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The Gemstone Arizona Petrified Wood
What is the Petrified Forest National Park?
Located in northeast Arizona, the Petrified
How Does Wood Petrify
Start with a semi tropical forest with a 200 foot canopy of conifers and tropical flora. Slow moving streams and swamps populated with fish, clams fallen logs and reptiles.
One of the most well-known fossils of the world, petrified wood is a fascinating example of mineral replacement. Petrified Wood is real wood that has turned into rock composed of quartz crystals. The wood was covered with such agents as volcanic ash, volcanic mud flows, sediments in lakes and swamps or material washed in by violent floods.
Wood from primeval forests became buried by thick layers of sediments. This excluded oxygen which prevented decay. A number of mineral substances (such as calcite, pyrite, marcasite) can cause petrifaction, but by far the most common is silica. Solutions of silica dissolved in ground water infiltrate the buried wood and through a complex chemical process are precipitated and left in the individual plant cells.
It is not wood that makes petrified wood colorful, but the chemistry of the petrifying groundwater. The silica can be agate, jasper, chalcedony or opal. The beautiful and varied colors of petrified wood are caused by the presence of other minerals that enter the wood in solution with the silica. Iron oxides stain the wood orange, rust, red or yellow. Manganese oxides produce blues, blacks or purple.
List of minerals and related color hues:
Copper - green/blue
Cobalt - green/blue
Chromium - green/blue
Manganese - pink
Carbon - black
Iron Oxides - red, brown, yellow
Manganese Oxides - black
Silica - white, Gary
Even though petrified wood is fragile, it is also harder than steel. Petrified wood is known for it's exquisite color and detail. Some pieces of petrified wood have retained the original cellular structure of the wood and the grain can easily be seen. Petrified wood can be found throughout the desert regions. It is easy to find and identify. It is used often in jewelry making and for other types of decorative artwork.
Petrifaction of the wood found in the Petrified Forest began during the Triassic Period around 180,000,000 years ago. Trapped in sediments that would eventually reach as much as 400 feet. The layer of sediments is known today as the Chinle Formation.
The petrified logs were buried in the sediment for millions of years, protected from the elements of decay. During this time the plain was covered by an ocean and another layer of sediment was deposited on top of the wood-rich Chinle Formation.
About 60 million years ago the ocean moved away and the erosion process began. More than 2600 feet of sediment have eroded to expose the top 100 feet of the Chinle Formation. Petrified Wood is the official State Fossil of Arizona.
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