mineral

Satin Spar Selenite

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White or pearly. Luster: Silky to pearlescent. Crystal structure: Monoclinic, typically fibrous. Cleavage: Perfect in one direction. Specific gravity: 2.3.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: White or pearly
Luster: Silky to pearlescent

Identified June 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, specifically in saline crusts or through the precipitation of calcium-rich waters in caves or dry lake beds. It is often found in sedimentary rock layers such as limestone or shale.

Uses & applications

Used in the production of plaster of Paris, drywall (gypsum board), and soil conditioners. In its fibrous 'Satin Spar' form, it is used for ornamental carvings, palm stones, and decorative metaphysical objects.

Geological facts

Selenite is named after the Greek word 'selene' meaning 'moon' because of its pale, moon-like glow. The famous 'Cave of the Crystals' in Naica, Mexico, contains some of the largest selenite crystals ever found, reaching up to 12 meters in length.

Field identification & locations

Identify in the field by its extreme softness (scratches with a fingernail) and silky, fibrous appearance. Commonly found in desert regions (USA, Mexico, Morocco) and near evaporite basins. Collectors should avoid water contact as it may dissolve or dull over time.

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