Abstract: Prior centrifugal concentrators for concentrating precious minerals use annular ribs or baffles to trap the precious minerals. Sand or magnetite tends to pack against such ribs, reducing the effectiveness of these devices. In the present invention, the inner surface of the rotating drum is free of obstacles, but forms three continuous zones, a migration zone, a retention zone and a lip zone. The precious mineral is retained in the retention zone by centrifugal force and friction while the unwanted slurry flows over the retention zone and out of the drum.