Depends what they are made of, how they are oriented in the ground, size, shape, and other variables. The best bet is to do an air test and then do a ground test. After you figure out those numbers, still dig everything when possible. One man's penny signal is another man's gold ring.
Yeah, there were dozens of them in the neighborhood and they were getting in the house. Once they get in the house, there is only one option, kill them. They will keep chewing holes in the house until they are dead if you try to fix the holes before removing them.
The first time I was in FL on the ocean and I was hitting crummy signals, I heard Kurt's voice in my head. "Dig it all".
That 1st trip I came home with 2 rings from a confirmed shipwreck from the 1700's.
If there was any chance of there being a deposit that rich the rich mining companies would have already bribed their way into closing off the entire area and they would find it and mine every gram out before leaving the public to reclaim it.