Cleon
Legend
Updated.
How's this for the cave-in/collapse ability?
Collapse Mine (Su): As a standard(?) action, a miner genie can cause a cave-in or collapse by merely touching a cavern wall. This cave-in or collapse has a 20-foot radius, with a 30-foot-radius slide zone. The save and check DCs are Strength-based (DC 19 for a typical miner genie).
I'd rather keep the original restriction to mines the genie has made itself, e.g.:
Collapse Mine (Su): As a standard action, a miner genie can strike the wall of ceiling of any excavation that was constructed or repaired by a miner genie, causing it to cave in or collapse. This cave-in or collapse has a 20-foot radius, with a 30-foot-radius slide zone. The save and check DCs are Strength-based (DC 19 for a typical miner genie).