mineral

Dumortierite Quartz

Al7BO3(SiO4)3O3 (Borosilicate mineral/Quartz inclusion)

Hardness: 7 (Mohs scale), Color: Denim blue to violet-blue with white/gray quartz matrix, Luster: Vitreous to dull, Crystal structure: Orthorhombic (within Trigonal quartz), Specific Gravity: 3.2 – 3.4

Identified March 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed in regional metamorphic rocks rich in aluminum, as well as in some granitic pegmatites. It typically occurs as fibrous inclusions within quartz crystals, often resulting in a massive, opaque blue stone.

Uses & applications

Used primarily in lapidary work for cabochons, beads, and carvings. Also used in the ceramics industry to create high-quality spark plug porcelain and laboratory equipment due to its thermal resistance.

Geological facts

First described in 1881 and named after the French paleontologist Eugène Dumortier. It is often mistaken for Lapis Lazuli or Sodalite, but it lacks the pyrite inclusions of Lapis and is significantly harder than both.

Field identification & locations

Identify by its distinct 'denim' blue color and superior hardness; it will scratch glass and cannot be scratched by a steel knife. Common locations include Brazil, Madagascar, and South Africa.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

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Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

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