Aegerine(alpha)

Formula : NaFe(SiO3)2

Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c
Dana class: 
65.1.3c.2 (65) Inosilicate Single-Width Unbranched Chains, W=1(65.1)with chains P=2 (65.1.3c)C2/c clinopyroxenes (Na clinopyroxenes)
High temperature: 
An authigenic mineral in some shales and marls. Based on the amphibole stability in the metamorphic environments and hydrothemal synthesis, aegirine may be stable around 200C to 800C. Its stability depends on the pressure and the H2O fugacity.
Geological context: 
Occurs commonly in alkalic igneous rocks, carbonatites, and pegmatites. From regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites.

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
231.004 64.370 -2417200 -2584500 170.570 169.88
Reaction properties

Aegerine(alpha) + 4H+ + 2H2O ⇌ Fe+3 + Na+ + 2H4SiO4

298.15 K, 1 bar log10K: 0.91 ΔH°r: 43313 J·mol-1
T(°C) 0 25 60 100 150 200 250 300
log10K 1.81 0.91 -0.09 -0.96 -1.81 -2.50 -3.15 -3.83