mineral

Selenite (gypsum) crystal

Gypsum, CaSO₄·2H₂O; transparent/white variety called selenite

AI-generated identification · may be incorrect

Typically colorless to white, vitreous to pearly, with perfect one-direction cleavage and monoclinic crystals; Mohs hardness 2, specific gravity about 2.3. The specimen appears to be a naturally elongated, possibly lightly shaped or cleaved crystal.

Identified August 23, 2026More mineral →

Explore 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

Forms when saline or groundwater evaporates, and in sedimentary evaporite beds, caves, hot springs, and volcanic environments. Gypsum deposits range from Paleozoic to modern; the image alone cannot establish its age.

Uses & applications

Used to manufacture plaster, drywall, cement, and soil conditioners; clear attractive pieces are sold as display minerals, wands, and carvings. It is too soft for durable jewelry.

Geological facts

Selenite is a hydrated calcium sulfate, not a variety of quartz. It can be scratched easily with a fingernail and may become dull or damaged by water abrasion.

Field identification & locations

Common localities include Mexico, Morocco, Spain, the United States, and the famous giant crystals of Naica, Mexico. Confirm with a fingernail scratch, very low hardness, flat cleavage, and lack of fizz in dilute acid.