mineral
Sodalite
Na8(Al6Si6O24)Cl2
Hardness: 5.5-6 on Mohs scale; Color: typically royal blue to violet, often with white calcite mottling; Luster: Vitreous to greasy; Crystal Structure: Isometric; Cleavage: Poor; Specific Gravity: 2.27-2.33.
- Hardness
- 5
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5.5-6 on Mohs scale; Color: typically royal blue to violet, often with white calcite mottling; Luster: Vitreous to greasy; Crystal Structure: Isometric; Cleavage: Poor; Specific Gravity: 2.27-2.33.
Formation & geological history
Forms in sodium-rich igneous rocks such as nepheline syenites or phonolites, as well as in contact metamorphic rocks. It lack significant silica, preventing the formation of quartz.
Uses & applications
Used primarily for ornamental purposes, such as jewelry (beads/cabochons), carvings, and decorative slabs. Historically used as a cheaper alternative to Lapis Lazuli.
Geological facts
Sodalite was first discovered in Greenland in 1811 but became popular in the 1890s after vast deposits were found in Ontario, Canada, earning it the nickname 'Princess Blue' after Princess Margaret's visit.
Field identification & locations
Identify by its deep blue color and characteristic white calcite veins. Unlike Lapis Lazuli, it rarely contains metallic pyrite flecks. Commonly found in Canada, Brazil, Namibia, and Russia.
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Potassium Feldspar (Orthoclase)
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Mineral/Rock