Finally getting to a place where the rules my mud dynamically invents mostly make sense!
rules for mine:
takes: direct (touchable), instrument (carried, optional)
means: get from the earth by excavation
check:
any tunnel it must not already be mined out
everywhere it must not already be depleted
everywhere you must be able to reach what you act on
everywhere you must be able to act
carry out:
any tunnel extract ore from the tunnel walls
any crawlspace mine the rubble for valuable materials
everywhere the source becomes depleted of its materials