Satin Spar (Gypsum)

Physical Properties

Hardness: 2 (Mohs scale), Color: White to pearly cream, Luster: Silky/Satin, Crystal Structure: Monoclinic, Cleavage: Perfect, Specific Gravity: 2.3

Formation & Geological History

Formed in evaporite deposits where saline water evaporates, or by the hydration of anhydrite. Found in sedimentary environments such as lake and marine beds.

Uses & Applications

Used in the manufacture of drywall (plasterboard), cement, fertilizer, and as an ornamental stone for carvings and decorative items.

Geological Facts

Satin spar is a fibrous variety of gypsum. It is often confused with Selenite, which is the clear, crystalline form, though both are chemically identical. It is so soft it can be easily scratched by a fingernail.

Field Identification & Locations

Identify by its silky, fibrous appearance and extreme softness (can be scratched by a human fingernail). Commonly found in desert regions or ancient seabed locations like Utah, Morocco, and Mexico.

Identified on: 4/13/2026

Mode: Standard