Sodalite
Sodalite · Semi-Precious Gemstone / Ornamental Stone
Crystal System
Cubic (Isometric); typically forms in massive or granular habits, rarely as distinct dodecahedral crystals.
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
Na4Al3(SiO4)3Cl
Formation Process
Igneous formation, crystallizing from sodium-rich magmas that are deficient in silica, often occurring in pegmatites and volcanic cavities.
About This Crystal
The specimen features polished beads of deep royal blue sodalite, interspersed with distinctive white and grey veining and mottling caused by calcite and other mineral inclusions. The beads possess a vitreous to greasy luster, ranging from translucent to completely opaque.
Physical Characteristics
Color is rich royal blue with white, grey, or colorless patches; streak is white; cleavage is poor in six directions (dodecahedral); fracture is conchoidal to uneven; specific gravity is approximately 2.15 to 2.30; tenacity is brittle; often exhibits a strong orange to yellow fluorescence under longwave UV light.
Optical Properties
Refractive index ranges from 1.483 to 1.487; isotropic (singly refractive) because it crystallizes in the cubic system; pleochroism is absent or very weak.
Hardness & Durability
Origin Region
Notable sources include Brazil, Canada, India, Namibia, and the United States (Bancroft, Ontario is famous for rich blue sodalite). It typically forms in silica-poor igneous rocks like nepheline syenites.
Hardness & Durability
Mohs hardness of 5.5 to 6; moderate toughness but relatively soft for daily-wear rings; sensitive to scratching and harsh chemical impacts; comparable in hardness to orthoclase feldspar.
Care & Maintenance
Clean with warm, soapy water and a soft cloth; avoid ultrasonic cleaners, steam cleaners, and harsh chemical detergents; store separately in a soft pouch to prevent scratching from harder gemstones like quartz.
Rarity & Value
Common; widely available and affordable, used extensively for beads, cabochons, and decorative carvings; value is determined by color saturation, uniformity, and the contrast of white calcite veining.
Special Characteristics
Notable for its strong orange-to-yellow fluorescence under ultraviolet light. Some varieties (known as hackmanite) exhibit tenebrescence, changing color when exposed to sunlight and fading in the dark.
Lore & History
Discovered in 1811 in Greenland and popularized as an ornamental stone in Victorian England following major finds in Canada. In modern crystal healing, it is associated with the throat chakra, promoting rational thought, objectivity, truth, and emotional balance, though these are traditional beliefs rather than scientific claims.