<Tr> <Td_colspan="2"> Infobox references </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> </Tr> <P> Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO and related hydrates . In the form of γ - anhydrite (the anhydrous form), it is used as a desiccant . One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum . It has many uses in industry . All forms are white solids that are poorly soluble in water . Calcium sulfate causes permanent hardness in water . </P> <P> The compound exists in three levels of hydration corresponding to different crystallographic structures and to different minerals in the nature: </P>

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