Petrified wood: a few hundred million years or more ago after trees were quickly buried underground, wood partially groundwater SiO2 (silicon dioxide) exchange from the trees fossils. It retains the trees of the wood structure and texture. Color is yellowish brown, yellow, brown, reddish brown, gray, dark gray, etc., with a glass surface can be polished shiny, opaque or slightly transparent, because some petrified wood texture rendering jade texture, also known as jade tree.