Huntite

Formula : CaMg3(CO3)4

Family: 
Carbonates
Space group: 
Trigonal - TrapezohedralH-M Symbol (3 2) Space Group: R 32
High temperature: 
It is a low temperature mineral, its stablity at room temperature is possible.
Geological context: 
It is a low temperature mineral, its stability at room temperature is possible.Occurs as a cave carbonate in areas where the country rocks are magnesium-rich; as a near-surface weathering product of magnesium-rich rocks such as brucite, marbles, dolomites, serpentinites, or magnesite; as a diagenetic mineral in recent sediment sequences; and as a sabkha mineral associated with evaporitic magnesite in desert.

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
353.029 122.900 (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. -4203442 (Ref.: Internal calculation) -4529600 (Ref.: 73hem/rob) Hemingway B. S. and Robie R. A., 1973. A calorimetric determination of the standard enthalpies of formation of huntite, CaMg3(CO3)4, and artinite, Mg2(OH)2CO3 z 3 H2O, and their standard Gibbs free energies of formation. J. Res. U.S. Geol. Survey, 1, pp. 535-541. 299.533 (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. 309.43 (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.
352.17 179.33 -85.52 (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

Huntite + 4H+ ⇌ 4HCO3- + Ca+2 + 3Mg+2

298.15 K, 1 bar log10K: 11.01 ΔH°r:-174120 J·mol-1 (Ref.: 73hem/rob) Hemingway B. S. and Robie R. A., 1973. A calorimetric determination of the standard enthalpies of formation of huntite, CaMg3(CO3)4, and artinite, Mg2(OH)2CO3 z 3 H2O, and their standard Gibbs free energies of formation. J. Res. U.S. Geol. Survey, 1, pp. 535-541.
T(°C) 0 25 60 100 150 200 250 300
log10K 13.69 11.01 7.66 4.30 0.55 -3.00 -6.63 -10.77
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-3644.140276 -0.586483 204451.967940 1322.340413 -11357532.545811