ABSTRACT
Different types of natural gypsum (habitus and crystal size criteria): —coarsely crystalline gypsum: selenite, marienglass, lenticular gypsum, fibrous gypsum: satin-spar, fascicular gypsum; —finely crystalline, granular and massive gypsum: alabaster, saccharoidal gypsum, fibrolamellar gypsum, sand or seed gypsum, kopi gypsum; —impure gypsum: clayey gypsum, saline gypsum, calcareous gypsum, dolomitic gypsum, siliceous gypsum. Different types of natural anhydrite (habitus and crystal size criteria): coarsely crystalline anhydrite, fibrous anhydrite, finely crystalline anhydrite, lamellar anhydrite, nodular anhydrite.
