14 Mart 2013 Perşembe

Louisiana State Fossil

Louisiana State Fossil

Petrified Palmwood (common name)
(scientific name)
Petrified palmwood is a silicified wood from an extinct genus of palm tree. The genus Palmoxylon contains over 200 species. These fossils date from the late Cretaceous epoch to the Oligocene epoch, approximately 25 to 85 million years ago. They have been found along the United States Gulf Coast, in the Patagonia region of southern South America, and in Egypt.
In mineral terms, petrified wood is chalcedony, which is microcrystalline quartz. The quartz has replaced all the organic material of the wood. Quartz crystals are colorless, but the elements manganese, copper, chromium, cobalt, carbon, and iron give petrified wood its color. The variety of colors includes red, orange, yellow, green, blue, pink, and black. Petrified logs tend to look as if they were cleanly cut because the physical characteristics of cylindrical quartz cause them to break cleanly when stressed.
Palmoxylon was discovered in the Toledo Bend area of Louisiana and Texas and in several parishes in Louisiana. The petrified palmwood found in Louisiana is from the Oligocene epoch, approximately 30 million years ago, when the northern part of the state was covered with forests and swamps. Palmoxylon was designated the official state fossil of Louisiana on July 31, 1976.
Petrified palmwood is also the state stone of Texas. Petrified wood is the official gemstone of the state of Washington. Various types of petrified wood are the state fossils of North Dakota, Arizona, and Louisiana.  Alberta, Canada, designated petrified wood its provincial stone.
The word "petrified" comes from the Greek root πέτρα (petro)meaning "rock" or "stone"; petrified literally means "turned into stone."
Wood becomes petrified when it is buried underground in sediment by volcanoes, mudslides, or other natural disasters. As groundwater passes through the sediment, minerals such as silica, dissolved from volcanic ash, are deposited in the wood. As the plant’s lignin and cellulose decay away, the silica hardens into quartz crystals. Petrifaction often maintains the structure of the wood. This may include tissues and tree rings, although they are not annual tree rings based on seasons and therefore cannot be used to determine the tree’s age. The process of petrifaction usually takes less than 100 years.
Petrified forests are widespread. Petrified Forest National Park in Arizona is the largest in the country and contains what may be the largest concentration of petrified wood in the world. Another very large U.S. deposit of petrified wood is found in Theodore Roosevelt National Park in North Dakota. The Petrified Forest National Monument in Chubut Province, Argentine Patagonia, is another of the world’s best petrified reserves. 
Because of chalcedony's abundance, durability, and beauty, early humans made weapons and tools from many varieties of chalcedony including agate, agatized coral, flint, jasper, and petrified wood. The earliest recorded use of chalcedony was for projectile points, knives, tools, and containers such as cups and bowls.
Petrified wood material is suitable for tumble polishing for use in baroque jewelry or for cutting into cabochons for jewelry and display. Freeform and calibrated slabs are polished for pen and pencil set bases and bases of other items, and polished slabs are used for clock faces. Additionally, large blocks, limb sections, and geometric shapes are used as bookends and decorator pieces. Objects of art, principally carvings, are produced, and furniture such as coffee tables and end tables are made from petrified wood.
Scientists at a laboratory in Washington state created artificial petrified wood by soaking pine in silica and tungsten solutions.

Click to enlarge an image
State Prehistoric Creature
Petrified Palmwood

Author: World Trade Press

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