How to Build a Magnetic Sluice
Build a magnetic sluice to separate out the black iron when prospecting for gold. Save your back by removing the iron at the site and returning it to the same location where you extracted it. Carry the same amount of gold out with you with less effort. A magnetic sluice can separate the gold by trapping it in different ridges as the larger sediment rolls over the top of the ridges.
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Things You'll Need
- Plywood sheet
- Hand saw
- 1-inch wood screws
- Drill with bit the same diameter as the screw shafts (not the thread diameter)
- Waterproof wood glue
- 1 by 4-foot piece of artificial turf
- 1 by 2-foot long, 3/4-inch raised expanded metal
- 1-foot square, 1/2-inch expanded metal
- 1-foot square, 3/16-inch layer
- 6 2-inch thick by 1-inch wide by 3/4-inch thick neodymium magnet (rare earth), grade N50
- PVC pipe, 1 foot long and 1-inch internal diameter
- Pump, siphon or bucket to get the sample into the trough
Instructions
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1
Cut four pieces of plywood using a hand saw. Cut the first piece to be 1 by 4 feet to make the base of the sluice. Cut two side walls 5 inches wide and 4 feet long. Cut the end board to attach a 13 1/2-inch wide by a 5-inch tall board.
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2
Make the sluice frame from the plywood. Pre-drill pilot holes for screws to hold the sidewalls to the base at a 90-degree angle. Glue the side walls onto the base using waterproof wood glue. Screw the side walls on with galvanized screws every 5 inches. Do the same thing to attach the 1-foot by 5-inch piece of plywood to the back. Add a bead of the waterproof wood glue in the corners where the wood boards meet to seal the sluice to keep it from leaking.
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3
Lay down a layer of artificial turf that is cut to fit the base of the sluice. Cut the artificial turf 1 foot wide and 4 feet long. Lay the artificial turf in the trough with the flat side down.
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Lay a 3/4-inch layer of raised expanded metal at the head of the trough (by the end board). Cut the expanded metal 1 foot wide and 2 feet long. Use wood screws every 6 inches, starting around the edges to hold the expanded metal to the trough. Screwing through the artificial turf and screw heads hold the trough down.
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Cut a 1/2-inch layer of raised expanded metal at the end of the previously laid layer of expanded metal. Cut the 1/2-inch expanded metal 1 foot wide and 1 foot long. Screw the artificial turf onto the trough as you did with the previously expanded metal.
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Cut a 3/16-inch layer of raised expanded metal. Make this layer of expanded metal 1 foot wide and 1 foot long. Add this to the artificial turf and lay it at the end of the 1/2-inch layer. Screw this layer down to the trough.
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Now add the magnetic part to your sluice. Get a 2-inch thick by a 1-inch wide by 3/4 inches thick neodymium magnet (rare earth) that is grade N50. This magnet can lift 142 pounds. Get six of these magnets and slide them into a 1-inch internal diameter PVC pipe. The PVC pipe should be 1 foot long. Slip the pipe into the tough at the head of the trough on top of the expanded metal so that the PVC pipe touches the metal. Use four screws through the side walls that go into the open pipe ends to hold the pipe in place, estimating the location and confirming it by sliding the pipe over the pre-drilled pilot holes.
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When pumping, siphoning or pouring the sample with a bucket into the sluice box at the head of the trough, let the sample run over the magnet. The iron will be held by the magnet and will also collect at the head of the sluice box where the magnetic field is going through the metal.
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Tips & Warnings
The screws in the bottom of the trough are used like cleats to hold the sluice onto the ground. If you prefer not to use the screws as cleats, use 3/4-inch long screws instead to screw the screens to the sluice box.
Make sure that the screws at the bottom of the trough do not poke or scratch you. Do not use the sluice in a location where it would violate mineral rights, local laws, state law, or federal law. Wear goggles. Read all safety and operation instructions that come with the equipment that you use. Be careful with neodymium magnets not to get the magnets close to anything that is magnetically sensitive. Do not allow the magnets to pinch any body parts. Use caution with these and all magnets. Other heavy metals may be collected along with gold which may be toxic.
