Magnesite(Natur)

Formula : MgCO3

Family: 
Carbonates
Space group: 
Trigonal - Hexagonal Scalenohedral HM symbol (-3 2/m) Space Group: R 3c
Dana class: 
14.1.1.2V - 14 Anhydrous Carbonates ; 14.1 Anhydrous Carbonates with Simple Formula A+ CO3 ; 14.1.1 Calcite Group (Trigonal: R3_c)
High temperature: 
Occurs widespread as an alteration product of rocks rich in magnesium (particularly sepentine); as bed in metamorphic rocks; in sedimentary deposits; as gangue mineral in hydrothermal ore veins; and rarely as a primary mineral in igneous rock.
Geological context: 
Stability field is large from a normal atmospheric conditions to the very high conditions existing in the mantle of the earth.

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
84.314 28.018 (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. -1034146 (Ref.: Internal calculation) -1117940 (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. 65.090 (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. 76.09 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 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.
81.12 52.25 -18.32 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
Reaction properties

Magnesite(Natur) + H+ ⇌ HCO3- + Mg+2

298.15 K, 1 bar log10K: 1.41 ΔH°r:-38990 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 2.01 1.41 0.66 -0.10 -0.95 -1.76 -2.61 -3.59
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-932.710202 -0.149116 52089.430207 338.095200 -2908556.684771