A relatively large crystal of this very rare species, which only has been found in a few places in the world in such crystals. Of those, these large hexagonal crystals are the only ones a collector can even really expect to see periodically on the market, though even then it is a rare thing (they were brought out by Carlos Barbosa, I think, in the late 1980s or early 90s). Ex. Ron Pellar thumbnail collection. Joe Budd photos.