Mining is the gateway to some pretty valuable resource extraction procedures: you'll be using a Pick to produce Chunks of Ore from special rocks scattered around the world. Though mining is hard work, the rewards are worth it.
Mining II increases the chance of special rewards and reduces the amount of energy you use to extract ore. Sweet.
Mining III reduces energy it takes to mine, reduces wear on your preferred mining instrument, and rewards more imagination.
Mining IV further improves your luck and doubles the imagination you get by mining.