metamorphic
Dumortierite Quartz
Dumortierite-bearing Quartzite (Al7BO3(SiO4)3O3 in SiO2)
AI-generated identification · may be incorrectHardness: 7 to 8.5 on the Mohs scale; Color: Denim blue, indigo, to grayish-blue with darker mottling and occasional reddish-brown inclusions; Luster: Vitreous to waxy; Crystal system: Orthorhombic (dumortierite) within Trigonal (quartz); Specific gravity: 2.7 - 3.4
- Hardness
- 7 to 8
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 to 8.5 on the Mohs scale; Color: Denim blue, indigo, to grayish-blue with darker mottling and occasional reddish-brown inclusions; Luster: Vitreous to waxy; Crystal system: Orthorhombic (dumortierite) within Trigonal (quartz); Specific gravity: 2.7 - 3.4
Formation & geological history
Formed in regional or contact metamorphic environments, particularly in aluminum- and boron-rich pegmatites and high-temperature metamorphic quartz veins.
Uses & applications
Used primarily as an ornamental stone, lapidary carvings (such as polished spheres and eggs), cabochons for jewelry, and occasionally as high-grade refractory porcelain material due to its heat resistance.
Geological facts
Dumortierite was named in 1881 after the French paleontologist Eugène Dumortier. Because of its distinctive denim-blue color, it is sometimes colloquially referred to in the gem trade as 'Blue Denim Stone' or mistaken for sodalite and lapis lazuli.
Field identification & locations
Recognized by its rich denim-blue hue with fibrous, mottled aggregates embedded in hard quartz, distinguishing it from softer blue minerals like sodalite or angelite. Notable deposits exist in Brazil, Madagascar, the United States (Nevada and California), and South Africa.
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