Digitally enhanced Landsat Thematic Mapper (TM) images of the Cerro Colorado Pluton, Northern Chile, were studied. The bulk of the intrusion is magnetic-rich and laboratory spectra of the fresh surfaces of field samples are severely quenched. Weathering and oxidation of the magnetite has reduced the quenching effects, allowing features due to the primary mineralogy of the rock to be resolved in the spectra of the weathered surfaces and, consequently, on the enhanced imagery. In most cases the weathering alters the overall albedo of the rock and it may introduce additional features into the rock spectra due to iron hydroxides and clay minerals. As yet it does not seem to the author that TM data alone could be used for lithological mapping. Some control is necessary, in the form of fieldwork or pre-existing maps. >