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www.mineralgallery.co.za Minerals A-E |
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Dumortierite |
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Name
Dumortierite
Chemistry
Al6.5 - 7(BO3)(SiO4)3(O, OH)3, Aluminum Boro-silicate Hydroxide.
Uses
As an ornamental stone
Color
Blue
Hardness
6.5
Specific gravity
3.3-3.4
Dumortierite is a boro-silicate mineral that is used as a popular ornamental stone. It has a deep violet to blue color that is very attractive and unusual. Although it is not used as a gemstone due to a lack of clarity, it does have good hardness and a bright color.
Massive dumortierite can be carved into cabochons, beads, sculptures, eggs and spheres. A variety of quartz called dumortierite quartz is massive quartz colored blue by included crystals of dumortierite. Dumortierite can be misidentified as other ornamental stones such as sodalite, lazurite and lazulite. Blue sodalite has more white portions and is much lighter in density. Lazurite and lazulite are not fibrous. In China, some dumortierite has been used as an imitation lapis lazuli in carvings.
Dumortierite is related to several other nesosilicate boro-silicates such as grandidierite, harkerite, holtite, kornerupine, magnesiodumortierite, prismatine and werdingite. Dumortierite is far more common than all of these. In fact, it is the most common boro-silicate with the exception of the more common members of the Tourmaline Group.
Dumortierite is commonly found in aluminum rich metamorphic rocks in contact metamorphic regions and in some pegmatites. It can alter to the mineral pyrophyllite. Dumortierite is named for the French paleontologist, Eugene Dumortier.