Petrified wood is a fossil. Literally, Wood turned to Stone. It formed when tree type plant material is buried by sediment and protected from decay due to oxygen and organisms. Over time, water rich in dissolved solids flows through the sediment, replacing the original plant material with silica, calcite, pyrite, or another inorganic material. The result is a fossil of the original woody material that often exhibits preserved details of the bark, wood, and cellular structures.
Petrified Forest National Park is located near Holbrook, Arizona. About 200 million years ago, a large number of trees were buried by stream sediments and volcanic ash. Over time, silica-rich ground water petrified the wood and converted it into chalcedony and gave the chalcedony vivid colors. Arizona petrified wood is some of the most colorful in the world, with brown, red, orange, yellow, white, blue, violet, & gray colors.