mineral

Gypsum (selenite and satin-spar varieties)

Gypsum, CaSO₄·2H₂O

AI-generated identification · may be incorrect

The translucent white and honey-colored pieces appear to be gypsum, with vitreous to pearly luster and visible cleavage. Gypsum has Mohs hardness 2, monoclinic crystal structure, and specific gravity about 2.3; the photo alone cannot confirm the identification.

Identified October 8, 2026More mineral →

Explore Gypsum (selenite and satin-spar varieties) 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 sulfate-rich water evaporates in sedimentary basins, commonly alongside halite and anhydrite. Deposits formed across many geological periods; the pieces’ age and locality cannot be determined from the image.

Uses & applications

Used to make drywall, plaster, and cement; clear selenite is also collected and sometimes carved into decorative objects.

Geological facts

Gypsum is soft enough to be scratched by a fingernail and can be shaped into fine, transparent selenite crystals.

Field identification & locations

Look for very soft, pale material that splits readily along smooth cleavage planes; a fingernail scratch is a useful field clue. Gypsum occurs worldwide in evaporite deposits, including large deposits in the United States, Mexico, and Spain.