Sodalite
Sodalite · Semi-Precious Gemstone and Decorative Stone.
Crystal System
Cubic (Isometric); typically occurs as massive or granular aggregates rather than distinct crystals.
Mineral Group
Silicates (Tectosilicate), specifically the Sodalite group within the Feldspathoid family.
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Igneous formation; crystallizes from alkaline magmas that are deficient in silica, commonly in nepheline syenites and pegmatites.
About This Crystal
A deep royal blue specimen, often appearing opaque but can be translucent on thin edges. This tumble-polished stone shows a vitreous to slightly greasy luster with characteristic white or grey veining (calcite) often absent in higher-grade royal blue specimens.
Physical Characteristics
Color is typically royal blue to violet-blue; streak is white; no distinct cleavage (instead shows a conchoidal to uneven fracture); specific gravity is 2.27–2.33; often displays a strong orange or red fluorescence under long-wave UV light.
Optical Properties
Refractive index of approximately 1.48 (Isotropic). It is singly refractive. It lacks strong dispersion or pleochroism due to its isometric structure.
Hardness & Durability
Origin Region
Prominent sources include Canada (Ontario - Princess Sodalite Mine), Brazil, Namibia, Russia (Ural Mountains), and the USA (Maine/Arkansas). Often found in silica-poor igneous rocks.
Hardness & Durability
Mohs hardness of 5.5 to 6. It is moderately brittle and softer than quartz, making it sensitive to scratches from household dust or harder gemstones.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic cleaners and steam cleaning. Sensitive to acids and harsh chemicals. Store separately from harder stones like diamonds or sapphires to prevent scratching.
Rarity & Value
Relatively common and affordable. Value is determined by the depth of the blue color and the lack of distracting white calcite or black inclusions. Frequently sold as tumbled stones or lapidary beads.
Special Characteristics
Known for its vivid orange-red fluorescence under UV light. Some varieties (Hackmanite) show tenebrescence (color change when exposed to light).
Lore & History
Discovered in Greenland in 1811, it gained popularity in 1901 after Princess Margaret of England visited Canada and chose the stone for interior decoration. In metaphysical lore, it is known as the 'Poet’s Stone,' associated with the throat and third eye chakras, and believed to promote rational thought, objectivity, and communication.