Hydromagnesite

Formula : Mg5(OH)2(CO3)4:4H2O

Family: 
Carbonates
Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: P 21/c
Dana class: 
16b.7.1.1V - 16b Carbonates - Hydroxyl or Halogen ; 16b.7 Carbonates - Hydroxyl or Halogen ; 16b.7.1
High temperature: 
This mineral is stable at near room temperature in saline medium and CO2 rich environment.
Geological context: 
As alteration product of serpentine and other magnesian rocks; as saline crust in artic climate; in lake saline sediments; and in caves.

Dernière mise à jour le 25.01.2021

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
 V°
cm3·mol-1
 ΔGºf
J·mol-1
 ΔHºf
J·mol-1
 Sº
J·mol-1·k-1
 CP
J·mol-1·K-1
467.636 208.800 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp. -5870184 (Ref.: Internal calculation) -6516000 (Ref.: 99kon/kon) Konigsberger E., Konisberger L.C., and Gamsjager H., 1999. Low temperature thermodynamic model for the system Na2CO3 MgCO3 CaCO3 H2O. Geochimica et Cosmochimica Acta, 63, p. 3105-3119. 520.000 (Ref.: 99kon/kon) Konigsberger E., Konisberger L.C., and Gamsjager H., 1999. Low temperature thermodynamic model for the system Na2CO3 MgCO3 CaCO3 H2O. Geochimica et Cosmochimica Acta, 63, p. 3105-3119. 571.31 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp.
CP(T) = a + b·T + ·c·T-2 (T in Kelvin)
a
J·mol-1·K-1
 b * 103
J·mol-1·K-2
 c * 10-5
J·K·mol-1
 Maier Kelley Ref.
591.87 273.13 -90.67 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp.
Reaction properties

Hydromagnesite + 6H+ ⇌ 4HCO3- + 5Mg+2 + 6H2O

298.15 K, 1 bar log10K: 31.00 ΔH°r:-293700 J·mol-1 (Ref.: 99kon/kon) Konigsberger E., Konisberger L.C., and Gamsjager H., 1999. Low temperature thermodynamic model for the system Na2CO3 MgCO3 CaCO3 H2O. Geochimica et Cosmochimica Acta, 63, p. 3105-3119.
T(°C) 0 25 60 100 150 200 250 300
log10K 35.62 31.00 25.51 20.32 14.90 10.15 5.59 0.68
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-4079.720208 -0.642868 233399.519616 1479.038975 -12464629.328658