Prospecting bugged...?

[sabinati]

Yeah, I've seen the same problem as the OP.

I also got "There appears to be copper below you" while in a cave, which means either mines and caves aren't in the same layer or it's using the wrong message .

there is in fact copper below you, which means that there is a layer under the cave/mine layer (if indeed caves and surface mines are on the same layer)

[Haba]

So... now I found a cave that is in the black space... I sure hope that... a) mine floor is buildable and that b) tin, copper and iron mines don't spawn in the black space...