Natural gypsum, also called calcium sulphate, is found in different forms, mainly as a dihydrate (CaSO4 · 2H2O) and anhydrite (CaSO4). They are products of partial or total evaporation of inland seas and lakes. Gypsum undergoes crystallization as translucent crystals of selenite, forming as an evaporite mineral and as a hydration form of anhydrite. Both the dihydrate and the anhydrite occur in nature in a variety of forms. The origin of gypsum, its genesis, varieties and properties are discussed, and the focus is then on the most common binding material produced from it, plaster of Paris.
Uses of Gypsum mainly depend on its paste-like setting, expansion, and adhesion properties. Whereas hardened gypsum for strength, bulk weight, thermal expansion, volume and linear changes under humidity fluctuations, moisture absorption, paintability, corrosivity, thermal and acoustic insulation behaviour, and fire resistance.
Gypsum has been studied as a raw material, as a rock constituent, as an indicator of geological and archaeological conditions, and from other points of view. However, its role in Earth’s surface processes, its relationship to life through calcium in the equilibrium of carbonates and its structural water molecules seems overlooked. The semi-solubility of gypsum explains its actions in many soils. Gypsum’s softness, fragility, and crystal water should be considered.
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