Sodalite
Introduction
Sodalite was discovered in 1806 in Greenland, but did not become important until vast commercial deposits were discovered in Canada in 1891.
Facts
Sodalite has a high sodium content and comes in a variety of shades of blue. It is easily confused with the rock Lapis Lazuli as it is a major constitunent of the latter. The main differences are that Lapis has brassy pyrite marks and Sodalite has white streaks of mineral calcite, which you can see clearly in polished pieces.
Sodalite is a semi-translucent opaque stone. It is 5.5 on Mohs's scale. Its crystal structure is Cubic and its composition is Sodium Aluminium Silicate with a vitreous to greasy lustre.
Igneous rocks contain masses of Sodalite. The volcano Vesuvius in Italy, has provided examples of rare crystals of Sodalite, twelve-sided in fact, but not large enough to be used in jewellery. Brazil, Canada, India, Namibia and the USA are other regions where this stone can be found.
At the same time as a visit to Bancroft, Ontario, Canada by the late Princess Margaret, Sodalite was discovered. Hence the name, Princess Blue, which refers to Sodalite from this area.
Cuts include: Cabochon and Cameo. It is a brittle stone to work with and therefore not suitable in an everyday ring. It is better suited to pendants and earrings.