Petrified wood is wood that has turned into stone. It is a type of fossil where all the organic materials have been replaced with minerals mostly a silicate, such as quartz, while retaining the original structure of the wood. The petrifaction process occurs underground, when wood becomes buried under sediment and is initially preserved due to a lack of oxygen. Mineral-rich water flowing through the sediment deposits minerals in the plant's cells and as the plant's lignin and cellulose decay away, a stone mould forms in its place. Elements such as manganese, iron and copper in the water/mud during the petrifaction process give petrified wood a variety of color ranges. Pure quartz crystals are colorless, but when contaminants are added to the process the crystals take on a yellow, red, or other tints.
Petrified wood can preserve the original structure of the wood in all its detail, down to the microscopic level. Structures such as tree rings and the various tissues are often observed features. Petrified wood has a Mohs hardness of 7, the same as quartz and can be polished to a high shine as granite. Petrified wood can be use for decorative and functional uses, such as sinks