1.4. Sifting and Magnetic Plunging

Note

To avoid leaving your sample out, this procedure should be immediately followed by Frantz magnetic separation.

1.4.1. Video tutorial

1.4.2. Steps

  1. Grab the 250μm sieve, the small wire brush, and the metal pick. Using the tools, clean the sieve so that NO grains are visible. Use compressed air to ensure all dust is off of the sieve.

  2. Make a tray or “boat” out of foil, large enough for the sieve to fit inside, and allow room for back-and-forth shaking of the sieve.

  3. Pour your sample — which should still be in the “heavy” foil tray from the water table— into the sieve. Shake and tap the sieve until you are satisfied that the sample has been thoroughly separated. Store the >250μm portion of the sample in a whirl-pack labeled with your sample name, and “Heavy >250μm”.

  4. The sample in the tray is now all <250μm. Wrap the gold magnet in a whirl-pack and pull the pack flush against the flat side of the magnet.

  5. Press the plunger in the magnet, and slowly waive the magnet a few millimeters above your sample. Once you have gathered a significant amount of material on the magnet, drop this material away from your main pile, and then pick it up again with the magnet. Repeat this pick up and drop step 3 times in different areas, or until you see very little sample left behind when you pick it up again. This will free non-magnetic grains that are being pulled up with the iron filings. Discard the magnetic material in the “Heavy” water table tray that is no longer being used.

  6. Repeat step 5 until you are satisfied that there is very little to no magnetic material being picked up by the gold magnet. You may move the sample around with the magnet gently, but be careful not to tear the foil.

  7. Leave the sample in the tray to await Frantz magnetic separation.

  8. Thoroughly clean the sieve in the same method as step 1 until there are no remaining grains.

  9. High-five yourself.