Minecraft wiki entry for Petrified_Oak_Slab, associated text: Petrified oak slabs make the sounds characteristic of stone.
They require a pickaxe to mine.
If broken with anything but a pickaxe, they will drop nothing.
They are not flammable.
They cannot be used as fuel in a furnace.
They have more blast resistance.
Note blocks placed on top of them produce bass drum sounds, similarly to other stone-like blocks.