Miner #1 asks: What length should a sluice box be?
I understand the width vs. flow issues but not about the length.
Is there a ratio of width to length?
If a 4 foot is good then an 8 foot is better? At what point is a sluice box too long?
Miner #2 comments: Keep in mind the faster the water flows over your system the more loss of small gold. Think of a leaf in the wind, the faster the wind the further the leaf will travel.
Miner #4 comments: I read a widely published in the 1930s account of working placer gold and shoveling in to a sluice box by a mine engineer. The box was one ft wide and one foot deep running nearly full of water. He claimed 98% of all his gold was within two feet of where he shoveled in, his box was 8 ft long and he claimed that longer would likely have saved more of the flower size particles but only if a screen classier was incorporated further down the box, the point is that for the most part it comes down to the fineness of the gold that you are after. He was shoveling in bank run material with no preclassification and yet 98% of his gold was saved in the first two feet of box.
Obviously the question comes down to one of gold particle size. The finer the gold the more preclassifying is necessary along with wider box and carpet or burlap to replace riffles.
Only riffles being needed for the course gold along with more water and greater water velocity to keep the gravel from clogging up the box, the course gold quickly finds the bottom and is trapped in the riffles.
Miner #5 comments: A longer sluice will keep the gold longer, the hydralic miners of old had 100 yard sluices called long toms which they cleaned out weekly, they still blew most of the fines through because it wasn't classified material. Maybe the first sluice runs 1 inch minus material which dumps into a second sluice covered with 1/4 inch or 1/8 inch perforated sheet suspended 1/2 inch over the rifles, Rocks just slide right over perforated sheet (punch plate). You might want to check out Keene engineering, they've got this new black rubber rifled matting to catch the fine stuff ( $8 per 1x30inch strip). I bought a 10 inch wide strip to do the exact same thing (as above), I hav'nt put it together yet but I'm hoping it works on lake Superior black sand.Anyway running the finer material through a second sluice ( or train of sluices) would be the only reason to go longer than 4 feet on a 10 to 12inch wide sluice. Good luck, Bill
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