This Specimen has been sold.
4 inch Petrified Wood Slab - Madagascar
This is a large, richly colored petrified wood slab mined near Ambilobe, Madagascar. It is approximately 4x4 inches and 1/2 inch thick. It's been polished on one side.
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.