mineral

Gypsum (Selenite variety)

Calcium sulfate dihydrate (CaSO4·2H2O)

AI-generated identification · may be incorrect

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: Colorless to white. Luster: Vitreous to pearly. Crystal Structure: Monoclinic; often occurs in bladed or tabular crystals. Cleavage: Perfect in one direction, yielding thin flakes. Specific Gravity: 2.3.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: Colorless to white
Luster: Vitreous to pearly

Identified June 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, typically from the evaporation of seawater or saline lake water. It can also form through the hydration of anhydrite or in hydrothermal veins.

Uses & applications

Used primarily in the manufacture of wallboard (drywall), plaster of Paris, and cement. Clear varieties like selenite are popular among mineral collectors and used in decorative carvings or spiritual practices.

Geological facts

Selenite is named after the Greek word for moon, ‘selene’, due to its moon-like glow. The famous Giant Crystal Cave in Naica, Mexico, contains selenite crystals reaching lengths of 39 feet.

Field identification & locations

Identify in the field by its extreme softness (scratchable with a fingernail) and its distinctive vitreous to silky luster. Commonly found in desert regions, clay beds, and near volcanic vents. Keep away from water as it is slightly soluble.