mineral
Tumbled sodalite
Sodalite, Na₈(Al₆Si₆O₂₄)Cl₂
AI-generated identification · may be incorrectTypically deep royal-blue to violet-blue with white calcite veining and occasional gray or black inclusions; vitreous to greasy luster. Mohs hardness 5.5–6, cubic crystal system, poor cleavage, and specific gravity about 2.27–2.33.
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Physical properties
Typically deep royal-blue to violet-blue with white calcite veining and occasional gray or black inclusions; vitreous to greasy luster. Mohs hardness 5.5–6, cubic crystal system, poor cleavage, and specific gravity about 2.27–2.33.
Formation & geological history
Forms in silica-poor, sodium-rich igneous rocks—especially nepheline syenites and related alkaline bodies—through magmatic crystallization. Most gem sodalite is Precambrian, though the specimen’s exact age cannot be determined visually.
Uses & applications
Used as an ornamental stone, beads, cabochons, carvings, and tumbled specimens; occasionally used as a blue pigment or decorative stone. This piece is likely a low-cost lapidary product.
Geological facts
The blue color comes mainly from sulfur-related defects in the sodalite structure. It can resemble lapis lazuli, but lapis usually contains abundant brassy pyrite and is generally denser.
Field identification & locations
Identify by its intense blue color, white calcite patches, moderate hardness, and lack of pyrite; a streak and acid test can help distinguish it from lapis, though polishing obscures field tests. Common sources include Canada, Brazil, Russia, Namibia, and Afghanistan.
