Phlogopite

Formula : KMg3(AlSi3)O10(OH)2

Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/m
Dana class: 
71.2.2b.1 (71 )Phyllosilicate Sheets of Six-Membered Rings (71.2)with 2:1 Layers (71.2.2b)Mica Group (Biotite subgroup)
High temperature: 
Near 500C-600C in porphyries environnement to 1400C in metamorphic terranes, these stability temperatures are strongly aH2O -dependant.
Geological context: 
Phlogopite is present In metamorphosed dolostones and magnesium-rich limestones; also in ultramafic rocks as kimberlites, peridotites, lamproites, and serpentinites.

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
417.260 149.660 (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. -5829459 (Ref.: Internal calculation) -6215000 (Ref.: 92cir/nav) Circone S. and Navrotsky A., 1992. Substitution of (6,4)Al in phlogopite : high pressure solution calorimetry , heat capacities and thermodynamic properties of the phlogopite -eastonite join. American Mineralogist, 77, p. 1191-1205. 315.900 (Ref.: 84rob/hem) Robie R. A. and Hemingway B. S., 1984. Heat capacities and entropies of phlogopite KMg3AlSi3O1O(OH)2 and paragonite NaAl2AlSi3O1O(OH)2 between 5 and 9OO K and estimates of the enthalpies and Gibbs free energies of formation. Amer. Miner., 69, p. 858-868. 353.60 (Ref.: 84rob/hem) Robie R. A. and Hemingway B. S., 1984. Heat capacities and entropies of phlogopite KMg3AlSi3O1O(OH)2 and paragonite NaAl2AlSi3O1O(OH)2 between 5 and 9OO K and estimates of the enthalpies and Gibbs free energies of formation. Amer. Miner., 69, p. 858-868.
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.
400.17 163.02 -84.60 (Ref.: 84rob/hem) Robie R. A. and Hemingway B. S., 1984. Heat capacities and entropies of phlogopite KMg3AlSi3O1O(OH)2 and paragonite NaAl2AlSi3O1O(OH)2 between 5 and 9OO K and estimates of the enthalpies and Gibbs free energies of formation. Amer. Miner., 69, p. 858-868.
Reaction properties

Phlogopite + 10H+ ⇌ Al+3 + K+ + 3Mg+2 + 3H4SiO4

298.15 K, 1 bar log10K: 41.10 ΔH°r:-353123 J·mol-1 (Ref.: 92cir/nav) Circone S. and Navrotsky A., 1992. Substitution of (6,4)Al in phlogopite : high pressure solution calorimetry , heat capacities and thermodynamic properties of the phlogopite -eastonite join. American Mineralogist, 77, p. 1191-1205.
T(°C) 0 25 60 100 150 200 250 300
log10K 46.65 41.10 34.54 28.54 22.62 17.85 13.78 10.02
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-2719.406726 -0.381065 173180.811099 969.566001 -9410264.620753