Sodalite
Sodalite · Semi-Precious Gemstone / Decorative Stone
Crystal System
Cubic (Isometric); typically occurs as massive, translucent to opaque aggregates, though dodecahedron crystals exist but are rare.
Mineral Group
Silicates (Tectosilicates); specifically part of the Feldspathoid group.
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Igneous formation; it crystallizes from sodium-rich, silica-deficient magmas (nepheline syenites) and can also form in hydrothermal environments.
About This Crystal
The specimen consists of small, tumbled blue chips with prominent white veining or mottling. The color is a deep royal blue, and the luster is vitreous to greasy. Most chips appear opaque with some slight translucency on thin edges.
Physical Characteristics
Color: Royal blue to grey-blue with white streaks; Streak: White; Cleavage: Poor/uneven; Fracture: Conchoidal to uneven; Specific Gravity: 2.27–2.33; Fluorescence: Often exhibits strong orange or pink fluorescence under longwave UV light.
Optical Properties
Refractive Index: 1.483–1.487 (Isotropic); Singly refractive; essentially no pleochroism or dispersion due to its cubic nature and opacity in tumbled form.
Hardness & Durability
Origin Region
Brazil, Canada (Bancroft), Namibia, and Russia. Forms primarily in silica-poor igneous rocks such as nepheline syenite and phonolite.
Hardness & Durability
Mohs hardness: 5.5 to 6. Toughness: Fair. It is relatively brittle and should be used cautiously in jewelry that receives daily impact, like rings.
Care & Maintenance
Clean with warm, soapy water and a soft cloth. Avoid ultrasonic cleaners and steam cleaning. Sodalite is sensitive to acids and can be scratched by harder stones like quartz.
Rarity & Value
Common and affordable. Value is determined by the depth of blue and the balance of white inclusions (calcite). It is often stabilized with resin but rarely dyed (though it is sometimes used as an imitation for lapis lazuli).
Special Characteristics
Often confused with Lapis Lazuli, but distinguished by its lack of pyrite (gold-flecked) inclusions. Known for exhibiting bright orange ‘hackmanite-like’ fluorescence in some specimens.
Lore & History
Historically used as a pigment and for ornamental carvings. Often called the 'Poet's Stone' or 'Stone of Logic' in traditional lore, it is culturally associated with the throat and third-eye chakras to aid communication and intuition.