Sodalite
Sodalite (IMA-approved name) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Cubic (Isometric); typically occurs as massive, granular, or tumbled aggregates as shown
Mineral Group
Silicates (Subgroup: Tectosilicates, Feldspathoid group)
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Igneous formation; crystallizes from alkali-rich magmas that are low in silica, often in plutonic environments or pegmatites.
About This Crystal
The specimen is a polished, tumbled stone with a mottled 'denim' blue and white appearance. It is opaque to translucent on thin edges with a vitreous to greasy luster. It features characteristic white calcite veining or mottling and dark specks of inclusions.
Physical Characteristics
Color: Royal blue to grey-blue with white streaks; Streak: White; Cleavage: Poor; Fracture: Conchoidal to uneven; Specific Gravity: 2.27–2.33; Fluorescence: Typically strong bright orange to pink under Longwave UV.
Optical Properties
Refractive Index: 1.48 (Isotropic); Single refraction; Lacks pleochroism and dispersion; Opalescence or chatoyancy is generally absent.
Hardness & Durability
Origin Region
Notable sources include Brazil, Canada (Bancroft), Namibia, and Russia. Typically found in alkaline igneous rocks like nepheline syenites.
Hardness & Durability
Mohs hardness: 5.5 to 6. Brittle tenacity. Sensitive to pressure and temperature changes. Suitable for low-impact jewelry like pendants or earrings.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic or steam cleaners. Sensitive to acids (even mild ones). Store away from harder stones like quartz or topaz to prevent scratching.
Rarity & Value
Relatively common and affordable. Value is determined by the richness of the blue color and the aesthetic balance of white calcite inclusions. Rarely treated, though some deeper blue varieties may be dyed.
Special Characteristics
Known for its Tenebrescence (rarely) and strong orange fluorescence under UV light. Often confused with Lapis Lazuli but distinguished by its lack of golden pyrite specks.
Lore & History
Historically discovered in Greenland in 1811 but became popular after Princess Margaret of England visited Ontario and chose it for interior decoration. Symbolically associated with logic, rational thought, and the throat chakra in traditional healing lore.