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Mineral speciesFormula
 Aegerine(alpha)NaFe(SiO3)2 
Mineralogy
Family: Pyroxene Group 
Space group: Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c 
Dana class: 65.1.3c.2 (65) Inosilicate Single-Width Unbranched Chains, W=1(65.1)with chains P=2 (65.1.3c)C2/c clinopyroxenes (Na clinopyroxenes) 
Geological context
High temperature: An authigenic mineral in some shales and marls. Based on the amphibole stability in the metamorphic environments and hydrothemal synthesis, aegirine may be stable around 200C to 800C. Its stability depends on the pressure and the H2O fugacity. 
Geological context: Occurs commonly in alkalic igneous rocks, carbonatites, and pegmatites. From regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites. 
Thermodynamics
Individual properties
Molar weight: 231.004 g/mol  ΔGºf-2,417,200 J/mol ref.  Sº: 170.57 J/mol/K ref. 
  ΔHºf-2,584,500 J/mol ref.  Cp: 169.88 J/mol/K ref. 
Reaction properties
Chemical reaction:  Aegerine(alpha) + 4H+ + 2H2O = Fe+3 + Na+ + 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
 -6.86875397e+2   -1.05989746e-1   3.79174708e+4   2.47707128e+2   -1.84232121e+6 
Van t'Hoff
@ 25°C, 1 bar: log 10(Keq)0.91
ΔH°r43,313 J/mol ref.
T (ºC) : 0 25 60 100 150 200 250 300
log 10(Keq):  1.81   0.91   -0.09   -0.96   -1.81   -2.50   -3.15   -3.83 
Maier Kelley
Cp(T) = a + b*10-3T + C*105T-2 (with T expressed in Kelvin)  ref.
a:199.40 J/mol/K 
b:61.97 J/mol/K2 
c:-42.67 J.K/mol 

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