Chromdravite Mineral Data

General Chromdravite Information

Chemical Formula:

NaMg3(Cr,Fe+++)6(BO3)3Si6O18(OH)4

Composition:

Molecular Weight = 1,114.61 gm

Sodium 2.06 % Na 2.78 % Na₂O

Magnesium 6.54 % Mg 10.85 % MgO

Chromium 20.99 % Cr 27.45 % CrO

Iron 7.52 % Fe 10.75 % Fe₂O₃

Silicon 15.12 % Si 32.34 % SiO₂

Boron 2.91 % B 9.37 % B₂O₃

Hydrogen 0.36 % H 3.23 % H₂O

Oxygen 44.50 % O

______ ______

100.00 % 96.77 % = TOTAL OXIDE

Empirical Formula:

NaMg₃Cr_4.5Fe³⁺_1.5(BO₃)₃Si₆O₁₈(OH)₄

Environment:

Magnesium and chromium-bearing tourmaline in micaceous metasomatites.

IMA Status:

Approved IMA 1983 (Dana # Changed)

Locality:

Onezhkii depression, central Karelia, Russia. Link to MinDat.org Location Data.

Name Origin:

Named for the compositional relationship to dravite.

Synonym:

Chromdravite - (61.3.1.11)

Tourmaline

Chromdravite Image

Images:

Chromdravite

Comments: Dark green chromdravite grains in matrix.
Location: Srednyaya Padma U-V deposit, Zaonezhie peninsula, Lake Onega, Karelia Republic, Northern Region, Russia. Scale: Specimen Size 2 cm.
© Jeff Weissman / Photographic Guide to Mineral Species

Chromdravite Crystallography

Axial Ratios:

a:c = 1:0.45127

Cell Dimensions:

a = 16.11, c = 7.27, Z = 3; V = 1,634.02 Den(Calc)= 3.40

Crystal System:

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

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

By Intensity(I/I_o): 2.62(1), 3.04(0.75), 3.58(0.75),

Physical Properties of Chromdravite

Cleavage:

None

Color:

Greenish black, Dark green.

Density:

3.4

Diaphaneity:

Translucent to Opaque

Habit:

Blocky - Crystal shape tends to be equant (e.g. feldspars).

Habit:

Striated - Parallel lines on crystal surface or cleavage face.

Hardness:

7-7.5 - Quartz-Garnet

Luminescence:

Non-fluorescent.

Luster:

Vitreous - Resinous

Streak:

greenish gray

Optical Properties of Chromdravite

Dichroism (e):

yellow green.

Dichroism (w):

dark green.

Gladstone-Dale:

CI meas= -0.029 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= -0.029 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2209,KPDmeas= 0.2209,KC= 0.2147
Ncalc = 1.73

Optical Data:

Uniaxial (-), e=1.722-1.724, w=1.778-1.78, bire=0.0560.

Calculated Properties of Chromdravite

Electron Density:

Bulk Density (Electron Density)=3.32 gm/cc
note: Specific Gravity of Chromdravite =3.40 gm/cc.

Fermion Index:

Fermion Index = 0.04
Boson Index = 0.96

Photoelectric:

PE_Chromdravite= 7.71 barns/electron
U=PE_Chromdravite x rElectron Density= 25.62 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Chromdravite is Not Radioactive

Chromdravite Classification

Dana Class:

61.03e.01.11 (61)Cyclosilicate Six-Membered Rings

(61.03e)with borate groups (Sodic Tourmaline Subgroup)

(61.03e.01)Schorl Subgroup

61.03e.01.09 Dravite! NaMg3Al6(BO3)3Si6O18(OH)4 R 3m 3m

61.03e.01.10 Schorl! NaFe3Al6(BO3)3Si6O18(OH)4 R 3m 3m

61.03e.01.10a Schorl-(F)! NaFe3Al6Si6O18)(BO3)3(OH)3(F,OH) R 3m 3m

61.03e.01.11 Chromdravite! NaMg3(Cr,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

61.03e.01.12 Vanadiumdravite! NaMg3V6(Si6O18)(BO3)3(OH)4 R 3m 3m

Strunz Class:

09.CK.05 09 - SILICATES (Germanates)

09.C - Cyclosilicates

09.CK -[Si6O18]12- 6-membered single rings, with insular complex anions

09.CK.05 Chromdravite! NaMg3(Cr,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Feruvite! (Ca,Na)(Fe,Mg,Ti)3(Al,Mg,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Dravite NaMg3Al6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Buergerite! NaFe3Al6(BO3)3Si6O21F R 3m 3m

09.CK.05 Foitite! []Na<0.5(Fe,Al)3Al6Si6O18(BO3)3(OH)4 R 3m 3m

09.CK.05 Liddicoatite! Ca(Li,Al)3Al6(BO3)3Si6O18(O,OH,F)4 R 3m 3m

09.CK.05 Elbaite Na(Li,Al)3Al6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Rossmanite! []LiAl2Al6(Si6O18)(BO3)3(OH)4 R 3m 3m

09.CK.05 Olenite! NaAl3Al6(BO3)3(Si6O18)(O,OH)4 R 3m 3m

09.CK.05 Povondraite! (Na,K)(Fe,Fe)3(Fe,Mg,Al)6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Schorl NaFe3Al6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Uvite (Ca,Na)(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH,F)4 R 3m 3m

09.CK.05 Vanadiumdravite! NaMg3V6(Si6O18)(BO3)3(OH)4 R 3m 3m

09.CK.05 Magnesiofoitite! [](Mg2Al)Al6(Si6O18)(BO3)3(OH)4 R 3m 3m

09.CK.05 Hydroxyuvite! CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH) R 3m 3m

09.CK.05 Schorl-(F)! NaFe3Al6Si6O18)(BO3)3(OH)3(F,OH) R 3m 3m

Other Chromdravite Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Dana8)

See Also:

Links to other databases for Chromdravite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Chromdravite

NaMg3(Cr,Fe+++)6(BO3)3Si6O18(OH)4
Dana No: 61.03e.01.11 Strunz No: 09.CK.05
Locality:

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