Petrified wood, also known as Fossilized Wood, is fossilized remains of ancient tree plants from the Paleocene Era. The name "Petrified" came from Greek "petro" that means "stone", literally, "wood turns to stone". During the long-term process (millions of years), called petrification, the wood structure completely transformed into the stone. The wide varieties of colors are the result of mineral impurities which were presented during the petrifications.
Petrified Wood Color
- The black color is an effect of a carbon and manganese dioxide existence;
- green and blue - cobalt, chrome oxide, and copper;
- yellow, red, and brown - iron oxide;
- pink and orange - manganese;
- yellow - manganese oxide,
- white - silicates of aluminum.
There are other names that used for petrified wood:
- Opalized wood - the original structure was replaced by opal;
- Agatized wood - wood has been replaced by agate;
- Silicified wood - wood has been replaced by any form of silica, including opal and agate.
Petrified Wood Formation
Petrified wood formed over millions of years ago from ancient walnut, Myrtlewood, sycamore, and birch. The petrification process involves gradual cellular replacement of decayed organic material by quartz crystals such as agate, jasper, amethyst, opal, and citrine. Washed into rivers, the wood has been slowly buried by sediments in the anaerobic (oxygen-free) environment while silica-rich water, absorbed by the porous wood structure, dissolved and replaced the plant's tissue with minerals. This type of petrification preserves the plant remarkably well with easily recognizable fine details including growth rings, veins, and insects. Experts can easily to determine the species and relative age of the tree.
Fossilized wood can be formed as Limb Casts. When it is engulfed by the lava or ash, the wood structure is either burned away or decayed. Later, the limb-shaped cavity is filled with minerals from groundwater. Though the inside of the limb cast does not preserve fine details of the tree, the specimens can show wood texture on its surface.
How to Spot Petrified Wood?
The identification of petrified wood can be a difficult task. Some small pieces can resemble agate but agate exhibits a rounder shape. Petrified wood may be identified by:
- the circular structure of the annual rings when observed from the end;
- the surface of the specimen resembles a tree bark.
Where to Find Petrified Wood?
Oregon is known for a wide of varieties of petrified wood such as petrified algae, tempskya, osmundite, crystallized wood, agatized wood, limb casts, jasperised wood and opalized wood. Petrified wood is found at many collecting sites of the state.
The collection of petrified wood for personal use is limited to 25 pounds each day, plus one piece, but no more than 250 pounds in any calendar year. The removal of the piece that exceeds 250 pounds is prohibited without a permit.
Gems and Minerals in Oregon. Oregon Department of Geology and Mineral Industries. OD http://www.oregongeology.org.
Dan R. Lynch, Bob Lynch. Rocks & Minerals of Washington and Oregon: A Field Guide to the Evergreen and Beaver States (Rocks & Minerals Identification Guides). 2012.