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Kathy Feick
Sodalite is a scare mineral which was named in reference to its sodium content by a Glasgow chemist, Professor Thomas Thomson. It is formed in Nepheline syenites, phonolites, and related rock types; in metasomatized calcareous rocks, and cavities in ejected volcanic blocks. More simply, sodalite is formed in silica poor rocks which contain other silica poor minerals and no quartz. Sodalite is actually the name of a group of minerals with a similar isometric structure and related chemistry. It was named for its most common member, sodalite.
The sodalite group is a member of the feldspathoid minerals. Colours can be white, gray, purple or green but the blue variety is the most familiar.
Sodalite. University of Waterloo Earth Sciences Museum
The Sodalite Group:
- Hauyne (Sodim Calcium Aluminum Silicate Sulphate): Found in the Vesubian Lavas on Mte Somma, Italy and in the Eifel Mountains in Germany. It is commonly used in jewellery, especially the neon-blue variety
- Lazurite (Sodium Calcium Aluminum Silicate Sulphate Sulphide Chloride): Lazurite is a deep blue to greenish in colour. It is the product of contact metamorphism of limestone.
- Nosean (Sodium Aluminum Silicate Sulphate); Nosean is white, green, blue or brown in colour. it is fluorescent.
- Sodalite (Sodium Aluminum Silicate Chloride): The only feldspathoid which contains chlorine in its structure. When sodalite is not blue, it is hard to distinguish it from other feldspathoids.
Uses:
- Dimension stone
- Decorative stone
- Ornamental stone
- Jewellery
Notable occurrences:
- Bancroft, Ontario
- Mt Vesuvius, Italy
- Brazil
- Ice River Area, British Columbia
- Maine, USA
Princess Sodalite Mine:
The Princess Sodalite mine is located 4km east of Bancroft, on Highway 28. The sodalite from this mine varies in its intensity of blue. The surrounding material is composed of a grayish-white mineral called Nepheline. Nepheline Syenite gneiss is the geologic name of the rock found in this mine.
The mine was named in 1901, when during her visit to the World`s Fair in Buffalo, New York, the Princess of Wales was so captivated by a gift of Bancroft sodalite that arrangements were made to quarry enough to decorate her London residence, Marlborough House. So, in 1906, 130 tons of rock were shipped to England to be used as a decorative stone in the Princess' royal home.
Sodalite boulder from Princess Sodalite Mine. University of Waterloo Peter Russell Rock Garden
References:
The mineral sodalite: http://www.galleries.com/Sodalite