Selenite (Satin Spar)
Gypsum var. Satin Spar · Semi-Precious Gemstone / Decorative Mineral Specimen
Crystal System
Monoclinic; commonly occurs in fibrous, parallel aggregates (Satin Spar habit) or massive beds.
Mineral Group
Sulfates (Hydrated Sulfate Class)
Chemical Formula
CaSO4·2H2O (Hydrous Calcium Sulfate)
Formation Process
Formed via chemical precipitation in evaporating saline lakewaters or marine lagoons (Sedimentary/Evaporite process).
About This Crystal
White to colorless translucent specimen carved into a star. It exhibits a distinct fibrous structure and a silky, pearly luster that creates a sharp band of light across its surface.
Physical Characteristics
Color: White/Colorless; Streak: White; Cleavage: Perfect in one direction, though obscured in fibrous forms; Specific Gravity: 2.3; Luster: Pearly/Silky; Tenacity: Brittle to sectile (can be scratched by a fingernail).
Optical Properties
Refractive Index: 1.520-1.530; Birefringence: 0.009 (weak); Displays strong Chatoyancy (cat's eye effect) due to the parallel fibrous structure reflecting light.
Hardness & Durability
Origin Region
Major deposits in Morocco (source of the star in the image), Mexico (Naica), USA, and Russia. Found in sedimentary evaporite environments.
Hardness & Durability
Mohs Hardness: 2 (very soft); Toughness: Poor; Highly sensitive to water and scratches. Not durable for jewelry wear except in protected settings.
Care & Maintenance
Never wash with water as it is slightly soluble and will lose its luster; clean with a soft dry cloth. Store away from harder stones to prevent scratching and avoid high heat.
Rarity & Value
Common; Value is generally low to moderate. Factors include size, purity of white color, and the quality of the chatoyancy band. Treatments are rare, though sometimes dyed.
Special Characteristics
Chatoyancy (the 'light beam' or satin effect caused by fibrous texture). Some specimens may show weak fluorescence under UV light.
Lore & History
Named after the Greek goddess of the moon, Selene. Historically used for window panes in ancient Rome (Lapis Specularis). In modern metaphysical beliefs, it is associated with the Crown Chakra and thought to promote mental clarity and energy cleansing.