Gypsum
Gypsum(CaSO4.2H2O) is a commonsulfate mineralmade ofcalcium sulfate.Gypsum has been used as a building material for a long time, possibly since theneolithic.Today, it is used indrywall,and as an ingredient ofplaster of Paris.It can also be used as afertilizer.It is softer than most minerals, with a value of 2 on theMohs scale of mineral hardness.This mineral can be, somewhat, scratched with your fingernail. A fingernail, with a value of 2.5 on theMohs scale of mineral hardnessis in fact higher than the mineral shown above. It is an ingredient ofPortland cement.Gypsum was used inancient EgyptandMesopotamiaby sculptors. It is also used in making surgical and orthopedic cast molds.
