Montdorite Mineral Data

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.

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 - PrismaticH-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.

Diaphaniety:

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

Optical Data:

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

Calculated Properties of Montdorite

Electron Density:

r_electron=3.09 gm/cc
note: r_Montdorite=3.17 gm/cc.

Fermion Index

Fermion Index = 0.01703
Boson Index = 0.98297

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)

Estimated Radioactivity from Montdorite - barely detectable

Montdorite Classification

Dana Class:

71.2.2a.10 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.2)with 2:1 Layers

(71.2.2a)Mica Group (Muscovite subgroup)

71.2.2a.1 Muscovite KAl2(Si3Al)O10(OH,F)2 C 2/m 2/m

71.2.2a.2 Paragonite NaAl2(Si3Al)O10(OH)2 C 2/c,Cc Mono

71.2.2a.3 Chernykhite (Ba,Na)V,Al)2(Si,Al)4O10(OH)2 C 2/c 2/m

71.2.2a.4 Roscoelite K(V,Al,Mg)2AlSi3O10(OH)2 C 2/m 2/m

71.2.2a.5 Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2 C 2/m 2/m

71.2.2a.6 Celadonite K(Mg,Fe)(Fe,Al)[Si4O10](OH)2 C 2/m 2/m

71.2.2a.6b Ferroceladonite! K2FeFeSi8O20(OH)4 C 2/m 2/m

71.2.2a.6c Ferro-aluminoceladonite! K2Fe2Al2Si8O20(OH)4 C 2/m 2/m

71.2.2a.6d Aluminoceladonite! KAl(Mg,Fe)[]Si4O10(OH)2 2/m

71.2.2a.6e Chromceladonite! KCrMg(Si4O10)(OH)2 C 2 2

71.2.2a.7 Tobelite (NH4,K)Al2(Si3Al)O10(OH)2 C 2/m 2/m

71.2.2a.8 Nanpingite Cs(Al,Mg,Fe,Li)2(Si3Al)O10(OH,F)2 C 2/c 2/m

71.2.2a.9 Boromuscovite KAl2(Si3B)O10(OH,F)2 C 2/m 2/m

71.2.2a.10 Montdorite (K,Na)(Fe,Mn,Mg)2.5[Si4O10](F,OH)2 C 2/c 2/m

71.2.2a.11 Chromphyllite! (K,Ba)(Cr,Al)2[AlSi3O10](OH,F)2 C 2c 2/m

71.2.2a.12 Shirokshinite! K(NaMg2)Si4O10F2 C 2/m 2/m

Strunz Class:

VIII/H.11-40 VIII - Silicates

VIII/H - Phyllosilicates (layered) Mica like layered silicates with [Si4O10]4- and related groups

VIII/H.11 - Mica group, Biotite series

VIII/H.11-00* Zinnwaldite KLiFeAl(AlSi3)O10(F,OH)2 C 2/m 2/m

VIII/H.11-10 Polylithionite KLi2AlSi4O10(F,OH)2 C 2/m 2/m

VIII/H.11-20 Tainiolite KLiMg2Si4O10F2 C 2/m 2/m

VIII/H.11-30 Norrishite K(Mn2Li)Si4O10(O)2 C 2/m 2/m

VIII/H.11-35 Shirokshinite! K(NaMg2)Si4O10F2 C 2/m 2/m

VIII/H.11-40 Montdorite (K,Na)(Fe,Mn,Mg)2.5[Si4O10](F,OH)2 C 2/c 2/m

VIII/H.11-50 Trilithionite! KLi1.5Al1.5AlSi3O10F2 C 2/m 2/m

VIII/H.11-60 Masutomilite K(Li,Al,Mn)3[(Si,Al)4O10](F,OH)2 C 2/m 2/m

VIII/H.11-70 Aspidolite NaMg3AlSi3O10(OH)2 C 2/m 2/m

VIII/H.11-80 Phlogopite KMg3(Si3Al)O10(F,OH)2 C 2/m 2/m

VIII/H.11-90 Tetra-ferriphlogopite! KMg3FeSi3O10(OH)2 2/m

VIII/H.11-100 Hendricksite K(Zn,Mg,Mn)3Si3AlO10(OH)2 C 2/m 2/m

VIII/H.11-102 Shirozulite! KMn3(AlSi3)O10(OH,F)2 C 2/m 2/m

VIII/H.11-105 Fluorannite! KFe3AlSi3O10F2 C 2/m 2/m

VIII/H.11-110 Annite KFe3AlSi3O10(OH,F)2 C 2/m 2/m

VIII/H.11-120 Tetra-ferri-annite K(Fe,Mg)3(Fe,Al)Si3O10(OH)2 C 2/m 2/m

VIII/H.11-130 Ephesite NaLiAl2(Al2Si2)O10(OH)2 C 2/c 2/m

VIII/H.11-140 Preiswerkite NaMg2Al3Si2O10(OH)2 C 2/m 2/m

VIII/H.11-150 Eastonite! KMg2Al[Al2Si2O10](OH)2 2/m

VIII/H.11-160 Siderophyllite KFe2Al(Al2Si2)O10(F,OH)2 C 2/m 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 -Google Images 4 -Google Scholar 5 -MinDAT 6 -MinMax(Deutsch) 7 -MinMax(English) 8 -Mineralienatlas (Deutsch) 9 -QUT Mineral Atlas

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Montdorite

(K,Na)(Fe++,Mn++,Mg)2.5[Si4O10](F,OH)2
Dana No: 71.2.2a.10 Strunz No: VIII/H.11-40
Locality:

Notes: