Three thiophenol collectors were tested for the flotation of marmatite without activation by copper sulfate. Flotation tests showed that marmatite flotation increased according to the following order: 2-fluoro thiophenol < 2-hydroxy thiophenol < 2-amino thiophenol. All these thiophenols exhibited a better flotation property for marmatite than butyl xanthate. Infrared spectra indicated that 2-amino thiophenol and 2-hydroxy thiophenol chemically adsorbed onto the surface of marmatite. 2-Fluoro thiophenol adsorbed physically onto the surface of marmatite. Quantum chemical calculations indicated that the energy of the highest occupied molecular orbital (HOMO) for 2-amino thiophenol was the highest among the tested collectors and we thus determined that its collecting ability should be the strongest. This agreed with the experimentally determined flotation results. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.