Dumortierite

Big Photo

Madagascar
0.15 carats
© irocks.com

Dumortierite was named after French paleontologist E. Dumortier. It is widely used as ornamental stone in its massive form. The deep violet to blue colour stones can be cut into attractive cabochons.

Dumortierite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 

Dumortierite Gemstones by Size

This table shows distribution of Dumortierite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.06 cts
Heaviest:8.18 cts
Average:3.16 cts
Total photos:14
Do you have a larger Dumortierite? Why not upload a photo?
0.06ct to 0.87ct0.87ct to 1.68ct1.68ct to 2.50ct2.50ct to 3.31ct3.31ct to 4.12ct4.12ct to 4.93ct4.93ct to 5.74ct5.74ct to 6.56ct6.56ct to 7.37ct7.37ct to 8.18ct
General Information
Chemical Formula
Al
 
7
(BO
 
3
)(SiO
 
4
)
 
3
O
 
3
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Photos of natural/un-cut material from mindat.org
Physical Properties of Dumortierite
Mohs Hardness7 to 8.5
Walter Schumann, Gemstones of the world (2001) Aggregates, mainly cut, have hadrness of 7; crystals - 8.5More from other references
Specific Gravity3.26 to 3.41
Walter Schumann, Gemstones of the world (2001)
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Cleavage QualityGood
Walter Schumann, Gemstones of the world (2001)
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FractureConchoidal
Walter Schumann, Gemstones of the world (2001)
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Optical Properties of Dumortierite
Refractive Index1.669 to 1.723
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) Rare red-brown crystals +/- 1.669More from other references
Optical CharacterBiaxial/-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Birefringence0.011 to 0.037
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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PleochroismStrong trichroism for rare red-brown crystals: black - red brown - brown
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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DispersionNone
Walter Schumann, Gemstones of the world (2001)
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Colour
Colour (General)Dark blue, violet-blue, red-brown, colourless
Walter Schumann, Gemstones of the world (2001)
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TransparencyTranslucent,Opaque
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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LustreVitreous
Arthur Thomas, Gemstones (2009) Dull
Fluorescence & other light emissions
Fluorescence (General)Weak; blue - blue-white - violet
Walter Schumann, Gemstones of the world (2001)
Fluorescence (Short Wave UV)Inert to chalky blue, often intergrown with quartz
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Crystallography of Dumortierite
Crystal SystemOrthorhombic
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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HabitCommonly fibrous aggregate
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Geological Environment
Where found:Dumortierite occurs in pegmatite veins or in aluminium-rich regionally metamorphosed rocks.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Dumortierite information at mindat.org
Significant Gem Localities
Peru
 
  • Lima
    • Canta Province
Copyright © Jolyon & Katya Ralph 1993-2019. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.