Illite Mineral Data

Illite Mineral Data +

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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 % K₂O

Magnesium 1.87 % Mg 3.11 % MgO

Aluminum 9.01 % Al 17.02 % Al₂O₃

Iron 1.43 % Fe 1.85 % FeO

Silicon 25.25 % Si 54.01 % SiO₂

Hydrogen 1.35 % H 12.03 % H₂O

Oxygen 55.06 % O

______ ______

100.00 % 95.27 % = TOTAL OXIDE

Empirical Formula:

K_0.6(H₃O)_0.4Al_1.3Mg_0.3Fe²⁺_0.1Si_3.5O₁₀(OH)₂·(H₂O)

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.

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 - PrismaticH-M Symbol (2/m) Space Group: C 2/m

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

By Intensity(I/I_o): 4.43(1), 2.56(0.85), 3.66(0.4),

Crystal Structure:

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drag2 - RMB Resize/Rotate
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Gualtieri A F , Journal of Applied Crystallography , 33 (2000) p.267-278, Accuracy of XRPD QPA using the combined Rietveld-RIR method, Locality: Napoli, Italy

Physical Properties of Illite

Cleavage:

[001] Perfect

Color:

White.

Density:

2.6 - 2.9, Average = 2.75

Diaphaniety:

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

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:

r_electron=2.77 gm/cc
note: r_Illite=2.75 gm/cc.

Fermion Index

Fermion Index = 0.01424
Boson Index = 0.98576

Photoelectric:

PE_Illite= 2.33 barns/electron
U=PE_Illite x r_electron= 6.45 barns/cc.

Radioactivity:

GRapi = 87.50 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Illite - barely detectable

Illite Classification

Dana Class:

71.2.2d.2 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.2)with 2:1 Layers

(71.2.2d)Mica Group (Hydromica subgroup)

71.2.2d.1 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

71.2.2d.2 Illite * (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/m 2/m

71.2.2d.3 Vermiculite (Mg,Fe,Al)3(Al,Si)4O10(OH)2·4(H2O) C 2/m 2/m

71.2.2d.4 Brammallite* (Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/c 2/m

Strunz Class:

VIII/H.19-15 VIII - Silicates

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

VIII/H.19 - Brammallite ? - Yakhontovite series

VIII/H.19-10 Brammallite* (Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/c 2/m

VIII/H.19-10a 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

VIII/H.19-15 Illite (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/m 2/m

VIII/H.19-20 Montmorillonite (Na,Ca)0,3(Al,Mg)2Si4O10(OH)2·n(H2O) C 2/m 2/m

VIII/H.19-30 Beidellite Na0.5Al2(Si3.5Al0.5)O10(OH)2·n(H2O) C 2/m or ORTH 2/m

VIII/H.19-40 Nontronite Na0.3Fe2(Si,Al)4O10(OH)2·n(H2O) C 2/m 2/m

VIII/H.19-50 Volkonskoite Ca0.3(Cr,Mg,Fe)2(Si,Al)4O10(OH)2·4(H2O) C 2/m 2/m

VIII/H.19-60 Swinefordite (Li,Ca0.5,Na)0.72(Li,Al,Mg)2.66(Si,Al)4O10(OH,F)2·2(H2O) C 2/m (MON or ORTH) 2/m

VIII/H.19-70 Yakhontovite (Ca,K)0.5(Cu,Fe,Mg)2Si4O10(OH)2·3(H2O) C 2/m 2/m

Other Illite Information

References:

NAME( Dana8) PHYS. PROP.(Eur. J. Min.,Vol.9,p821-827,1997) OPTIC PROP.(Heinrich65)

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Print or Cut-and-Paste your Illite Specimen Label here :

Illite

(K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]
Dana No: 71.2.2d.2 Strunz No: VIII/H.19-15
Locality:

Notes: