mineral
Sodalite
Sodalite (Na8(Al6Si6O24)Cl2)
AI-generated identification · may be incorrectHardness: 5.5-6.0 (Mohs); Color: Royal blue with white streaks or patches of calcite; Luster: Vitreous to greasy; Crystal Structure: Isometric; Cleavage: Poor; Specific Gravity: 2.2-2.3.
- Hardness
- 5
- Color
- Royal blue with white streaks or patches of calcite
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5.5-6.0 (Mohs); Color: Royal blue with white streaks or patches of calcite; Luster: Vitreous to greasy; Crystal Structure: Isometric; Cleavage: Poor; Specific Gravity: 2.2-2.3.
Formation & geological history
Forms in sodium-rich igneous rocks (syenites, trachytes) and contact metamorphic rocks. It develops in environments where quartz is absent. Significant deposits date from various geological periods, often associated with alkaline massifs.
Uses & applications
Commonly used for ornamental carvings, tumble polishing, beads for jewelry, and occasionally as architectural stone for countertops or tiles.
Geological facts
Sodalite is a member of the feldspathoid group. It is often confused with Lapis Lazuli, but Sodalite rarely contains the golden flecks of pyrite that are characteristic of Lapis and has a lower specific gravity. It is known to fluoresce orange under ultraviolet light.
Field identification & locations
Identify by its rich blue color mixed with white vein-like inclusions of calcite. It lacks the pyrite 'gold' of Lapis. Major sources include Bancroft (Canada), Brazil, and Namibia. In the field, look for it in nepheline syenites.
