Dravite
Image: James St. John (CC BY 2.0)
Mineral NameDravite
Chemical FormulaNaMg3Al6(BO3)3Si6O18(OH)4
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavageindistinct/poor basal, sometimes none
Fractureconchoidal
Specific Gravity3.03
Colorsbrown, yellowish-brown, dark brown, black, green, blue, colorless
Transparencytransparent
Type LocalityWorldwide, notable localities include Austria, Brazil, Tanzania, Australia, Russia.
Mineral GroupSilicates
Usesgemstone, collector's item
Associated Mineralsquartz, feldspar, mica, calcite, garnet
Rarityuncommon
Description
Dravite typically forms prismatic crystals, often with a triangular cross-section and vertical striations, commonly appearing in shades of brown to black. It can also be found as transparent, gem-quality crystals in various colors.
Geological Context
Dravite is a common tourmaline found primarily in metamorphic rocks such as schists and gneisses, and less frequently in pegmatites and hydrothermal veins. It forms under high-temperature and high-pressure conditions, often associated with boron-rich environments.
