Slurries of magnetic and nonmagnetic particles in water are treated in a high intensity magnetic separator including at least one turntable that defines at least one circular channel therethrough in which a matrix material is positioned. Rotation of the turntable in a generally horizontal plane about a generally vertical virtual axis causes the circular channel(s) to rotate through a plurality of magnetic and nonmagnetic zones generated by magnet members. Treatment slurry is directed into the channel(s) in one or more of the magnetic zones as the turntable rotates. A tailings fraction passing through the channel(s) in a generally downward direction in the magnetic zones is collected in tailings launders. Magnetic particles attracted to the matrix material in the magnetic zones remain in the channel(s) until they pass into an adjacent nonmagnetic zone, where the magnetic particles are washed from the channel(s) into concentrate launders.