Gemstone Glossary

Dumortierite

Named after the French paleontologist, Eugene Dumortier, Dumortierite is typically blue, violet, pink or brown in color and is commonly used as a semi precious/ornamental stone, in the manufacture of high-grade ceramics/porcelain and as mineral specimens. Displaying a vitreous to dull luster, its crystals are translucent to transparent with massive specimens appearing nearly opaque. Having an uneven fracture Dumortierite has a hardness of 7 - 8.5 and a specific gravity of 3.3 - 3.4. Interestingly, Dumortierite is pleochroic from red to blue to violet, with some specimens fluorescing a blue color with a yellow matrix under long wave UV light or a white fluorescence under short wave UV light. Massive quartz colored blue by included Dumortierite crystals is commonly referred to as Dumortierite quartz.


Dumortierite, a boro-silicate mineral, is made unusual by its very attractive deep violet blue color. Interestingly, Dumortierite is the most common boro-silicate with the exception of the Tourmaline Group.

While not used as a precious gemstone due to a lack of clarity, it displays a bright coloring and good hardness. Massive specimens are carved into cabochons, beads, sculptures, eggs and spheres and in China it has been used as a lapis lazuli imitation. While Dumortierite can be misidentified as other ornamental stones (i.e. sodalite, lazurite and lazulite), blue sodalite is less dense and has whiter portions, while lazurite and lazulite are not fibrous.

Dumortierite occurs in Beaunan, France as well as Quartzite, La Paz County, Arizona; Colorado; Oreana, Nevada; New York, New York and Alpine, San Diego County and Los Angeles County, California, USA; Magadanskaya, Siberia, Russia; India and Sahatany, Madagascar. It has many associated minerals including quartz, kyanite, sillimanite, staurolite, andalusite, muscovite, lazulite and pyrophyllite.