An apparatus for removing magnetic particles from a mud slurry is disclosed, and includes one or more endless belts or chains enclosed almost wholly within a pipe. A motor drives the chain around the pipe. When the pipe is located within a mud slurry, magnetic particles in the mud slurry are drawn to the pipe and carried along the outside and away from the slurry until a collar is reached. Once separated the particles can be collected for disposal. The chain comprises a series of units linked together. Each unit includes a magnet with pole pieces at either pole to direct magnetic flux. Wear discs prevent the magnets and pole pieces from abrasion as they are drawn through the pipe. Units can be included in the chain which units do not include a magnet, thereby providing a break in the field, allowing particles to fall away from the collar region.