Directional and gradient filters have been applied in Landsat TM image to help rock discrimination in a study area of SW Angola, where Precambrian basement rocks are well exposed. A well defined limit has been drawn on filtered images, primarily on the basis of lineation pattern, between the two main rock groups outcropping in the area, namely the Schistose Mainly Metasedimentary Complex and the Gneissic-migmatitic-granitoid Complex. Various lithological units have been mapped within the two complexes on the basis of other features still related to texture, such as lineation density which, at this level, can be associated to bedding planes, foliation and/or schistosity. Discrimination of the recent continental cover took benefit from this technique as the lineation-free lithologies stand out as smooth patches in all the products. By displaying at least 5 major textural patterns in the whole area, directional and gradient filters highlight rock properties and structure which must be related not only to lithology but also to geological history. Although less powerful than a multispectral approach, the present one can support traditional analysis and integrate a spectrally-based study when, as in the present case, texture enters as Intensity in an IHS transformation.