Specimen of the Month: Petrified Wood

 By Summer Naturalist Intern and guest contributor, Elliot Witscher.

I recently put together a box of rocks for a kids program provided by the Museum. One of these geological specimens was a piece of petrified wood, and immediately, one of the kids picked it up and exclaimed, "WOW! This looks just like a tree but it's so heavy!"

This kid immediately picked up on one of the most interesting characteristics of petrified wood: the fact that it retains the texture and appearance of the wood it comes from, while also being made entirely of silica (the mineral that makes up most rocks). 

Look closely to notice the rainbow of colors found in this piece of petrified wood. These colors are a result of chemical impurities like iron, carbon, and manganese. The structure of the wood, such as the pattern of the bark and the tree rings visible on the cut end, is exquisitely preserved. This is because the original plant material was quickly buried under a thick layer of ash or other sediment, slowing the process of decay. After the wood is buried, mineral-rich water seeps into the cells, replacing the organic material with rock. 

Most fossils are impressions or prints of an animal or plant, meaning they don't retain the details of the inside of the organism. Petrified wood is unique because it retains all of the structures of the original material - creating a seemingly permanent sample of a tree who grew long ago.