Petrified wood is a type of fossil, but some claim to have seen wooden fence posts that have already become petrified. Is it scientifically possible for wood to fossilise in such a short period? We ask how petrified wood is formed, and what exactly does it consist of? Plus, you may instinctively be able to count three items in a pile, but how many items before you have to stop and count? Like this podcast? Please help us by supporting the Naked Scientists