Sodalite
Sodalite (Chlorine sodium aluminum silicate) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Cubic (Isometric); typically occurs as massive or granular aggregates, rarely as dodecahedral crystals.
Mineral Group
Silicates (Tectosilicate), Sodalite group/Feldspathoid.
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Igneous; crystallizes from alkali-rich magmas that are deficient in silica. It frequently occurs in pegmatites and within the cavities of volcanic rocks.
About This Crystal
A deep royal blue mineral often mottled with white calcite veins and occasional dark inclusions of magnetite or biotite. This specimen is carved into a polished hexagonal point (obelisk), exhibiting a vitreous to greasy luster and an opaque to translucent transparency.
Physical Characteristics
Color: Royal blue to violet-blue with white, grey, or pink patches. Streak: White. Cleavage: Poor (dodecahedral). Fracture: Conchoidal to uneven. Specific Gravity: 2.27–2.33. Fluorescence: Often shows a strong bright orange to pink fluorescence under long-wave UV light.
Optical Properties
Refractive Index: 1.483–1.487 (Isotropic). It is singly refractive. Birefringence: None. Pleochroism: None. It does not exhibit fire or light dispersion.
Hardness & Durability
Origin Region
Notable sources include Brazil (Bahia), Canada (Bancroft, Ontario), Namibia, Russia, and Greenland. It is often found in silica-poor igneous rocks like nepheline syenites.
Hardness & Durability
Mohs Hardness: 5.5 to 6. Toughness is poor to fair; it is somewhat brittle and can be scratched by quartz-based household dust or harder gemstones.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic cleaners and steam cleaning. Sodalite is sensitive to acids and sudden temperature changes. To avoid fading, do not store in prolonged direct sunlight.
Rarity & Value
Relatively common and affordable. Value is determined by the intensity of the blue color and the lack of distracting white or black inclusions. Most industrial and decorative material is untreated.
Special Characteristics
Hackmanite, a variety of sodalite, exhibits tenebrescence (color change when exposed to UV light). Normal sodalite is noted for its distinctive orange fluorescence under UV and its lack of pyrite inclusions (which distinguishes it from Lapis Lazuli).
Lore & History
Discovered in 1811 in Greenland, it became popular as an ornamental stone after a visit by the Princess of Wales to the Bancroft mines in Ontario, Canada (leading to the name 'Princess Blue'). Traditionally associated with the Throat and Third Eye chakras, it is believed to promote logic, truth, and inner peace.