Magnetite

Formula : Fe3O4

Family: 
Oxides
Space group: 
Isometric - Hexoctahedral H-M Symbol (4/m 3 2/m) Space Group: F d3m
Dana class: 
7.2.2.3 (7) Multiple Oxides (7.2) (A+ B++)2 X4 Spinel group (7.2.2 (Iron subgroup)
High temperature: 
Magnetite is a widespread mineral, stable in a large range of temperatures : fromambient temperature to magmatic.
Geological context: 
Common accessory mineral in igneous and metamorphic rocks. It can be biogenically produced by a wide variety of organisms. It occurs also as fine mineral in metallugical slags.

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
231.539 44.524 (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. -1012529 (Ref.: Internal calculation) -1115726 (Ref.: 90hem) Hemingway B. S. (1990) Thermodynamic properties for bunsenite, NiO, magnetite, Fe3O4, and hematite, Fe2O3, with comments on selected oxygen buffer reactions. American Mineralogist 75(7-8), 781-790. 146.140 (Ref.: 90hem) Hemingway B. S. (1990) Thermodynamic properties for bunsenite, NiO, magnetite, Fe3O4, and hematite, Fe2O3, with comments on selected oxygen buffer reactions. American Mineralogist 75(7-8), 781-790. 150.92 (Ref.: 90hem) Hemingway B. S. (1990) Thermodynamic properties for bunsenite, NiO, magnetite, Fe3O4, and hematite, Fe2O3, with comments on selected oxygen buffer reactions. American Mineralogist 75(7-8), 781-790.
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.
149.10 110.91 -27.78 (Ref.: 90hem) Hemingway B. S. (1990) Thermodynamic properties for bunsenite, NiO, magnetite, Fe3O4, and hematite, Fe2O3, with comments on selected oxygen buffer reactions. American Mineralogist 75(7-8), 781-790.
Reaction properties

Magnetite + 8H+ ⇌ 2Fe+3 + Fe+2 + 4H2O

298.15 K, 1 bar log10K: 10.36 ΔH°r:-215594 J·mol-1 (Ref.: 90hem) Hemingway B. S. (1990) Thermodynamic properties for bunsenite, NiO, magnetite, Fe3O4, and hematite, Fe2O3, with comments on selected oxygen buffer reactions. American Mineralogist 75(7-8), 781-790.
T(°C) 0 25 60 100 150 200 250 300
log10K 13.81 10.36 6.39 2.76 -0.88 -3.92 -6.62 -9.22
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1352.077422 -0.214981 80017.746619 485.026317 -3734499.702660