Satin Spar Selenite
Gypsum var. Satin Spar · Collector Mineral / Decorative Stone
Crystal System
Monoclinic system; typically forms in fibrous, parallel bundles or 'satin-like' masses.
Mineral Group
Sulfates; specifically the Gypsum group.
Chemical Formula
CaSO4·2H2O (Hydrous Calcium Sulfate)
Formation Process
Sedimentary process through the evaporation of saline water (evaporite) or hydrothermal precipitation in caves and veins at low temperatures.
About This Crystal
White to colorless translucent specimen with a distinct fibrous structure. It exhibits a silky, pearly luster and a characteristic shimmer when light hits the parallel fibers.
Physical Characteristics
Color: White; Streak: White; Cleavage: Perfect in one direction, though often hidden in fibrous forms; Fracture: Splintery; Specific Gravity: 2.3; Tenacity: Brittle to sectile; Fluorescence: Often fluorescent (white/blue) under UV light.
Optical Properties
Refractive Index: 1.520–1.530; Birefringence: 0.010; exhibit chatoyancy (cat's eye effect) due to its fine parallel fiber structure; doubly refractive.
Hardness & Durability
Origin Region
Major sources include Morocco (Oujda), Mexico (Naica), USA (Utah/New Mexico), and various evaporite basins globally.
Hardness & Durability
Mohs Hardness: 2 (very soft, can be scratched by a fingernail); Poor toughness; highly susceptible to damage and chemical erosion.
Care & Maintenance
Extremely fragile. Avoid water (it is slightly soluble and will lose its luster), ultrasonic cleaners, and steam. Clean only with a soft dry cloth. Store away from harder stones to prevent scratching.
Rarity & Value
Common; Very affordable and widely available. Value is determined by size and the absence of brown/orange iron staining.
Special Characteristics
Strong fiber-optic effect where light travels along the length of the fibers; creates a natural 'glow' or shimmer known as chatoyancy.
Lore & History
Named after the Greek word 'selene' (moon). Historically used in windowpanes before glass was common. Traditionally associated with mental clarity, purity, and cleansing the aura or 'charging' other crystals.