Sodalite
Sodalite · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Cubic (Isometric); commonly found in massive or granular habits, rarely as dodecahedral crystals.
Mineral Group
Silicates; Tectosilicate (Feldspathoid group)
Chemical Formula
Na8(Al6Si6O24)Cl2
Formation Process
Igneous formation; it crystallizes from sodium-rich magmas that are deficient in silica. It can also occur in contact metamorphic zones of calcareous rocks.
About This Crystal
A deep royal blue to violet-blue opaque mineral, often characterized by white veins or patches of calcite. This specific tumbled specimen shows a slightly waxy to vitreous luster and typical mottled blue-and-white color zoning.
Physical Characteristics
Color: Royal blue, mottled with white; Streak: White; Cleavage: Poor/Indistinct; Fracture: Conchoidal to uneven; Specific Gravity: 2.27–2.33; Fluorescence: Strong orange-red under Longwave UV (due to its chlorine content).
Optical Properties
Refractive Index: 1.483–1.487; Single refraction (Isotropic); Lacks pleochroism and dispersion; Opacity is typically opaque to translucent on thin edges.
Hardness & Durability
Origin Region
Notable sources include Bancroft (Ontario, Canada), Brazil, Namibia, Afghanistan, and Greenland. It typically forms in silica-poor igneous rocks like nepheline syenites and phonolites.
Hardness & Durability
Mohs Hardness: 5.5 to 6. Toughness is poor to fair as it is somewhat brittle. It is soft enough to be scratched by quartz or steel files.
Care & Maintenance
Clean with warm, soapy water and a soft cloth. Avoid ultrasonic cleaners and steam cleaning. Sodalite is sensitive to acids and should be stored away from harder gemstones to prevent scratching.
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, though some low-grade material may be dyed.
Special Characteristics
Distinguished from Lapis Lazuli by the lack of golden pyrite inclusions and its characteristic bright orange fluorescence under ultraviolet light.
Lore & History
Discovered in Greenland in 1811 and became popular after the Princess of Wales visited Canada in 1901 and chose it for interior decoration. In crystal lore, it is known as the 'Poet's Stone,' associated with logic, truth, and the throat chakra.