After the sample is dried, it is ready for magnetic separation. The magnetic separation process is necessary in order to rid the sample of any metals already within the original sample. Furthermore, metals also react and destroy the heavy liquids by producing a precipitate that is difficult to filter.
- This step can either be done before or after the initial roller leaching. If there is not much sample material it is best to do magnetic separation after the initial leach. This is because the quartz grains will become detached from the host mineral during the physical and chemical abrasion of the roller leach.
- Pour the dried sample through a funnel stuck between the arms of a hand magnet before passing it through the magnetic separator. Save the magnetite grains in a sample bag. Label the bag twice with the sample name, the grain size, and the word "magnetic."
- Clean the magnetic separator with the wet/dry vacuum. Pay special attention to the loading hopper, the loaf pan trays, and the brush under the wheel. Vacuum first, and then blow out the brush and the gap between the magnet and the wheel.
- Turn on the magnet and the wheel. The magnet should have a current of about 4.0.
- The magnetic grains will come out of the two chutes on the left, while the non-magnetic grains will come out of the rightmost chute. Place two loaf pans to catch the magnetic and non-magnetic grains separately.
- Turn on the vibrating hopper. Adjust the flap between the two chutes on the bottom right so that the nonmagnetic grains go into the rightmost chute only. Use the plastic shield to prevent grains from flying out of the separator.
- Pour the magnetic grains into the sample bag. Save the nonmagnetic grains in a bag labeled with the sample name and the words, "Leached in aqua regia; nonmagnetic".