Click on a letter above to view the list of gems.    

Dumortierite
Current inventory:  1 gem
 

Chemistry:  Al₇(BO₃)(SiO₄)₃O₃

Discovered in 1881;   IMA status: Valid (pre-IMA; Grandfathered).
Dumortierite is named after Eugμene Dumortier (1802-1873), French paleontologist, of Lyons, France.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/B.31-20

8 : Silicates
B : Nesosubsilicates, with anions unfamiliar to tetraheders, cations of octahedral and tetrahedral orientation [4/6]
31 : Kornerupine - Harkerite series

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

As fibrous or columnar crystals, having generally poor face development, to 6 cm; as coarsely crystalline to intimate parallel aggregates of needles; massive.
Twinning: Common on [110], which may produce trillings.

Physical Properties

Cleavage:

[100] Distinct, [110] Indistinct

Fracture:

Fibrous

Tenacity:

Brittle

Moh's Hardness:

7.0 - 8.5

Density:

3.21 - 3.41 (g/cm³)

Radioactivity:

Not Radioactive

Optical Properties

Color:

Pale to dark Blue, Greenish Blue, Greenish, Brown, Violet, Pink

Transparency:

Transparent to Translucent

Luster:

Vitreous to Dull

Refractive Index:

1.668 - 1.688  Biaxial ( - )

Birefringence:

0.150 - 0.370

Dispersion:

Strong

Pleochroism:

Strong; X = deep blue or violet; Y = yellow to red-violet or nearly colorless; Z = colorless or very pale blue.

Occurances

Geological Setting:

In aluminum-rich regionally metamorphosed rocks, disseminated and in veinlets cutting schists; also in pegmatitic veins.

Type Locality:

Chaponost, Beaunan, Rhône, Rhône-Alpes, France

Year Discovered:

1881

View mineral photos:

Dumortierite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Dumortierite is a fairly common mineral in massive, fibrous and granular form but extremely rare as crystals. The massive material is a beautiful and very hard material suitable for cabochons and use in jewelry. Faceted gems are extremely rare and usually small and included. The only current source of facetable crystals is Mina Gerais, Brazil.
 

  
Dumortierite gems for sale: