There are rings in the game that give you buffs, often in sets. The Ring of Rock gives +13 armor, the Ring of Stone gives +14 mining damage, and the set bonus gives +49 mining damage. I had seen that there would be a pair earlier, but i finally got the set and acheivement yesterday.
That's it, lad!
ROCK AND STONE, TO THE BONE!!
DID I HEAR A ROCK AND STONE?
Rock... And... Stone!