Dravite Mineral Data

Dravite Mineral Data +

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General Dravite Information

Chemical Formula:

NaMg3Al6(BO3)3Si6O18(OH)4

Composition:

Molecular Weight = 958.75 gm

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

Empirical Formula:

NaMg₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Environment:

Metasomatically altered magnesian or dolomitic limestones in contact-metamorphic aureoles.

IMA Status:

Valid Species (Pre-IMA) 1883 (Dana # Changed)

Locality:

Drava River, Austria. Link to MinDat.org Location Data.

Name Origin:

After its locality.

Synonym:

Dravite - (61.3.1.9)

ICSD 72937

PDF 44-1457

Tourmaline

Dravite Image

Images:

Dravite

Comments: Doubly terminated dravite crystal on white mica shist matrix.
Location: Yinnietharra Station, Gascoyne, Western Australia. Scale: 4 x 4 x 2.9 cm.
© Fabre Minerals

Images:

Dravite

Comments: Greenish-brown chrome-rich dravite tourmaline crystals up to 13 mm long with complex terminations. Fluoresces mildly under UV illumination.
Location: Shako Ranch, Mwatate Kabanga, Voi, Taita-Taveta district, Coast Province, Kenya. Scale: 14x13x10 mm.
© John Betts - Fine Minerals

Dravite Crystallography

Axial Ratios:

a:c = 1:0.45172

Cell Dimensions:

a = 15.941, c = 7.201, Z = 3; V = 1,584.73 Den(Calc)= 3.01

Crystal System:

Trigonal - Ditrigonal PyramidalH-M Symbol (3m) Space Group: R 3m

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.576(1), 2.961(0.85), 3.99(0.85),

Crystal Structure:

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Hawthorne F C , MacDonald D J , Burns P C , American Mineralogist , 78 (1993) p.265-270, Reassignment of cation site occupancies in tourmaline: Al-Mg disorder in the, crystal structure of dravite

View Additional jPOWD Structure files for Dravite
[1] [2] [3] [4] [5] [6] [7] [8]

Physical Properties of Dravite

Cleavage:

[???] Indistinct

Color:

Black, Green, Red, Blue, White.

Density:

2.98 - 3.2, Average = 3.09

Diaphaniety:

Transparent to translucent to opaque

Fracture:

Sub Conchoidal - Fractures developed in brittle materials characterized by semi-curving surfaces.

Habit:

Columnar - Forms columns

Habit:

Divergent - Crystals radiate from a center without producing stellar forms.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Hardness:

7-7.5 - Quartz-Garnet

Luminescence:

Non-fluorescent.

Luster:

Vitreous - Resinous

Streak:

colorless

Optical Properties of Dravite

Dichroism (e):

pale yellow or colorless.

Dichroism (w):

dark yellowish brown or light yellow.

Gladstone-Dale:

CI meas= 0.034 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.009 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.21,KPDmeas= 0.2045,KC= 0.2118

Optical Data:

Uniaxial (-), e=1.612-1.63, w=1.631-1.655, bire=0.0190-0.0250.

Calculated Properties of Dravite

Electron Density:

r_electron=2.99 gm/cc
note: r_Dravite=3.01 gm/cc.

Fermion Index

Fermion Index = 0.02279
Boson Index = 0.97721

Photoelectric:

PE_Dravite= 1.42 barns/electron
U=PE_Dravite x r_electron= 4.25 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Dravite is Not Radioactive

Dravite Classification

Dana Class:

61.3e.1.9 (61)Cyclosilicate Six-Membered Rings

(61.3e)with borate groups (Sodic Tourmaline Subgroup)

(61.3e.1)Dana Group

61.3e.1.9 Dravite ! NaMg3Al6(BO3)3Si6O18(OH)4 R 3m 3m

61.3e.1.10 Schorl! NaFe3Al6(BO3)3Si6O18(OH)4 R 3m 3m

61.3e.1.11 Chromdravite! NaMg3(Cr,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

61.3e.1.12 Vanadiumdravite! NaMg3V6(Si6O18)(BO3)3(OH)4 R 3m 3m

Strunz Class:

VIII/E.19-20 VIII - Silicates

VIII/E - Cyklosilicates, six rings [Si6O18]12-

VIII/E.19 - Tourmaline group

VIII/E.19-05 Rossmanite! []LiAl2Al6(Si6O18)(BO3)3(OH)4 R 3m 3m

VIII/E.19-10 Elbaite Na(Li,Al)3Al6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-15 Magnesiofoitite! [](Mg2Al)Al6(Si6O18)(BO3)3(OH)4 R 3m 3m

VIII/E.19-20 Dravite NaMg3Al6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-30 Chromdravite! NaMg3(Cr,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-35 Vanadiumdravite! NaMg3V6(Si6O18)(BO3)3(OH)4 R 3m 3m

VIII/E.19-50 Schorl NaFe3Al6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-55 Foitite! []Na<0.5(Fe,Al)3Al6Si6O18(BO3)3(OH)4 R 3m 3m

VIII/E.19-60 Olenite! NaAl3Al6(BO3)3(Si6O18)(O,OH)4 R 3m 3m

VIII/E.19-70 Buergerite! NaFe3Al6(BO3)3Si6O21F R 3m 3m

VIII/E.19-75 Povondraite! (Na,K)(Fe,Fe)3(Fe,Mg,Al)6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-80 Liddicoatite! Ca(Li,Al)3Al6(BO3)3Si6O18(O,OH,F)4 R 3m 3m

VIII/E.19-90 Uvite (Ca,Na)(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH,F)4 R 3m 3m

VIII/E.19-100 Feruvite! (Ca,Na)(Fe,Mg,Ti)3(Al,Mg,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

Other Dravite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Dravite

NaMg3Al6(BO3)3Si6O18(OH)4
Dana No: 61.3e.1.9 Strunz No: VIII/E.19-20
Locality:

Notes: