Abstract Layer charge is recognized as the single most important characteristic of 2:1 phyllosilicates. It indicates a mineral's capacity to retain cations and to adsorb water and various polar organic molecules. The affinity of organic-clays for sorption of organic contaminants in aqueous systems is now attracting considerable attention. The layer charge is also considered an important criterion for the classification of 2:1 silicate clay minerals. It is generally agreed that the magnitude of the layer charge can be taken into account to resolve the classification problem. Studies on structural chemistry also confirm the importance of layer charge for characterization of silicate clays.”