Okenite

Formula : CaSi2O4(OH)2:H2O

Space group: 
Triclinic Space Group: P1 or P1
Dana class: 
72.3.2.5 (72)Phyllosilicate Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings (72.3)with 3-, 4-, or 5-membered rings and 8-membered rings (72.3.2) Tobermorite group (5- 8-membered rings)
High temperature: 
Described with the cement phases the stability of Okenite at low temperature cannot be dismissed.
Geological context: 
Secondary mineral from the alteration of basalts.

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
212.277 94.770 (Ref.: 92wol) Wolery T.J., 1992. EQ3/6: A software Package for Geochemical Modelling of Aqueous Systems: Package Overview and Installation Guide. Technical Report UCRL-MA-110662 PT I ed., Lawrence Livermore National Laboratory (USA). -2881719 (Ref.: 10abla/bou) Blanc, Ph.; Bourbon, X.; Lassin, A.; Gaucher, E.C. 2010 - Chemical model for cement-based materials: Temperature dependence of thermodynamic functions for nanocrystalline and crystalline C-S-H phases. Cement and Concrete Research, 40, p. 851-867 -3135700 (Ref.: 10abla/bou) Blanc, Ph.; Bourbon, X.; Lassin, A.; Gaucher, E.C. 2010 - Chemical model for cement-based materials: Temperature dependence of thermodynamic functions for nanocrystalline and crystalline C-S-H phases. Cement and Concrete Research, 40, p. 851-867 206.746 (Ref.: Internal calculation) 210.70 (Ref.: 10abla/bou) Blanc, Ph.; Bourbon, X.; Lassin, A.; Gaucher, E.C. 2010 - Chemical model for cement-based materials: Temperature dependence of thermodynamic functions for nanocrystalline and crystalline C-S-H phases. Cement and Concrete Research, 40, p. 851-867
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.
210.70 0.00 0.00 (Ref.: 10abla/bou) Blanc, Ph.; Bourbon, X.; Lassin, A.; Gaucher, E.C. 2010 - Chemical model for cement-based materials: Temperature dependence of thermodynamic functions for nanocrystalline and crystalline C-S-H phases. Cement and Concrete Research, 40, p. 851-867
Reaction properties

Okenite + 2H+ + H2O ⇌ Ca+2 + 2H4SiO4

298.15 K, 1 bar log10K: 9.19 ΔH°r:-39192 J·mol-1 (Ref.: 10abla/bou) Blanc, Ph.; Bourbon, X.; Lassin, A.; Gaucher, E.C. 2010 - Chemical model for cement-based materials: Temperature dependence of thermodynamic functions for nanocrystalline and crystalline C-S-H phases. Cement and Concrete Research, 40, p. 851-867
T(°C) 0 25 60 100 150 200 250 300
log10K 9.75 9.19 8.44 7.75 7.12 6.66 6.30 5.96
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-967.545023 -0.120115 61769.903012 343.104984 -3877639.725453