Anorthite

Formula : Ca(Al2Si2)O8

Family: 
Feldspar
Space group: 
Triclinic - Pinacoidal H-M Symbol ( 1) Space Group: P1,11
Dana class: 
76.1.3.6 (76) Tectosilicate Al-Si Framework (76.1) with Al-Si frameworks (76.1.3) Plagioclase series
High temperature: 
More than 300C for plagioclase (Na1-xCaxAl2-xSi2-xO8)
Geological context: 
Magmatic and metamorphic rocks and in some geothermal field. More than 300C for plagioclase (Na1-xCaxAl2-xSi2-xO8)

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
278.207 100.790 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. -4008265 (Ref.: Internal calculation) -4234000 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. 199.300 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. 211.34 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 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.
244.72 93.18 -54.37 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
Reaction properties

Anorthite + 8H+ ⇌ 2Al+3 + Ca+2 + 2H4SiO4

298.15 K, 1 bar log10K: 24.24 ΔH°r:-303522 J·mol-1 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
T(°C) 0 25 60 100 150 200 250 300
log10K 29.00 24.24 18.57 13.28 7.93 3.50 -0.38 -3.99
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1978.828380 -0.291902 126122.010812 704.259737 -6717326.632502