Illite Mineral Data
General Illite Information
Chemical Formula:
(K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]
Composition:
Molecular Weight = 389.34 gm
Potassium 6.03 % K 7.26 % K2 O
Magnesium 1.87 % Mg 3.11 % MgO
Aluminum 9.01 % Al 17.02 % Al2 O3
Iron 1.43 % Fe 1.85 % FeO
Silicon 25.25 % Si 54.01 % SiO2
Hydrogen 1.35 % H 12.03 % H2 O
Oxygen 55.06 % O
______ ______
100.00 % 95.27 % = TOTAL OXIDE
Empirical Formula:
K0.6 (H3 O)0.4 Al1.3 Mg0.3 Fe2+ 0.1 Si3.5 O10 (OH)2 �(H2 O)
Environment:
Weathering or hydrothermal alteration of muscovite-phengite. Also authigenic alteration of K-spar or recrystallization of smectites in marine sediments. Group name for dioctahedral interlayer-deficient clays.
IMA Status:
Not Approved IMA 1998
Locality:
Maquoketa shale, Gilead, Calhoun County, Illinois, USA. Link to MinDat.org Location Data.
Name Origin:
Named in 1937 for the state of Illinois where the mineral was first described.
Name Pronunciation:
Illite
Synonym:
Gumbelite
Hydromica
Hydromuscovite
Illite Image
Images:
Illite
Comments: Wispy, authigenic illite crystals lining a pore space in sandstone. SEM image from a core sample.
Location: Unknown.
Scale: Picture size 33 µ-m.
© OMNI Laboratories, Inc
Illite Crystallography
Axial Ratios:
a:b:c =0.5768:1:1.1492
Cell Dimensions:
a = 5.18, b = 8.98, c = 10.32, Z = 2; beta = 101.83° V = 469.85 Den(Calc)= 2.75
Crystal System:
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/m
X Ray Diffraction:
By Intensity(I/Io ): 4.43(1), 2.56(0.85), 3.66(0.4),
Physical Properties of Illite
Cleavage:
{001} Perfect
Color:
White.
Density:
2.6 - 2.9, Average = 2.75
Diaphaneity:
Translucent
Habit:
Aggregates - Made of numerous individual crystals or clusters.
Hardness:
1-2 - Between Talc and Gypsum
Luster:
Earthy (Dull)
Streak:
white
Optical Properties of Illite
Gladstone-Dale:
CI meas = 0.021 (Excellent) - where the CI = (1-KPDmeas /KC ) CI calc = 0.021 (Excellent) - where the CI = (1-KPDcalc /KC )
KPDcalc = 0.2079,KPDmeas = 0.2079,KC = 0.2124 Ncalc = 1.55 - 1.62
Optical Data:
Biaxial (-), a=1.535-1.57, b=1.555-1.6, g=1.565-1.605, bire=0.0300-0.0350, 2V(Calc)=42-68, 2V(Meas)=5-25. Dispersion none.
Pleochroism (x):
colorless.
Pleochroism (y):
colorless.
Pleochroism (z):
colorless.
Calculated Properties of Illite
Electron Density:
Bulk Density (Electron Density)=2.77 gm/cc note: Specific Gravity of Illite =2.75 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PEIllite = 2.33 barns/electronU=PEIllite x r electron = 6.45 barns/cc.
Radioactivity:
GRapi = 87.50 (Gamma Ray American Petroleum Institute Units)
Concentration of Illite per GRapi unit = 1.14 (%)
Estimated Radioactivity from Illite - barely detectable
Illite Classification
Dana Class:
71.02.02d.02 (71) Phyllosilicate Sheets of Six-Membered Rings
(71.02) with 2:1 Layers
(71.02.02d) Mica Group (Hydromica subgroup)
71.02.02d.01 Hydrobiotite [K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2]•[(Mg,Fe,Al)3(Si,Al)4O10(OH)2•4(H2O)] C 2/m 2/m
71.02.02d.02 Illite * (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/m 2/m
71.02.02d.03 Vermiculite (Mg,Fe,Al)3(Al,Si)4O10(OH)2•4(H2O) C 2/m 2/m
71.02.02d.04 Brammallite * (Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/c 2/m
Strunz Class:
09.EC.60 09 - SILICATES (Germanates)
09.E - Phyllosilicates
09.EC -Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
09.EC.60 Aliettite [Mg3Si4O10(OH)2](Ca0.5,Na)0.33(Al,Mg,Fe)2-3(Si,Al)4O10(OH)2•n(H2O) Unk Mono
09.EC.60 Dozyite (Mg7Al2)(Si4Al2)O15(OH)12 Cm m
09.EC.60 Corrensite (Ca,Na,K)(Mg,Fe,Al)9(Si,Al)8O20(OH)10•n(H2O) Unk Ortho
09.EC.60 Kulkeite Na0.35Mg8AlSi7O20(OH)10 Unk Mono
09.EC.60 Karpinskite (Mg,Ni)2Si2O5(OH)2(?) Unk Mono
09.EC.60 Illite * (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/m 2/m
09.EC.60 Hydrobiotite [K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2]•[(Mg,Fe,Al)3(Si,Al)4O10(OH)2•4(H2O)] C 2/m 2/m
09.EC.60 Lunijianlaite LiAl6(Si7Al)O20(OH)10 Unk Mono
09.EC.60 Rectorite (Na,Ca)Al4(Si,Al)8O20(OH)4•2(H2O) Unk Mono
09.EC.60 Saliotite Na0.5Li0.5Al3AlSi3O10(OH)5 C 2/m 2/m
09.EC.60 Tosudite Na0,5(Al,Mg)6(Si,Al)8O18(OH)12•5(H2O) Unk Ortho
09.EC.60 Brinrobertsite ! (Na,K,Ca)x(Al,Fe,Mg)4(Si,Al)8O20(OH)4•3.54(H2O)[x=0.35,n=3.54] pseudo 2/m 2/m
Other Illite Information
References:
NAME( Dana8) PHYS. PROP.(Eur. J. Min.,Vol.9,p821-827,1997) OPTIC PROP.(Heinrich65)
See Also:
Links to other databases for Illite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - Franklin Minerals(Dunn)
6 - GeoScienceWorld
7 - Google Images
8 - Google Scholar
9 - MinDAT
10 - Mineralienatlas (Deutsch)
11 - Online Mineral Museum
12 - QUT Mineral Atlas
13 - Ruff.Info
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Illite
(K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]
Dana No: 71.02.02d.02 Strunz No: 09.EC.60
Locality:
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