Carcalzite

Carcalzite, a granite in which the felspar has been converted into kaolin or china-clay (q.v.), consisting, therefore, of quartz, kaolin, and mica, and constituting the "soft growan" of Carclaze, near St. Austell, Cornwall, where it is largely worked as a material for the porcelain manufacture. It is practically infusible, constituting what the Chinese call the bone of the ware, i.e. its less translucent part.