Margarite

Formula : CaAl2(Al2Si2)O10(OH)2

Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c
Dana class: 
71.2.2c.1 (71)Phyllosilicate Sheets of Six-Membered Rings (71.2) with 2:1 Layers (71.2.2c)Mica Group (Margarite subgroup)
High temperature: 
The lower stability limit of maragrite is constrained by a pressure about 3 Kbars for a temperature below 400C, the upper limit is around 700C for 10 Kb.

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
398.184 129.630 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. -5859267 (Ref.: Internal calculation) -6244000 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. 263.600 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. 321.48 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
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.
373.08 171.60 -91.35 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
Reaction properties

Margarite + 14H+ ⇌ 4Al+3 + Ca+2 + 2H4SiO4 + 4H2O

298.15 K, 1 bar log10K: 37.00 ΔH°r:-513642 J·mol-1 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
T(°C) 0 25 60 100 150 200 250 300
log10K 45.12 37.00 27.45 18.58 9.61 2.16 -4.40 -10.53
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-2990.011453 -0.457424 187867.849717 1066.877285 -9479386.303965