mineral

Dumortierite Quartz

Al7BO3(SiO4)3O3 (Aluminum borate silicate)

AI-generated identification · may be incorrect

Hardness: 7.0 to 8.5 (aggregate); Color: Deep blue, violet-blue, or grayish-blue; Luster: Vitreous to dull; Crystal structure: Orthorhombic; Cleavage: Good; Specific gravity: 3.26 to 3.50

Hardness: 7
Color: Deep blue, violet-blue, or grayish-blue
Luster: Vitreous to dull

Identified March 20, 2026More mineral →

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Physical properties

Hardness: 7.0 to 8.5 (aggregate); Color: Deep blue, violet-blue, or grayish-blue; Luster: Vitreous to dull; Crystal structure: Orthorhombic; Cleavage: Good; Specific gravity: 3.26 to 3.50

Formation & geological history

Formed in high-temperature aluminum-rich regional metamorphic rocks, specifically pegmatites and metamorphic schists. Most specimens date from the Late Proterozoic to Phanerozoic eras.

Uses & applications

Used primarily in lapidary work for cabochons and beads, as well as in the production of high-grade spark plug porcelain and electrical insulators due to its high aluminum content.

Geological facts

Often mistaken for Sodalite or Lapis Lazuli, but it is significantly harder and lacks the brassy pyrite inclusions common in Lapis. It was named after the French paleontologist Eugène Dumortier.

Field identification & locations

Identify in the field by its distinct waxy to vitreous luster and its resistance to scratching by a steel file. Commonly found in Brazil, Namibia, Madagascar, and the United States (California/Nevada). Collectors look for deep even color saturation.