The recovery may be improved by laying 1/4 inch screen on top of at least part of the matting. The addition of a few drops of a surfactant (like Jet-Dry, a dishwasher rinse agent) to the recirculating water should help keep the little guys from floating through on the surface tension. These things work best if the material is classified through a 20 mesh screen. Window screen would work. It's pretty easy to pan the stuff that won't go through the screen. Also, the material should not be dry.

Mini-Sluice
Bob Oswin in Edmonton, Alberta contributed this drawing and the associated text file. It requires bending an aluminum trough which you can have done by a sheet metal shop or you can try to do it yourself. See the instructions for the mini-highbanker plans for suggestions on bending aluminum. This design should work better than the rain gutter design below because the bottom is flatter and wider. I also like the hopper and spray bar.

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Rain gutter sluice for black sand

This sluice is simply a piece of PVC rain gutter with ribbed rubber floor matting contact cemented in. What ever contact cement you use, test it on a small piece of your rain gutter before you you glue in the matting. I used 3M77 contact cement but it has been reformulated since I used it. The matting is three feet long so the gutter needs to be about 6 inches longer. There is a hose attachment with a 1/2 inch PVC gate valve to control the water flow. The valve is cemented to an end cap which should be availble where you bought the gutter. Mine is pretty flinsy though. Also, I made an aluminum water spreader to keep the water from just squirting out of the inlet. You could use a "tee" with 3/8 inch holes drilled in the bottom so the water squirts down. If anyone has any trouble figuring out how to build this thing, let me know and I will draw up a sketch to make it all clearer. I use a 500 gallon per hour submersible 12V pump. Use a 120V pump at your own risk.

For any recirculating water system used at home, I use a large tub with a 5 gallon bucket and the submersible pump in the tub. This way, the black sand stays in the bucket and doesn't get into the pump (not a good thing). I fill the bucket and let it overflow into the tub until the pump is submerged enough to do its job. Cut a notch or hole in the bucket so it doesn't completely fill up which could interfere the tailings coming off the sluice.

Set up the sluice with the top about 4 inches above the bottom to start. Drop a tablespoon of screened (minus 12 mesh) concentrates at the top of the matting. Let the material clear out from the top area of the sluice before adding more. If you see gold below a few inches down, you need to reduce the angle of the sluice and/or the water flow. If the material doesn't seem to be moving through, increase the angle and/or the flow.

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