Petrified Wood: A Rock or a Fossil?

Petrified Wood: A Rock or a Fossil?
Petrified wood or Permineralized rocks are literally ‘wood turned into stone’. In other words, mineralized wood. They are the remains of terrestrial vegetation, trees or tree-like plants that are replaced by stones or quartz crystals through a process called permineralization and replacement. The Petrified wood is a rock and a fossil. They are made up of almost solid quartz, giant crystals with varying colors which are products of impurities in the quartz such as carbon, manganese and iron.

They are fossils because they are remains of terrestrial vegetation that are preserved as rocks.


In most instances, the original outlook of the tree and its stem tissue may either completely or partially preserve. In petrified woods the three-dimensional outlook of the plants is usually retained. Unlike other plant fossils which may have undergone several degradations, decay and only have its impressions and compressions retained.


The Petrification process occur when the wood or its stem gets buried in a water saturated sediment or an anaerobic environment. The water saturation reduces the availability of oxygen which reduces the aerobic decaying or decomposition of the wood. The mineral rich water flowing through the sediment then leads to the precipitation of crystals out of solution which fills the interiors of cells and other spaces within the wood. This process is referred to as permineralization. The petrified wood is usually associated with woods that are buried in fine grained sediments of floodplains, deltas and ash beds.


Arizona has one of the largest deposits of petrified woods on Earth (Petrified Forest National Park – Northeastern Arizona). Other places where there are petrified woods are, Egypt, New Zealand, Argentina, Namibia, Canada and more.