From the alkaline type locality of Mt. St. Hilaire, this is a relatively large example of the species. Carletonite crystals, like this one, are clearly tetragonal, glassy and gemmy and the best exhibit this lovely, ice blue color. Large and complete all around, this is a significant thumbnail crystal and one seldom sees good pieces for sale today. There is a very clean, lock-fit repair at the bottom, though, and hence a price lower than the $500-750 otherwise valued for it.