DRAVITE

    Class : Silicates
    Subclass : Cyclosilicates
    Crystal system : Trigonal
    Chemistry : NaMg3Al6(BO3)3Si6O18(OH)4
    Rarity : Common

Dravite is a magnesium tourmaline. It is a mineral of metamorphic origin, but which is also found as an accessory mineral to granites and pegmatites. It owes its name to its locality of discovery : Drava in Austria. An exception in the tourmaline group, dravite is rarely well crystallized. Its crystals are short prisms, sometimes reminiscent of garnet, with a triangular section with curved edges, and pyramidal endings. Rarely, it can be fibrous or acicular, and therefore difficult to recognize. Its color is variable, most often brown-black to black, sometimes yellow, rarely blue-green or red. Gemmy varieties are used in jewelry.

Main photo : Dravite from Brumado, Bahia, Brazil © Luciana Barbosa

Dravite from Brumado, Bahia, Brazil © Frédéric Verrier
Dravite from Pierrepont, New York, USA © Terry Burtzalff
Dravite from Yinnietharra Dravite North mine, Australia © Terry Burtzalff
Dravite on gypsum from Arignac, Ariège, France

Dravite in the World

The most beautiful dravite crystals come from the metamorphic limestones and dolomites of New York State (De Kalb, Pierrepont, Gouverneur, etc...), which have yielded frequently hemimorphic crystals measuring 15 cm by 7.5 cm. Dravite is also common in the metamorphic formations of the American East. The mica-schists of Yinnietharra (Western Australia) gave the largest known crystals : specimens of 25 cm in diameter. Brumado (Bahia, Brazil) supplied magnificent 15 cm crystals, and dark red gem crystals are produced in the Narok district of Kenya. In Europe, dravite forms beautiful centimeter-sized crystals in the Austrian dolomites of Dobrowa (Carinthia) and the Swiss dolomites of Binn (Valais).

Dravite in France

The most beautiful French dravites come from the Arignac sector (Ariège) and are placed on gypsum. We also find 5 mm crystals in Cayola Bay (Vendée) on schist. It is also reported in sub-millimeter crystals at Cap Garonne (Var), in the Alps at St-Jean-de-Maurienne (Savoie), as well as in numerous rivers and alluvium.

Twinning

Rare twins known on {10-11} and on {40-41}.

Fakes and treatments

No fake listed for this mineral species.


Hardness : 7
Density : 3.03 to 3.18
Fracture : Irregular to conchoidal
Streak : Brown to white

TP : Translucent to transparent
RI : 1.612 to 1.660
Birefringence : 0.022 to 0.029
Optical character : Uniaxial -
Pleochroism : Strong
Fluorescence : Yellow under short UV

Solubility : Insoluble


Magnetism : Paramagnetic
Radioactivity : None

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