mineral

Likely selenite (gypsum) cleavage fragment

Gypsum, CaSO₄·2H₂O; selenite is its transparent-to-translucent crystalline variety

AI-generated identification · may be incorrect

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.

Identified September 26, 2026More mineral →

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Physical properties

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.