mineral

Dumortierite Quartz

Al7(BO3)(SiO4)3O3

Hardness: 7 (in quartz matrix) to 8.5; Color: Deep blue to violet-blue; Luster: Vitreous to dull; Crystal structure: Orthorhombic; Specific Gravity: 3.26–3.41

Hardness: 7 (in quartz matrix) to 8
Color: Deep blue to violet-blue
Luster: Vitreous to dull

Identified April 13, 2026More mineral →

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Physical properties

Hardness: 7 (in quartz matrix) to 8.5; Color: Deep blue to violet-blue; Luster: Vitreous to dull; Crystal structure: Orthorhombic; Specific Gravity: 3.26–3.41

Formation & geological history

Formed in aluminum-rich regional metamorphic rocks and high-temperature pegmatites. It often appears as needle-like inclusions within quartz crystals, which is likely the polished specimen shown.

Uses & applications

Used primarily as a decorative gemstone, in lapidary work for cabochons and beads, and historically in the manufacture of high-grade porcelain and spark plugs due to its heat resistance.

Geological facts

Often mistaken for lapis lazuli due to its deep blue color, but it lacks the gold pyrite inclusions typical of lapis. It was named after the French paleontologist Eugène Dumortier.

Field identification & locations

Identify by its distinct denim-blue color and lack of calcite or pyrite. Commonly found in Brazil, Namibia, Madagascar, and the USA (California and Nevada).