The electronic structure of H 2 S adsorbed on the goethite (110) surface has been studied by ASED-MO cluster calculations. We have studied both the perpendicular and the parallel H 2 S molecular adsorption on the FeOOH(110) surface. We have analyzed the adsorption configuration energies including rotation. The parallel species does not rotate during adsorption and corresponds to the most stable configuration. We have also studied the bonding contributions for the minimum energy configuration and the density of states plots.