Satin Spar (Selenite)

Physical Properties

Hardness: 2 on Mohs scale (can be scratched by a fingernail); Color: White, pearly, or colorless; Luster: Silky or pearly; Crystal Structure: Monoclinic with fibrous habit; Cleavage: Perfect in one direction.

Formation & Geological History

Formed as an evaporite mineral in sedimentary environments, often in saline lakes, lagoons, and caves where calcium sulfate-rich waters evaporate. It can be found in strata dating back to the Permian and Triassic periods.

Uses & Applications

Used primarily in the manufacture of drywall (plasterboard), cement, and plaster of Paris. In its crystalline form, it is popular for ornamental carvings, metaphysical healing practices, and as a collector's mineral.

Geological Facts

The name 'Selenite' is derived from the Greek word 'selene' meaning moon, referring to its moon-like glow. The world's largest crystals are selenite, found in the Cave of the Crystals in Naica, Mexico.

Field Identification & Locations

Identify by its extreme softness (scratches with a fingernail) and its distinctive fibrous, silky appearance. It is commonly found in Morocco, Mexico, and the USA (Utah/New Mexico). Note: It is water-soluble and should not be soaked.

Identified on: 4/13/2026

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