Kalsilite(alpha)

Formula : K(AlSi)O4

Space group: 
Trigonal - Ditrigonal Pyramidal H-M Symbol (3m) Space Group: P 31c
Dana class: 
76.2.1.1 (76) Tectosilicate Al-Si Framework (76.2) Feldspathoids and related species (76.2.1) Nepheline group
High temperature: 
The lowest stability limit is about 500C, upper limit is unknown.
Geological context: 
In the groundmass of some potassium-rich and silica-deficient lavas and tuffs; rare in syenites. It may be formed by the breakdown of silica-rich leucite in alkalic ultramafic rocks; from a granulite-facies emery deposit.

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
158.163 59.890 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp. -2015432 (Ref.: Internal calculation) -2131363 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp. 133.260 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp. 119.75 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp.
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.
123.14 72.63 -22.26 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp.
Reaction properties

Kalsilite(alpha) + 4H+ ⇌ Al+3 + K+ + H4SiO4

298.15 K, 1 bar log10K: 11.21 ΔH°r:-118038 J·mol-1 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp.
T(°C) 0 25 60 100 150 200 250 300
log10K 13.05 11.21 9.00 6.93 4.85 3.12 1.59 0.16
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-917.684786 -0.133381 58042.568897 327.280430 -3186814.078183