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Mineral speciesFormula
 BerndtiteSnS2 
Mineralogy
Family: Melonite Group 
Space group: Trigonal - Hexagonal Scalenohedral H-M Symbol (3 2/m) Space Group: P 3m1 
Dana class: 2.12.14.5 (2)Sulfides - Including Selenides and Tellurides (2.12)where Am Bn Xp, with (m+n):p=1:2 (2.12.14)Melonite Group (Trigonal: P3m1) AX2 type 
Geological context
High temperature: Hydrothermal and supergene. 
Geological context: Secondary mineralin hydrothermally altered in tin sulfide veins and in a high temperature deposit, also described in oxidation zone of mineralized bodies 
Thermodynamics
Individual properties
Molar weight: 182.842 g/mol  ΔGºf-145,394 J/mol ref.  Sº: 87.45 J/mol/K ref. 
  ΔHºf-153,695 J/mol ref.  Cp: 70.13 J/mol/K ref. 
Reaction properties
Chemical reaction:  Berndtite + 0.75H2O = 1.5HS- + Sn+2 + 0.25S2O3-2 
log10(Keq) = A + B.T + C.T-1 + D.log10(T) + E.T−2 (with T expressed in Kelvin)
A B C D E
 -1.56736491e+3   -2.52971471e-1   7.76031665e+4   5.69626284e+2   -5.25789633e+6 
Van t'Hoff
@ 25°C, 1 bar: log 10(Keq)-32.15
ΔH°r-1,345,463 J/mol ref.
T (ºC) : 0 25 60 100 150 200 250 300
log 10(Keq):  -34.99   -32.15   -29.10   -26.52   -24.26   -22.78   -21.95   -21.78 
Maier Kelley
Cp(T) = a + b*10-3T + C*105T-2 (with T expressed in Kelvin)  ref.
a:64.89 J/mol/K 
b:17.57 J/mol/K2 
c:0.00 J.K/mol 

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