Petrified wood is a type of fossil: it consists of fossil wood where all the organic materials have been replaced with minerals (most often a silicate, such as quartz), while retaining the original structure of the wood. The petrifaction process occurs underground, when wood becomes buried under sediment. Mineral-rich water flowing through the sediment deposits minerals in the plant's cells and as the plant's lignin and cellulose decay away, a stone mould forms in its place. The wood is preserved due to a lack of oxygen.
Elements such as manganese, iron and copper 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 a yellow, red or other tint.
Following is a list of contaminating elements and related color hues:
* carbon - black
* cobalt - green/blue
* chromium - green/blue
* copper - green/blues
* iron oxides - red, brown, yellow
* manganese - pink/orange
* manganese oxides - black
Petrified wood can preserve the original structure of the wood in all its detail, down to the microsopic level. Structures such as tree rings and the various tissues are often observed features.
Petrified wood has a Mohs hardness of 7, the same as quartz.
Petrified wood is also the state gem of Washington.
Source: Wikipedia.Org
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