Spessartine(alpha)

Formula : Mn3Al2Si3O12

Family: 
Garnet
Space group: 
Isometric - Hexoctahedral H-M Symbol (4/m 3 2/m) Space Group: I a3d
Dana class: 
51.4.3a.3 (51) Nesosilicate Insular SiO4 Groups Only (51.4) with cations in [6] and >[6] coordination (51.4.3a) Garnet group (Pyralspite series)
High temperature: 
Based on the garnet stability, spessartine may be stable around 500C and less with the increase of pressure.
Geological context: 
Occurs commonly in granite pegmatites, granites, and rhyolites. Formed in some skarns and metasomatic manganese-rich rocks adjacent to igneous intrusions or in regionally metasomatized areas.

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
495.027 117.900 (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. -5309908 (Ref.: Internal calculation) -5646300 (Ref.: 98hol/pow) Holland T.J.B., and Powell R., 1998. An internally consistent thermodynamic data set for phases of petrological interest. Journal of Metamorphic Geology, 16, p. 309 343. 311.708 (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. 346.78 (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.
395.30 139.08 -80.00 (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

Spessartine(alpha) + 12H+ ⇌ 2Al+3 + 3Mn+2 + 3H4SiO4

298.15 K, 1 bar log10K: 49.89 ΔH°r:-471069 J·mol-1 (Ref.: 98hol/pow) Holland T.J.B., and Powell R., 1998. An internally consistent thermodynamic data set for phases of petrological interest. Journal of Metamorphic Geology, 16, p. 309 343.
T(°C) 0 25 60 100 150 200 250 300
log10K 57.31 49.89 41.13 33.02 24.91 18.27 12.52 7.20
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-3078.223059 -0.448002 196823.782008 1098.686642 -10409111.849110