Hedenbergite

Formula : CaFe(SiO3)2

Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c
Dana class: 
65.1.3a.2 (65) Inosilicate Single-Width Unbranched Chains, W=1 (65.1) with chains P=2 (65.1.3a) C2/c clinopyroxenes (Ca clinopyroxenes)
High temperature: 
Based on clinopyroxene data it is possible to locate its stability around 700C and more. Stability depends also on pressure, aO2, aCO2, P.
Geological context: 
A common constituent of metamorphosed iron formations or other ferruginous siliceous sediments; common in Fe-Mn skarns. In alkalic granites, syenites, and in xenoliths in kimberlite. It is also present in smetling slags from polymetallic ores. Its an high temperature mineral.

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
248.092 68.270 -2673568 -2838056 170.289 168.87
Reaction properties

Hedenbergite + 4H+ + 2H2O ⇌ Ca+2 + Fe+2 + 2H4SiO4

298.15 K, 1 bar log10K: 19.96 ΔH°r: -145672 J·mol-1
T(°C) 0 25 60 100 150 200 250 300
log10K 22.30 19.96 17.29 14.87 12.48 10.53 8.85 7.29