Gypsum
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 4.0)
Mineral NameGypsum
Chemical FormulaCaSO₄·2H₂O
Mohs Hardness2
Crystal Systemmonoclinic
Lustervitreous
Streak Colorwhite
Cleavageperfect on {010}, good on {100} and {111}
Fractureconchoidal
Specific Gravity2.32
Colorscolorless, white, light grey
Transparencytransparent
Type LocalityNiccioleta Mine, Massa Marittima, Grosseto Province, Tuscany, Italy
Mineral Groupsulfates
Usesplaster, drywall, fertilizer, cement, sculpture, collector
Associated Mineralsanhydrite, halite, calcite, dolomite, sulfur
Raritycommon
Description
A striking cluster of large, transparent to translucent, bladed and tabular gypsum crystals, exhibiting a bright vitreous luster, growing on a matrix of smaller, granular crystals.
Geological Context
Gypsum is a common evaporite mineral, forming in sedimentary environments such as lagoons, shallow seas, and salt lakes where calcium sulfate-rich waters evaporate. It can also form in hydrothermal veins or as a hydration product of anhydrite.
