Plainly Tough

Artist's commentary
Hang in There, Kogasa-san 1875
After you take a quick scoop, you rock it a bit first. That way, the comparatively heavier gold sinks below the sand, apparently. If you toss the sand out in a hurry, you'll toss the gold dust out with it, so it's pretty tricky.
What I experienced here is the Beginner-Level Course, by the way.