The hammer can be used to break cobblestone into gravel, gravel into sand, stone bricks into cracked stone bricks, and sandstone into sand. Crafting it is very simple, you just need two sticks and two stones/iron/gold/diamonds. Craft like so:

 

• You can use the hammers in the Miner to automatically hammer blocks.
• Using iron, gold, or diamonds instead of stone will increase the durability of the hammer, but the speed will only increase for cobblestone, stone bricks, and sandstone when used by hand.