Imagine you are a you boy, interested in rocks and stones. You particularly love going out and finding rocks in the countryside, and then bringing them home to be cut and polished. So often the rock which looked uninteresting when you first discovered it is shown to be a fascinating and beautiful specimen, with just a little work. The one which you are most pleased by though is the petrified wood you found. When it was cut into slices and polished, it became so beautiful, and you can even see where the bark was, and the rings of the tree. Just amazing!
When I showed the children these slices of petrified wood, they were quite intrigued. They had heard of petrified wood, and seen very small samples in the past, but these slices are large enough to see the pattern of the wood, and also have remains of the bark around the wood which are intact. The children were amazed to see that petrified wood does indeed look just like a slice of wood, but hard as stone. The other thing which particularly intrigued them though was how beautiful the wood is. As one child said ‘it’s like a piece of wood, but the prettiest wood ever!’
Petrified wood is a type of fossil and is a term used to describe land vegetation like trees or tree like plants which have been preserved and transformed into stone. In fact the word petrified comes from the Greek word petro which means rock or stone – the term literally describes wood which has turned into stone. The process by which wood is petrified involves all of the organic material in the wood being replaced by mineral materials, usually silicates like quartz. The stone is stained by other minerals in the environment, like iron and copper and this is what gives petrified wood its beautiful colour ranges. In order to be petrified wood is buried and petrifaction actually happens underground. It is the underground conditions, and the lack of oxygen which they contain which allows the wood to be petrified at all. If oxygen is present decomposition can occur and the wood would not be able to be preserved at all.
It might seem that, if wood only petrifies when it is buried, only small pieces of wood are preserved, but this is not the case. In fact, whole trees can be petrified, and there are examples in Argentina which are 3 metres wide and 30 metres long! There are also examples in places like the Petrified Forest National Park in America where multiple trees were petrified after falling into water and being buried by sediments. There are even trees which have had their stumps petrified. The most amazing thing about these trees though is the detail in which they are preserved. In the petrifaction process, the original structure of the wood, including rings and bark are preserved, but the wood itself is gone, replaced by stone. Often, you can even detect the cell structure of the original tree, and so they are very important study materials for those interested in ancient plants and forests.