18 Şubat 2013 Pazartesi

Fossil Representative of South Carolina

Fossil Representative of South Carolina

Petrified Wood (common name)
Petrified wood has the form of sections of tree branches or trunks, but it is no longer made of wood. In mineral terms, petrified wood is chalcedony (kăl-sĕd-ən-ē), which is microcrystalline quartz. Over decades, a piece of wood changes to chalcedony as quartz gradually replaces 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.
Although South Carolina has not designated an official state fossil, petrified wood is representative of the state’s geology and history. Like most of the state’s fossils, it can be found on the Coastal Plain of South Carolina. Petrified wood logs are also on display at the South Carolina State Museum in Columbia.
Petrified wood is the official gemstone of the states of Washington and Arizona. Various types of petrified wood are the state fossils of North Dakota, Arizona, and Louisiana. Petrified palmwood is the state stone of Texas. Alberta, Canada, designated petrified wood its provincial stone.
The name for this fossil comes from the Greek root 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 the tree rings are not annual or 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. The Petrified Forest National Monument in Chubut Province in the Argentine Patagonia is considered to be one of the world’s best petrified reserves. One of the largest deposits of petrified wood in the United States is found in Theodore Roosevelt National Park in North Dakota. The largest in the country is probably Petrified Forest National Park in Arizona; it contains what is possibly the largest concentration in the world.
Because of its 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 Wood Cross Section
State Prehistoric Creature
Petrified Wood Sections
State Prehistoric Creature
Petrified Wood Close-up

Author: World Trade Press

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