Illite(FeII)

Formula : K0.85Fe0.25Al2.35Si3.4O10(OH)2

Space group: 
Monoclinic - Prismatic HM symbol (2/m) Space Group: C 2/m
Dana class: 
71.2.2d.2VIII- 71 Phyllosilicate Minerals ; 71.2 Phyllosilicates Phyllosilicate Sheets of Six-Membered Rings with 2:1 Layers ; 71.2.2d Mica Group (Hydromica subgroup)
High temperature: 
Low temperature mineral. At higher temperatures( 700C), micas can form in acid environments as long as excess potassium is available.
Geological context: 
Illites are the dominant clay minerals in shales and mudstones, and they also occur in other sediments such as limestones. The illites of sediments may have been deposited as such after their formation by surface weathering of silicates, principally feldspars, but in some occurrences they are derived by alterationof other clay minerals, during diagenesis.

Dernière mise à jour le 25.01.2021

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
 V°
cm3·mol-1
 ΔGºf
J·mol-1
 ΔHºf
J·mol-1
 Sº
J·mol-1·k-1
 CP
J·mol-1·K-1
400.101 140.670 (Ref.: 15bla/vie) Blanc, P., Vieillard, P., Gailhanou, H., Gaboreau, S., Gaucher, E.C., Fialips, C.I., Made, B., Giffaut, E., 2015. A generalized model for predicting the thermodynamic properties of clay minerals. American Journal of Science 315, 734-780. -5426695 (Ref.: Internal calculation) -5796290 (Ref.: 15bla/vie) Blanc, P., Vieillard, P., Gailhanou, H., Gaboreau, S., Gaucher, E.C., Fialips, C.I., Made, B., Giffaut, E., 2015. A generalized model for predicting the thermodynamic properties of clay minerals. American Journal of Science 315, 734-780. 314.230 (Ref.: 15bla/vie) Blanc, P., Vieillard, P., Gailhanou, H., Gaboreau, S., Gaucher, E.C., Fialips, C.I., Made, B., Giffaut, E., 2015. A generalized model for predicting the thermodynamic properties of clay minerals. American Journal of Science 315, 734-780. 329.00 (Ref.: 15bla/vie) Blanc, P., Vieillard, P., Gailhanou, H., Gaboreau, S., Gaucher, E.C., Fialips, C.I., Made, B., Giffaut, E., 2015. A generalized model for predicting the thermodynamic properties of clay minerals. American Journal of Science 315, 734-780.
CP(T) = a + b·T + ·c·T-2 (T in Kelvin)
a
J·mol-1·K-1
 b * 103
J·mol-1·K-2
 c * 10-5
J·K·mol-1
 Maier Kelley Ref.
329.00 0.00 0.00 (Ref.: 15bla/vie) Blanc, P., Vieillard, P., Gailhanou, H., Gaboreau, S., Gaucher, E.C., Fialips, C.I., Made, B., Giffaut, E., 2015. A generalized model for predicting the thermodynamic properties of clay minerals. American Journal of Science 315, 734-780.
Reaction properties

Illite(FeII) + 8.4H+ + 1.6H2O ⇌ 2.35Al+3 + 0.25Fe+2 + 0.85K+

298.15 K, 1 bar log10K: 9.47 ΔH°r:-208568 J·mol-1 (Ref.: 15bla/vie) Blanc, P., Vieillard, P., Gailhanou, H., Gaboreau, S., Gaucher, E.C., Fialips, C.I., Made, B., Giffaut, E., 2015. A generalized model for predicting the thermodynamic properties of clay minerals. American Journal of Science 315, 734-780.
T(°C) 0 25 60 100 150 200 250 300
log10K 12.66 9.47 5.52 1.79 -1.97 -5.10 -7.87 -10.54
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-2476.630908 -0.343733 154685.072290 877.652369 -9060298.515244