Pyrite

Formula : FeS2

Family: 
Sulfides
Space group: 
Cubic H-M Symbol (2/m 3) Space Group: P a3
Dana class: 
2.12.1.1 (2)Sulfides - Including Selenides and Tellurides (2.12) where Am Bn Xp, with (m+n):p=1:2(2.12.1) Pyrite Group (Isometric: Pa3) 2.12.1.1 Pyrite FeS2 P a3 2/m 3
High temperature: 
The stability of pyrite is only limited by the oxigen fugacity.Melting point is around 1177-1188 C.
Geological context: 
Pyrite is the most abundant of the sulphide and its occurrence is widespread in all the geological context

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
119.979 23.940 (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. -159572 (Ref.: Internal calculation) -171050 (Ref.: 05wal/pel) Waldner, P., Pelton, A.D. (2005) Thermodynamic modeling of the Fe-S system. Journal of Phase Equilibria and Diffusion 26, 23-38. 52.930 (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. 62.19 (Ref.: 05wal/pel) Waldner, P., Pelton, A.D. (2005) Thermodynamic modeling of the Fe-S system. Journal of Phase Equilibria and Diffusion 26, 23-38.
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.
72.29 9.01 -11.36 (Ref.: 05wal/pel) Waldner, P., Pelton, A.D. (2005) Thermodynamic modeling of the Fe-S system. Journal of Phase Equilibria and Diffusion 26, 23-38.
Reaction properties

Pyrite + 0.75H2O ⇌ Fe+2 + 1.5HS- + 0.25S2O3-2

298.15 K, 1 bar log10K: -23.59 ΔH°r:107901 J·mol-1 (Ref.: 05wal/pel) Waldner, P., Pelton, A.D. (2005) Thermodynamic modeling of the Fe-S system. Journal of Phase Equilibria and Diffusion 26, 23-38.
T(°C) 0 25 60 100 150 200 250 300
log10K -25.40 -23.59 -21.70 -20.17 -18.93 -18.24 -18.06 -18.43
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1591.887240 -0.257749 81293.960986 578.331552 -5205658.635700