Gypsum
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Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is widely mined and is used as a fertilizer and as the main constituent in many forms o
Gypsum from southwest France (27 × 22 cm)
Gypsum crystals are soft enough to bend under pressure of the hand. Sample on display at Musée cantonal de géologie de Lausanne.
Large gypsum crystals in Lechuguilla Cave's "chandelier ballroom"
Gypsum crystals in the Cave of the Crystals in Mexico (person at lower right for scale)
Selenite (gypsum)
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Selenite is a mostly clear, transparent variety of the sulfate mineral gypsum.
Gypsum
…and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk chalk. Gypsum also crystallizes as translucent crystals of selenite. It forms as an evaporite mineral and as a hydration product of anhydrite. The Mohs scale of mineral hardness defines gypsum as hardness value 2 based…
Gypse sélénite 3
Columnar crystal habit
"Gypsum flower" speleothem, Mammoth Cave National Park, Kentucky. Orange color is iron oxide from groundwater.
Azurite-gypsum "Buda Rock", Ray Mine Arizona. A core of glassy and colorless gypsum crystals up to 1 cm in length with a druse of royal blue azurite, to 0.5 cm in length on the smaller gypsum crystals and included within the larger ones.