Petrified wood is a fossil in 3-D. I don't usually think about it that way. Many of the fossils we find are the molds or imprints left by animals or plants. Petrified wood like petrified bones has everything down to the cell structure replaced by minerals. In the example shown, carbon has replaced the wood so it has a brown color. If the mineral was cobalt the petrified wood would be green/blue or if the mineral was manganese the color would be pink/orange. A laboratory in Washington made artificial petrified wood by taking pine, soaking it in an acid bath for 2 days, then in a silica solution for 2 days, then cooked it at 1400 degrees C in an argon atmosphere for 2 hours. Interesting but is it really worth it?