I am a gold prospector. Gold will not coat mercury. Mercury coats gold. Gold is attracted to mercury like a magnet, sort of, in that if mercury comes in contact with gold, the mercury will coat the gold. If to much gold is in the mercury it will look dull, kind of like lead. This is why prospectors throw nithing out that is in their pan. It is common in a lot of rivers where gold is found. In the pan it looks like a silver flake.