Smectite(MX80)

Formula : Na0.409K0.024Ca0.009(Si3.738Al0.262)(Al1.598Mg0.214Fe0.208)O10(OH)2

Space group: 
Monoclinic - Prismatic HM symbol (2/m) Space Group: C 2/m
Dana class: 
71.3.1b.2VIII- 71 Phyllosilicate Minerals ; 71.3 Phyllosilicates Phyllosilicate Sheets of Six-Membered Rings with 2:1 clays ; 71.3.1b Smectite group (Trioctahedral Smectites)
High temperature: 
Low temperature mineral. At higher temperatures(> 500C), detachment of (OH) ions takes place.
Geological context: 
Montmorillonite and beidellite are the principal constituents of bentonite clay deposits. Montmorillonite results from the weathering of basic rocks mainly in conditionsof poordrainage when magnesium is not removed.

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
376.697 134.920 (Ref.: 12gai/bla) Gailhanou, H., Blanc, P., Rogez, J., Mikaelian, G., Kawaji, H., Olives, J., Amouric, M., Denoyel, R., S., B., Montouillout, V., Vieillard, P., Fialips, C. I., Giffaut, E., Michau, N., and Gaucher, E. C., 2012, Thermodynamic properties of illite IMt-2, smectite MX-80 and beidellite SBld-1 by calorimetric methods: Enthalpies of formation, heat capacities , entropies and Gibbs free energies of formation. : Geochimica Cosmochimica Acta, v. 89, p. 279-301. -5293162 (Ref.: Internal calculation) -5656370 (Ref.: 12gai/bla) Gailhanou, H., Blanc, P., Rogez, J., Mikaelian, G., Kawaji, H., Olives, J., Amouric, M., Denoyel, R., S., B., Montouillout, V., Vieillard, P., Fialips, C. I., Giffaut, E., Michau, N., and Gaucher, E. C., 2012, Thermodynamic properties of illite IMt-2, smectite MX-80 and beidellite SBld-1 by calorimetric methods: Enthalpies of formation, heat capacities , entropies and Gibbs free energies of formation. : Geochimica Cosmochimica Acta, v. 89, p. 279-301. 301.920 (Ref.: 12gai/bla) Gailhanou, H., Blanc, P., Rogez, J., Mikaelian, G., Kawaji, H., Olives, J., Amouric, M., Denoyel, R., S., B., Montouillout, V., Vieillard, P., Fialips, C. I., Giffaut, E., Michau, N., and Gaucher, E. C., 2012, Thermodynamic properties of illite IMt-2, smectite MX-80 and beidellite SBld-1 by calorimetric methods: Enthalpies of formation, heat capacities , entropies and Gibbs free energies of formation. : Geochimica Cosmochimica Acta, v. 89, p. 279-301. 321.59 (Ref.: 12gai/bla) Gailhanou, H., Blanc, P., Rogez, J., Mikaelian, G., Kawaji, H., Olives, J., Amouric, M., Denoyel, R., S., B., Montouillout, V., Vieillard, P., Fialips, C. I., Giffaut, E., Michau, N., and Gaucher, E. C., 2012, Thermodynamic properties of illite IMt-2, smectite MX-80 and beidellite SBld-1 by calorimetric methods: Enthalpies of formation, heat capacities , entropies and Gibbs free energies of formation. : Geochimica Cosmochimica Acta, v. 89, p. 279-301.
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.
319.57 282.08 -72.97 (Ref.: 12gai/bla) Gailhanou, H., Blanc, P., Rogez, J., Mikaelian, G., Kawaji, H., Olives, J., Amouric, M., Denoyel, R., S., B., Montouillout, V., Vieillard, P., Fialips, C. I., Giffaut, E., Michau, N., and Gaucher, E. C., 2012, Thermodynamic properties of illite IMt-2, smectite MX-80 and beidellite SBld-1 by calorimetric methods: Enthalpies of formation, heat capacities , entropies and Gibbs free energies of formation. : Geochimica Cosmochimica Acta, v. 89, p. 279-301.
Reaction properties

Smectite(MX80) + 7.048H+ + 2.952H2O ⇌ 1.86Al+3 + 0.009Ca+2 + 0.173Fe+3

298.15 K, 1 bar log10K: 5.28 ΔH°r:-175308 J·mol-1 (Ref.: 12gai/bla) Gailhanou, H., Blanc, P., Rogez, J., Mikaelian, G., Kawaji, H., Olives, J., Amouric, M., Denoyel, R., S., B., Montouillout, V., Vieillard, P., Fialips, C. I., Giffaut, E., Michau, N., and Gaucher, E. C., 2012, Thermodynamic properties of illite IMt-2, smectite MX-80 and beidellite SBld-1 by calorimetric methods: Enthalpies of formation, heat capacities , entropies and Gibbs free energies of formation. : Geochimica Cosmochimica Acta, v. 89, p. 279-301.
T(°C) 0 25 60 100 150 200 250 300
log10K 7.93 5.28 1.94 -1.24 -4.48 -7.19 -9.64 -12.03
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-2426.704177 -0.337122 150385.833912 860.211967 -8928468.672922