Sodalite is quite rare and beautiful stone. In 1811 this mineral was first described by Thomas Thomson, the English chemist and mineralogist. Also, it is assumed that this stone was known to the ancient Incas, who lived in South America. They used this stone for cladding the walls and the floor, or cut out various ornaments and sculptures of it. Sodalite powder was used as raw material for ultramarine blue paint. The name of the stone was suggested after its main component – sodium, which came from Greek and was added to the prefix lithos, meaning “stone”. Sodalite is also known as “Canadian jade”, “glaucolite” or “hackmanite”. Alumite is more like a trade name of sodalite, which refers to the stones of beautiful deep blue hues and various texture patterns.
Formation of sodalite and peculiarities of its structure
Sodalite is usually mined in places where volcanic rocks are formed: mineral can be formed in the areas of volcanic eruptions or on the fractures in the form of crystals. Note that sodalite crystals are extremely rare (they are characterized by a cubic form). Basically, this mineral occurs as acinose masses, massive (massive intergrown crystals), stepped or solid formations. Sodalite can be also formed in alkaline igneous rocks and pegmatites. Sodalite is chlorinated sodium aluminosilicate. It is characterized by vitreous luster, and greasier one on fracture planes. Transparent or translucent specimens of sodalite are rare, this stone is mostly opaque.
Color and structure of sodalite
Coloring of sodalite has a wide range of blue shades. It is for this external sign sodalite is very similar to lapis lazuli, but there is a number of significant differences between these minerals. For example, in the sodalite structure you will not find golden pyrite inclusions typical for lapis lazuli. Besides, sodalite has more vitreous luster. The color of the stone is very changeable. For example, sodalite can have intense blue color, or light blue and greenish hues. Furthermore, this stone may be colorless, yellowish or grayish and light blue. We should also mark out a special variety of sodalite – hackmanite. This variety of stone was named after the scientist Victor Axel Hackman, who in 1903 explored the stone’s ability to change its color in the ambient conditions. Hackmanite is characterized by pinkish or reddish hues, often purple or lilac. In particular, red stones have surprising property: affected by the air, they can change their color to almost black. But such stones can be returned to their original color by heating in sodium vapors and subsequent X-ray irradiation. This method is also applied to colorless sodalites to give them beautiful blue shade. Sodalite color is largely due to different impurities. For example, in blue or light blue stones you can see white spots and streaks or beautiful blotchiness of calcite and albite.
The use of sodalite
Beautiful blue or blue translucent sodalite stones are highly valuable for jewelers. In particular, blue sodalite is used for beautiful jewelry and stones of other colors are used more as ornamental ones for decorative interior objects (statuettes, stands for bronze sculptures, stationery, various figures, etc). Sodalite is also used for inlays in mosaics of natural stone. Translucent sodalite stones of a beautiful blue color are very valuable for collectors.
Deposits of sodalite
Sodalite is rock-forming in igneous rocks, that’s why traditionally this stone is mined where the volcanic rocks are formed. For example, on the Kola Peninsula (Russia), near Mount Vesuvius (Italy), in the mountains of Portugal, Germany, Romania, India, the USA, Brazil and Canada. Sodalites of high jewelry quality also occur in Namibia.