Selenite (Gypsum)

Physical Properties

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: Colorless to white. Luster: Vitreous to pearly. Crystal structure: Monoclinic with tabular or bladed habit. Cleavage: Perfect in one direction.

Formation & Geological History

Formed as an evaporite mineral in sedimentary environments such as saline lakes, lagoons, and deep-sea basins where calcium-rich water evaporates. Often found in clay beds.

Uses & Applications

Used in the manufacture of drywall (plasterboard), cement, fertilizer, and as a filler in paper and paints. Transparent varieties are popular for meditation crystals and minor ornamental carvings.

Geological Facts

The name 'Selenite' comes from the Greek word 'selēnitēs', meaning 'moon-stone,' because of its moon-like glow. The famous Naica Mine in Mexico contains giant selenite crystals over 36 feet long.

Field Identification & Locations

Identified in the field by its extreme softness (scratches with a fingernail) and its distinct tabular or bladed transparency. Commonly found in desert regions and sedimentary basins worldwide.

Identified on: 5/2/2026

Mode: Standard