mineral
Selenite (gypsum) crystal
Gypsum, CaSO₄·2H₂O; variety selenite
AI-generated identification · may be incorrectColorless to milky white, translucent, vitreous to pearly luster; monoclinic crystal structure with prominent cleavage. Mohs hardness 2; easily scratched by a fingernail. The image appears to show a large, cut or shaped crystal.
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Physical properties
Colorless to milky white, translucent, vitreous to pearly luster; monoclinic crystal structure with prominent cleavage. Mohs hardness 2; easily scratched by a fingernail. The image appears to show a large, cut or shaped crystal.
Formation & geological history
Forms when calcium-sulfate-rich waters evaporate in sedimentary settings, or in caves and hydrothermal deposits. Gypsum deposits occur across many geological ages; the specimen’s specific age and locality cannot be determined from the image.
Uses & applications
Used to make plaster, drywall, and cement; clear selenite is also collected and used decoratively.
Geological facts
Selenite is a transparent-to-translucent variety of gypsum, not a distinct mineral species.
Field identification & locations
Identify by its softness, pale color, and good cleavage; common in evaporite basins worldwide, including the United States, Mexico, and Spain. Avoid water and abrasion, as it scratches easily and can dissolve slowly.
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