 petrified wood with Quarz (ca. 100 x 150 mm) |
petrified wood 1: North America (Wyoming, Washington)
a) the Big Sandy Reservoir located north of Farson
b) the region around Oregon Buttes
c) the legendary Blue Forest
Eden Valley petrified wood was formed from plants living about 58 million years ago (Eocene geologic age). The the rock exhibits features not found in fossil wood anywhere else in the world. The fossil wood is known for the light blue agate surrounding many of the pieces.
The petrifaction process for this area involved shallow “algae growing” lakes. In many cases for undetermined reasons the wood came to be in this water in its live condition before it had a chance to dry out. This wood became coated with algae which adhered to the surface making a cast or mold around the wood. Later the wood dried and shrunk in the mold made of algae. Over times these algae casts became part of a layered rock formation. Silica-rich water solutions seeping through the rock then petrified the wood and filled in the spaces left between the dried wood and the hardened cast with blue agate, calcite and quartz.
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petrified wood with Quarz (ca. 100 x 150 mm) |
As the agate coated the inside surface of the algae cast, perfect impressions of the bark were left in the agate. Because the petrifaction process seems to have been protected by the algae cast formation, unusually detailed representations of the wood have been preserved.
wood from the „Blue Forest“
 (ca. 150 x 100 mm) |
 (ca. 100 x 100 mm) |
 (ca. 80 x 90 mm) |
 (ca. 70 x 70 mm) |
 (ca. 100 x 70 mm) |
 (ca. 250 x 160 mm) |
 palm (ca. 120 x 100 mm) |
A special form of petrified wood are limb casts. Limb casts are although classed as petrified wood. They are formed when the wood of trees or their roots rots away and the space left is filled by other minerals, but usually agate. Sometimes it´s still possible to see the look of the bark all the way around the outside. A very well known place for these limb casts is the Crooked River location.
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 Unitha County (ca. 100 x 100 mm) |
2. Washington
Washington petrified woods offer many
fine examples of permineralisation. Tertiary forests and volcanic activity
combined to produce a wide varity of petrified woods, preserving trees similar
to their surviving descendants. At least 35 distinct species have been
identified. The Ginko Petrified Forest State Park, Saddle Mountain and
Yakima Canyon (eastern Washington) are the most extensive and well known sites.
The petrified wood is often very woody in colour. Earth tones are typically for
the coloration. Places like Vantage, Sunnyside and the Rattlesanke Hills produce
wood with unusual stark differences in tone. A lot of different species (hardwoods
and softwoods) were found in Washington. Listed genera included sycamore,
sweet gum, oak, alder, elm, hickory etc. The geologic age is late Eocene age.
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