Petrified wood
From Wikipedia, the free encyclopedia
Petrified wood is a type of fossil: it consists of fossil wood where all the organic materials have been replaced with minerals (most often a silicate, such as quartz), while retaining the original structure of the wood. The petrifaction process occurs underground, when wood becomes buried under sediment. 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 mold forms in its place. The wood is preserved due to a lack of oxygen.
Elements such as manganese, iron and copper in the water/mud during the petrification 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 tint.
Following is a list of contaminating elements and related color hues:
- carbon - black
- cobalt - green/blue
- chromium - green/blue
- copper - green/blue
- iron oxides - red, brown, yellow
- manganese - pink/orange
- manganese oxides - black
Petrified wood can preserve the original structure of the wood in all its detail, down to the microsopic 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.
Petrified wood is also the state gem of Washington.
Contents |
[edit] Locations
- Argentina - Considered to be one of the world's best petrified reserves, the Petrified Forest National Monument in Santa Cruz in the Argentine Patagonia has many trees that measure more than 3 m (10 ft) in diameter and 30 m (100 ft) long. Compared to petrified trees in the United States that measure less than 1.8 m (6 ft) in diameter, the trees of the Central Steppes of Argentina are significantly larger.
- Canada - In the badlands of southern Alberta; petrified wood is the provincial stone of Alberta. Axel Heiberg Island in Nunavut has among the largest petrified forests in the world
- Czech Republic, Nová Paka - The most famous locality on Permian-Carboniferous rocks in the Czech Republic.
- Greece - Petrified Forest of Lesvos, at the western tip of the island of Lesbos, is possibly the largest of the petrified forests, covering an area of over 150 km² and declared a National Monument in 1985. Large, upright trunks complete with root systems can be found, as well as trunks up to 22 m in length.
- United States - A famous petrified wood site is Petrified Forest National Park in Arizona. Wood from the area (though not from the park) is a prized commercial item, particularly cut and polished samples.
- Australia - Has vast deposits of petrified and opalised wood.
- India - A geological site famous for its petrified woods Thiruvakkarai Village in Chennai, Tamil Nadu. The site is protected by the Geological Survey of India. Petrified woods covers a large area in this site.
- New Zealand - Curio Bay along the Catlins Coast contains many petrified wood examples.
[edit] Artificial petrified wood
Artificial petrified wood has been produced in a Washington lab. In the process small cubes of pine were soaked in an acid bath for two days then in a silica solution for another two. The product was then cooked at 1400 °C in an argon atmosphere for two hours. The result was silicon carbide ceramic which preserved the intricate cell structure of the wood. Soaking in a tungsten solution produced a tungsten carbide petrified wood. [1][2]
[edit] See also
[edit] References
- ^ Petrified Wood in Days, Physorg.com, January 25, 2005 http://www.physorg.com/news2801.html
- ^ Presto! Instant Petrified Wood Created in Lab, Live Science, 27 January 2005 http://www.livescience.com/technology/050127_petrified_wood.html
[edit] External links
