Dumortierite
Image: Nessa Eull (CC0)
Mineral NameDumortierite
Chemical Formula(Al,Fe)7(BO3)(SiO4)3(O,OH)3
Mohs Hardness7
Crystal Systemorthorhombic
Lustervitreous
Streak Colorwhite
Cleavagegood on {100}, poor on {110}
Fractureuneven
Specific Gravity3.3
Colorspurple, blue, pink-red, brown
Transparencytranslucent
Type LocalityOreana, Nevada
Mineral GroupBorosilicates
Usesjewelry, ornamental, collector
Associated Mineralsquartz, muscovite, andalusite, kyanite
Rarityuncommon
Description
This specimen is a roughly 7 cm, massive, purple-pink rock with a fine-grained to fibrous texture, showing some lighter white patches. The color is characteristic of dumortierite.
Geological Context
Dumortierite is typically found in aluminum-rich metamorphic rocks, granitic rocks, and some ore deposits, often formed under high-temperature conditions.
