A spiral separator for separating more-desired material from less-desired material has a feed arrangement for feeding a slurry of mixed more-desired material and less-desired material, a spiral trough, and a splitting arrangement for off-take of a concentrate band of more desired material, and the spiral trough is configured to provide an effective cross-trough floor slope of less than 8 degrees to horizontal in a turn immediately upstream of the splitting arrangement. The separator may be a multi-stage separator and include a slurry preparation apparatus between each pair of stages.