Free surface energy values of quartz-water interface were measured in
300-600-degrees-C temperature range at 50 and MPa pressure. The measur
ements were obtained by the determination of solubility of thin- and c
oarsegrained fraction of quartz powder. It was found that free surface
energy value decreases corresponding to water density increase with t
he linear dependence of reciprocal density value. Such behavior of fre
e surface energy values could be interpreted in terms of water adsorpt
ion decrease with increase in temperature. Similar free surface energy
behavior is assumed for all minerals having a hydrofile surface.