CaSO4·2H2OMonoclinic
Gypsum
CaSO4·2H2O
SulfatesChemical FormulaCaSO4·2H2O
Crystal SystemMonoclinic
Mohs Hardness2
Specific Gravity2.32
ColorColorless, white, gray, yellow
LusterVitreous to silky
StreakWhite
CleavageOne direction
FractureSplintery
Occurrence
Found in evaporite deposits. Alabaster and selenite are varieties. Used in drywall.