dumortierite

Dumortierite is a rare aluminoborosilicate mineral with the chemical formula Al8B7O16(OH)3. It is typically found in metamorphic rocks, particularly in quartz veins and pegmatites. The mineral is known for its distinctive blue color, which can range from pale blue to a deep, intense blue. Sometimes, it can also appear as greenish-blue or purplish-blue. Its luster is vitreous to greasy. Dumortierite is relatively hard, ranking between 7 and 8.5 on the Mohs hardness scale, and it has a specific gravity of about 3.3 to 3.4.

The mineral was first discovered in 1881 in the Gaa mine near Saint-Yrieix-la-Perche, France, and was named in honor of the French paleontologist Eugène Dumortier. While it is not a common gemstone, fine specimens of dumortierite are used in jewelry, particularly when they exhibit a vibrant blue color and are cabochoned or cut into beads. Due to its rarity and distinctive color, it is a sought-after mineral among collectors. It is often found associated with other minerals such as quartz, andalusite, and kyanite.