metamorphic
Dumortierite Quartz
Dumortierite (Al7BO3(SiO4)3O3 / inclusion in SiO2)
Hardness: 7.0 (on Mohs scale); Color: Vibrant blue to violet-blue; Luster: Vitreous to dull; Crystal structure: Orthorhombic (fibrous inclusions); Cleavage: Indistinct; Specific Gravity: 2.6 – 3.4.
- Hardness
- 7
- Color
- Vibrant blue to violet-blue
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7.0 (on Mohs scale); Color: Vibrant blue to violet-blue; Luster: Vitreous to dull; Crystal structure: Orthorhombic (fibrous inclusions); Cleavage: Indistinct; Specific Gravity: 2.6 – 3.4.
Formation & geological history
Formed in regional metamorphic environments, specifically in aluminum-rich metamorphic rocks like gneiss or schist, and in boron-rich pegmatites. The blue color is due to the inclusion of fibrous dumortierite crystals within a quartz matrix.
Uses & applications
Used primarily as decorative stone, gemstones for jewelry (cabochons), and for industrial purposes in the manufacturing of high-grade ceramics and porcelain due to its high alumina content.
Geological facts
First described in 1881 by Eugene Dumortier. While often mistaken for sodalite or lapis lazuli, it is significantly harder and lacks the brassy pyrite inclusions common in lapis.
Field identification & locations
Identify by its distinctive denim-blue color and hardness (it will scratch glass and steel). Common locations include Brazil, South Africa, Madagascar, Norway, and Nevada, USA.
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