Ninjawa said:
How about an errata or house rule that said something along the lines of "this ability can only be used if there is an underground, dark or mountain location in play." That way it fits better flavour-wise and the resource gain is a bonus rather than a guarantee. It would also mean that future quests would only have to account for the miner's effect if they had these locations.
I like that a lot. Makes perfect sense, thematically.