We used semi-empirical calculations at the PM3 level to investigate the adsoprtion of amines onto silicate clay surfaces.  We used a cluster model to represent the siloxane surface of montmoillonite clay.  Atoms in the clay cluster were constrained, and the amines were left free to find an optimal conformation.  In each case the amine adsorbed to the clay surface through hydrogen bonds, with the lengths of these bonds ranging from 2.0 to 2.7 angstroms.  The hydrogen bond length increased with increasing molecular weight of the amine.  An aluminum charge site was also placed in the clay to simulate natural behavior.  To neutralize the charge, we used quaternary ammonium ions of the form NR⁺_4, with R representing hydrogen or an alkyl group.  When this megative site was placed in the clay, hydrogen bond lengths decreased to the range of 1.3 to 1.8 angstroms.