Petrified wood is a type of fossil that forms when trees or wood are buried under sediment and mineral-rich water seeps in. Over time, the organic material in the wood is replaced by minerals, such as silica, calcite, or pyrite, turning it into stone while preserving the original structure of the wood. This process can take millions of years and results in beautiful, colorful patterns within the stone. Petrified wood can be found in various locations around the world, including the famous Petrified Forest National Park in Arizona, where visitors can see large deposits of this unique fossilized material.