How can wood become a stone that still looks like wood?

A petrified log may preserve rings and even tiny cell details, yet much of it is mineral. Groundwater moving through buried wood can carry dissolved substances, including silica. Under suitable chemical conditions, minerals form inside the wood’s small spaces.

Filling natural pores with mineral is called permineralization. Imagine a wood cell wall surrounding a space: mineral can occupy that space while the original wall remains. The original structure helps give the deposit its shape. Infilling is therefore different from simply coating the outside of a log.

Replacement is another process. As original material is lost, mineral takes its place. It can retain fine structural detail when these changes occur in a way that preserves the pattern. Infilling and replacement can happen together in the same log; they are not two steps that every specimen must complete in order.

Silica is important in many petrified woods, including those at Petrified Forest National Park. Other minerals can contribute color. Preservation depends on conditions, and wood can decay instead. The extraordinary result is a record of a living structure carried into a different material, rather than a tree merely painted with stone.