Sodalite
Sodalite (IMA-approved mineral species) · Semi-Precious Gemstone and Decorative Stone.
Crystal System
Cubic (Isometric); crystals are rare, typically found in massive, granular, or tumbled forms.
Mineral Group
Silicates (Tectosilicates); specifically the Feldspathoid group.
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Forms in silica-poor igneous rocks such as nepheline syenites and phonolites, as well as in contact metamorphic rocks.
About This Crystal
The specimen is a tumbled, polished stone approximately 1.5 cm in size. It exhibits a deep royal blue color with distinct white veins and patches of calcite or nepheline. It is opaque with a vitreous to greasy luster.
Physical Characteristics
Color: Royal blue with white/grey inclusions; Streak: White; Cleavage: Poor (undiscovered in massive form); Fracture: Conchoidal to uneven; Specific Gravity: 2.27–2.33; Fluorescence: Often exhibits strong orange-red fluorescence under Longwave UV.
Optical Properties
Refractive Index: 1.483–1.487; Single refraction (isotropic); Birefringence: None; Lacks pleochroism due to cubic structure.
Hardness & Durability
Origin Region
Prominent sources include Bancroft (Ontario, Canada), Greenland, Brazil, Namibia, and the Kola Peninsula in Russia.
Hardness & Durability
Mohs hardness: 5.5 to 6. Toughness is poor to fair. It is relatively soft and susceptible to scratches from harder minerals like Quartz.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic cleaners and steam cleaning. Sensitive to acids and harsh chemicals. Store separately from harder gemstones to prevent surface damage.
Rarity & Value
Relatively common and affordable. Value is determined by the depth of the blue color and the aesthetic balance of white inclusions. Rarely treated or enhanced.
Special Characteristics
Often confused with Lapis Lazuli but lacks the characteristic gold-colored pyrite inclusions. Notable for its vivid orange-red fluorescence under UV light.
Lore & History
Discovered in Greenland in 1811; it became popular in Canada after the Princess of Wales visited and chose it for decorating Marlborough House. Traditionally known as the 'Poet's Stone' and associated with the Throat Chakra, believed to enhance logic and communication.