Almandine(alpha)

Formula : Fe3Al2Si3O12

Family: 
Space group: 
Isometric - Hexoctahedral H-M Symbol (4/m 3 2/m) Space Group: I a3d
Dana class: 
51.4.3a.2 (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, almandine may be stable around 500C and less with the increase of pressure.
Geological context: 
The most common garnet, typically in mica schists and gneisses, from regionally metamorphosed argillaceous sediments and pelites; also in contact metamorphic hornfels and in granites and eclogites.

Dernière mise à jour le 11.06.2018

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
cm3·mol-1
ΔGºf
J·mol-1
ΔHºf
J·mol-1
J·mol-1·k-1
CP
J·mol-1·K-1
497.753 115.280 -4933875 -5264700 316.310 361.83
Reaction properties

Almandine(alpha) + 12H+ ⇌ 2Al+3 + 3Fe+2 + 3H4SiO4

298.15 K, 1 bar log10K: 42.16 ΔH°r: -465683 J·mol-1
T(°C) 0 25 60 100 150 200 250 300
log10K 49.61 42.16 33.58 25.69 17.79 11.28 5.59 0.32