metamorphic
Dumortierite Quartz
Dumortierite (Al7BO3(SiO4)3O3) in Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Denim blue to violet-blue with white/gray quartz matrix, Luster: Vitreous to dull, Crystal Structure: Orthorhombic (as inclusions), Cleavage: Indistinct, Specific Gravity: 2.6 - 3.4
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Physical properties
Hardness: 7 (Mohs scale), Color: Denim blue to violet-blue with white/gray quartz matrix, Luster: Vitreous to dull, Crystal Structure: Orthorhombic (as inclusions), Cleavage: Indistinct, Specific Gravity: 2.6 - 3.4
Formation & geological history
Formed in regional metamorphic rocks rich in aluminum and boron, often occurring in high-temperature environments. Most specimens come from Precambrian to Paleozoic formations.
Uses & applications
Commonly used for tumbled stones, lapidary cabochons, decorative carvings, and beads for jewelry. In industry, pure dumortierite is used to manufacture high-grade spark plug porcelain.
Geological facts
Named after the French paleontologist Eugène Dumortier. It is often mistaken for Sodalite or Lapis Lazuli, but it is significantly harder and lacks the pyrite inclusions typical of Lapis.
Field identification & locations
Identify in the field by its distinct denim-blue color and high hardness (it cannot be scratched by a steel knife). Common locations include Brazil, South Africa, Nevada (USA), and Madagascar.
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