Anvil

An Anvil is an upcoming block that is expected to be in 1.4. It will be used for the new item repair interface. When placed above air it will fall. It will also inflict 6 hearts damage when dropped on players or mobs. If it lands on a transparent block (like torches, rails, etc.), it will destroy it instead of dropping itself as an item like sand and gravel do. Also, it will sink to the bottom of water.

Anvils require a pickaxe to be destroyed.