Montdorite Mineral Data

General Montdorite Information

Chemical Formula:

(K,Na)(Fe++,Mn++,Mg)2.5[Si4O10](F,OH)2

Composition:

Molecular Weight = 467.53 gm

Potassium 6.27 % K 7.56 % K₂O

Sodium 1.23 % Na 1.66 % Na₂O

Magnesium 2.60 % Mg 4.31 % MgO

Manganese 9.40 % Mn 12.14 % MnO

Iron 14.33 % Fe 18.44 % FeO

Silicon 24.03 % Si 51.41 % SiO₂

Hydrogen 0.11 % H 0.96 % H₂O

Oxygen 35.93 % O

Fluorine 6.10 % F 6.10 % F

- % F -2.57 % -O=F₂

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

K_0.75Na_0.25Fe²⁺_1.2Mn²⁺_0.8Mg_0.5Si₄O₁₀F_1.5(OH)_0.5

Environment:

Small grains in perialkaline rhyolite.

IMA Status:

Approved IMA 1979

Locality:

Mt. Dore stratovolcano, near La Bourboule, France. Link to MinDat.org Location Data.

Name Origin:

Named for the locality.

Name Pronunciation:

Montdorite + Pronunciation

Montdorite Image

Images:

Montdorite

Comments: Pale green fine granular montdorite in iron-stained matrix.
Location: Charlunnes, Mont Dore, Puy-de-Dome, France. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Montdorite Crystallography

Axial Ratios:

a:b:c =0.5771:1:1.1065

Cell Dimensions:

a = 5.31, b = 9.2, c = 10.18, Z = 2; beta = 99.9° V = 489.91 Den(Calc)= 3.17

Crystal System:

Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c

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

By Intensity(I/I_o): 2.52(0.4), 3.41(0.4), 9.97(0.4),1.669(0.3), 2.17(0.3), 2.71(0.3), 3.14(0.3), 3.34(0.1),

Physical Properties of Montdorite

Color:

Green, Brownish green.

Diaphaneity:

Translucent

Habit:

Microscopic Crystals - Crystals visible only with microscopes.

Optical Properties of Montdorite

Gladstone-Dale:

CI calc= 0.05 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1882,KC= 0.1982
Ncalc = 1.63

Optical Data:

Biaxial (-), a=1.58, b=1.605, g=1.605, bire=0.0250

Calculated Properties of Montdorite

Electron Density:

Bulk Density (Electron Density)=3.09 gm/cc
note: Specific Gravity of Montdorite =3.17 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Montdorite= 8.32 barns/electron
U=PE_Montdorite x r_electron= 25.76 barns/cc.

Radioactivity:

GRapi = 88.32 (Gamma Ray American Petroleum Institute Units)
Concentration of Montdorite per GRapi unit = 1.13 (%)

Estimated Radioactivity from Montdorite - barely detectable

Montdorite Classification

Dana Class:

71.02.02a.10 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.02)with 2:1 Layers

(71.02.02a)Mica Group (Muscovite subgroup)

71.02.02a.01 Muscovite KAl2(Si3Al)O10(OH,F)2 C 2/m 2/m

71.02.02a.02 Paragonite NaAl2(Si3Al)O10(OH)2 C 2/c,Cc Mono

71.02.02a.03 Chernykhite (Ba,Na)V,Al)2(Si,Al)4O10(OH)2 C 2/c 2/m

71.02.02a.04 Roscoelite K(V,Al,Mg)2AlSi3O10(OH)2 C 2/m 2/m

71.02.02a.05 Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2 C 2/m 2/m

71.02.02a.06 Celadonite K(Mg,Fe)(Fe,Al)[Si4O10](OH)2 C 2/m 2/m

71.02.02a.06b Ferroceladonite! K2FeFeSi8O20(OH)4 C 2/m 2/m

71.02.02a.06c Ferroaluminoceladonite! K2Fe2Al2Si8O20(OH)4 C 2/m 2/m

71.02.02a.06d Aluminoceladonite! KAl(Mg,Fe)[]Si4O10(OH)2 2/m

71.02.02a.06e Chromceladonite! KCrMg(Si4O10)(OH)2 C 2 2

71.02.02a.07 Tobelite (NH4,K)Al2(Si3Al)O10(OH)2 C 2/m 2/m

71.02.02a.08 Nanpingite Cs(Al,Mg,Fe,Li)2(Si3Al)O10(OH,F)2 C 2/c 2/m

71.02.02a.09 Boromuscovite KAl2(Si3B)O10(OH,F)2 C 2/m 2/m

71.02.02a.10 Montdorite (K,Na)(Fe,Mn,Mg)2.5[Si4O10](F,OH)2 C 2/c 2/m

71.02.02a.11 Chromphyllite! (K,Ba)(Cr,Al)2[AlSi3O10](OH,F)2 C 2c 2/m

71.02.02a.12 Shirokshinite! K(NaMg2)Si4O10F2 C 2/m 2/m

Strunz Class:

09.EC.15 09 - SILICATES (Germanates)

09.E - Phyllosilicates

09.EC -Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets

09.EC.15 Boromuscovite KAl2(Si3B)O10(OH,F)2 C 2/m 2/m

09.EC.15 Celadonite K(Mg,Fe)(Fe,Al)[Si4O10](OH)2 C 2/m 2/m

09.EC.15 Chernykhite (Ba,Na)V,Al)2(Si,Al)4O10(OH)2 C 2/c 2/m

09.EC.15 Chromphyllite! (K,Ba)(Cr,Al)2[AlSi3O10](OH,F)2 C 2c 2/m

09.EC.15 Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2 C 2/m 2/m

09.EC.15 Aluminoceladonite! KAl(Mg,Fe)[]Si4O10(OH)2 2/m

09.EC.15 Ferroaluminoceladonite! K2Fe2Al2Si8O20(OH)4 C 2/m 2/m

09.EC.15 Ferroceladonite! K2FeFeSi8O20(OH)4 C 2/m 2/m

09.EC.15 Montdorite (K,Na)(Fe,Mn,Mg)2.5[Si4O10](F,OH)2 C 2/c 2/m

09.EC.15 Nanpingite Cs(Al,Mg,Fe,Li)2(Si3Al)O10(OH,F)2 C 2/c 2/m

09.EC.15 Tobelite (NH4,K)Al2(Si3Al)O10(OH)2 C 2/m 2/m

09.EC.15 Roscoelite K(V,Al,Mg)2AlSi3O10(OH)2 C 2/m 2/m

09.EC.15 Muscovite KAl2(Si3Al)O10(OH,F)2 C 2/m 2/m

09.EC.15 Paragonite NaAl2(Si3Al)O10(OH)2 C 2/c,Cc Mono

09.EC.15 Tainiolite KLiMg2Si4O10F2 C 2/m 2/m

09.EC.15 Chromceladonite! KCrMg(Si4O10)(OH)2 C 2 2

09.EC.15 Ganterite! [Ba0.5(Na,K)0.5]Al2(Si2.5Al1.5O10)(OH)2 C 2/c 2/m

Other Montdorite Information

References:

NAME( Dana8) PHYS. PROP.(Dana8) OPTIC PROP.(Dana8)

See Also:

Links to other databases for Montdorite :
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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Print or Cut-and-Paste your Montdorite Specimen Label here :

Montdorite

(K,Na)(Fe++,Mn++,Mg)2.5[Si4O10](F,OH)2
Dana No: 71.02.02a.10 Strunz No: 09.EC.15
Locality:

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