Mineral description : Dravite

Dravite crystals in chlotite schist from Altemark talc mine, Norway.
Dravite with kyanite from Store Akersvatnet, Norway.
Transparent dravite in quartz from Store Akersvatnet, Norway.

Mineral class Silicates : Cyclosilicates : Beryl - Tourmaline group.
Chemical formula NaMg3(Al,Fe)6(BO3)3(Si6O18)(OH)4
Crystal system Trigonal / Hexagonal.
Habitus As rounded triangular striated crystals. Often as hexagonal crystals. Commonly as radiating aggregates. Also in compact and massive habitus.
Cleavage Very indistinct, basally partening, fracture uneven to conchoidal.
Hardness 7-7.5
Density 3.2+
Color Brown to brownish black, transparent to opaque.
Streak Colorless.
Luster Vitreous.
Description Dravite is the magnesia rich member of the tourmaline family.
Occurance Pegmatites and granites, also in some metamorphic rock.
Associates  
Notes Insoluble in acids.
Separated from schorl through crushing the edge, if the powder is brown instead of black it's most likely dravite. Easy to mistake dark varietys for schorl.
Locations A more rare mineral than schorl in Sweden.
  • Västanåberget, Näsum. As small crystals up to 3-7 mm in schist.
  • Stora Vika limestone quarry, Nynäshamn, Stockholm. As crystals in cavities in pegmatite.
  • Vena copper mine, Närke. In a pegmatite vein.
  • Stakholmen, Hassela. Together with prismatine, sillimanite, enstatite and talc.
  • Ekeberg marble quarry, Glanshammar, Örebro, Närke.
  • Långban, Värmland.
  • Hålsjöberg, Värmland.
  • Björkdalsgruvan, Västerbotten.
  • Altemark talc mine, Norway. As dark crystals up to dm length in chlorite and talc.
  • Store Akersvatnet, Norway. As double terminated black crystals up to 3cm in a cavity with kyanite and quartz. Also as a transparent light brown crystal 10 mm long in quartz.

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Last changed : 1998-05-04