mineral

Likely selenite (gypsum) crystal

Gypsum, CaSO₄·2H₂O; variety likely satin spar or fibrous selenite

AI-generated identification · may be incorrect

Very pale gray-white, translucent, pearly to silky luster, and strongly fibrous/elongated crystal structure. Mohs hardness 2, perfect cleavage in one direction, and low specific gravity (~2.3); the thin form appears naturally splintery rather than glassy.

Identified September 1, 2026More mineral →

Explore Likely selenite (gypsum) crystal in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Gypsum forms when saline or evaporitic waters evaporate, commonly in sedimentary basins, caves, and hydrothermal settings. Deposits range from ancient evaporites to modern cave growth; the image alone cannot establish a precise age.

Uses & applications

Used in drywall, plaster, cement, fertilizer, and soil amendments; clear selenite is also sold as a decorative and collecting mineral. This specimen is likely low-value unless unusually transparent, large, or aesthetically distinctive.

Geological facts

Selenite is a transparent crystalline variety of gypsum, while satin spar is the fibrous variety; trade names are often used loosely. Gypsum can be scratched easily with a fingernail and may form delicate spear-, blade-, or rosette-shaped crystals.

Field identification & locations

Common localities include Mexico, Morocco, Spain, the United States, and evaporite regions worldwide. Test cautiously with a fingernail: gypsum scratches readily and should not be confused with harder calcite or glass.