mineral

Selenite Gypsum

Hydrous calcium sulfate (CaSO4·2H2O)

Hardness: 2 on Mohs scale; Color: Colorless, white, or honey-brown; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 2.3

Hardness: 2 on Mohs scale
Color: Colorless, white, or honey-brown
Luster: Vitreous to pearly

Identified June 24, 2026More mineral →

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Physical properties

Hardness: 2 on Mohs scale; Color: Colorless, white, or honey-brown; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 2.3

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, specifically from the evaporation of seawater in massive prehistoric basins or in clay beds and caves through the oxidation of sulfides.

Uses & applications

Primary source of plaster of paris, drywall, and fertilizer; transparent varieties are used for metaphysical purposes and decorative carvings.

Geological facts

The famous Cave of the Crystals in Naica, Mexico, contains giant selenite crystals measuring up to 12 meters in length. It is so soft that it can be scratched with a fingernail.

Field identification & locations

Identify in the field by its extreme softness and its fibrous or tabular crystal habit. Commonly found in desert regions or near saline lake deposits.

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