mineral
Tumbled sodalite (probable)
Sodalite, Na₈(Al₆Si₆O₂₄)Cl₂
AI-generated identification · may be incorrectBlue to violet-blue, commonly mottled with white or gray; vitreous to greasy luster, hardness 5.5–6 Mohs, granular cubic crystal system, poor cleavage, and specific gravity about 2.25–2.35. The rounded surface indicates machine tumbling and polishing.
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Physical properties
Blue to violet-blue, commonly mottled with white or gray; vitreous to greasy luster, hardness 5.5–6 Mohs, granular cubic crystal system, poor cleavage, and specific gravity about 2.25–2.35. The rounded surface indicates machine tumbling and polishing.
Formation & geological history
Forms in silica-poor, alkaline igneous rocks such as nepheline syenite and related pegmatites, commonly during Precambrian to Phanerozoic alkaline magmatism. The identification is approximate from the photograph; lazurite or dyed blue stone are possible alternatives.
Uses & applications
Used as an ornamental stone, beads, cabochons, carvings, and inexpensive lapidary material; it has little industrial use.
Geological facts
Sodalite is a major component of some lapis lazuli, although lapis typically also contains pyrite and calcite. It can fluoresce orange under shortwave ultraviolet light.
Field identification & locations
Check for a rich blue color, white veining, moderate hardness, and a nonmetallic luster; a streak test and hardness comparison help distinguish it from dyed stones and lapis. Common sources include Canada, Brazil, Namibia, and Russia.
