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Mineral speciesFormula
 ChromiteFeCr2O4 
Mineralogy
Space group: Isometric - Hexoctahedral HM symbol (4/m -3 2/m) Space Group: F d3m 
Dana class: 7.2.3.3III - 7 Multiple Oxides ; 7.2 Multiple Oxides (A+ B++)2 X4 Spinel group ; 7.2.3 (Chromium subgroup) 
Geological context
Geological context: A cumulus mineral in ultramafic portions of layered mafic igneous rocks; an accessory mineral in alpine-type peridotites; also detrital. Common in all meteorites, except carbonaceous chondrites, and in lunar mare basalts. 
Thermodynamics
Individual properties
Molar weight: 223.777 g/mol  ΔGºf-1,344,469 J/mol ref.  Sº: 146.00 J/mol/K ref. 
  ΔHºf-1,445,500 J/mol ref.  Cp: 133.58 J/mol/K ref. 
Reaction properties
Chemical reaction:  Chromite + 8H+ = 2Cr+3 + Fe+2 + 4H2O 
log10(Keq) = A + B.T + C.T-1 + D.log10(T) + E.T−2 (with T expressed in Kelvin)
A B C D E
 -1.36551181e+3   -2.16126591e-1   8.35174751e+4   4.88067516e+2   -3.79878694e+6 
Van t'Hoff
@ 25°C, 1 bar: log 10(Keq)15.13
ΔH°r-98,470 J/mol ref.
T (ºC) : 0 25 60 100 150 200 250 300
log 10(Keq):  19.42   15.13   10.17   5.64   1.10   -2.65   -5.93   -9.01 
Maier Kelley
Cp(T) = a + b*10-3T + C*105T-2 (with T expressed in Kelvin)  ref.
a:140.35 J/mol/K 
b:56.09 J/mol/K2 
c:-20.89 J.K/mol 

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