19 Mart 2013 Salı

Texas State Stone

Texas State Stone

Petrified Palmwood

Petrified wood is a type of fossilized wood in which all the organic material has been replaced by minerals, usually quartz. This makes it technically a fossil instead of a stone. Quartz crystals are colorless, but the elements manganese, copper, chromium, cobalt, carbon, and iron give petrified wood its color. Petrified logs tend to look like they were cleanly cut because the physical characteristics of cylindrical quartz cause it to break cleanly when stressed.
Petrified palmwood comes from an extinct genus of palm calledpalmoxylon. The suffix -oxylon means that the ancient palms resembled modern palms in structure, although the two may not be closely related. Rod-like structures within the wood give the fossil its spotted or lined appearance, depending upon the lapidary techniques used and the angle at which they are cut.
Some of the best agate, jasper, chert, and petrified wood (particularly petrified palmwood) found in the nation comes from Texas. Fine-quality palmwood comes from Live Oak and Webb counties. In 1969, Texas designated petrified palmwood its official state stone.
Petrified wood is the state gemstone of Washington and the state fossil of Louisiana. The state fossil of North Dakota is Teredo petrified wood. Alberta, Canada, designated petrified wood its provincial stone.
The Greek root petra or πέτρα means "rock" or "stone," or literally, "wood turned into stone." The fossil is the petrified wood of ancient palm trees.
Wood becomes petrified when it is buried underground in sediment by volcanoes, mudslides, or other natural disasters. Minerals from groundwater replace the organic material that once existed in the wood. As the plant's lignin and cellulose decay away, the minerals harden. Because this process is done cell by cell, the resulting fossil is a copy of the original, maintaining characteristics such as tree rings.
Fossilized coral, sponges, and mollusks have been found near petrified palmwood localities. This suggests that the ancient palms grew near tropical, prehistoric seas. 
Petrified palmwood from the Miocene and Oligocene periods, approximately 20 to 35 million years ago, occurs in west Texas, eastern Louisiana, and parts of Mississippi. It is most abundant in a band along the Gulf Coast, up to 100 miles inland.
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 is possibly the largest concentration in the world.
  • Argentina: Petrified Forest National Monument in Chubut Province, Patagonia
  • Australia
  • Belgium: Geosite Goudberg near Hoegaarden
  • Brazil: Paleorrota Geopark
  • Canada: Badlands of southern Alberta; Axel Heiberg Island in Nunavut
  • Czech Republic: Nová Paka
  • Ecuador: Puyango Petrified Forest
  • Greece: Petrified Forest of Lesvos, on the island of Lesbos
  • India: Thiruvakkarai Village in Chennai, Tamil Nadu
  • Libya: Great Sand Sea
  • Namibia: Petrified Forest
  • New Zealand: Curio Bay
  • Peru: Piedra Chamana Petrified Forest
  • United States: Petrified Forest National Park, Arizona; Petrified Forest, Calistoga, California; Florissant Fossil Beds National Monument near Florissant, Colorado; Grotto of the Redemption in West Bend, Iowa; Mississippi Petrified Forest in Flora, Mississippi; Petrified Wood Park in Lemmon, South Dakota; Ginkgo Petrified Forest State Park in Vantage, Washington
Native Americans once used petrified palmwood to make knives, projectile points, and other tools. Today it is prized by collectors for its variety of colors, its structure, and its design.
Its color, beauty, and hardness, added to the fact that it takes a nice polish, make petrified palmwood a popular jewelry and decorative item. 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.
State Rock
Shiny Petrified Palmwood Specimen
State Rock
Petrified Palmwood Up Close
Name: Petrified Wood
Chemical Formula: SiO2
Color: Occurs in an infinite range of colors. Most commonly white, purple, brown, and colorless. Many specimens are multicolored or banded.

Author: World Trade Press

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