225-MillionYear-Old Petrified Opal Tree Trunk

As groundwater flowed through, the wood absorbed silica through a process known as “capillary attraction” allowing fossilization to occur.

Wood petrifies when it sinks in soggy earth and stays there. Minerals can penetrate it through the sediment, but otherwise there is a barrier from the common causes of decay. Minerals access the wood because they are present in the groundwater in which it’s resting.