Kreeger Riffle Technology
US Patent Number 9586211

Note: An undisturbed flow of slurry contains three distinct layers. The bottom layer contains most of the heaviest material like gold and black sand. The middle layer contains most of the slightly lighter materials like gravels and sands. The top layer contains most of the lightest materials like silt and blonde sands.

The first component of this riffle is the drop (1). The heavy bottom layer is free to deposit itself here while most of the lighter materials pass by.

The second component is the shear wall (2). This pushes back against the flow, causing a powerful vortex that purges black sand quickly from the drop. It is also a physical escape barrier to gold that is in
the drop.

The third component is the down ramp (3). This receives the processed slurry that has been heaved over the shear wall. At the top of the down ramp, all three layers of flow are thoughrouly mixed together. The slurry gains considerable acceleration as it begins to travel down the ramp. This acceleration reconstitutes the flow to its original three layered condition. It is now ready for processing in the next drop, at the next riffle. This ability to restore the flow to an optimal state is a unique advantage exclusive to the Kreeger Riffle System. The most important effect in this system is that solid materials actually increase in velocity as they are pulled through this sluice. That keeps this sluice constantly at the ready to accept and process more materials.