dark grey hot rocks?

[mlamp20412]

I believe I have pretty mineralized soil. I get a fair amount of false signals. I would dig an nothing is there. Now I have a pinpointer and I am finding blackish gray rocks about thumbnail size more or less, light weight with nothing different in the core when crushed. Kinda like coal bit not quite as dark and harder. Strange thing is once I dig them up, the detector is not picking the up, only the pinpointer will. The signal in the hole is gone too.

Any ideas on what this is? Extremely deteriorated iron with haloing giving of false signals????

Thanks!

[mlamp20412]

boobieinPa,

I may have to try the magnet out. Good idea.

Thanks