Synthetic gypsum, which is now used in about 30% of drywall, is a byproduct of coalfired power plants. It is sometimes confused with fly ash another coal combustion product with which it has very little in common. In excess of 80% of coal fly ash sold in the United States is used in gypsum board.
Gypsum block is a massive lightweight building material composed of solid gypsum, for building and erecting lightweight, fireresistant, nonload bearing interior walls, partition walls, cavity walls, skin walls, and pillar casing indoors. Gypsum blocks are composed of gypsum, plaster, water and in some cases additives like vegetable or wood fiber for greater strength.