Petrified wood is formed over millions of years after a tree has been knocked down (often by a volcanic eruption) and then covered in mud or volcanic ash. Over time the organic materials are replaced by minerals and the tree retains its shape. These limb pieces are 1.5-2.5" in diameter and 2-3" tall. One end has been polished to a high sheen. The pictures are representative; each piece is a unique bit of the planet's history!