Gypsum is a naturally occurring mineral that contains calcium sulfate, which is used to make wall board, cement and fertilizer.Gypsum is what my friend at TWRA said is used to mix with coal ash, which is then manufactured into drywall and cinder block.Anyway, rumor has it that TVA???s Johnsonville Fossil Plant outside of Waverly, TN is operating with a sludge pond (pictured at right) which is 20 y