What black sand actually is, and why you should save it

Black sand concentrate is mostly magnetite along with other dense minerals that settle alongside gold during panning because they share a similarly high density. It should be saved rather than dumped, fine gold is very easy to lose inside a pile of black sand if you are not looking carefully. Once your concentrate is dry, a strong magnet passed near it, not touching it directly, will pull out most of the magnetite while leaving gold behind, since gold is not magnetic. Keep the magnet a small distance away rather than dragging it straight through the pile, this reduces the chance of dragging fine gold along with the magnetite by static attraction. What remains after the magnet pass is a much smaller amount of material that is far easier to search through with a loupe and a snuffer bottle or tweezers.