Petrified wood slice #4

Petrified Wood is a mineral and a fossil at the same time. Wood can only become petrified, when the tree is buried in an impenetrable layer, like volcanic ash or muck in a swamp. Because of the layer on top, no oxygen can reach the tree, which means it cannot decompose. When water, with quartz and other minerals dissolved in it (silicic acid), runs through the ground past the tree, it can wash away the tree’s molecules and replace them with minerals. This way the tree changes, cell by cell and molecule by molecule, in stone. That is also the reason a lot of the tree’s details like growth rings and knots are so well preserved in the ‘wood’. Of course, this takes quite a while and there are no petrified wood specimens younger than 15 million years old. Petrified Wood is almost always mainly Quartz, even though it contains metals that give the quartz its colour, but other minerals and even gold are sometimes found in the Petrified Wood.