Image: <bdi><a href="https://www.wikidata.org/wiki/Q126871368" class="extiw" title="d:Q126871368"><span title="photographer from the United States">Darla Sondrol</span></a></bdi> (CC0)
monocliniccommonSulfates
Gypsum
CaSO4·2H2O
The image displays a large, translucent to transparent gypsum crystal, likely a 'swallowtail twin,' exhibiting a reentrant angle at its top. It is colorless to white and shows characteristic monoclinic crystal forms.
Gypsum Physical Properties
Mohs Hardness
2Crystal System
monoclinicLuster
vitreousStreak Color
whiteCleavage
Perfect on {010}, distinct on {100} and {101}Fracture
unevenSpecific Gravity
2.32Colors
colorless, white, gray, yellow, red, brownTransparency
transparentType Locality
Naica, Mexico (for large crystals); worldwide in evaporite depositsMineral Group
SulfatesUses
plaster of Paris, drywall, fertilizer, cement retarder, carving (alabaster)Associated Minerals
halite, anhydrite, sulfur, calcite, dolomite, celestineRarity
commonGeological Context
Gypsum commonly forms in evaporite deposits from the precipitation of calcium sulfate from evaporating saline waters, such as ancient seas or lakes. It can also occur in hydrothermal veins or as a secondary mineral.
