Halloysite

Formula : Al2Si2O5(OH)4

Space group: 
Monoclinic - Domatic H-M Symbol (m) Space Group: Cc
Dana class: 
71.1.1.4 (71) Phyllosilicate Sheets of Six-Membered Rings (71.1) with 1:1 layers (71.1.1) Kaolinite group
High temperature: 
Formed by dehydration of endellite [Al2Si2O5(OH)4.2(H2O)] above 110C. Stability range <120C.
Geological context: 
A product of hydrothermal alteration or surface weathering of aluminosilicate minerals, as feldspars.

Dernière mise à jour le 11.06.2018

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
cm3·mol-1
ΔGºf
J·mol-1
ΔHºf
J·mol-1
J·mol-1·k-1
CP
J·mol-1·K-1
258.160 99.300 -3771950 -4092600 203.300 246.30
Reaction properties

Halloysite + 6H+ ⇌ 2Al+3 + 2H4SiO4 + H2O

298.15 K, 1 bar log10K: 10.32 ΔH°r: -192418 J·mol-1
T(°C) 0 25 60 100 150 200 250 300
log10K 13.40 10.32 6.79 3.56 0.34 -2.31 -4.65 -6.84