mineral
Likely gypsum (selenite)
Gypsum, CaSO₄·2H₂O; probably a transparent-to-translucent selenite fragment
AI-generated identification · may be incorrectWhite to pale yellow, pearly/glassy luster, excellent cleavage, and a platy crystal habit. Mohs hardness 2, specific gravity about 2.3; the apparent square faces and soft, easily scratched surface support gypsum, though the image alone cannot exclude calcite or a coated glass fragment.
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Physical properties
White to pale yellow, pearly/glassy luster, excellent cleavage, and a platy crystal habit. Mohs hardness 2, specific gravity about 2.3; the apparent square faces and soft, easily scratched surface support gypsum, though the image alone cannot exclude calcite or a coated glass fragment.
Formation & geological history
Gypsum forms by evaporation in sedimentary evaporite basins, saline lakes, and caves; deposits range from recent to hundreds of millions of years old. Selenite crystals commonly grow in clay-rich or saline environments.
Uses & applications
Gypsum is used for plaster, drywall, cement, soil conditioning, and fertilizer; clear selenite is collected and occasionally sold as a decorative mineral. It is generally inexpensive.
Geological facts
Gypsum can be scratched easily with a fingernail and may split into thin sheets along cleavage planes. “Selenite” refers to clear or translucent gypsum, not a separate mineral.
Field identification & locations
Test with a fingernail: genuine gypsum should scratch readily; calcite will not. Look for flexible cleavage sheets and avoid strong acids or soaking, which can damage some specimens. Common sources include Mexico, Morocco, Spain, the United States, and India.
