Gypsum is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.Approximately 75 per cent of the gypsum used in North America is calcined, meaning that three-quarters of the water has been removed by heating to form stucco or plaster of Paris.
Calcined gypsum is one of the most common building materials in the world. It is used for interior wall partitions and ceilings, either as plaster or in prefabricated products. Regular wallboard and type-x wallboard with its fire-resistant characteristics make up over three-quarters of the market for calcined gypsum. Minor uses for calcined gypsum include dental plaster, modelling casts, moulds, surgical casts and drilling muds.