Scientific Name: Calcium sulfate hydrate
Chemical composition: CaSO4.2H2O
Colors: Colorless, white, light brown, yellow, pink
Formation: Monoclinic crystal; prismatic to tabular form
Principal Sources: Worldwide
Special Notes: The Romans discovered that heating gypsum to 600 degrees F made a plaster that sets hard when mixed with water. This plaster was used for building and is still widely used today.