Image: Gianfranco Ciccolini (CC0)
monocliniccommonSulfates
Gypsum
CaSO4·2H2O
This specimen features a clear, well-formed, tabular crystal of gypsum, showcasing its typical monoclinic habit. Gypsum can also appear in massive, fibrous, or granular forms.
Gypsum Physical Properties
Mohs Hardness
2Crystal System
monoclinicLuster
vitreousStreak Color
whiteCleavage
perfect on {010}, good on {100}, distinct on {101}Fracture
conchoidalSpecific Gravity
2.32Colors
colorless, white, gray, yellow, red, brownTransparency
transparentType Locality
Le Cetine di Cotorniano Mine, Chiusdino, Siena Province, Tuscany, ItalyMineral Group
SulfatesUses
plaster of Paris, drywall, fertilizer, cement, sculptureAssociated Minerals
onoratoite, anhydrite, halite, calcite, dolomiteRarity
commonGeological Context
Gypsum is a common evaporite mineral, forming in sedimentary environments from the precipitation of calcium sulfate from saline waters, such as in playa lakes, lagoons, and caves. It can also form from the hydration of anhydrite.
