Dumortierite
Species
Uncommon · Al₇(BO₃)(SiO₄)₃O₃
Aluminium borosilicate forming blue to violet fibrous and columnar masses in aluminium-rich metamorphic rocks and pegmatitic veins. It is strongly pleochroic, from deep blue to nearly colourless. It was once mined commercially in Nevada, and is cut as an ornamental stone.
Identity
- Formula
- Al₇(BO₃)(SiO₄)₃O₃
- Chemical class
- Silicate
Crystallography
- Crystal system
- Orthorhombic
- Habits
- Prismatic, Massive, Fibrous
- Fracture
- Subconchoidal
Physical properties
- Mohs hardness
- 7
- Density
- 3.3 g/cm³
- Luster
- Vitreous, Silky
- Colors
- blue, violet-blue, pink, brown
- Streak
- white
- Transparency
- Translucent, Opaque
Geology
- Origins
- Metamorphic, Igneous
- Host rocks
- Granite, Schist and gneiss
- Associated minerals
- Quartz, Kyanite, andalusite, Mica
- Found in
- Pegmatite deposit
- Geography
- France, Madagascar, Namibia, USA, India
Classification
- Rarity
- Uncommon
- Gem quality
- Yes
Arcane properties
- Affinity
- Arcane, Mind
- Effects
- Mind, Warding
- Planar origin
- Material Plane
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Dumortierite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
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