IN EXISTENCE. Any crystals over 1 cm is big, and up to 1.5 cm is considered huge! I have been told that the part of the mine that produced these specimens is now mined out and we will most likely never see them again. This piece is valued at $3,500 simply for the fact that it has a very good number of large crystals, and it's actually very displayable, which can't be said of most of them. From the private collection of Brian Kosnar, who personally imported all of the best specimens in 2004 directly from Bolivia.