Marcassite

Formula : FeS2

Family: 
Sulfides
Space group: 
Orthorhombic - Dipyramidal HM symbol (2/m 2/m 2/m) Space Group: Pnnm
Dana class: 
2.12.2.1II- 2 Sulfide Minerals ; 2.12 Sulfides - Including Selenides and Tellurides where Am Bn Xp, with (m+n):p=1:2 ; 2.12.2 Marcasite Group (Orthorhombic: Pnnm)

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 24.580 (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. -155411 (Ref.: Internal calculation) -166600 (Ref.: 76gro/wes) Gronvold and Westrum, 1976. F. Gronvold and E.F. Westrum, Heat capacities of iron disulfides. Thermodynamics of marcasite from 5 to 700 K, pyrite from 300 to 780 K, and the transformation of marcasite to pyrite. J. Chem. Therm. 8 (1976), pp. 1039-1048 53.900 (Ref.: 76gro/wes) Gronvold and Westrum, 1976. F. Gronvold and E.F. Westrum, Heat capacities of iron disulfides. Thermodynamics of marcasite from 5 to 700 K, pyrite from 300 to 780 K, and the transformation of marcasite to pyrite. J. Chem. Therm. 8 (1976), pp. 1039-1048 62.43 (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.
74.55 5.60 -12.26 (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

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

298.15 K, 1 bar log10K: -22.86 ΔH°r:103451 J·mol-1 (Ref.: 76gro/wes) Gronvold and Westrum, 1976. F. Gronvold and E.F. Westrum, Heat capacities of iron disulfides. Thermodynamics of marcasite from 5 to 700 K, pyrite from 300 to 780 K, and the transformation of marcasite to pyrite. J. Chem. Therm. 8 (1976), pp. 1039-1048
T(°C) 0 25 60 100 150 200 250 300
log10K -24.60 -22.86 -21.06 -19.60 -18.43 -17.80 -17.66 -18.08
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1590.715702 -0.257586 81459.616566 577.891969 -5202027.366362