It's me again.... I'm deleting the other design until I can get around to working on it, but until then, here's a faster way to collect those filings (especially if you have stronger magnets then I).
1. Metal chute (I used a lighting fixture part)
2. Strong magnet(s) (I technically had three, but they weren't strong enough alone)
Step 1: A picture is worth....
1. Take your metal chute and place the magnet(s) on the underside.
2. Put your ramp on an angle and pour a handful of dirt (gravel) down it.
3. Using the magnet, shake off the excess dirt.
4. Place the end of the chute over your container and remove the magnet(s). Brush any of the remaining filings off into the container with you other hand.
5. Follow the other steps (grinding and seperating) found in the original mining instructable: http://www.instructables.com/id/EGPTPN17FFES1764M3/
(except instead of using a plastic bag, use a small cupcake paper lining to seperate the filings)
Design improvement idea: Use a magnetic sweeper as the main magnet on the underside of the chute.