Petrified wood is a special type of fossilized remains of terrestrial vegetation. From the Greek root petro meaning "rock" or "stone"; literally means "wood turned into stone".
The process of turning wood to stone:
Wood is buried or covered before it decomposes with sediments like volcanic ash or lava, mud-flows or material washed in by floods. The wood is initially preserved due to the lack of oxygen and organisms which inhibit decomposition. Trees have microscopic tubes which allow the transport of water and nutrients from the roots to the leaves. Over time through a complex chemical process involving heat and pH balance, mineral laden water flows through the covered material and are deposited in the plant's cells. The minerals that replace the organic material and individual plant cells undergo changes. The result is a fossil of the original woody material that often exhibits preserved details of the bark, wood, rings, and cellular structures. Specimens that exhibit clearly recognizable bark and woody structures are very common. This process can take millions of years.
What gives petrified wood all its colors?
A great deal of geology and chemistry, are involved in the mineralization of wood. Elements such as copper, iron, manganese in the water/mud during the petrification process give petrified wood a variety of color ranges. Pure quartz crystals are colorless, but when contaminants are added to the process the crystals take on yellow, red, and other tints.
If the following elements are present in the sediments they cause these color hues:
- Carbon – black
- Chromium – green/blue
- Cobalt – green/blue
- Copper – green/blue
- Iron oxides – red, brown, and yellow
- Manganese – pink/orange
- Manganese Oxides – blackish/yellow
Petrified wood rates between 7 and 8 on Mohs Hardness Scale, with talc at 1 and diamonds at 10. It can be very brittle and shatter like glass. However, it is as strong as steel. It is also very heavy and weighs between 160-200 pounds per cubic foot.
To log this cache choose one of the pieces in the area that has its colors exposed and use it answer the following questions,
When you have the answers send us an email.
1. What colors do you see in the piece of petrified wood that you chose?
2. What elements were present that may have caused these colors?
3. Estimate the height and circumference of your specimen. About how much does it weigh?
4. Looking at the pieces in the area, is there any evidence that they were once trees? If so, what is the evidence?
Please do not post the answers in your log.
Congrats to albuquerquebill for the FTF
Sources:
Geology.com/Wikipedia