I can't speak for all of history but at least in the US West gold panning was used to locate rich ore veins upstream. The idea is that you pan for gold, steadi

I can't speak for all of history but at least in the US West gold panning was used to locate rich ore veins upstream. The idea is that you pan for gold, steadily moving up the stream until the relative amount of gold flakes drops, meaning you've gone just a bit too far and you probably now have a great idea of where a lot of gold is.