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| 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) |
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Chemistry
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Chemical
Formula: |
NaMg3Al6(BO3)3Si6O18(OH)4
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complex Sodium Magnesium Boro-Aluminum Silicate Hydroxide
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Molecular
Weight: |
958.75 gm
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Composition: |
Sodium |
2.40 % |
Na |
3.23 % |
Na2O |
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Magnesium |
7.61 % |
Mg |
12.61 % |
MgO |
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Aluminum |
16.89 % |
Al |
31.90 % |
Al2O3 |
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Silicon |
17.58 % |
Si |
37.60 % |
SiO2 |
|
Boron |
3.38 % |
B |
10.89 % |
B2O3 |
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Hydrogen |
0.42 % |
H |
3.76 % |
H2O |
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Oxygen |
51.73 % |
O |
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100.00 % |
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100.00 % |
= TOTAL OXIDE |
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Classification
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Mineral
Classification: |
Silicates
(Germanates)
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Strunz 8th
Ed. ID:
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8/E.19-20
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Nickel-Strunz 10th
Ed. ID:
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9.CK.05
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9 : SILICATES (Germanates)
C : Cyclosilicates K : [Si6O18]12- 6-membered single rings, with insular complex anions
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Related
to: |
Tourmaline
Group. Dravite - Elbaite Series. Dravite - Schorl Series. Dravite - Uvite Series. Dravite - Buergerite Series. The OH
analogue of
Fluor-dravite.
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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
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Varieties: |
Chromian Dravite,
Lime-Dravite, Soda-Dravite
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Synonyms: |
Coronite (of Hunt),
Gouverneurite, Mg-Turmalin
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Crystal
Data
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Crystallography:
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Trigonal
- Ditrigonal Pyramidal
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Crystal
Habit:
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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.
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Twinning:
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Rare,
on {1011} and {4041)
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Physical
Properties
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Cleavage: |
Very
poor on {1120},{1011}
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Fracture: |
Irregular/Uneven,
Conchoidal
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Tenacity:
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Brittle
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Moh's
Hardness: |
7.0
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Density:
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3.03
- 3.18 (g/cm3)
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Luminescence:
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Fluorescent;
yellow to orange under SW
UV. |
Radioactivity:
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Not
Radioactive |
Other: |
Piezoelectric
and Pyroelectric
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Optical
Properties
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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
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Occurances
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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
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View
mineral photos: |
Dravite
Mineral Photos and Locations |
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More
Information
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Mindat.org
Webmineral.com
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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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Dravite
gems for sale:
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have not photographed the Dravite gems yet. Please
check back soon.
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