How do you mine with a pick-axe monster hunter tri

First go into Area 4. It's a cave and it's dark so you might want to get a torch from Area 1. Then either find a crack in the wall or a colorful rock on the ground next to a wall. You will then see a pick axe symbol over your head. Then either swing the nunchuk or, if you're not holding a torch, press A. You must have a pick axe in your pouch.