Merwinite

Formula : Ca3Mg(SiO4)2

Family: 
Melilite
Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: P 21/a
Dana class: 
51.4.2.1 (51) Nesosilicate Insular SiO4 Groups Only (51.4) with cations in [6] and >[6] coordination (51.4.2) Dana Group
High temperature: 
During the process of cement production Merwinite appears around 1000 to 1250C, but it depends on aCO2.
Geological context: 
Merwinite is a high temperature mineral: it occurs in metamorphosed limestone along the contact with intrusive body; in Maqarin site where bitumen has burned and pyrometamorphosed limestone to natural cement; also as klinker phase.

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
328.705 104.400 (Ref.: 78hel/del,92ajoh) -4336825 (Ref.: 78hel/del,92ajoh) -4564175 (Ref.: Internal calculation) 253.132 (Ref.: 78hel/del,92ajoh) 252.26 (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.
305.31 50.04 -60.42 (Ref.: 78hel/del,92ajoh)
Reaction properties

Merwinite + 8H+ ⇌ 3Ca+2 + Mg+2 + 2H4SiO4

298.15 K, 1 bar log10K: 69.29 ΔH°r:-449547 J·mol-1 (Ref.: Internal calculation)
T(°C) 0 25 60 100 150 200 250 300
log10K 76.42 69.29 60.97 53.35 45.81 39.78 34.71 30.21
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1896.905686 -0.271669 130725.267884 679.572072 -6473437.444221