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Mineral speciesFormula
 BassaniteCaSO4:0.5H2O 
Mineralogy
Family: Bassanite - Ardealite series 
Space group: Orthorombic Space Group: Unk 
Dana class: 29.6.1.1VI- 29 Hydrated Acid and Sulfates ; 29.6 Hydrated Acid and Sulfates where A XO4 . x(H2O) ; 29.6.1 
Geological context
High temperature: Stable at around 80C from gypsum 
Geological context: In cavities in leucite-tephrite blocks, 1906 eruption. Dehydrates at 130C. Hydrates to gypsum in a humid atmosphere. 
Thermodynamics
Individual properties
Molar weight: 145.149 g/mol  ΔGºf-1,437,756 J/mol ref.  Sº: 130.54 J/mol/K ref. 
  ΔHºf-1,577,897 J/mol ref.  Cp: 119.45 J/mol/K ref. 
Reaction properties
Chemical reaction:  Bassanite = Ca+2 + SO4-2 + 0.5H2O 
log10(Keq) = A + B.T + C.T-1 + D.log10(T) + E.T−2 (with T expressed in Kelvin)
A B C D E
 -1.58343880e+3   -2.53478769e-1   8.81153251e+4   5.73467473e+2   -5.28508068e+6 
Van t'Hoff
@ 25°C, 1 bar: log 10(Keq)-3.92
ΔH°r-17,358 J/mol ref.
T (ºC) : 0 25 60 100 150 200 250 300
log 10(Keq):  -3.73   -3.92   -4.34   -4.93   -5.77   -6.72   -7.85   -9.29 
Maier Kelley
Cp(T) = a + b*10-3T + C*105T-2 (with T expressed in Kelvin)  ref.
a:119.45 J/mol/K 
b:0.00 J/mol/K2 
c:0.00 J.K/mol 

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