This study investigates on two gray clays used traditionally in the ceramic industry of Fès region and belonging to Saiss Basin (Morocco). They were sampled and characterized from their physical, chemical, mineralogical and ceramic stand points to evaluate their potential suitability as raw materials in various ceramic applications. Both clays, easily recognized by local experienced artisans, present different aspects although they were extracted from the same deposit and even from the same blocks: a smooth one with a dense aspect (FS1) and a grainy clay (FS2). Both clays showed similarities for thermal behavior, chemical composition and XRD diagrams. Both rocks are mainly composed by quartz, calcite, smectite, kaolinite and illite as dominant mineral phases while chlorite and some mixed layers were identified as minor phases. Physical, mineralogical, chemical and thermal properties showed the complementarily of these clayey materials and justified the reasons for their using in the local traditional ceramic industry. Suitable formulations that depend on the type of the fabricated pottery (zellij, housewares or decoration articles) were discussed. According to their interesting properties, perspective of their use as membrane supports for filtration of wastewaters is pointed out.