Epidote

Formula : Ca2FeAl2Si3O12(OH)

Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: P 21/m
Dana class: 
58.2.1a.7 (58) Sorosilicate Insular, Mixed, Single, and Larger Tetrahedral Groups (58.2 )with cations in [6] and higher coordination; single and double groups (n=1,2) (58.2.1a) Epidote group (Epidote subgroup)
High temperature: 
Temperature stability range between 240-300C to 700C.
Geological context: 
Epidote (Pistacite), occurs chiefly in regionally metamorphosed igneous and sedimentary rocks; in acid rocks contaminated by calc-silicate materials; as an alteration of plagioclase.

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
483.223 139.010 (Ref.: 04got) -6078118 (Ref.: Internal calculation) -6462600 (Ref.: 04got) 332.800 (Ref.: 04got) 362.89 (Ref.: 04got)
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.
513.30 -3.47 -132.78 (Ref.: 04got)
Reaction properties

Epidote + 13H+ ⇌ 2Al+3 + 2Ca+2 + Fe+3 + 3H4SiO4

298.15 K, 1 bar log10K: 32.23 ΔH°r:-411613 J·mol-1 (Ref.: 04got)
T(°C) 0 25 60 100 150 200 250 300
log10K 38.69 32.23 24.55 17.41 10.20 4.23 -1.04 -6.02
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-3156.738795 -0.464880 196767.746605 1126.069248 -10558252.361678