The selective separation, due to the interplay of gravity and magnetic forces, has been analysed for coexisting pairs of minerals, both of which are either paramagnetic or ferromagnetic. The extent of the maximum region of selectivity has been determined, and the influence of the dynamics of the separation process on the usable working space, within the region of selectivity, has been considered. The region of selectivity has also been determined for separators in which gravity has been replaced by centrifugal acceleration. The adoption of a non-Laplacian profile is proposed for the bipolar magnet used in such a separator. This may produce a more efficient system than standard profiles giving constancy of the gradient of either field or (field)2. Magnetic fluidization may provide a means of separating coexisting minerals which are so similar in the relevant property that the effective working space in a conventional separator becomes vanishingly small. The dynamics of the rotation of a magnetized particle in a uniform field has been considered. It is concluded that an alternating field must have a peak value, which lies in a range which is specific to one component of a mineral mixture, to selectively fluidize that component. When this condition is met for a ferromagnetic component, a coexisting paramagnetic phase is unlikely to fluidize.