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Mineral speciesFormula
 Corundum(alpha)Al2O3 
Mineralogy
Family: Hematite Group 
Space group: Trigonal - Hexagonal Scalenohedral H-M Symbol (3 2/m) Space Group: R 3c 
Dana class: 4.3.1.1 (4) Simple Oxides (4.3) with a cation charge of 3+ (A+++2 O3)(4.3.1) Corundum-Hematite group (Rhombohedral: R3_c) 
Geological context
High temperature: High temperature mineral, related to metamorphisme and udersaturated magmas. 
Geological context: Contact and regionally metamorphosed rocks but also in magma with low silica content (alkaline context) 
Thermodynamics
Individual properties
Molar weight: 101.961 g/mol  ΔGºf-1,582,257 J/mol ref.  Sº: 50.92 J/mol/K ref. 
  ΔHºf-1,675,700 J/mol ref.  Cp: 79.03 J/mol/K ref. 
Reaction properties
Chemical reaction:  Corundum(alpha) + 6H+ = 2Al+3 + 3H2O 
log10(Keq) = A + B.T + C.T-1 + D.log10(T) + E.T−2 (with T expressed in Kelvin)
A B C D E
 -9.48604422e+2   -1.57877803e-1   6.08326965e+4   3.39149563e+2   -2.60110293e+6 
Van t'Hoff
@ 25°C, 1 bar: log 10(Keq)18.30
ΔH°r-258,590 J/mol ref.
T (ºC) : 0 25 60 100 150 200 250 300
log 10(Keq):  22.42   18.30   13.51   9.08   4.60   0.87   -2.39   -5.41 
Maier Kelley
Cp(T) = a + b*10-3T + C*105T-2 (with T expressed in Kelvin)  ref.
a:98.25 J/mol/K 
b:36.75 J/mol/K2 
c:-26.83 J.K/mol 

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