Petrified Wood Is Almost Solid Quartz

Petrified wood looks like wood and weighs like stone, because stone is what it has become. The U.S. National Park Service states that the petrified wood found in Petrified Forest National Park and the surrounding region is made up of almost solid quartz. Its rainbow of colors is produced by impurities in the quartz, such as iron, carbon and manganese. The process began over 200 million years ago. Logs washed into an ancient river system and were buried quickly and deeply enough by sediment that oxygen was cut off and decay slowed. Minerals, including silica dissolved from volcanic ash, soaked into the porous wood and crystallized within it, replacing the organic material as it broke down. The logs look sawn into sections today. The Park Service explains that the brittle quartz fractured cleanly under stress as the land was uplifted.