Prospecting tip: Screening off larger worthless gravel is a great aid to quick clean up and panning. Classifying your material is also essential to any successful sluice box operation. Remember, reduce the size of your material to the approximate size of the gold you expect to find and increase your gold recovery rates greatly. Also clay is a sluice box robber - break up those clumps of clay in your classifier screen before panning and sluicing.