Jacobsite

Formula : Mn(FeO2)2

Family: 
Oxides
Space group: 
Isometric - Hexoctahedral H-M Symbol (4/m 3 2/m) Space Group: F d3m
Dana class: 
7.2.2.2 (7)Multiple Oxides (7.2)(A+ B++)2 X4 Spinel group (7.2.2)(Iron subgroup)
High temperature: 
As primary high temperature mineral but it secondary origin cannot be discarded.
Geological context: 
Occurs as a primary mineral or and alteration product of othe rmanganese-bearing minerals in some metamorphosed Mn deposits. Dimorphous with iwakiite and forms a series with magnetite.

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
230.630 44.530 (Ref.: 73bar/kna) Barin I. and Knacke O., 1973, Thermochemical Properties of Inorganic Substances. Berlin: Springer-Verlag. -1121825 (Ref.: Internal calculation) -1226330 (Ref.: 73bar/kna) Barin I. and Knacke O., 1973, Thermochemical Properties of Inorganic Substances. Berlin: Springer-Verlag. 146.440 (Ref.: 73bar/kna) Barin I. and Knacke O., 1973, Thermochemical Properties of Inorganic Substances. Berlin: Springer-Verlag. 149.54 (Ref.: 73bar/kna) Barin I. and Knacke O., 1973, Thermochemical Properties of Inorganic Substances. Berlin: Springer-Verlag.
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.
144.77 85.94 -18.54 (Ref.: 73bar/kna) Barin I. and Knacke O., 1973, Thermochemical Properties of Inorganic Substances. Berlin: Springer-Verlag.
Reaction properties

Jacobsite + 8H+ ⇌ 2Fe+3 + Mn+2 + 4H2O

298.15 K, 1 bar log10K: 15.74 ΔH°r:-236318 J·mol-1 (Ref.: 73bar/kna) Barin I. and Knacke O., 1973, Thermochemical Properties of Inorganic Substances. Berlin: Springer-Verlag.
T(°C) 0 25 60 100 150 200 250 300
log10K 19.53 15.74 11.40 7.43 3.47 0.21 -2.67 -5.41
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1348.802492 -0.213507 81033.524241 484.255665 -3719725.958445