Petrified Wood is a fossil. It forms when plant material is buried by sediment and protected from decay by oxygen and organisms. Then, groundwater rich in dissolved solids flows through the sediment replacing the original plant material with silica, calcite, pyrite or another inorganic material such as opal. Some specimens of petrified wood are such accurate preservation that people do not realize they are fossils until they pick them up and are shocked by their weight. These specimens with near perfect preservation are unusual; however, specimens that exhibit clearly recognizable bark and woody structures are very common. This petrified wood is from Utah and Arizona.