Sodalite
Sodalite · Semi-Precious Gemstone, Collector Mineral, Decorative Stone
Crystal System
Cubic (Isometric); usually occurs as massive or granular aggregates; dodecahedral crystals are rare.
Mineral Group
Silicates (Tectosilicates); specifically a member of the Feldspathoid group and Sodalite group.
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Forms in igneous environments, specifically through the crystallization of alkaline magmas deficient in silica (magmatic crystallization in nepheline syenites and pegmatites).
About This Crystal
A deep royal blue or navy blue mineral, often mottled with white veins or patches of calcite. This specimen is a tumbled stone with a vitreous to greasy luster, opaque transparency, and characteristic white marbling.
Physical Characteristics
Color: Royal blue with white calcite streaks; Streak: White; Cleavage: Poor; Fracture: Uneven to conchoidal; Specific Gravity: 2.27–2.33; Tenacity: Brittle; Fluorescence: Often exhibits strong orange/red fluorescence under longwave UV.
Optical Properties
Refractive Index: 1.48 (Isotropic/Singly refractive); Dispersion: Low; lacks prominent optical phenomena like labradorescence (distinguishing it from Lapis Lazuli which contains golden pyrite).
Hardness & Durability
Origin Region
Notable sources include Bancroft (Ontario, Canada), Greenland, Brazil, Namibia, and the Kola Peninsula (Russia). Found in silica-poor igneous rocks like nepheline syenite.
Hardness & Durability
Mohs hardness: 5.5 to 6. Fair toughness but brittle. Sensitive to pressure and high heat. Moderate wearability; best for pendants or earrings rather than rings.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic or steam cleaners. Sensitive to acids and harsh chemicals. Store away from harder gemstones like quartz or diamonds to prevent scratching.
Rarity & Value
Relatively common and affordable. Value is determined by color intensity (deeper blue is preferred) and the pattern of white marbling. Tumbled stones are widely available and inexpensive.
Special Characteristics
Strong orange-red fluorescence under UV light is a diagnostic feature. Unlike Lapis Lazuli, it typically lacks brassy pyrite inclusions and has a lower specific gravity.
Lore & History
Known as the Stone of Logic or the Poet's Stone. Traditionally associated with the Throat and Third Eye chakras. Historically gained popularity in 1800s Canada during a royal visit by Princess Margaret, leading to it sometimes being called Princess Blue.