Gypsum

The mineral Gypsum precipitated some 100 to 200 million years ago when sea water evaporated. From a chemical point of view it is Calcium Sulphate Dihydrate (CaSO4.2H2O) deposited in sedimentary layers on the sea bed. Under high pressure and temperature Gypsum turns into Anhydrite (CaSO4). In nature, Gypsum and Anyhdrite occur as beds or nodular masses up to a few metres thick. Gypsum is formed by the hydration of Anhydrite. The content of Gypsum in sedimentary rock varies from 75% to 95%, the rest being clay and chalk.

The word gypsum is derived from the Greek word γύψος (gypsos), "plaster". Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum (calcined gypsum) used for various purposes, this dehydrated gypsum became known as plaster of Paris. Upon adding water, after a few tens of minutes, plaster of Paris becomes regular gypsum (dihydrate) again, causing the material to harden or "set" in ways that are useful for casting and construction.

Natural Gypsum will continue to cover the basic raw material needs of the Gypsum industry, followed by FGD Gypsum, an intelligent alternative that comes from the flue gas desulphurisation plant (FGD) of the power station industry.