File:Stromatolite-encrusted fossil wood (Eocene; Blue Forest locality, Wyoming, USA) 1.jpg

English: Stromatolite-encrusted fossil wood from the Eocene of Wyoming, USA. (rough surface)

"Petrified wood" refers to fossil wood that has had its microscopic porosity filled with minerals as groundwater percolated through, while buried in sediments. This fossilization process is technically known as permineralization ("petrified" is a horrible term - never use it in a scientific context). Permineralization can also occur with fossil bones. The most common permineralization mineral is quartz (~pure silica - SiO2), the most common mineral in Earth's crust.

This sample of fossil wood is from Wyoming's "Blue Forest" locality. Slightly bluish-gray chalcedony is often present in the wood - it fills fractures and cavities. Chalcedony is translucent, microcrystalline, fibrous quartz. The wood was deposited in ancient Lake Gosiute, a large inland body of water that covered much of southern and southwestern Wyoming, plus parts of far-northwestern Colorado during the Eocene.

The lighter-colored material surrounding the wood is a stromatolite - a layered structure built up by mats of cyanobacteria (see: www.flickr.com/photos/jsjgeology/albums/72157632477572336 ). Most ancient stromatolites grew in shallow ocean or lake environments.

Stratigraphy: Green River Formation or Bridger Formation, Eocene

Locality: unrecorded/undisclosed site in southwestern Wyoming, USA

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See info. at:

Mustoe et al. (2019) - Mineralogy of Eocene fossil wood from the "Blue Forest" locality, southwestern Wyoming, United States. Geosciences 9(1)(35). 26 pp. [click the blue box "Download full-text PDF" at: www.researchgate.net/publication/330292211_Mineralogy_of_...]