mineral
Sodalite in Feldspar (or Sodalite Syenite / Yooperite-type rock)
Na8(Al6Si6O24)Cl2 (Sodalite) with KAlSi3O8 (Feldspar)
Hardness: 5.5-6.0 on Mohs scale; Color: Mottled royal blue, white, tan, and brownish-pink; Luster: Vitreous to greasy; Crystal Structure: Isometric (sodalite); Cleavage: Poor/Dodecahedral (sodalite), Perfect in two directions (feldspar); Specific Gravity: 2.27-2.33.
- Hardness
- 5
- Color
- Mottled royal blue, white, tan, and brownish-pink
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 5.5-6.0 on Mohs scale; Color: Mottled royal blue, white, tan, and brownish-pink; Luster: Vitreous to greasy; Crystal Structure: Isometric (sodalite); Cleavage: Poor/Dodecahedral (sodalite), Perfect in two directions (feldspar); Specific Gravity: 2.27-2.33.
Formation & geological history
Formed in silica-poor igneous rocks such as nepheline syenites and associated pegmatites. The blue sodalite crystallizes alongside alkali feldspar and nepheline during late-stage magmatic crystallization.
Uses & applications
Used primarily as polished gemstones, lapidary cabochons, tumbled stones, decorative carvings, and mineral collection specimens.
Geological facts
Sodalite gets its deep blue color from sodium and chloride within its silicate framework. Some sodalite specimens exhibit fluorescence under shortwave UV light (sodagrem / yooperite).
Field identification & locations
Can be identified by its distinctive patch of deep blue lazurite-like color interspersed with pale matrix/feldspar. Common locations include Bancroft (Ontario, Canada), Greenland, Brazil, and Namibia. Collectors appreciate polished specimens with high contrast between the blue sodalite and surrounding mineral matrix.
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