Petrified wood is the name given to a special type of fossilized remains of terrestrial vegetation. It is the result of a tree having turned completely into stone by the process of permineralization. All the organic materials have been replaced with minerals (mostly a silicate, such as quartz), while retaining the original structure of the wood. Unlike other types of fossils which are typically impressions or compression, petrified wood is a three dimensional representation of the original organic material. The petrifaction process occurs underground, when wood becomes buried under sediment and is initially preserved due to a lack of oxygen which inhibits aerobic decomposition. Mineral-laden water flowing through the sediment deposits minerals in the plant's cells and as the plant's lignin and cellulosedecay, a stone mould forms in its place.
In general, wood takes less than 100 years to petrify. The organic matter needs to become petrified before it decomposes completely.( From Wikipedia)
