"Petrified" Silicified Wood - General Discussion
Some ancient wood escaped the natural process of decay by
being buried in sediments or volcanic ash. In some cases, dissolved
minerals seeped into the cellular voids and crystallized. The
most common minerals were calcite or silica (SiO2 silicon dioxide).
When the cells of the wood have been replaced by the latter,
they are said to be silicified or converted into silica. The
result is commonly called "petrified" or "agatized"
wood. The most important deposits are in the western part of
the United States in Arizona, California, Oregon, Utah, Washington
and Wyoming. A variety known as Texas Palm Wood is found near
San Antonio and Houston.
EDEN VALLEY WOOD AGATE
Brown, Black, Mohs Hardness is 7 - SiO2 silicon dioxide
The mountains south of the Lamar River in Yellowstone National
Park reveal more than fifteen different forests of sequoia, pine,
chestnut and plant trees, superimposed on each other in successive
layers. The agatized wood from the Eden Valley between Farson
and Lander, Sweetwater Conty, Wyoming was such a forest. Agatized
portions are black but limb portions are perfect casts of the
original twigs and limbs. Specimens of silicified wood from the
Eden Valley, Wyoming are perfect casts of the original twigs
and limbs.
DUBOIS PETRIFIED WOOD AGATE
Blue-grey To Colorless Mohs Hardness = 7 - SiO2 silicon dioxide,
A transluscent blue grey calcedonic cast of logs, limbs and stumps
from an area near Dubois, north of Eden Valley, Wyoming. Some
exhibit iris when cut in thin slabs. Others contain dendritic
inclusions of manganese oxides.
ARAUCARIOXYLON ARIZONICUM - Early Jurassic, Chinle Formation,
Arizona, Most all (90%) of the medium and larger logs of petrified
wood from Arizona are this species.
OAK - QUERCUS SP., Miocene, Columbia River Basalt, Deschutes
River Canyon, Oregon
|
