From the collection of my own former mentor, a world class competitive exhibitor of thumbnails in Tucson for decades, this is a significant Texas crystal of the rare species chambersite. A true rarity, and yet in size enough for any collector of both thumbnails or important species. They have a bizarre but classic pyramidal form. This one is an unusually sharp, museum-quality specimen of an unusual mineral so rare that most people have never seen one. These were found as floaters in salt dome formations down here in Texas and Louisiana (there are just ten localities worldwide, so far as I know, but these grow the biggest). As a bonus, this large crystal is very tasnlucent and deeply PURPLE AND GEMMY when backlit!