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Mineral speciesFormula
 AnorthiteCa(Al2Si2)O8 
Mineralogy
Family: Feldspar Group 
Space group: Triclinic - Pinacoidal H-M Symbol ( 1) Space Group: P1,11 
Dana class: 76.1.3.6 (76) Tectosilicate Al-Si Framework (76.1) with Al-Si frameworks (76.1.3) Plagioclase series 
Geological context
High temperature: More than 300C for plagioclase (Na1-xCaxAl2-xSi2-xO8) 
Geological context: Magmatic and metamorphic rocks and in some geothermal field. More than 300C for plagioclase (Na1-xCaxAl2-xSi2-xO8) 
Thermodynamics
Individual properties
Molar weight: 278.207 g/mol  ΔGºf-4,002,095 J/mol ref.  Sº: 199.30 J/mol/K ref. 
  ΔHºf-4,227,830 J/mol ref.  Cp: 50.47 J/mol/K ref. 
Reaction properties
Chemical reaction:  Anorthite + 8H+ = 2Al+3 + Ca+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
 -1.28544734e+3   -2.04196248e-1   7.99959364e+4   4.60838841e+2   -3.28813550e+6 
Van t'Hoff
@ 25°C, 1 bar: log 10(Keq)25.31
ΔH°r-314,358 J/mol ref.
T (ºC) : 0 25 60 100 150 200 250 300
log 10(Keq):  30.36   25.31   19.55   14.35   9.22   5.06   1.49   -1.80 
Maier Kelley
Cp(T) = a + b*10-3T + C*105T-2 (with T expressed in Kelvin)  ref.
a:86.98 J/mol/K 
b:86.98 J/mol/K2 
c:-55.51 J.K/mol 

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