The correlation between red mud characteristics and separability will be discussed. A new X-ray Diffraction Database and Phase Analytical System, completed by thermogravimetry, was applied to determine the quantitative mineralogical composition of various bauxites and red muds. The effects of technology (lime chemistry, goethite-hematite conversion, etc.) on the separability of red mud has been determined. A laboratory soft gamma-ray absorption model settler has been developed and used in order to simulate the continuous settling process and to determine the loading capacity of the plant settlers. The main features and advantages of the dry stacking of red mud will be demonstrated.