Sluice box

A sluice box apparatus for recovering heavy material, such as gold, the apparatus comprising:

• (a) a fine recovery channel and a coarse recovery channel, the recovery channels each having a receiving end, riffles, and matting for collecting fines of said material;
• (b) a hopper adjacent the receiving ends of the channels having a receiving end for aggregate, a wall for retaining the aggregate, a discharge end adjacent the receiving ends of the channels, a bottom, an open top, a perforated plate extending substantially across the hopper near the discharge end, the plate being spaced-apart from the bottom, a coarse material discharge opening in the wall adjacent the coarse recovery channel for a flow of water and aggregate passing over the perforated plate to the coarse recovery channel, the coarse material discharge opening being above the perforated plate when the apparatus is positioned for use, and a fine material discharge opening means in the wall between the bottom and the perforated plate and adjacent the fine recovery channel, the fine material discharge opening means allowing a flow of water and fine material passing through the perforated plate to enter the fine recovery channel;
• (c) water distributing means near the top and the discharge end of the hopper for washing fines from the aggregate;
• and
• (d) means for adjusting the fine material discharge opening means to a size which limits the flow of water to the fine recovery channel to such an extent that water recirculates upwardly through the perforated plate to aggregate on the perforated plate and washes additional fines from the aggregate.