Pyrophyllite

Formula : Al2Si4O10(OH)2

Space group: 
Triclinic - Pinacoidal H-M Symbol ( 1) Space Group: P1
Dana class: 
71.2.1.1 (71) Phyllosilicate Sheets of Six-Membered Rings (71.2) with 2:1 Layers 71.2.1) Pyrophyllite-talc group
High temperature: 
Pyrophyllite stability domains range between 200 to 300C.
Geological context: 
Pyrophyllite occurs in metamorphic aluminous rocks and in hydrothermal haloes.

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
360.314 128.100 (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. -5266110 (Ref.: Internal calculation) -5640000 (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. 239.400 (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. 293.76 (Ref.: 76rob/hem) Robie R.A., Hemingway B.S. and Wilson H.W. (1976) - The heat capacities of calorimetry conference copper and of muscovite, pyrophylite, and illite between 15 and 375 K and their standard entropies at 298.15 K. J. Research U.S. Geol. Survey., 4, p. 631-644.
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.
314.07 198.15 -70.57 (Ref.: 76rob/hem) Robie R.A., Hemingway B.S. and Wilson H.W. (1976) - The heat capacities of calorimetry conference copper and of muscovite, pyrophylite, and illite between 15 and 375 K and their standard entropies at 298.15 K. J. Research U.S. Geol. Survey., 4, p. 631-644.
Reaction properties

Pyrophyllite + 6H+ + 4H2O ⇌ 2Al+3 + 4H4SiO4

298.15 K, 1 bar log10K: -0.42 ΔH°r:-128924 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 1.47 -0.42 -2.92 -5.35 -7.86 -9.99 -11.95 -13.91
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-2359.506082 -0.323730 145853.943577 835.240913 -8919352.575220