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Mineral speciesFormula
 AntigoriteMg48Si34O85(OH)62 
Mineralogy
Family: Kaolinite-Serpentine Group 
Space group: Monoclinic - Domatic H-M Symbol (m) Space Group: Cm 
Dana class: 71.1.2a.1 (71) Phyllosilicate Sheets of Six-Membered Rings (71.1)with 1:1 layers (71.1.2a)Serpentine group 
Geological context
High temperature: As a replacement of siliceous dolostone along contacts with diabase sills. Antigorite may be stable from about 200C to 650C, its stability domain is strongly dependant on the fugacity of the water. 
Geological context: Commonly replaces ultramafic rocks, pervasively or in crosscutting veinlets. 
Thermodynamics
Individual properties
Molar weight: 4,535.951 g/mol  ΔGºf-66,126,875 J/mol ref.  Sº: 3,591.00 J/mol/K ref. 
  ΔHºf-71,417,980 J/mol ref.  Cp: 4,370.46 J/mol/K ref. 
Reaction properties
Chemical reaction:  Antigorite + 96H+ = 48Mg+2 + 34H4SiO4 + 11H2O 
log10(Keq) = A + B.T + C.T-1 + D.log10(T) + E.T−2 (with T expressed in Kelvin)
A B C D E
 -1.79720863e+4   -2.70163631e+0   1.12087973e+6   6.48893673e+3   -4.78623046e+7 
Van t'Hoff
@ 25°C, 1 bar: log 10(Keq)499.90
ΔH°r-3,822,754 J/mol ref.
T (ºC) : 0 25 60 100 150 200 250 300
log 10(Keq):  561.65   499.90   430.44   368.79   309.46   262.71   223.37   187.65 
Maier Kelley
Cp(T) = a + b*10-3T + C*105T-2 (with T expressed in Kelvin)  ref.
a:5,074.25 J/mol/K 
b:2,253.72 J/mol/K2 
c:-1,222.94 J.K/mol 

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