Over kill for sure! a rare earth magnet of a handy size (bought online)would do just fine and put it into a medicine bottle to keep the magnetic material off the magnet. Just shake it up-n-down to drop the material. OR just go to any mining supply shop and buy one.
Never throw away what you take a magnet to. Think of a oreo cookie with the two black halves as black sands and the center as your gold. The stronger the magnet the more gold you will capture this way. Just run through a sluice or some concentrator prior to disposal-Roses are iron loving plants-and see what gold was wedged in between. John
A good super magnet ranging from the size of a dime to quarter sized, a 3 inch X 1/8 inch bolt and a 35mm film cassette will make up a great tool for removing those magnetic sands.
Simply make a small hole in the lid of the cassette lid and run the bolt through it. Put a nut on the end of the bolt and tack it in place with some super glue and set the magnet on it. Snap the lid onto the cassette (with the magnet inside of course) and you're ready to rock n roll. Run the contraption over your cons till it's covered with the magnetic sands then pull up on the bolt to release them into your holding container.
When I'm using my magnet, I prefer to do it with about an inch of water in the pan. Draw the magnetic sand up through the water to the magnet. This washes the sands and helps to keep the gold on your pan instead of allowing it to be trapped. When finished I dry the sands and go though them again with the magnet in small amounts. Anything that is left gets run through my rod mill and then cleaned yet again. I've been able to pull out quite a bit of micron sized gold this way. Remember... It may be small, but it all adds up!