Chrysotile

Formula : Mg3Si2O5(OH)4

Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: A2/m
Dana class: 
71.1.2d.0 (71) Phyllosilicate Sheets of Six-Membered Rings (71.1)with 1:1 layers (71.1.2d) Serpentine group (Chrysotile subgroup)
High temperature: 
Possible at 25C but the reaction may be limited by the kinetic. The upper stability limit is given around 400C.
Geological context: 
Occurs mainly as compact cross-fiber veinlet in serpentine.

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
277.112 108.500 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp. -4032380 (Ref.: Internal calculation) -4360000 (Ref.: 04eva) Evans B. (2004) The serpentine multisystem revisited: Chrysotile is metastable, International Geology Review, 46, 479-506 221.330 (Ref.: 04eva) Evans B. (2004) The serpentine multisystem revisited: Chrysotile is metastable, International Geology Review, 46, 479-506 274.14 (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.
296.63 167.14 -64.29 (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

Chrysotile + 6H+ ⇌ 3Mg+2 + 2H4SiO4 + H2O

298.15 K, 1 bar log10K: 33.18 ΔH°r:-244552 J·mol-1 (Ref.: 04eva) Evans B. (2004) The serpentine multisystem revisited: Chrysotile is metastable, International Geology Review, 46, 479-506
T(°C) 0 25 60 100 150 200 250 300
log10K 37.05 33.18 28.67 24.60 20.66 17.56 14.97 12.62
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1803.987683 -0.247433 115529.312438 643.757062 -6176316.334358