This is quite the specimen! It is a quartz pseudomorph after calcite, and the quartz is amethystine. The quartz evidently grew in quickly, as the pseudomorph exhibits skeletal growth. And… it’s an epimorph – it is hollow, lined with tiny amethyst crystals. It’s not too easy to see into the hollow, but it appears that the epimorph we see is quite thin. In good condition overall with some chipping – some of which happened before the end of the crystallization of this piece. A unique epimorph from the John S. White quartz collection.