mineral

Satin Spar Selenite

Gypsum (CaSO4·2H2O)

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

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

Identified March 17, 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 in marine basins or saline lakes. It can occur across various geological ages from the Permian to the Holocene.

Uses & applications

Primarily used in the manufacture of drywall (plasterboard), cement, and plaster of Paris. In its satin spar form, it is widely sold for ornamental use, metaphysical 'cleansing', and as inexpensive gemstone carvings.

Geological facts

The name 'Selenite' comes from the Greek word 'selēnitēs', meaning 'moonstone' or 'stone of the moon', due to its soft glow. Although often called 'Selenite' in the trade world, true Selenite is the transparent variety, while this fibrous variety is scientifically 'Satin Spar'.

Field identification & locations

Identify in the field by its extreme softness (scratches with a fingernail) and its distinct silky, fibrous texture that reflects light like a cat's eye. Found commonly in arid regions like Morocco, Mexico, and the USA (Utah and New Mexico). Collectors should avoid water as it is slightly soluble.