Sodalite
Sodalite · Semi-Precious Gemstone / Decorative Stone
Crystal System
Cubic (Isometric); usually occurs as massive, mottled aggregates or rounded grains; rarely forms dodecahedral crystals.
Mineral Group
Silicates; Tectosilicates (Feldspathoid group)
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Igneous formation; specifically occurs in nepheline syenites, phonolites, and related rock types that crystallized from alkali-rich, silica-undersaturated magmas. Also found in contact metasomatic environments.
About This Crystal
A deep royal blue to violet-blue opaque mineral often with white veining or mottling. The specimen shown is a tumbled, polished stone with a waxy to vitreous luster and a smooth, rounded surface with some visible grain boundaries.
Physical Characteristics
Color: Royal blue, grey, or violet; Streak: White; Cleavage: Poor; Fracture: Uneven to conchoidal; Specific Gravity: 2.27–2.33; Tenacity: Brittle; Fluorescence: Often bright orange or red under longwave UV.
Optical Properties
Isotropic (singly refractive); Refractive Index: 1.483–1.487; Birefringence: None; Luster: Vitreous to greasy; typically opaque in bulk form.
Hardness & Durability
Origin Region
Prominent sources include Bahia (Brazil), Ontario and Quebec (Canada), Greenland, Namibia, and the Kola Peninsula (Russia). Found in silica-poor igneous rocks.
Hardness & Durability
Mohs hardness: 5.5 to 6. Toughness is poor to fair. It is relatively soft and can be scratched by quartz or steel, making it best for low-wear jewelry like pendants or earrings.
Care & Maintenance
Avoid ultrasonic cleaners and steamers. Clean with warm soapy water and a soft cloth. Sensitive to acids and household chemicals. Store separately from harder gemstones like quartz or topaz to prevent scratches.
Rarity & Value
Relatively common and affordable. Value is determined by the intensity and uniformity of the blue color and the patterns created by white inclusions (calcite). Higher value for deep blue pieces with minimal white.
Special Characteristics
Often exhibits strong orange-red fluorescence under longwave UV light due to sulfur impurities or other activators. Hackmanite, a variety of sodalite, exhibits tenebrescence (color change upon exposure to light).
Lore & History
Discovered in 1811 in Greenland, it gained popularity in Canada ('Princess Blue') after a royal visit in 1901. Metaphysically associated with the Throat and Third Eye chakras, believed to promote logic, truth, and inner peace.