By Chisom Ibemere
Dumortierite is a fibrous aluminium boro silicate mineral that has varieties of colours. It crystallizes in the orthorhombic system typically forming fibrous aggregates of slender prismatic crystals.
It has a vitreous crystal with numerous colours of brown, blue, green, violet and pink. Its colour variation results in iron and other trivalent element substitution for aluminium. It has a Mohs hardness of 7 and a specific gravity of 3.3 to 3.4. Its crystals display pleochroism from red to blue to violet. Its quartz has a blue colour and an abundant of dumortierite inclusions.
Dumortierite occurs in high temperature aluminium rich regional metamorphic rocks, those that results from contact metamorphism and also in boron rich pegmatites. It is basically used in the production of high grade porcelain. It is sometimes confused for sodalite. Because of its similarity, it is often used as a cost-saving substitute for lapis which costs two to three times as much. Some of the sources of Dumortierite include Austria, Brazil, Canada, France, Italy, Madagascar, Namibia, Nevada, Norway, Peru, Poland, Russia and Sri Lanka etc.
The blue denim stone is the name for the deep blue dumortierite. Its name is given for a French paleontologist, Eugène Dumortier, who discovered it in 1881. It is sometimes mistaken for sodalite and lapis lazuli.