text: Typical spiral concentrators will use a slurry from about 20%-40% solids by weight, with a particle size somewhere between 0.75—1.5mm (17-340 mesh), though somewhat larger particle sizes are sometimes used. The spiral separator is less efficient at the particle sizes of 0.1—0.074mm however. For efficient separation, the density difference between the heavy minerals and the light minerals in the feedstock should be at least 1 g/cm; and because the separation is dependent upon size and density, spiral separators are most effective at purifying ore if its particles are of uniform size and shape. A spiral separator may process a couple tons per hour of ore, per flight, and multiple flights may be stacked in the same space as one, to improve capacity. 
  Many things can be done to improve the separation efficiency, including:
  * changing the rate of material feed
  *changing the grain size of the material
  *changing the slurry mass percentage
  *adjusting the cutter bar positions
  *running the output of one spiral separator (often, a third, intermediate, cut) through a second.
  *adding washwater inlets along the length of the spiral, to aid in separating light minerals
  *adding multiple outlets along the length, to improve the ability of the spiral to remove heavy contaminants
  *adding ridges on the sluice at an angle to the direction of flow.