mineral
Likely selenite (gypsum) cleavage fragment
Gypsum, CaSO₄·2H₂O; selenite is its transparent-to-translucent crystalline variety
AI-generated identification · may be incorrectPale tan, pearly to vitreous sheen, with flat cleavage surfaces and fine striations; Mohs hardness 2, monoclinic crystal system, perfect cleavage in one direction, specific gravity about 2.3. The photo alone cannot confirm the identification.
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Physical properties
Pale tan, pearly to vitreous sheen, with flat cleavage surfaces and fine striations; Mohs hardness 2, monoclinic crystal system, perfect cleavage in one direction, specific gravity about 2.3. The photo alone cannot confirm the identification.
Formation & geological history
Gypsum forms when calcium-sulfate-rich water evaporates, commonly in sedimentary evaporite deposits; deposits range from recent to hundreds of millions of years old.
Uses & applications
Gypsum is used in drywall, plaster, cement, and soil amendments; clear selenite is collected and sometimes carved or used decoratively.
Geological facts
Gypsum is soft enough to be scratched by a fingernail and can be split into thin sheets along its cleavage planes.
Field identification & locations
Check for a fingernail scratch and flat, sheet-like cleavage; common sources include evaporite basins worldwide, including New Mexico and Oklahoma. Avoid water, which can slowly damage gypsum.
