The Ore Smasher smashes ores. It is only useful with Ex Nihilo Omnia installed, and is disabled for Ex Nihilo Adscensio.
Right-clicking with an Ore Smasher will place Ore Gravel or Ore Sand from your inventory to where you're pointing. If you have none of these in your inventory, it will attempt to automatically craft them from Broken or Crushed Ores in your inventory.
The Ore Smasher is as fast as a Diamond Hammer when smashing blocks, but is limited to ore blocks. Other hammerable blocks (such as cobblestone) can not be broken with this.