Oxide
Spinel
MgAl₂O₄
Tectosilicate (Feldspathoid)
Sodalite
Na₈(Al₆Si₆O₂₄)Cl₂
About Sodalite
Sodalite is a rich, royal blue mineral widely used as an ornamental gemstone. While it can look similar to lapis lazuli, it is typically a more saturated blue and rarely contains the golden pyrite flecks common in lapis. Instead, it is often crisscrossed with white veins of calcite. Its name refers to its high sodium content.
Formation & Geology
Sodalite is a member of the feldspathoid group and forms in silica-poor igneous rocks (syenites and trachytes) and their associated pegmatites. It is rarely found in crystals and usually occurs in massive, granular forms. A unique variety called 'Hackmanite' shows 'tenebrescence'—it changes color when exposed to sunlight and fades back in the dark.
Physical Characteristics
Sodalite has a hardness of 5.5 to 6, making it suitable for carvings and beads but somewhat soft for rings. It has a vitreous to greasy luster and is typically translucent to opaque. It belongs to the isometric (cubic) crystal system, though distinct crystals are extremely rare. The most defining feature is its deep blue color, which is caused by the presence of chlorine in its structure.
Historical Significance & Uses
Sodalite was first discovered in Greenland in 1811 but didn't become popular until 1891, when vast deposits were found in Ontario, Canada. It became known as 'Princess Blue' after Princess Margaret of England visited Canada and chose sodalite for the interior decoration of Marlborough House. Today, it is used for beads, cabochons, carvings, and even large architectural slabs for countertops and flooring.
Princess Blue
Sodalite has been known for centuries, but it gained royal status in 1901 when the Prince and Princess of Wales (later King George V and Queen Mary) visited Bancroft, Ontario. They fell in love with the blue stone, and significant quantities were shipped to England to decorate Marlborough House. This earned Canadian sodalite the nickname "Princess Blue."
Colors & Varieties
Royal blue, gray, white, pink
Key Properties
- Deep royal blue color
- White calcite veining
- High sodium content
- Greasy to vitreous luster
- Translucent to opaque
- Isometric structure
Uses & Applications
- Ornamental carvings and sculptures
- Beads and cabochons
- Architectural slabs (countertops)
- Industrial pigment (rarely)
- Collector specimens
Where to Find
- Canada (Bancroft, Ontario) - primary source
- Greenland
- Brazil
- Namibia
- Russia
- United States (Montana)
Frequently Asked Questions
What is Hackmanite?
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Hackmanite is a rare, sulfur-rich variety of sodalite that exhibits "tenebrescence." When first mined (or kept in the dark), it may be violet or pink. When exposed to sunlight, the color fades to gray or white. When placed back in the dark (or under UV light), the violet color returns. It is a natural color-changing chameleon.
Is Sodalite the same as Lapis Lazuli?
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They look similar, but they are different. Lapis Lazuli is a rock composed of several minerals (including lazurite, calcite, and pyrite). Sodalite is a single mineral. Lapis usually has gold pyrite flecks; Sodalite rarely has pyrite but often has white calcite streaks.
What is the hardness of Sodalite?
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Sodalite has a hardness of 5.5 - 6 on the Mohs scale.
Where is Sodalite found?
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Sodalite is primarily found in Canada (Bancroft, Ontario) - primary source, Greenland, Brazil.
What color is Sodalite?
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Sodalite typically occurs in royal blue, gray, white, pink.