Dravite (variety of Tourmaline)
Current inventory:  0 gems
 

  
Dravite is named for the river Drau (in Latin, Drave), on which the type locality is situated.

Discovered in 1883; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

NaMg₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

complex Sodium Magnesium Boro-Aluminum Silicate Hydroxide

Molecular Weight:

958.75 gm

Composition:

Sodium

2.40 %

Na

3.23 %

Na₂O

Magnesium

7.61 %

Mg

12.61 %

MgO

Aluminum

16.89 %

Al

31.90 %

Al₂O₃

Silicon

17.58 %

Si

37.60 %

SiO₂

Boron

3.38 %

B

10.89 %

B₂O₃

Hydrogen

0.42 %

H

3.76 %

H₂O

Oxygen

51.73 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/E.19-20

Nickel-Strunz 10th Ed. ID:

9.CK.05

9 : SILICATES (Germanates)
C : Cyclosilicates
K : [Si₆O₁₈]₁₂- 6-membered single rings, with insular complex anions

Related to:

Tourmaline Group. Dravite - Elbaite Series. Dravite - Schorl Series. Dravite - Uvite Series. Dravite - Buergerite Series. The OH analogue of Fluor-dravite.

Members of Group:

Tourmaline Group: Adachiite, Buergerite, Chromium-dravite, Chromo-alumino-povondraite, Darrellhenryite, Dravite, Elbaite, Feruvite, Fluor-buergerite, Fluor-dravite, Fluor-elbaite, Fluor-feruvite, Fluor-liddicoatite, Fluor-schorl, Fluor-tsilaisite, Fluor-uvite, Foitite, ICSD 85557, IMA1996-018, Liddicoatite, Luinaite-(OH), Magnesio-foitite, Maruyamaite, Olenite, Oxy-chromium-dravite, Oxy-dravite, Oxy-rossmanite, Oxy-schorl, Oxy-vanadium-dravite, PDF(76-1951), Povondraite, Rossmanite, Schorl, Tsilaisite, UM2000-64-SiO:BFeHKMg, Unnamed (Pb-dominant Tourmaline), Uvite, Vanadio-oxy-chromium-dravite, Vanadio-oxy-dravite, Vanadiumdravite

Varieties:

Chromian Dravite, Lime-Dravite, Soda-Dravite

Synonyms:

Coronite (of Hunt), Gouverneurite, Mg-Turmalin

Crystal Data

Crystallography:

Trigonal - Ditrigonal Pyramidal

Crystal Habit:

Crystals equant or short to long prismatic, with dominant pyramid faces, to 20 cm. Striated || [0001], cross sections typically triangular with curved convex sides. Commonly radiating, granular, and massive.

Twinning:

Rare, on {1011} and {4041)

Physical Properties

Cleavage:

Very poor on {1120},{1011}

Fracture:

Irregular/Uneven, Conchoidal

Tenacity:

Brittle

Moh's Hardness:

7.0

Density:

3.03 - 3.18 (g/cm³)

Luminescence:

Fluorescent; yellow to orange under SW UV.

Radioactivity:

Not Radioactive

Other:

Piezoelectric and Pyroelectric

Optical Properties

Color:

Brown to black, red, yellow, blue, green, colorless, white; colorless to yellow in thin section

Transparency:

Transparent to Translucent

Luster:

Vitreous to Resinous

Refractive Index:

1.612 - 1.661  Uniaxial ( - )

Birefringence:

0.0190 - 0.0250

Dispersion:

0.017

Pleochroism:

Very strong; O = pale yellow; E = colorless, yellowish, greenish, brownish

Occurances

Geological Setting:

Commonly in metamorphosed limestones or mafic igneous rocks with metasomatically introduced boron; rarely in pegmatites; as authigenic overgrowths in sedimentary rocks.

Common Associations:

Quartz, Calcite, Dolomite, Epidote, Microcline, Albite, Muscovite, Fluorite, Titanite

Common Impurities:

Fe, Mn, Ti, Ca, Cr, V, K, F

Type Locality:

Dobrova, Dravograd (Unterdrauburg), Slovenia

Year Discovered:

1883

View mineral photos:

Dravite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Dravite is a rare member of the Tourmaline Group of minerals that includes Achroite, Dravite, Liddicoatite, Povondraite, Rubellite, Uvite and Schorl. Dravite is a magnesium rich member of the Tourmaline Group. Other more common and more well know Tourmalines are Elbaite (various colors and colorless, lithium rich), Schorl (opaque black, iron rich), Uvite and Liddicoatite. Most colored Tourmaline used as gemstones are Elbaite Tourmaline. Dravite is named for the river Drau (in Latin, Drave), on which the type locality is situated. It is available in colors of brown to black, red, yellow, blue, green, colorless, white and colorless to yellow in thin section.

Distribution: Found around Dravograd (Unterdrauberg), Slovenia. From Beura, Val d'Ossola, Piedmont, Italy. At Arendal and Snarum, Norway. From Outokumpu, and Kaavi, Kuopio, Finland. In the USA, ¯ne crystals from Gouverneur, Pierrepont, and Macomb, St. Lawrence Co., New York; at Franklin and Hamburg, Sussex Co., New Jersey; and Newry, Oxford Co., Maine. In Canada, in Hull Township, Quebec; at Wilberforce, Ontario; and many other places. From Brumado, Bahia, Brazil. Large crystals from Yinnietharra, 800 km north of Perth, Western Australia. At Osarara, Narok district, Kenya. From Gujarkot, Nepal. Increasingly distinguished from other tourmaline group members.
 

  
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