Sodalite, whose name reflects its sodium content, is found in all shades of blue. It is a major constituent of the rock lapis lazuli. Hence, the two gemstones are often confused. Unlike lapis lazuli, sodalite very rarely contains brassy pyrite specks and has a lower specific gravity. Sodalite may contain white streaks of the mineral calcite. Moreover, it can be carved into jewelry.
The most important commercial source of sodalite is Bancroft in Ontario, Canada. It was discovered during a royal visit by Princess Margaret of England. For this reason, sodalite from Bancroft is sometimes called Princess Blue.
Occurrence
Sodalite usually occurs as masses in igneous rocks. Crystals are very rare, but twelve-sided crystals have been found in the lavas of volcano Vesuvius in Italy. However, they are too small to be used in jewelry. Other localities include Brazil, Canada, Namibia, the USA, and India.
Sodalite Properties
- Specific Gravity: 2.27
- Refractive Index: 1.48 (mean)
- Birefringence (DR): None
- Luster: Vitreous to greasy
- Crystal Structure: Cubic
- Composition: Sodium aluminum silicate
- Hardness: 5½
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