Dravite

Big Photo

Sri Lanka
0.15 carats
© Giovanni Scapin 2015

Dravite is named after a deposit near the river Drave, Carinthia/Austria. It is a magnesium tourmaline, usually dark yellow to brownish black colour.
General Information
A variety or type of:Tourmaline
Chemical Formula
Na(Mg
 
3
)Al
 
6
(Si
 
6
O
 
18
)(BO
 
3
)
 
3
(OH)
 
3
(OH)
Gemdat.org, Management Team (2012)
Photos of natural/un-cut material from mindat.org
Dravite Treatments
Color may be improved or created by irradiation of colorless to light colored stones (not detectable) - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 5
Physical Properties of Dravite
Mohs Hardness7 to 0
Anthony et al, Handbook of mineralogy (2001)
Specific Gravity3.03 to 3.18
Anthony et al, Handbook of mineralogy (2001)
TenacityBrittle
Anthony et al, Handbook of mineralogy (2001)
Cleavage QualityPoor
Anthony et al, Handbook of mineralogy (2001) Very poor
FractureUneven,Irregular,Conchoidal
Anthony et al, Handbook of mineralogy (2001)
Optical Properties of Dravite
Refractive Index1.614 to 1.666
Walter Schumann, Gemstones of the world (2001)
Optical CharacterUniaxial/-
Anthony et al, Handbook of mineralogy (2001)
Birefringence0.014 to 0.032
Walter Schumann, Gemstones of the world (2001)
PleochroismVery strong: pale yellow - colorless,
yellowish, greenish, brownish.
Anthony et al, Handbook of mineralogy (2001)
Dispersion0.017
Walter Schumann, Gemstones of the world (2001)
Colour
Colour (General)Yellow brown to orangy
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) Not always dravite species!More from other references
Causes of ColourYellow to brown, related to titanium; due to Fe2+-O-Ti4+ charge transfer, with those low in iron yellow and those rich in iron brown. Red, Fe3+ pairs.
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTransparent,Translucent
Anthony et al, Handbook of mineralogy (2001)
LustreVitreous,Resinous
Anthony et al, Handbook of mineralogy (2001)
Fluorescence & other light emissions
Fluorescence (Short Wave UV)May weakly fluoresce
Anthony et al, Handbook of mineralogy (2001)
Crystallography of Dravite
Crystal SystemHexagonal
Anthony et al, Handbook of mineralogy (2001)
HabitCrystals equant or short to long prismatic, with dominant pyramid faces, to 20 cm. Striated, cross sections typically triangular with curved convex sides. Commonly radiating, granular, and massive.
Anthony et al, Handbook of mineralogy (2001)
Geological Environment
Where found:Commonly in metamorphosed limestones or mafic igneous rocks with metasomatically introduced boron; rarely in pegmatites; as authigenic overgrowths in sedimentary rocks.
Anthony et al, Handbook of mineralogy (2001)
Further Information
Mineral information:Dravite information at mindat.org
Significant Gem Localities
Myanmar
 
  • Mandalay Region
    • Pyin-Oo-Lwin District
      • Mogok Township
        • Kyauk-Pyat-That
          • Thurein-taung
Ted Themelis (2008) Gems & mines of Mogok
        • Mogok Valley
          • Dattaw-taung (Dattaw hill)
Ted Themelis (2008) Gems & mines of Mogok
        • Pein-Pyit (Painpyit; Pyan Pyit)
Ted Themelis (2008) Gems & mines of Mogok
Sri Lanka
 
  • Sabaragamuwa Province
    • Ratnapura District
      • Ratnapura
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