Turtmannite Mineral Data

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General Turtmannite Information

Chemical Formula:

(Mn,Mg)25.5[(V,As)O4]3(SiO4)3[AsO3]xO5-5x(OH)20+x

Composition:

Molecular Weight = 2,396.92 gm

Magnesium 2.54 % Mg 4.20 % MgO

Manganese 52.72 % Mn 68.07 % MnO

Vanadium 4.78 % V 8.54 % V₂O₅

Silicon 3.52 % Si 7.52 % SiO₂

Arsenic 3.28 % As 1.24 % As₂O₃ / 3.60 % As₂O₅

Hydrogen 0.84 % H 7.53 % H₂O

Oxygen 32.33 % O

______ ______

100.00 % 100.69 % = TOTAL OXIDE

Empirical Formula:

Mn²⁺₂₃Mg_2.5(VO₄)_2.25(AsO₄)_0.75(SiO₄)₃(AsO₃)_0.3O_3.5(OH)_20.03

Environment:

Manganoan paleokarst lenses in Triassic marbles metamorphosed to upper greenshist facies. Similar to mcgovernite; structure

IMA Status:

Approved IMA 2000 (Dana # Added)

Locality:

Barrhorn Unit (Central Alps) in the Triassic marbles near Turtmanntal, Valais, Switzerland. Link to MinDat.org Location Data.

Name Origin:

Named after the locality.

Turtmannite Image

Images:

Turtmannite

Comments: Orange-brownish grains of turtmannite in matrix.
Location: Pipji Glacier, Turtmanntal (Turtmann Valley), Wallis (Valais), Switzerland. Scale: Picture size 4 mm.
© Thomas Witzke / Abraxas-Verlag

Turtmannite Crystallography

Axial Ratios:

a:c = 1:2.47003

Cell Dimensions:

a = 8.259, c = 20.4, Z = 1; V = 1,205.08 Den(Calc)= 3.30

Crystal System:

Trigonal - Hexagonal ScalenohedralH-M Symbol (3 2/m) Space Group: R 3c

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

By Intensity(I/I_o): 2.86(1), 1.559(0.9), 3.26(0.8),4.13(0.7), 2.38(0.6), 3.46(0.6), 2.35(0.5),

Crystal Structure:

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Brugger J , Armbruster T , Meisser N , Hejny C , Grobety B , American Mineralogist , 86 (2001) p.1494-1505, Description and crystal structure of turtmannite, a new mineral with a, 68 Angstrom period related to mcgovernite, Note: z-coordinate of Mn12 has been modified

Physical Properties of Turtmannite

Cleavage:

{0001} Perfect

Color:

Bright yellow, Orange.

Density:

3.6 - 4, Average = 3.8

Diaphaneity:

Transparent

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

Anhedral Grains - Granular minerals without the expression of crystal shapes

Habit:

Micaceous - Platy texture with "flexible" plates.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Luster:

Vitreous (Glassy)

Streak:

colorless

Optical Properties of Turtmannite

Gladstone-Dale:

CI meas= 0.065 (Fair) - where the CI = (1-KPDmeas/KC)
CI calc= -0.077 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2385,KPDmeas= 0.2071,KC= 0.2215
Ncalc = 1.73 - 1.89

Optical Data:

Uniaxial (-), e=1.787.

Calculated Properties of Turtmannite

Electron Density:

Bulk Density (Electron Density)=3.62 gm/cc
note: Specific Gravity of Turtmannite =3.80 gm/cc.

Fermion Index:

Fermion Index = 0.0044526019
Boson Index = 0.9955473981

Photoelectric:

PE_Turtmannite= 17.04 barns/electron
U=PE_Turtmannite x rElectron Density= 61.62 barns/cc.

Radioactivity:

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

Turtmannite Classification

Dana Class:

43.04.09.02 (43)Compound Phosphates, etc.

(43.04)(Anhydrous Compound Anions With Hydroxyl or Halogen)

(43.04.09)Mcgovernite Group

43.04.09.01 Mcgovernite Mn9Mg4Zn2As2Si2O17(OH)14 R 3c 3 2/m

43.04.09.02 Turtmannite! (Mn,Mg)25.5[(V,As)O4]3(SiO4)3[AsO3]xO5-5x(OH)20x R 3c 3 2/m

Strunz Class:

08.BE.45 08 - PHOSPHATES, ARSENATES, VANADATES

08.B - Phosphates, etc. with Additional Anions, without H2O

08.BE -With only medium-sized cations, (OH, etc.):RO4 > 2:1

08.BE.45 Dixenite CuMn14Fe(AsO3)5(SiO4)2(AsO4)(OH)6 R 3 3

08.BE.45 Hematolite (Mn,Mg,Al)15(AsO3)(AsO4)2(OH)23 R 3 3

08.BE.45 Kraisslite (Mn,Mg)24Zn3Fe(AsO3)2(AsO4)3(SiO4)6(OH)18 P 6₃22 6 2 2

08.BE.45 Mcgovernite Mn9Mg4Zn2As2Si2O17(OH)14 R 3c 3 2/m

08.BE.45 Turtmannite! (Mn,Mg)25.5[(V,As)O4]3(SiO4)3[AsO3]xO5-5x(OH)20x R 3c 3 2/m

08.BE.45 Arakiite! (Zn,Mn)(Mn,Mg)12(Fe,Al)2(AsO3)(AsO4)2(OH)23 Cc m

Other Turtmannite Information

References:

NAME( AmMin, Vol 86, p 1494-1505) PHYS. PROP.(AmMin, Vol 86, p 1494-1505) OPTIC PROP.(AmMin, Vol 86, p 1494-1505)

See Also:

Links to other databases for Turtmannite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - Mineralienatlas (Deutsch)
8 - Online Mineral Museum
9 - QUT Mineral Atlas
10 - Ruff.Info

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Turtmannite

(Mn,Mg)25.5[(V,As)O4]3(SiO4)3[AsO3]xO5-5x(OH)20+x
Dana No: 43.04.09.02 Strunz No: 08.BE.45
Locality:

Notes: