An average value for the surface energy (gamma s) of Palygorskite was determined from experimental data of spreading pressure, the surface tension of water and its contact angle using a formula based on the combination of the Young equation with a general equation of pair interaction. The value found is 226.6 mJ m(-2). Some factors that affect the determination of surface energy via solid-liquid interaction are exposed. The backgrounds of previous formulas for the calculation of the surface energy of palygorskite are also critically examined. (c) 2006 Elsevier B.V. All rights reserved.