Sodalite
Sodalite (Chlorine-bearing sodium aluminum silicate) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Cubic (Isometric); usually occurs in massive, granular, or tumbled forms rather than distinct crystals.
Mineral Group
Silicates; Tectosilicate (Feldspathoid group)
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Igneous; forms in alkaline igneous rocks (plutonic) such as nepheline syenites or phonolites, often crystallizing from sodium-rich magmas or through hydrothermal alteration.
About This Crystal
A mottled combination of royal blue to deep indigo patches mixed with white Calcite veins or inclusions. It is generally opaque with a vitreous to greasy luster when polished, as seen in this tumbled specimen.
Physical Characteristics
Color: Blue with white 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 LWUV.
Optical Properties
Refractive Index: ~1.48; Birefringence: None (isotropic); Luster: Vitreous to greasy; Transparency: Opaque to translucent on thin edges.
Hardness & Durability
Origin Region
Notable sources include Brazil (Bahia), Canada (Bancroft), Namibia, Greenland, and Russia. It is found in silica-poor igneous rocks like nepheline syenites.
Hardness & Durability
Mohs Hardness: 5.5 to 6. It is relatively soft compared to Quartz and can be easily scratched by metal files or harder gemstones.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic or steam cleaners. Sensitive to acids and household chemicals. Store separately to prevent scratching.
Rarity & Value
Common; widely available and affordable. Value is determined by the intensity of the blue color and the aesthetic pattern of the white inclusions. Generally not treated, though occasionally dyed for deep blue uniformity.
Special Characteristics
Often confused with Lapis Lazuli, but Sodalite typically lacks the gold Pyrite inclusions common in Lapis and includes white Calcite instead. Noted for its potential for bright orange fluorescence under ultraviolet light.
Lore & History
First discovered in Greenland in 1811; became popular as an ornamental stone after a visit by the Prince of Wales to Bancroft, Ontario. Historically called the 'Poet's Stone' or 'Thinker's Stone' in traditional lore, believed to stimulate the Third Eye and Throat chakras to enhance logic and intuition.