This is a 16.2" wide petrified wood round from Hampton Butte, Oregon. It's polished to a mirror like finish one one side and is a pretty unusual piece. This specimen has green around the exterior and the interior appears to be jasper replaced with very little wood detail remaining.
Comes with a rebar display stand.
Petrified wood is the name given to wood that has been turned into stone (fossilized) through the process of permineralization. All of the organic matter becomes replaced by minerals, while much of the original structure such as tree rings in retained. For this to happen the wood needs to be buried in an environment both low in oxygen (preventing decomposition) and with flowing, mineral-laden water. The coloration is due to the various minerals that are present during fossilization. For example red colors are due to iron compounds, greens due to copper, etc.