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Mineral speciesFormula
 AkermaniteCa2MgSi2O7 
Mineralogy
Family: Melilite Group 
Space group: Tetragonal - Scalenohedral H-M Symbol (4 2m) Space Group: P 421m 
Dana class: 55.4.1.1 (55) Sorosilicate Si2O7 Groups, Generally with No Additional Anions (55.4) with cations in [8] and lower coordination(55.4.1) Melilite group 
Geological context
High temperature: High temperature mineral. 
Geological context: A product of contact metamorphism of siliceous limestones and dolostones, and in rocks of the sanidinite facies. Also, forms from alkalic magmas rich in calcium and during smelting processes. 
Thermodynamics
Individual properties
Molar weight: 272.628 g/mol  ΔGºf-3,679,251 J/mol ref.  Sº: 209.33 J/mol/K ref. 
  ΔHºf-3,876,679 J/mol ref.  Cp: 211.98 J/mol/K ref. 
Reaction properties
Chemical reaction:  Akermanite + 6H+ + H2O = 2Ca+2 + Mg+2 + 2H4SiO4 
log10(Keq) = A + B.T + C.T-1 + D.log10(T) + E.T−2 (with T expressed in Kelvin)
A B C D E
 -9.66203484e+2   -1.51669524e-1   6.59264459e+4   3.50027375e+2   -2.64293615e+6 
Van t'Hoff
@ 25°C, 1 bar: log 10(Keq)46.08
ΔH°r-312,880 J/mol ref.
T (ºC) : 0 25 60 100 150 200 250 300
log 10(Keq):  51.11   46.08   40.34   35.13   30.00   25.89   22.42   19.32 
Maier Kelley
Cp(T) = a + b*10-3T + C*105T-2 (with T expressed in Kelvin)  ref.
a:251.42 J/mol/K 
b:47.70 J/mol/K2 
c:-47.70 J.K/mol 

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