Greenalite

Formula : Fe3Si2O5(OH)4

Space group: 
Monoclinic Space Group: Unknown
Dana class: 
71.1.2b.4 (71) Phyllosilicate Sheets of Six-Membered Rings (71.1) with 1:1 layers (71.1.2b) Serpentine group (Lizardite subgroup)
High temperature: 
Literature is poor about this mineral, estimated temperature for Chamosite Greenalite Stilpnomelane Siderite Pyrite parageneses is around 300C.
Geological context: 
A primary phase in some banded iron formations related to regional metamorphisme.

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
371.738 115.000 (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. -3002962 (Ref.: Internal calculation) -3301000 (Ref.: 83miy/kle) Miyano T, Klein C (1983 a) Phase relations of orthopyroxene, olivine, and grunerite in high-grade metamorphic iron-formation.Am Mineral 68:699-716 304.500 (Ref.: 83miy/kle) Miyano T, Klein C (1983 a) Phase relations of orthopyroxene, olivine, and grunerite in high-grade metamorphic iron-formation.Am Mineral 68:699-716 302.32 (Ref.: 83miy/kle) Miyano T, Klein C (1983 a) Phase relations of orthopyroxene, olivine, and grunerite in high-grade metamorphic iron-formation.Am Mineral 68:699-716
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.
303.39 166.34 -45.04 (Ref.: 83miy/kle) Miyano T, Klein C (1983 a) Phase relations of orthopyroxene, olivine, and grunerite in high-grade metamorphic iron-formation.Am Mineral 68:699-716
Reaction properties

Greenalite + 6H+ ⇌ 3Fe+2 + 2H4SiO4 + H2O

298.15 K, 1 bar log10K: 21.77 ΔH°r:-172552 J·mol-1 (Ref.: 83miy/kle) Miyano T, Klein C (1983 a) Phase relations of orthopyroxene, olivine, and grunerite in high-grade metamorphic iron-formation.Am Mineral 68:699-716
T(°C) 0 25 60 100 150 200 250 300
log10K 24.47 21.77 18.57 15.65 12.78 10.49 8.53 6.67
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1729.966488 -0.240079 108017.978515 617.814948 -6019571.329151