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

Abstract

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 H 2 O, may do so at 25°C and 1 atmosphere total pressure depending on the status of H 2 O. It is further shown that the conditions of H 2 O chemical potential needed to stabilize boehmite + H 2 O relative to gibbsite + H 2 O or gibbsite + boehmite, are unlikely to occur in natural waters in the zone of weathering.