The wood is a normal brown log of an unidentified tree.
The firewood is exclusive to Rock Island. To get it you must first toggle on the campfire icon. This will make three pieces of firewood and a dirt circle surrounded by rocks appear. If a Pygmy is near a piece of firewood, it will pick it up, walk over to the dirt circle and drop it in. Once all three pieces are in the dirt circle, you can strike it with lightning to create a campfire. Also, the firewood can be picked up, where it can be dropped back into the water. It is also affected by gravity and can be picked up by the hurricane power.