Preface
In the
next two episodes of our Mineral-of-the-Month we will be visiting Petrified Wood. Not just
on the surface, but deep within this ancient wood’s cells. Part I will cover the chemistry and science
of what makes it, i.e., the process of petrification, it’s geology, and what
gives it its array of colors.
We will see some lapidary examples, as well. And,
we will begin nearest our clubhouse in the United
States to trek our petrified forests.
In part II, we will go into paleobotany, more lapidary uses, lore and metaphysical
applications, and
travel internationally, to see what the rest of the world proudly offers as paleo-beauty
from their homes,
as well.
So, put on your hardhat and safety sunglasses. We’re
off to explore the many preserves of ancient
flora. Let’s go!
Introduction
Good
morning! I hope you are all ready for our
excursion into sunny petwood country. As your
guide,
I will suggest places for us to collect, or in the case of special parks and preserves, to
just soak in the
multi-hued beauty of stony logs and trunks, to be admired where they fell a long time ago.
As there are several public and private locations for us to visit on our itinerary,
we’ll have to hurry, so
everyone on the club bus, please. All aboard!
We’ll travel south from Delaware, then venture across the country westward, until we
reach California.
We can spend the next virtual month scouring the southwest for fossilized plant specimens,
while working
on our suntans. Next month, we’ll
endeavor to cross the ocean to sunny Australia, then onto Asia and
other spots on the globe.
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Delaware Petrified Wood
Photo by Ken Casey ©2005 |
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Pentoxylon (Jurrasic),
Australia
Photo courtesy of
Dr. Stephen Ervin |
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Australian "aussie
john"
Photo by and courtesy of
Jackie Lapin, SpheresToYou.com ©2006 |
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We’ll
need a primer on petrified wood. So, as the
wheels on the bus roll us southward, let’s study up
on our current favorite. We’ll begin
with science.
What’s
In a Name?
The word
“petrified” comes from the Greek “petra”, meaning rock. So, wood
that has transformed into
rock is “petrified wood”.
By general definition, petrified wood is tree material that has undergone mineralization. This could
loosely apply to man-made pressure-treated lumber or naturally preserved ancient kauri
wood from New
Zealand. More on that later.
For our intensive purpose here, we intend to visit nature’s fully fossilized trees.
Petrified wood is a fossil created by the replacement of a tree’s plant cell shapes
with minerals,
such as quartz, calcite, or pyrite. A stone
cast is left after the lignin and cellulose decay. It’s
telltale
colorful grain patterns and concentric rings are fostered by staining minerals, such as
iron, manganese,
or copper. Pure
silica exhibits a bluish-white hue.
The quartz variety predominates the world’s paleoforests. On the Moh’s scale of hardness it rates
a 7, equal to quartz. It is tough, yet
brittle, breaking as does cryptocrystalline quartz. Amazingly,
it
can weigh many times that of a piece of similarly sized wood.[i]
| Color
Chart: |
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Petrified
Wood comes in all colors of
the rainbow. The following minerals
give the wood it's characteristic palatte:
http://en.wikipedia.org/wiki/Petrified_wood
(Left) Closeup
of Petrified Wood from the Petrified Forest National Park, Arizona
Photo courtesy of Christy Marx, Professional
Photographer ©1997-2006 |
There are three main steps towards permineralization of living plant matter: (1.)
encapsulation,
or removal from an environment that causes decomposition, (2.) introduction of sufficient
quantity
of a mineral-laden solution to bring about chemical-biochemical replacement of cell
structure, and
(3.) time.
At what point during the petrification process (or preservation process) do we determine
that
wood is in fact “petrified wood”? Is
a partially or fully done process sufficient for our definition? Can
it be man-made, or is nature the sole producer? Or,
is age a factor?
There is a debate over whether certain, recently recovered wood from the ground has
actually
undergone the process of petrification. There
are three examples that come to mind. They
are:
New Zealand kauri wood, century-old sunken logs, and flood-covered landscape living tree
remnants.
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The
first is the southern hemisphere’s millenias old kauri wood. Recently recovered or “mined” from the
peat bog-laden earth, ancient kauri (Agathis australis) is estimated by
radio-carbon dating to have been “preserved” in the ground for around 50,000
years. The only officially-licensed New
Zealand “mining” company explains that harvesting is state-monitored, so it is
rare and can be expensive.[iii]
Partial mineralization has occurred, thus giving this workable wood some superior degree
of hardness and a cognac-colored sheen that underscores a beginning to fossilization. Though not fully petrified, natural longer-scale
preservation has increased its beauty and value. Buried
under a peat swamp, after having lived for about 2,000 years, each tree has rested,
untouched since the last Ice Age. We
can compare the old wood to modern trees, as kauri still graces the New Zealand landscape.
One can both visit the living members at the Northland Forest Park,
and later procure online some ancient lumber from a hardwood vendor, Ancientwood, Ltd.
of La Pointe, Wisconsin, for use and study. If
you are keen on paleobotany, this job is for you. Some
folks enjoy working it as wood.
(Left): Agathis australis (Kauri tree)
from New Zealand, called 'Te Matua Ngahere' after the Maori 'Father of the Forest'
(wikipedia) |
The
second is the spoils of latent logjams. For
about 100 years, some cut logs sent downriver
from antique logging transportation operations have sunk to river or lake bottoms, only to
have their
harvesting deferred to recent times. These
water-logged bonuses are fully useable in modern
carpentry and woodworking projects. Whether
some mineralization has occurred to harden the
lumber is at issue.
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The
third is flood-preserved stands of trees. One
recent example are the remains of ancient forests that can be seen poking their highest
limbs above the lower water levels of Lake Powell in the awesome Glen Canyon
National
Recreation Area. These plants have
been submerged by man-made projects for about 40 years.
One could study these.
Naturally-occurring ancient examples are coastline forests, since sea-levels have risen
since times BCE. An inland example is the
shifting of water levels in Yosemite National Park. Dead stumps stand in testament to volcanic and
tectonic processes, perhaps preserved by dissolved volcanic gases or related
mineral-bearing waters.
(Left): Looking downslope of an erosion channel at the
Petrified Forest National Park
Photo by and courtesy of Christy Marx
©2006 |
As
an historic supervolcano in the west spewed an ash cloud into the believed prevailing
paleowinds, deposits reached as far east as Nebraska.
I wonder if the process is occurring right
now under the fallen forest on the slopes of the currently active Mt. St. Helen’s
volcano at the
Mt. St. Helen’s
National Monument in Washington state.
Pressure-treated
Lumber
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Today’s pressure-treated pine wood is just that, lumber infused with chemicals, like
chromated
copper arsenic (CCA), under intense pressure. These
minerals act to preserve the wood, thus making it resistant to insect infestation and
decay from ground and water contact. Some
lumber manufacturers guarantee their product for up to forty years!
Last year, during our club’s Junior Booth Labeling Party in preparation for our March 2005 Show,
I found a small piece of P-T pine. It was
used as a base to mount a mineral specimen, I believe. Determined to label it, I
suggested we sell it as “petrified wood”, as it was chemically-preserved wood.
Laughing, we put it back in the box, but didn’t offer it for sale.
(Left): Photo courtesy of FLW Wood
©2006 |
Here
is an example of a middleground two-fold process: man-made, then naturally lithified. A
story reported in Australia’s outback gives proof that planted timber fenceposts have
been partially
fossilized in recent history, thus giving credence to a faster than previously believed
permineralization
process occurring in nature. The 1918 flood
laid sediment and water conducive towards creating
fossilizing conditions.[iv]
Experimental
chemistry has brought petrification to the forefront of the news. A man-made
process has brought about a ceramic compound that mimics petrified wood. It is amazing
that
with a nearby petrified forest, that scientists in Washington state are creating
artificial petrified
wood. Why, do you ask?
Benefits
include filtering pollutants, acting as catalysts, and sponging up contamination.
The process involves hardening a softwood, such as pine or poplar,
bathing it in acid, then
soaking it in silica solution for days. After air-drying, it is cooked in an
argon-filled furnace to
1,400 degrees Celsius, Many experimental and industrial crystals are grown in an argon
atmosphere. The replicated petwood consists of a new silicon carbide.[v]
In the article “Instant Petrified Wood Yields Super Ceramics”, “Materials scientists at the
Department of Energy's Pacific Northwest National
Laboratory have developed a chemical
process that adds a promising new dimension to the search for advanced catalyst
technologies,
as well as to cutting tools, abrasives and coatings.”
These
laboratory versions of petrified wood borrow the best aspects of metal and carbon to
create a superstrong material that can take temperatures up to 1,400 degrees Celsius. They
create it in days, instead of millions of years.
The idea it to build ceramics on
“wood templates”. Silicon,
titanium, and argon are used.
The useable end products are silicon carbide (SiC) and titanium carbide (TiC).[vi]
The
amazing porosity of the material lends itself to use as a catalyst or a filter. This wood
flours can be infused with metals, creating better cutting tools. And, all this from a renewable
resource! What will they think of next?
So, a modified type of
truly petrified wood can be of use beyond its outward structure
and beauty.
Another application
touts a petrifying effect:
Both
a Popular
Science, October
1992 article, and U. S. Patent File #4,612,050,
outline an
invention owned by Mr.
Hamilton Hicks of Greenwich, Connecticut, which explain
a process whereby
fresh wood can be altered
by chemical solutions in the lab to create an analogous petrified wood.[vii]
His Sodium
silicate composition patent file abstract
reads: “A mineralized sodium silicate
solution for the application to wood has a composition causing it to penetrate the wood
and jell
within the wood so as to give the wood the non-burning characteristics of petrified
wood.”[viii]
Australian
scientists of Nanotec Pty. Ltd.
have devised a newly marketed product which they
tout repels water and UV rays. Their
“Nanoseal Wood” may be defined as man-made petrified,
but actually may serve as
building material.
It is a “water
based, ultra hydrophobic, colloidal solution with self assembling properties to
form the functional surface structure. The repellent effect is
done by a combination of molecular
structural surface changes and added on hydrophobic properties.”[ix]
The topically applied
liquid seals out air and moisture, thus halting decay, much like the
encapsulated environment in which petrified wood forms.
One must ask how long will it last,
and are we creating petrified wood over time?
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As
the vast Triassic paleoforest that spanned Texas
to Utah consisted of ancient conifers, some comparison
can be logically made. Technology has almost
defeated the process of aerobic decay. Even
decades
old loblolly pine carpentered building members
encased in plaster harden with age.
The
afore-mentioned lab-created woods seem to mimic
nature’s processed pieces to a defining degree of
form. So, are these cultured products really
comparable to this month’s favorite mineral?
(Right): A 15" round cross-section of Utah petwood
Photo by and courtesy of sticks-in-stones.com ©2006 |
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Let’s
review by reading a passage written about natural petrification, and see how it compares.
“Sometimes
the original cellular structure is obliterated and what remains is simply a cast
of the original log; other times, growth rings, bark, knots, and even cellular structure
is
preserved with remarkable fidelity. This later, more detailed preservation is possible
because
silica and other inorganic molecules are much smaller than organic molecules; rather than
"molecule for molecule" replacement, the organic molecules are actually coated
and surrounded
with silica. Small amounts of impurities add color to the fossilized wood: yellow, brown
and red
indicate iron; black and purple take their hue from carbon or manganese.”[x]
Doesn’t
this describe
the major technical features of our chemists’ processes above?
So,
what constitutes laboratory petrification as a similar, chemical replacement process to
nature, can thus retain our definition of petrified wood.
In past articles, we have
mentioned substitutes for nature’s bounty, especially when
quantities are scarce. For example,
turquoise, diamond, and opal have all been man-made.
Though having uses beyond the gemstone, why should petrified wood be treated any
differently?
Geology
As stated above,
similar conditions around the globe create the environment to petrify wood.
It seems that all three main geologic processes contribute to the creation of our
preserved
paleoforests. Volcanic lava, ejecta, and
silicieous ash (igneous), soil and mud deposition
(sedimentary), and mineral-laden groundwater replacement casting (metamorphic), work in
sequence to bring about our painted landscapes of today.
Experts
differ as to the timeframe of formation. Some
believe that millions of years were
required; whereas, others cite instances of objects, such as modern fenceposts being
fossilized after floods. Most submit that
eons have passed before natural examples were
completely mineralized.
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One of the most
studied areas is the Petrified Forest
National Park in Arizona. Stratigraphers
in one paper state that, two layers of the Upper Triassic Chinle Group contain
the bulk of petwood
in the park. Also, the Sonsela Member of the
Petrified Forest Formation holds the more brightly
colored logs for which the park is known.
These
scientists, Andrew B. Heckert and Spencer G. Lucas,
conclude their age-dating as “[a]vailable
biochronological evidence, including tetrapods,
megafossil plants, pollen, and calcareous
microfossils, indicates that both the Sonsela Member and
the Black Forest Bed are of early- to
mid-Norian (220-215 Ma) age.”[xi]
Though
scientists and theologians have disagreed
over the age and specific event(s) that produced
the petrified forests of the world, many seem to
agree on the composition of the final product. Our goal is to focus upon the petrification
process
that occurred after the trees were buried, and upon
the colorful wonders that we see today.
(Right): Fluvial erosion at the Petrified Forest National
Park. Photo by and courtesy of Scott W. Parker ©2003 |
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The
references this author makes to prehistory are based both upon popular scientific
belief and upon the premise that perhaps some petrified wood formed before man. Even many
of the world’s cultural creation scenarios agree that plants existed before mankind;
therefore,
it could be possible that some petrified wood could have formed before, as well.
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Let’s
look at a couple of examples. One wood that
is
still known today, living in some of earth’s forests, is Gingko. The Gingko Petrified Forest
State Park located on the
Columbia River in Washington State hosts Miocene
(5.3 to 23.8 mya) Ginkgos (Gingko biloba).[xii] (Left): Gingko biloba leaves
Photo courtesy of Reinhard Kraasch |
Another is
the Mississippi Petrified
Forest boasts Eocene Epoch (Tertiary) 36 million
year old wood. These primeval remnants of
perhaps a bald cypress forest (a tree known
today) lay testament to the passage of time. Palmwood occurs around
Louisiana.
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Palmoxylon, Louisiana
Photo courtesy of Dr. Stephen Ervin |
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2.5" Diameter Palmwood
Sphere, Lousiana/Texas
Photo by and courtesy of SpheresToYou.com
©2006 |
fossil record. This month, we will leave them
lie, in favor of space for more descriptive
pictures. I will introduce some of Linnean
scientific names, so that they will appear more
familiar to you in our next excursion. Next
month, we’ll uncover more about paleobotany
and plant taxonomy.
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Petrifed wood in the field,
Odessa, Delaware
Photo by and courtesy of Gene Hartstein ©2006 |
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2.5" Diameter Palmwood Sphere,
Lousiana/Texas
Photo by and courtesy of SpheresToYou.com
©20 |
layers. Over time, iron- and silica-laden
groundwater seeped into wood cells, thus causing
the mineral(s) to replace cell walls. This
gives us the brightly colored quartz logs we see
today. Perhaps the heat of lavaflows hastened
the process in some closer to the volcanic
cone.
In
the Petrified Forest
National Park, geologic uplifting of the Colorado plateau,
sedimentary erosion, and the surficial freeze-thaw cycle produces the fractured stone
logs,
as pictured here.[xiii]
Silicification
is the main process forming petrified wood, though others exist. For example,
coalification, calcification, and pyritization, happen, too. So, how do these other processes
compare to silicification?
Coalification
and bogs predominated the eastern climate, like in the massive coal areas
of Pennsylvania and Ohio, so fewer petwood areas were created for us to see now. Some
form seams, other more acidic conditions can produce “coal balls”. As erosion and uplifting
are key factors in releasing or exposing the layers in which lithified logs loom, our
eastern
paleoclimate brought
less to the surface for us to dig.
The
exceptions are the present mountainous areas in the east, such as the Appalachian
Range. It’s orogeny pushed rock
containing our favored fossil to collectable depths.
(See the
list of states just
below)
When
logs are calcified, the resultant stones are white. Upon
exposure to the sun’s
UV rays over time, they
turn to a dark brown/black.[xiv]
Opalization
is similar to silicification, in that
quartz is the major constituent. The addition
of some water in the quartz matrix gives rise to the multi-hued effect.
Pyrite
and marcasite (iron sulfides) can replace wood cells, but essentially leave a cast
of the basic wood form. The environment for
change can be clay burial or an introduction
of seawater.
Locations
According the the U. S. National Park Service,
petrified wood is found in all 50 states,
and in many countries.[xv]
One of my favorite online mineral
databases, mindat.org, has listed 352
locales around
the globe. Jolyon Ralph has tallied these U. S. states as documented locales: AL,
AZ, AR,
CA, CO, CT, FL, GA, ID, IL, IA, KY, LA, MD, MS, MO, NE, NV, NM, NC, ND, OH, OK, OR,
PA, SC, TN, TX, UT, VA, WA, WV, WY.[xvi] That’s 33 states!
Most
petrified forests in the U. S. can be found in the western part of the country. The
most eastern is in Mississippi. So, the best
collecting opportunities abound out west. Let’s
visit some of them!
United States law prohibits
collection of fossil, rock, and mineral materials from National
Parks and Monuments, unless specifically permitted. Each state, county, town, or
area has
their own rules pertaining to their public spaces, as well. It’s always best to
study a guidebook,
a reliable websource, and inquire locally.
We
can access these online museums and sites on our laptops and PDAs in between
stops as we roll down the road:
Museums (Actual & Online)
We will
visit just a few of the various and sundry places. You’ll
have to make side trips
on your own, as we have only four short weeks this month to explore, before we are ready
to
travel to other continents. (Yes, even to
Antarctica!) Well, here they are:
Arizona
Home to our featured locale, the Petrified Forest National
Park, Arizona, boasts some of the
more prevalently displayed petrified paleoforest landscapes on earth! Look below. Could these
two photographs taken by two different photographers at two different times be of the same
logs?
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Fractured log in the
Petrified Forest National Park, Arizona
Photo by and courtesy of Dr. Stephen Ervin ©2006 |
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Fractured log in the Petrified
Forest National Park, Arizona
Photo by and courtesy of Scott W. Parker ©2003 |
Much
of the area was set aside by President Theodore Roosevelt in 1906 as a National
Monument. In 1962, it became a National Park.[xvii]
Today, it is still tradition for any seated U. S. President to
declare a National Park to
conserve important lands and landmarks for the future. By
act of the State Legislature,
“Araucarioxylon arizonicum is a fossil conifer that is
the state fossil
of Arizona.”[xviii]
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Specimens of Araucaria
arizonicum (Far Left): Log in situ at
the
Petrified Forest National Park, AZ
Photos by and courtesy of
Chris and Candida Provencher
©2006
(Left): Colorful slab from Arizona
Photo by and courtesy of
Gene Hartstein
©2006 |
Together, these proclaimed symbols account for an historical place of grand note for all
of us to visit and enjoy. With an unspoiled
landscape, our roving eye might have us envision
a past, living environment. Tall trees
swaying, and earth-shaking creatures walking out of
past times, might spur us to move quickly, to avoid being trampled by these--dinosaurs!
At any time, we can open our minds eyes to the possibility,
or return to our current beauteous
desolation. With this exercise, we have
developed our “paleo-view”, to help us understand
more about our world.
Here, our “paleo-viewpoint” shows us that, “In the Triassic
period, this species of tree
flourished in what is now known as the Black Forest, part of the 37,851 ha (93,492-acre)
Petrified Forest
National Park in eastern Arizona. Prehistoric Arizona was a flat stretch of
tropical turf in the northwest corner of a supercontinent
known to modern geologists as
Pangaea.”[xix]
"Many
of the fossilized logs are from a tree called Araucarioxylon arizonicum. Two
others, Woodworthia and Schilderia, occur in small quantities in the
northern part of the
park. All three are now extinct.”[xx]"
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Schilderia from
Arizona
Photo by and courtesy of Dr. Stephen Ervin ©2006 |
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Woodworthia from
Madagascar
(Though not from Arizona, it does represent the species)
Photo by and courtesy of sticks-in-stones.com ©2006 |
The
park has seen man venture across its vastness over millennia, since the
end of the
dinos. From the Anasazi, Mogollon, and
Sinagua peoples up to 10,000 years ago, to the
sixteenth-century Spaniards,
up to modern times, many explorers and natives alike have
walked the park.[xxi]
Some Native American oral history recounts the role that petrified wood played in the
grand scheme. (We will visit these stories in
our next installment, so stay tuned.)
Now,
with a brief history and new perspective to our lovely land, let’s feast our eyes on
it’s wonders! Look out the windows, this
is what you will see. We’ll disembark,
so everyone
take a bag lunch as you leave the bus.
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Petrified
Forest National Park
Photos by and courtesy of Chris and Candida Provencher ©2006 |
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Petrified Forest
National Park
Photo by and courtesy of Scott W. Parker ©2003 |
If you like, we can employ any of these Touring Websites about the Petrified
Forest
National Park:
Petrified Forest National
Park, Arizona
White Mountains Online
Holbrook, Arizona, city
of the Petrified Forest
Park Vision
DesertUSA
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