Grand Canonical Monte Carlo molecular simulations have been performed for argon and nitrogen adsorption on the basal surfaces of phyllosilicates without surface cations. The results have been compared with derivative isotherms analysis of experimental data. An optimization of the surface-Ar interaction has been performed by varying the oxygen atom LJ epsilon/k(B) parameter and the optimized value was used to perform the nitrogen adsorption simulations. The analysis of the argon adsorption simulation indicates that adsorption mechanisms are more complex than may be suggested by experimental results obtained by low-pressure adsorption. The structure of the adsorbed film has a marked dynamic behaviour and the monolayer capacity strongly depends on the equilibrium relative pressure. For nitrogen adsorption, while high pressure behaviour is simulated adequately, some deviation is observed in low-pressure region of the isotherms suggesting that additional simulation and perhaps the use of a more sophisticated potential to model the nitrogen molecule can be necessary to understand fully the behavior of this gas on clay minerals. (C) 2007 Elsevier B.V. All rights reserved.