This is quite simply my intellectual favorite of the collection, bar none. You will NEVER SEE one of these again, I'd bet, outside of a book on historic minerals of Cornwall (and even then, I don't think there was a photo in THE History of Cornwall Minerals book, was there?!). I had never seen one, outside of browsing a copy of Sowerby's Exotic Mineralogy! They were found rarely in the late 1700s or early 1800s; and nobody I have spoken to knows of another piece of any significance to hit the market in decades. Moreover, aside from the significance of its mere existence and availability for sale, it is as dramatic as a grey-colored mineral can be, with sparkly crystals rising dramatically to 3 cm in height! I have privately shown the specimen to several European experts who have confirmed that it is as rare and desirable as I say, and that it is indeed English and not French or German. Note also that it was an early specimen in the collection of Carl Bosch, who was noted for his superb suites of old classics. The back of the old label seems to indicate whom he purchased it from. It belongs in a museum and I would prefer to place it to go to one.