Diopside

Formula : CaMg(SiO3)2

Family: 
Pyroxenes
Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c
Dana class: 
65.1.3a.1 (65) Inosilicate Single-Width Unbranched Chains, W=1(65.1)with chains P=2 (65.1.3a)C2/c clinopyroxenes (Ca clinopyroxenes)
High temperature: 
The minimal stability temperature of diopside can be estimated around 550C but this latter is strongly dependant on aH2O,aCO2.
Geological context: 
Basic and ultrabasic igneous and metamorphic rocks.

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
216.550 66.090 (Ref.: 78hel/del,92ajoh) -3028296 (Ref.: 78hel/del,92ajoh) -3202488 (Ref.: Internal calculation) 143.093 (Ref.: 78hel/del,92ajoh) 156.90 (Ref.: 78hel/del,92ajoh)
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.
221.21 32.80 -65.86 (Ref.: 78hel/del,92ajoh)
Reaction properties

Diopside + 4H+ + 2H2O ⇌ Ca+2 + Mg+2 + 2H4SiO4

298.15 K, 1 bar log10K: 21.74 ΔH°r:-153574 J·mol-1 (Ref.: Internal calculation)
T(°C) 0 25 60 100 150 200 250 300
log10K 24.13 21.74 18.87 16.22 13.61 11.51 9.72 8.08
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1332.805993 -0.181986 86038.580060 474.909495 -4880235.100030