The Stability of Gibbsite and Boehmite at the Surface of the Earth

Ward Chesworth*
Department of Land Resource Science, University of Guelph, Ontario, Canada
* Present address: Départment de Géologie et Minéralogie, Université de Clermont, Clermont-Ferrand, France.

Abstract: Two mutually exclusive views exist concerning the relative stabilities of gibbsite and boehmite in soils. These are examined in terms of experimental and thermodynamic evidence and it is shown that all three possible divariant assemblages of two phases that can exist between gibbsite, beohmite and H2O, may do so at 25°C and 1 atmosphere total pressure depending on the status of H2O. It is further shown that the conditions of H2O chemical potential needed to stabilize boehmite + H2O relative to gibbsite + H2O or gibbsite + boehmite, are unlikely to occur in natural waters in the zone of weathering.

Clays and Clay Minerals; December 1972 v. 20; no. 6; p. 369-374; DOI: 10.1346/CCMN.1972.0200604
© 1972, The Clay Minerals Society
Clay Minerals Society (www.clays.org)