mineral
Gypsum (selenite/alabaster variety)
Gypsum, CaSO₄·2H₂O
AI-generated identification · may be incorrectTan to reddish-brown, earthy to pearly luster, with visible layered cleavage; monoclinic crystals. Mohs hardness 2; specific gravity about 2.3.
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Physical properties
Tan to reddish-brown, earthy to pearly luster, with visible layered cleavage; monoclinic crystals. Mohs hardness 2; specific gravity about 2.3.
Formation & geological history
Forms when calcium-sulfate-rich water evaporates in sedimentary basins, often alongside halite and anhydrite. The image alone does not establish the specimen’s age or locality.
Uses & applications
Gypsum is used to make plaster, drywall, and cement; clear or well-formed crystals are collected and sometimes carved.
Geological facts
Gypsum is soft enough to be scratched by a fingernail and can be scratched with it to leave a white streak.
Field identification & locations
The pale, layered, soft-looking material is consistent with gypsum, though a photograph cannot confirm the identification. It is common in evaporite deposits worldwide; check softness and a white streak, avoiding destructive tests on a valued specimen.
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Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
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Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral