The present article follows two previous publications on magnetic jigging, which is a new method for mineral benefication. The idea of magnetic jigging, the mathematical model of batch magnetic jigs, bed dynamics and results of the analyses of the suggested mathematical model were described in Part 1. The classical model of the particle-bed interaction that allows for an adequate description of the motion and the separation of the particles in continuous jigs and the analysis of the suggested mathematical model of continuous magnetic jigging were described in Part 2. The present paper is devoted to the analysis of the bed effects during the jigging process based on the mathematical model described in Parts 1 and 2. The primary importance of the jigging bed for separation of fine particles has been proven. A theoretical explanation of this fact is given using the analysis by the suggested mathematical model. The concept of multifrequency jigging without sub-sieve liquid is formulated and explained.