Nice thanks for that tip! My friend that I go rockhounding with has told me about the black sand but we weren't sure. We were aware that we probably had to dig, but the black sand seems to be running off from somewhere as it's usually a pretty thin layer. So seeing as to how it was on the shoreline, and the black sand was indeed wet, that explains why his metal detector went crazy. It's also a much older metal detector. I want a new one.