Sodalite
Sodalite (Mineral variety: Sodalite) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Cubic; habit is usually massive or granular as seen in this polished sphere
Mineral Group
Silicates (Subgroup: Tectosilicate; Feldspathoid group)
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Igneous: Crystallizes from silica-poor magmas in alkaline rocks like nepheline syenites and pegmatites
About This Crystal
An opaque, dark royal blue stone with mottled patches and streaks of white or grey inclusion material. It displays a vitreous to greasy luster when polished
Physical Characteristics
Color: Royal blue to greyish-blue; Streak: White; Fracture: Conchoidal to uneven; Specific Gravity: 2.27-2.33; Fluorescence: Strong orange under longwave UV
Optical Properties
Isotropic (singly refractive); Refractive Index: 1.483-1.487; No pleochroism or dispersion; opaque transparency
Hardness & Durability
Origin Region
Brazil, Canada (Bancroft), Namibia, Greenland, and Russia
Hardness & Durability
Mohs hardness: 5.5 to 6; Poor toughness; brittle; suitable for beads and cabochons but sensitive to scratches
Care & Maintenance
Clean with warm soapy water only; avoid ultrasonic cleaners, steam, and harsh chemicals/acids which can etch the surface
Rarity & Value
Relatively common; affordable; value is determined by the richness of the blue color and lack of excessive white calcite veining
Special Characteristics
Known for distinct orange-red fluorescence under UV light and its association with white calcite and occasionally dark needles of aegirine
Lore & History
First discovered in Greenland in 1811; historically used for ornamental purposes; traditionally associated with the throat chakra and truth-seeking