What is Gypsum?
[[File:Gypsum - Sieroszowice mine, Lubin, Lower Silesia, Poland.jpg|thumb|250px|Gypsum]] '''Gypsum''' (CaSO<sub>4</sub>.2H<sub>2</sub>O) is a common [[sulfate mineral]] made of [[calcium sulfate]]. Gypsum has been used as a building material for a long time, possibly since the [[neolithic]]. Today, it is used in [[drywall]], and as an ingredient of [[plaster of paris|plaster of Paris]]. It can also be used as a [[fertilizer]]. It is softer than most minerals, with a value of 2 on the [[Mohs scale of mineral hardness]]. This mineral can be, somewhat, scratched with your fingernail. A fingernail, with a value of 2.5 on the [[Mohs scale of mineral hardness]] is in fact higher than the mineral shown above. It is an ingredient of [[Portland cement]]. Gypsum was used in [[ancient Egypt]] and [[Mesopotamia]] by sculptors. It is also used in making surgical and orthopedic cast molds. {{sci-stub}} [[Category:Minerals]] [[Category:Calcium compounds]]