Sodalite
Sodalite (IMA-approved mineral species) · Semi-Precious Gemstone / Decorative Stone / Mineral Specimen
Crystal System
Cubic (Isometric); typically occurs as massive, mottled aggregate or rounded grains rather than well-formed crystals.
Mineral Group
Silicates (Subgroup: Tectosilicates / Feldspathoid group)
Chemical Formula
Na8(Al6Si6O24)Cl2 (Sodium aluminum silicate chloride)
Formation Process
Igneous; forms in silica-deficient rocks such as nepheline syenites and phonolites. Also found in contact metamorphic environments.
About This Crystal
An opaque, deep royal blue to violet-blue stone with a dull to vitreous luster. It is famously characterized by white or light-gray veining and mottling caused by calcite or other silicate inclusions. This specimen is polished into a heart shape, showing a mottled blue-grey texture.
Physical Characteristics
Color: Blue, gray, white; Streak: White; Cleavage: Poor; Fracture: Conchoidal to uneven; Specific Gravity: 2.27–2.33; Fluorescence: Typically orange to red under longwave UV (LWUV).
Optical Properties
Isotropic (singly refractive); Refractive Index: 1.483–1.487; Birefringence: None; Luster: Vitreous to greasy; typically lacks fire or pleochroism due to opacity.
Hardness & Durability
Origin Region
Prominent sources include Bahia, Brazil; Bancroft, Ontario, Canada; Namibia; Greenland; and the Ural Mountains, Russia.
Hardness & Durability
Mohs Hardness: 5.5 to 6. Toughness is poor to fair (brittle). It is suitable for pendants and earrings but requires protection in rings due to potential scratching.
Care & Maintenance
Avoid ultrasonic and steam cleaners. Clean with warm, soapy water and a soft cloth. Sensitive to acids and household chemicals. Should be stored away from harder stones like quartz or corundum.
Rarity & Value
Common; relatively affordable. Value is determined by the intensity of the blue color and the attractiveness of the white veining. High-grade 'Royal Blue' from Namibia is most prized.
Special Characteristics
Orange fluorescence under UV light is a diagnostic feature. It is a major constituent of the ornamental rock 'Lapis Lazuli' but lacks the golden pyrite specks characteristic of Lapis.
Lore & History
Historically used as an ornamental stone since the 19th Century. In metaphysical lore, it is known as the 'Poet's Stone,' associated with the Throat and Third Eye chakras, believed to enhance logic, rationality, and communication.