Monticellite

Formula : CaMgSiO4

Family: 
Melilite
Space group: 
Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: P nma
Dana class: 
51.3.2.1 (51) Nesosilicate Insular SiO4 Groups Only (51.3)with all cations in octahedral [6] coordination (51.3.2) Monticellite - Kirschsteinite series
High temperature: 
More than 340C and it melts incongruently at 1499C to form MgO and a liquid
Geological context: 
Occurs in banded iron formations subjected to low-grade regional metamorphism and in MgO riche skarn. Monticellite is also present in kimberlites and in smelting byproducts.

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
156.466 51.470 (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. -2145677 (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. -2262825 (Ref.: Internal calculation) 110.458 (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. 123.06 (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.
154.06 22.34 -33.47 (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

Monticellite + 4H+ ⇌ Ca+2 + Mg+2 + H4SiO4

298.15 K, 1 bar log10K: 30.09 ΔH°r:-206036 J·mol-1 (Ref.: Internal calculation)
T(°C) 0 25 60 100 150 200 250 300
log10K 33.36 30.09 26.28 22.80 19.36 16.61 14.30 12.24
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-999.451874 -0.141997 67213.518887 357.523712 -3397947.474473