How Does Wood Become Petrified?
In order for the petrified wood you see here to become petrified, the wood must first be covered with such agents as volcanic ash, volcanic mud flows, sediments in lakes and swamps or material washed in by violent floods – by any means which would exclude oxygen and thus prevent decay. A number of mineral substances (such as calcite, pyrite, marcasite) can cause wood to petrify, but by far the most common is silica. Solutions of silica dissolved in ground water infiltrate the buried wood and through a complex chemical process are precipitated and left in the individual plant cells. Here the silica may take a variety of forms; it may be agate, jasper, chalcedony or opal. The beautiful and varied colors of fossil wood are caused by the presence of other minerals that enter the wood in solution with the silica. Iron oxides stain the wood orange, rust, red or yellow. Manganese oxides produce blues, blacks or purple.
