This is an incredibly well preserved slice of Fossilized Ponga / Silver Tree-Fern / Cyathea dealbata found by a "Rockhoound" in New Zealand more than half a century ago!
Sliced Ponga trunks have a very unique internal structure with many cavities, and all that has been perfectly preserved in this beautiful slice of Fossilized Ponga trunk.
Petrified wood (from the Greek root petro meaning "rock" or "stone"; literally "wood turned into stone") is the name given to a special type of fossilized remains of terrestrial vegetation.
It is the result of a tree or tree-like plants having completely transitioned to stone by the process of permineralization. All the organic materials have been replaced with minerals (mostly a silicate, such as quartz), while retaining the original structure of the stem tissue.
Unlike other types of fossils which are typically impressions or compression's, petrified wood is a three-dimensional representation of the original organic material. The petrifaction process occurs underground, when wood becomes buried under sediment and is initially preserved due to a lack of oxygen which inhibits aerobic decomposition.