a common white or colorless mineral (hydrated calcium sulphate) used to make cements and plasters (especially plaster of Paris)
"The construction crew crushed the rock on site, revealing that it was gypsum ready for mixing into plaster."
A mineral consisting of hydrated calcium sulphate. When calcinated, it forms plaster of Paris.
"The geologist identified the white rock as gypsum after noting its characteristic reaction to acid and its potential use for making plaster."