Riffles and Sluice Boxes Gold Fever Prospecting
Most will have riffles, spaced evenly along the length of the sluice, usually every few inches, perpendicular to the length of the sluice. Riffles cause small barriers to the water flow which creates eddies in the water, giving the heavier material (black sand and gold) a chance to drop to the bottom, behind the riffles.