What is Petrified Wood?

Petrified Wood (from the Latin root Petro meaning 'rock' or 'stone'; literally 'wood turned into stone') is the name given to a special type of fossilized remains of terrestrial vegetation. Petrifaction is the result of a tree or tree-like plants having been replaced by stone via a mineralization process that often includes permineralization and replacement. The organic materials making up cell walls have been replicated with minerals (mostly silicane the form of opal, chalcedony, or quartz). In some instances, the original structure of the stem tissue may be partially retained. Unlike other plant fossils, which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material. 

The petrifaction process occurs underground, when wood becomes buried in water-saturated sediment or volcanic ash. The presence of water reduces the availability of oxygen which inhibits aerobic decomposition by bacteria and fungi. Mineral-laden water flowing through the sediments may lead to permineralization, which occurs when minerals precipitate out of solution filling the interiors of cells and other empty spaces. During replacement, the plant's cell walls act as a template for mineralization. There needs to be a balance between the decay of cellulose and lignin and mineral templating for cellular detail to be preserved with fidelity. Most of the organic matter often decomposes, however some of the lignin may remain. Silica in the form of opal-A, can encrust and permeate wood relatively quickly in hot spring environments. However, petrified wood is most commonly associated with trees that were buried in fine grained sediments of deltas and floodplains or volcanic lahars and ash beds.

Permineralization

Is a process of fossilization in which mineral deposits form internal casts of organisms. Carried by water, these minerals fill the spaces within organic tissue. Because of the nature of the casts, permineralization is particularly useful in studies of the internal structures of organisms, usually of plants. Process of permineralization, a type of fossilization, involves deposits of minerals within the cells of organisms. Water from the ground, lakes, or oceans seeps into the pores of organic tissue and forms a crystal cast with deposited minerals. Crystals begin to form in the porous cell walls. This process continues on the inner surface of the walls until the central cavity of the cell, the lumen, is completely filled. The cell walls themselves remain intact surrounding the crystals.

Silification

In silicification, the weathering of rocks releases silicate minerals and the silica makes its way into a body of still water. Eventually, the mineral-laden water permeates the pores and cells of some dead organism, where it becomes a gel. Over time, the gel will dehydrate, forming an opaline crystal structure that is an internal cast of the organism. This accounts for the detail found in permineralization. Silicification reveals information about what type of environment the organism was likely to have lived in. Most fossils that have been silicified are bacteria, algae, and other plant life. Silicification is the most common type of permineralization. 

Petrified wood forms when woody stems of plants are buried in wet sediments saturated with dissolved minerals. The lack of oxygen slows decay of the wood, allowing minerals to replace cell walls and to fill void spaces in the wood.