Petrified Wood From Western Washington
How to identify Petrified wood and
Reference resources for information on Petrified wood

By Ed Strauss     estrauss51@yahoo.com  (Please, no attachments)

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Petrified Wood from Western Washington
By Ed Strauss estrauss51@yahoo.com  (Please, no attachments)

When most people hear the phrase "petrified wood from Washington State" they think of the Ginkgo Petrified Forest State Park, Saddle Mountain, and Yakima Canyon in Eastern Washington. These are after all the most extensive and well known sites of fossil wood in Washington. Scores of articles have been written about Eastern Washington's petrified wood in scientific journals, geology bulletins, and rock and gem magazines. A good bibliography is included in the excellent article by L Steve Edmondson which appeared in the July/August 1991 issue of Rocks and Minerals. The Columbia plateau basalt flow of Miocene age is not the only host geologic formation of fossil wood in Washington State however. Petrified wood is also found west of the Cascades Mountains.

There are three collecting sites in Southwest Washington mentioned in rock hound guides. They are Salmon Creek near Toledo, Silver Lake near Kelso and Tono near the coal mine. Petrified wood can also be found on Washington beaches but it is scarce (Pattie, 1983). To my knowledge no one has published a serious study of these fossils.

History
The only published reports of fossil wood from Western Washington that I know of appeared in the Mineralogist (Anonymous, 1936) and Mineral News (Beck 1941). They both tell of a collection of fossil woods from the Chehalis Valley gathered by Hugh Brown and studied by the renowned pioneer of Washington's petrified wood, Professor George Beck, from Washington State College. Quoting Prof. Beck from the articles "...examples of red-to buff- colored silicified wood, mostly water worn pebbles... The absence of palm wood argues against earliest Tertiary for the Chehalis woods...These Chehalis woods match fairly well the lists from the old classic forests of Amethyst Mountain, Yellowstone..." Listed genera included Platanus (sycamore), Licquidambar (sweet gum), Quercus (live oak), Alnus (alder), Fagus (beech), Ulmus (elm), and Tetracentron types among other hardwoods and softwoods.

Charles E. Isham of Vancouver Wa. made a study of leaf fossils from a Puget Series collecting site in the 1950's. His location, known as the "Ladd Mine", is also in this area. Many of the leaf fossils were tentatively identified by Dr. Ralph Chaney and a graduate student, Jack Smiley of the University of California at Berkeley in 1955 (Wehr 1996). So far I have Identified corresponding fossil wood for about half of the genera.

Geology

I am studying fossil wood from Southern Pierce and Thurston Counties, Washington. The geology of the collecting sites is Hayden Creek (glacial) drift (Schasse 1987). It is described as "undifferentiated yellowish brown to brown stony till and boulder gravel out wash deposits... probably as old as 130,000 to 140,000 years b.p." The fossil wood was not created by a glacier but some or all of it was moved by a glacier to its present location (Pabian & Zarins 1994). Where it originated is harder to determine.

I received a letter from Kitty Reed of the Wa. DNR. She related sharing a letter I sent with Ray Lasmanis the State Geologist, he agreed with my guess that the Northcraft Formation of middle to late Eocene age (35-45 million years B.P.) was the host geologic formation (Reed 1995). This formation may also underlie the glacial till. The Northcraft includes pyroclastic rocks and tuff breccia which are possible parent materials for the silicification of wood (Schasse 1987, Pabian & Zarins 1984). The association of the fossils with carnelian agate (also found in other sites near the Northcraft) and the absence of ring porous oaks (which evolved later) argue for the Northcraft. The other possible parent formation would be the Ohanapecosh of Oligocene age.

I have indeed found many petrified wood collection sites in the Ashford Hills associated with the Ohanapecosh formation but they were different in three ways. The fossil wood of the Ashford hills is in situ, it is still weathering out of the welded tuff where it was formed.

All the pieces are angular like a broken rock, not appearing water worn. The fossils range in color from tan to brown to black, they contain no red or yellow. All of this circumstantial evidence points to the Northcraft as the most likely parent formation. This formation is interbeded with the Puget Series (Shasse 1984). The Puget Series contains many leaf fossil collecting sites of Eocene age (Wolf 1968).

 I have found about one half of the genera identified from the Chehalis woods that Beck examined (Beck 1941). It should be noted that I have not seriously studied the gymnosperm (softwood) fossils yet and half of the angiosperm (hardwoods) genera that I have differentiated have yet to be matched sufficiently to be named. In the future the comparison of Southern Counties woods to the "Ladd Mine" fossils and the Chehalis woods could be even closer. There is also a favorable comparison to the Yellowstone woods of Eocene age (Wheeler et. al. 1977,1978).

Identifying

The method that I have used to determine what trees the fossil woods represent is a tedious and time consuming process. Out of thousands of pieces of petrified wood I have selected about three hundred to be cubed. I shape the pieces that show the best promise of retaining diagnostic cell structure. I either start with a small piece or use a rock saw to cut off a small chunk. If possible I use the saw to make flat surfaces, if not I use a grinding wheel to grind the surfaces flat. I work the piece into a cube about 3/4 of an inch on each side. Particular care must be taken to align the sample to match the axial growth of the tree and the radial axis of the wood's rays. The specimens are also sanded on successively finer grits to eliminate all cutting, grinding, and sanding marks. Finally after about an hour I have one specimen. Finding the specimens is more enjoyable but without careful preparation definitive identification is usually not possible. Even after preparation some specimens that first looked promising do not retain accurate cell structure.

The next step is to examine the specimens under magnification. The micrograph at left shows an example of Pterocarya under 25X magnification (Manchester, 1993). The parenchyma bands and diagonal pore arrangement are key diagnostic features. I use a 10X hand lens and a microscope with 40X and 100X. The reason I have not studied the softwoods yet is that to identify them with certainty it takes 400X. That means I would have to thin section slices of fossil to a thickness of one to two cells so they would be translucent and mount them on a slide (Panshin & De Zeeuw 1970). That requires even more time and perhaps more sophisticated equipment. I have started with the hardwood fossils which are easier to identify because their cell structure is more diverse. It has taken a couple of hundred hours to learn what I am looking at and what to call it when the specimens are examined. Wood anatomists use a special technical language as all scientists do to be precise. There are books available to those who wish to learn this (Wheeler et. al. 1989).
 
 
 
 
 

The micrograph above is of sycamore it shows: 1 & 2 pores and rays, transverse view (low and medium magnification). 5 & 6 vessel pits and perforations, tangential view (high magnification), (Wheeler, 1995)

 

Using this technical language and micro measurements, the cell structure features of each specimen is recorded. The next step is to compare the recorded features to published records of other fossil or extant woods and see what matches.

 This process has been greatly simplified by the aid of a computer program designed for this purpose. It was developed by North Carolina State University in conjunction with the International Association of Wood Anatomists. This computer aided wood identification program is called General Unknown Entry and Search System or GUESS. This search system has been expanded and is available for use on-line at North Carolina State University web site insidewood.

 There are three separate programs, one for extant hardwoods, one for extant softwoods, and one for fossil hardwoods. The data base for the fossil hardwoods contains coded entries for 1,356 different published (and a few unpublished) specimens from around the world. These represent over 1,200 species. The program is not difficult to use and puts a wealth of information at one's finger tips. However, matching a specimen in the program is not the final step in identification. It is best to look up the scientific journal where it was published and read the full formal description by the author and examine the drawings or micro photographs of the specimen (Wheeler et. al. 1986). Usually large universities or colleges subscribe to the journals. The Suzzallo Library at the University of Washington has an extensive natural sciences periodical section. It is open to the public.

One thing that Paleobotanists have learned from studying Eocene fossil leaves, flowers, and fruits is that things were different then. Many trees have radically changed, diversified, or even become extinct (Page 1967, Manchester & Wheeler 1993). This is also true of the xylem or wood of hardwoods trees but not as much. Paleobotanists believe that the evolution of xylem is more conservative and that the cell structure of many trees remained similar while their leaves and fruits changed to a greater extent ( Page 1967, Wehr 1995).

Issues

One problem that Paleobotanists have is that fossil wood is almost never found with leaves or fruit still attached (Wehr 1995). All study of fossil wood was originally based on the comparison to living trees. Now that there are more and more published records of fossil wood which have been dated to approximate age, fossil wood can now be compared to other fossil woods. Some Eocene fossil wood's cell structure is so similar to extant genera that it has been named after it. Because some genera's wood structure has changed, Paleobotanists sometimes refer to Eocene fossil wood by the form that the cell structure resembles rather than the name of the extant genus (Page 1967). Rather than naming the Eocene xylem that resembles sycamore Platanus, it is referred to by the form name Plataninium. Plataninium can include fossils that may or may not actually be from the PLATANACEAE family but who's cell structure resembles it closely (Wheeler et. al. 1977). Another form name that has been widely used besides "inium" is "oxylon". The use of the suffix oxylon dates back to the turn of the last century (Beyer 1954). Why one is sometimes preferred over the other I do not know but the meaning is the same.

Some species of hardwood trees have very distinctive cell structure features while others have structure that closely resembles many other species (Panshin & de Zeeuw 1964). Some families of hardwoods have genera which are fairly different from one another's cell anatomy (Hall 1952). Some families of trees have species that have more similarities to other families than members of their own (Page 1969). All of these phenomenon make the determination of represented genus of a fossil wood specimen one of the more difficult branches of Paleobotany (Prakash & Barghoorn 1961). Because the determination of represented genera of fossil wood samples has little if any commercial value there are very few experts in this field. It is probably safe to say that there are less than a dozen in the U. S. today.

I am attracted to fossil wood Paleobotany because it is esoteric, challenging, and often times "ground breaking". Also the collection site is close by.

So far in my study of Southern Pierce and Thurston Counties fossil hardwoods I have identified 17 different families represented by 22 different genera. Some match so well with published formal descriptions and their illustrations that I am confident that they are the same species. Others vary slightly from published descriptions but match nothing else closely, so I name it for the genus but leave the species name open (sp.).

If leaf and/or pollen fossils of that genus have been published as being found in the Puget Series it reinforces my belief (Sparks 1967, Wolf 1968). Some match the features of a published form genus so well that again I believe it is the same species while others vary slightly but their leaf fossils are present in the Puget Series so I use the genus form name but leave the species name open. Here is what I've found so far: 

*Micro photographs of the South Counties petrified wood*

All of these specimens were collected, prepared, and photographed through a microscope by the author Ed Strauss. Click on the Genus  species  name below to view the photos.
 
FAMILY Genus   species Authority   year
ACERACEAE  Acer momijiyamense Suzuki 1998 
BETULACEAE  Alnus latissima Wheeler,Scott,Bargh. 1977 
BETULACEAE  Carpinus absarokensis  Wheeler,Scott,Bargh. 1997 
CERCIDIPHYLLACEAE  Cercidiphyllum sp. Scott & Wheeler 1982 
CORNACEAE  Cornoxylon sp. Krausel & Schonfeld 1924 
EBENACEAE  Diospyroxylon sp. Prakash & Barghoorn 1961 
FAGACEAE  Fagoxylon sp. Suss 1986 
FAGACEAE  Quercinium lamarense Wheeler,Scott,Bargh. 1978 
HAMAMELIDACEAE  Licquidambaroxylon weylandi  Greegus & Gotwald 1992 
JUGLANDACEAE  Carya tertiara  Prakash & Barghoorn 1961 
JUGLANDACEAE  Pterocarya rhoifilia Warti 1952 
LAURACEAE  Laurinoxylon sp.  Suss & Gottwald 1992 
LEGUMINOSAE  Robinioxylon sp. Selmeier 1979 
MAGNOLIACEAE  Magnolia sp. Scott & Wheeler 1982 
MAGNOLIACEAE  Lirodendroxylon sp. Cevallos-Ferriz & St. 1990 
NYSSACEAE  Nyssoxylon sp. Suzuki 1975
OLEACEAE  Fraxinoxylon sp.  Prive-Gill 1990 
PLATANACEAE  Plataninium haydenii Wheeler,Scott,Bargh. 1997 
ROSACEAE  Prunus sp.  Suzuki 1984 
TROCHODENDRACEAE  Trochodendron beckii  Scott & Wheeler 1982 
ULMACEAE  Ulmus sp.  Prakash & Barghoorn 1961 
ULMACEAE  Zelkovoxylon sp.  Wheeler,Scott,Bargh. 1978 
The authors and publication information of the formal descriptions are listed in the reference section under: Wheeler, E. A.; Bass, P. 1991.

The common names of these genera (in order) are:
maple, alder, hornbeam, katsura, dogwood-like, persimmon-like, beech-like, live oak-like, sweet gum-like, pecan, wingnut, laurel-like, black locust-like, magnolia, tulip tree-like, tupelo-like, ash-like, sycamore-like, cherry, trochodendron, elm, and oriental elm-like.

The Southern Counties fossil woods have some interesting general features. Probably 80 to 90% of all samples represent gymnosperms or softwoods. Out of the angiosperms or hardwoods the live oak-like and sycamore-like are the most common. About 15% of all samples have boring insect damage. About 40% of the samples appear to be the hardest and knarred part of the tree or roots. Many samples resemble flood debris, having a wear pattern that would be almost impossible to create by glacier or stream transportation. Some samples look as though they were partially decayed at the time they were silicified. Some samples appear to be casts. Perhaps they formed when a cavity in the volcanic tuff was created by wood which disappeared before the cavity was filled with chalcedony (jasper). Besides small clear, yellow, and red agates an unusual crystalline agate (not of gem quality) is always found in association with the fossil wood.
 
 
 
1. 
2. 
3.
4.

 Trochodendron; a vesseless hardwood with wide rays, believed to be one of the earliest hardwood trees to evolve.
 1. transverse view, 10X  2. transverse view, 40X; 3. radial view, 130X showing scalaraform perforations on tracheid walls; 4. tangential view, 40X showing broad multiseriate rays. (Page,1969)

 Biologists from around the world have cataloged about eighteen thousand different species of woody plants living today ( Wiedenhoeft 2000). It is not unreasonable to think that over the course of nearly 200 million years that even more species have lived. Paleobotanists have cataloged a mere fraction of that amount. That would mean that there are thousands of species yet to be discovered and described (Selmier 1989). In my own study I have found a few examples which fit that category. I have found the only fossil xylem of Trochodendron ever discovered in Washington State. I cannot say for certain without further scientific collaboration, but it appears that I have found the oldest or nearly the oldest known specimens of persimmon-like, black locust-like, and wingnut fossil wood. I have also found what may be the predecessor of platycarya. My hope is that this article will generate interest in the identification of fossil wood. I hope that those who have evidence to support or criticize my findings will contact me. Although the history of Western Washington's forests are definitely "written" in stone the description of them is not. Like all natural sciences Paleobotany and fossil wood identification are constantly changing as new discoveries are made.

  Acknowledgements

I would like to thank Howard and Tally Hull and their family for introducing me to the collection site. I would like to thank Rich Welsh my collecting partner for helping to find new deposits. I would like to thank Wes Wehr of the Burke Museum for all of his generous donations of research literature, time, and support. I would like to thank Steve Manchester and Elisabeth Wheeler for the donated literature and encouragement. I would also like to thank the editors of this article.
 

                                                         References

Anonymous, 1936, Chehalis fossil wood: Mineralogist, vol. 4, p. 22.

Beck, George F., 1941, Fossil woods of the far West: Central Washington College geology newsletter, vol. 1, no. 5, p. 2.

Beyer, A. F., 1954, Some petrified woods from Specimen Ridge area of Yellowstone National Park: American Midlands Naturalist, vol. 51, p. 556.

Edmondson, S. L., 1991, Petrified wood from Washington: Rocks and minerals, vol. 66, no. 4, pp. 321-325.

Hall, John W., 1952, The comparative anatomy and phylogeny of the Betulaceae: Botanical gazette, vol. 113, no. 3, pp. 244 & 251.

Manchester, S. R., 1980, Chattawaya; a new genus of wood from the Eocene of Oregon: American journal of botany, vol. 67, p. 59.

Manchester, S. R., Wheeler E. A., 1993, Extinct Juglandaceae from the Eocene of Oregon: IAWA journal, vol. 14(1), pp. 103-111.

Pabian, R. K., Zarins, A., 1994, Banded agates origins and inclusions: University of Nebraska-Lincoln conservation and survey division, educational circular, no. 12, p. 7.

Page, V. M., 1969, Angiosperm wood from the upper Cretaceous of Central California: American journal of botany, vol. 54, pp. 510-511.

Page, V. M., 1969, How to identify fossil woods: Gems and minerals, 7 installments published as a separate booklet, pp. 1-40.

Panshin, A.J., de Zeeuw, C., 1964, Textbook of wood technology: 3rd. ed.:McGraw-Hill books, pp. 1-705.

Pattie, Bob, 1983, Gems and minerals of Washington, Wa. D.N.R., pamphlet.

Prakash, U., Barghoorn, E. S., 1962, Miocene fossil woods from the Columbia basalts of Central Washington: Journal of the Arnold arboretum, vol. 17, no. 2, p. 165.

Reed, Katherine, 1995, Wa. D.N.R. geology division, publication editor, written communication.

Schasse, H. W. (compiler), 1987, Geologic map of the Central Quadrangle Washington: Wa. division of geology and earth resources, O.F.P. 87-11, pp. 6, 13, & map.

Selmeier, A., 1989, Anatomical identification of silicified woods from Southern Germany, Austria, and Switzerland: IAWA bulletin, vol. 10(3), no. 19, p. 346.

Sparks, Dennis M., 1967, Micro fossil zonation and correlation of some lower Tertiary rocks in Southwest Washington and some conclusions concerning a paleoecology of the flora: Michigan State University Ph. D. thesis, p. 71.

Wehr, Wesley C., 1995, Early Tertiary flowers, fruits, and seeds of Washington State and adjacent areas: Washington geology, vol. 23, no. 3, pp. 7 & 15.

Wehr, Wesley C., 1996, Early Northwest fossil plant collectors: University of Washington press (in preparation), p. 5.

Wheeler, E. A.; Baas, P., 1991, A Survey of the Fossil Record for Dicotyledonous Wood and its Significance for the Evolutionary and Ecological Wood Anatomy: IAWA Bulletin, vol. 12 (3) pp. 257 - 332.

Wheeler, E. A.; Baas, P.; Gasson, P. E. (editors), 1989, IAWA list of microscopic features for hardwood identification: International association of wood anatomists, bulletin no. 10(3) pp. 219-332.

Wheeler, E. A.; Pearson, R. G.; Lapasha, C. A.; Zacck, T.; Hatley, W., 1986, Computer-aided
wood identification, North Carolina agricultural research service, bulletin 474.

Wheeler, E. A.; Scott, R. A.; Barghoorn, E. S., 1977, Fossil dicotyledonous woods from Yellowstone National Park I: Journal of the Arnold arboretum, vol. 58, no. 3, pp. 280-301.

Wheeler, E. A.; Scott, R. A; Barghoorn, E. S., 1978, Fossil dicotyledonous woods from Yellowstone National Park II: Journal of the Arnold arboretum, vol. 59, no. 3, pp. 1-26.

Wheeler, E. A., 1995, Wood of  Plantus kerrii: IAWA journal, vol. 16(2), p. 129.

Wiedenhoeft, Alex, Botanist, Center for Wood Anatomy Research, Forest Products Laboratory, Madisen, Wisconsen; E-communication, 2000.

Wolf, J., 1968, Paleogene biostatigraphy of non-marine rocks in King County Wa.: USGS professional papers,., vol. 571.

Copyright© 1998 by Ed Strauss. All  rights reserved


How is petrified wood formed?

Written by Ed Strauss

 

  Quick answer: In many different ways.


Long answer : Petrified wood in general must be buried before it can be preserved. It can be buried in silt (run off sediment), mud flows, lahars, pyroclastic flows, volcanic ash flows, lava flows and meteorite "fall out". Probably the most common is pyroclastic and volcanic ash flows (which are similar).
99.999% of all living trees eventually decay, burn, or are eaten;  or a combination of these that leaves no fossil remains.  Also, if the cavity that the buried wood occupies collapses only a compression or impression fossil can form; similar to a leaf fossil.
If however the cavity that the buried wood occupies does not collapse (regardless of whether the wood disappears or not) a cast fossil can be formed. For petrified wood to be formed the uncollapsed cavity (containing the wood) must be filled with a "secondary" mineral. Many different minerals or combination of minerals can be the secondary filling agent. Silica, calcite, pyrite, hematite, and other minerals alone or in combination can fill these cavities. By far the most common is quartz or silica. It is believed that no matter how the wood was buried, at some point afterwards it must be over laden with silica rich volcanic "ash" (it's like an avalanche of hot sand) to become silicified. An exception could be silica that is deposited from the "fall out" of a meteorite strike. The silica that fills wood molds is seldom pure and other minerals (such as iron or manganese) add color to the petrified wood. The silica that fills the molds is usually dissolved in water. The water which contains the dissolved silica is usually hot. For some reason the dissolved silica in the water precipitates or is left in the mold, attaching itself to the lignun and cellulose of the wood ( if it is still there). First it dehydrates into silica gel. Then after a relatively short period of time it dehydrates further and hardens into opal. Finally after a much longer period of time it dehydrates further and hardens into chert or cryptocrystaline quartz. Jasper and agate are examples of other forms of microcrystaline or cryptocrystaline quartz.
Wood must be buried in an anaerobic (no air and bacteria) environment or it will decay to dust or "mud" and retain no cell structure. Petrified wood that retains observable cellular structure is a cast from a cavity (mold) that still had wood in it (which retained cell structure). Some people describe the mineralization of petrified wood that retains cell structure as encasement . I like to use the term saturation. The wood molecules (lignun and cellulose) become inseparably bonded to the silica molecules and it changes almost all of the wood's characteristics (e.g. color, odor, weight, porosity, and hardness). The characteristic that it does not necessarily change is its cell structure. That is why some petrified wood is identifiable as to family, genus or even specie. Over time however cell structure preservation can deteriorate as the silica of the petrified wood dehydrates or undergoes metamorphosis. 

 All of these different processes and conditions explain why there are so many different looking types of petrified wood, even from one small locality. It is because the individual environments they are formed in have subtle to major differences in amounts of available silica, beginning temperature, rate of dehydration, rate of cooling, and mineral composition. This makes understanding the complete processes complicated , but it provides nearly unlimited variety for collectors. 

Copyright© 2002 by Ed Strauss. All rights reserved. 

 


 

The Limitations of Tertiary Wood Identification
Using Low (10X) Magnification
by Ed Strauss
I am an amateur paleobotanist and wood anatomist from Washington State. I have studied  wood anatomy and fossil wood cell structure for several hundred hours over the last 5 years. The reading and examinations I have done have led me to the conclusion that only 5 families and part or all of 4 other genera can be exclusively distinguished with a (10X) hand lens. This number greatly increases with the use of a microscope at 100X. In this discussion I will use common names so you don't have to look everything up, but by using common names we will lose a little something in the translation. First let's keep in mind that the collection of different identified species of extant (modern) woods at the Forest Products Laboratory in Madison, Wisconsin numbers over 14,000! Ninety-five percent of these woods are not utilized commercially and most of us have never even heard of them. Remember that petrified wood can represent any species, not just the familiar ones.
Hardwoods- There are hundreds of species of  fossil hardwoods that have small pores (vessels) and small (narrow) rays that are evenly distributed. Some of these can be identified with a microscope, but none can be identified with a hand (10X) lens.
The specimens with smallest pores and rays are sometimes referred to as the "soft gum type", like sweet gum. This is no indication of the type of tree it represents, but only describes its type of cell structure. Sweet gum, tupelo, katsura, madrone, and cottonwood are each from different families yet they all have this "type" of structure.
The same is true of fossil woods that have medium-small pores and medium-small rays. They can be referred to as a "maple type" but could be any one of a hundred different species. Maple, birch, cherry, tulip tree, magnolia, and laurel have this "type" of structure. They can be separated with a microscope, but not a hand lens. An exception is noted by Dr. Elisabeth Wheeler, (professor of wood and paper science, North Carolina State University). She points out that "birch can be separated from the hard maples" because hard maples have "two size classes of rays and rays wider than the pores, [but this information would only work if you could be sure you were looking at a wood that was related to those that occur in the north temperate zone]".
The most common fossil wood that is recognizable with 10X magnification is oak. With only a hand lens the oaks can be separated into two groups. The first group is all ring porous oaks which include all red and white oaks. The second group contains the live oak and tan oak genera which are diffuse porous. Using a microscope, the ring porous oaks can be further divided into red and white genera based on the presents or absence of tyloses in the pores and the thickness of the fiber wall. Some rock hounds from Eastern washington claim to have identified over a dozen different species of fossil oaks, but scientists can't even do that with thin sections at 800X.
Other fossil hardwoods that have very broad multiseriate or compound rays that can be distinguished with a hand lens are alder and the group containing sycamore and beech. Alder has very small vessels when compared with oak or sycamore. It's rays are compound, composed of many uniseriate rays "bundled" together. Usually the annual growth ring dips slightly where it crosses a compound ray. Sycamore has pores smaller and much more crowded than oak but not as small or crowded as alder. Sycamore has distended rays, in that they get wider or flare out slightly at the growth ring boundary. Even though sycamore and beech are from two different families their structure is so similar that it is hard to tell them apart even with a microscope.
The walnut family usually has distinctive bands of parenchyma cells that can be seen with a hand lens in a specimen that has good cell structure. Persimmon and woods from other families also have this feature however, even oaks. Woods from the walnut family usually have medium sized pores that occur in multiples of 1-4 and are relatively sparse (not crowded). Another feature that some walnut family members exhibit is a tendency for a diagonal pore arrangement pattern. This along with banded parenchyma and multiple pores make a stronger case for the walnut family, but to be certain a microscope is needed to identify walnut, pecan, hickory or wingnut with certainty. Terms like "probably from the walnut family" and "a walnut type" are more accurate when identifying with a hand lens.
Elm and hackberry are two genera from the elm family. They closely resemble osage orange and mulberry from another family. They all have distinctive wavy bands of small vessels in the latewood potion of each growth ring. They can be distinguished as an "elm type" with a hand lens, but a microscope is needed to tell one from another.
Dr. Elisabeth Wheeler notes; "I think that it is possible to distinguish ring porous elms from the locusts of the legume family". She also says I should mention "that the chance of identifying wood with a hand lens is higher for geologically younger woods (Miocene/Pliocene) than for early Tertiary -- Eocene woods a mixture of temperate, subtropical and tropical woods".
Trochodendron is a family that has a group of two genera that can be distinguished with a hand lens. They are trochodendron and tetracentron. These are very unique woods because that have very wide distended rays like sycamore but their pores are tiny and appear to be tracheids like a softwood (conifer). They are very rare in the fossil record and always a joy to discover. I am not aware of a common name for these trees.
Jim Mills an advanced wood collector from California points out that grape (Vitaceoxylon) and snakewood (Mennegoxylon) two form genera can be identified with a hand lens. I looked them up and confirmed his information. (Tidwell, William D., 1998)
Conifers- There are no species or single genera that can be identified with a hand lens. There are groups of genera that can be distinguished however. The easiest is the group of genera in the pine family that contain regular resin ducts. This group contains all pine, douglas fir, spruce, and larch genera. Collectively they are some times referred to as Pityoxylon or "pine type". Sometimes fossils from this group, with good cell structure, can be further divided into the pine genus and the group containing douglas fir, spruce and larch. These last three are sometimes referred to as piceoxylon or "spruce type". The "pine" type usually has large singular evenly distributed resin ducts where as the "spruce type" usually has small ducts which appear in rows that are isolated and infrequent. The only other distinction than can be made with conifers is some woods from the bald cypress family. They have relatively large tracheids, no regular resin ducts and abundant parenchyma cells. All redwood genera and bald cypress genera have these features. It should be stated that to identify any conifer with certainty it should be thin sectioned and examined with transmitted light at 800X under all three views (transverse, tangential and radial). It is the cross field pitting, spiral thickenings, and tracheid dentations that make identification certain.
Gingko- Ginkgo is identifiable with a microscope at 100X, but not a hand lens. It has cell structure that resembles conifers as well as "soft gums". It is one of the most, if not the most expensive fossil woods ever sold. I recommend reading the formal description by Scott, Prakash and Barghoorn, published in the American journal of Botany, vol. 49, no. 10, pp. 1095-1101, Nov.-Dec. 1962 and examination with a microscope before investing money in this fossil wood. If you truly believe that it can be identified with a hand lens, then I have a couple of tons I'd like to sell you :o).

The Paleobotanists that I have submitted this article to for peer review have unanimously agreed with its findings (exceptions noted above). For balance;  to present one differing viewpoint, I will quote Virginia Page, professor emeritus, Stanford University,  from her excellent series of articles ("How to Identify Fossil Wood") published in Rocks and Minerals Magazine, 1969. She states; " Unfortunately only a few forms can be identified by this simple technique (hand lens). Gymnosperms (softwoods) can be distinguished from angiosperms (hardwoods), and oaks, palm, and certain ferns can be recognized." (parenthesis added)

It has been my experience at rock and mineral shows and at various web sites, including E-bay, that some fossil wood has been named solely to promote interest in it or artificially increase it's value. Often times when I question people, especially vendors, why they think the fossil wood is what they have labeled it, they give evasive answers. I am usually told that many years ago it was identified by a professor at some college. When questioned further they can never seem to remember either the professor's name or which college he was from. It is true that professors at colleges have identified hundreds of fossil wood specimens, but I can almost guarantee you that they have not seen or identified the particular piece that is for sale! Hopefully with the information in this article petrified wood collectors can use common sense, know the limitations of hand lens identification and use language to describe fossil wood specimens that is more accurate. The identification of fossil wood is not guesswork, it is a science.

 If you have concrete evidence that either supports or refutes my findings please contact me.  The history of Tertiary forests is "written in stone" but the description of them is not. estrauss51@yahoo.com  (Please, no attachments)

References

    Beck, George F., 1937, 1938, Determination of Fossil Woods, 5 part series: The Mineralogist, vol. 5, nos. 2-5, vol. 6 no. 7. *
    Beck, George F.,  August 1, 1941, Fossil woods of the far West: Central Washington College geology newsletter, vol. 1, no. 5, p. 1.
    Beck, George F., 1955-56, Fossil woods of the Far West, 5 part series (re-edited version): Mineral News 9:12-15, 10:10-22, 11:16-19, 12:12-14, 14:19-20. *
    Hoadley, R. Bruce, 1990, Identifying Wood, Accurate results with simple tools: The Taunton Press, pp. 1-223. ***
    Page, V. M., 1969, How to identify fossil woods: Gems and minerals, 7 installments published as a separate booklet, pp. 1-40.
    Panshin, A.J., de Zeeuw, C., 1964, Textbook of wood technology: 3rd. ed. :McGraw-Hill books, pp. 1-705. ***
    Prakash, U., Barghoorn, E. S., 1962, Miocene fossil woods from the Columbia basalts of Central Washington: Journal of the Arnold arboretum, vol. 17, no. 2, p. 165.
    Tidwell, William D., 1998, Common Fossil Plants of Western North America, Second Edition; Smithsonian Institution Press, pp. 231 and 244.
    Wheeler, E. A.; Pearson, R. G.; Lapasha, C. A.; Zacck, T.; Hatley, W., 1986, Computer-aided wood identification, North Carolina agricultural research service, bulletin 474. **
    Wheeler, E. A.; Scott, R. A.; Barghoorn, E. S., 1977, Fossil dicotyledonous woods from Yellowstone National Park I: Journal of the Arnold arboretum, vol. 58, no. 3, pp. 280-301.
    Wheeler, E. A.; Scott, R. A; Barghoorn, E. S., 1978, Fossil dicotyledonous woods from Yellowstone National Park II: Journal of the Arnold arboretum, vol. 59, no. 3, pp. 1-26.
    Wiedenhoeft, Alex, 2000, Botanist; Center for Wood Anatomy Research, Forest Products Laboratory, Madisen, Wisconsen; E-communication.
    * Hand lens identification key
    ** Microscope identification key
    *** Hand lens and microscope identification keys

Copyright© 2000 by Ed Strauss. All  rights reserved.


 

 


The Monetary value of Fossil (Petrified) Wood  

Written by Ed Strauss

 

 Question - I have acquired some petrified wood.  How much is it worth?
     Quick Answer - Somewhere between nothing and several thousand dollars.


     Long Answer - Petrified wood is usually of greatest value to the person who collects it. There are some exceptions however. This guide is very general and can give you an overall view of pricing. It explains some of the reasoning behind prices but may not reflect the actual value of a specific piece.

The value of petrified wood depends on these factors:
            1. Is it an entire trunk or large branch with concentric growth rings?
                "Rounds" that contain the pith or center of the tree and concentric growth rings are most valuable. The more circular the " round" is the greater its value.
            2. Does the specimen have unique or unusual features?
                Specimens that contain quartz geodes, boring insect galleries, cashes of petrified hickory nuts, or other unusual features have greater value; as do petrified burls with spiral cell growth patterns.
            3. What color is the outside ; the inside?
                 Generally the brighter and more colorful the specimen the higher the value. The greater the number of different colors in the specimen the higher the value.
            4. Are annual growth rings clearly visible?
                 If the growth rings are clearly visible the specimen is worth more, unless it is a type of fossil wood that has no growth rings (e.g. palm).
            5. Does the specimen have any cut and polished surfaces?
                Specimens that have been skillfully prepared for display with lapidary equipment are more valuable than ones that have poor workmanship or no preparation at all.
            6. Is the place it was collected still open?
                Some collecting areas that were open in the past are now closed or depleted, making specimens from that area more valuable because of scarcity.
            7. Where (county and state) was the specimen collected?
                Specimens from new collecting sites add value until supply catches up with demand.
            8. Is the outside angular with fractured or broken surfaces or does resemble a natural wood surface?
                Specimens that are casts with the outside appearing as the natural wood form are worth more than ones that have been fractured and broken away from larger pieces. This is especially true of examples that don't have much else going for them. It doesn't really apply to "rounds".
            9. Does it retain good cell structure under magnification?
                Depending on the interests of the buyer a specimen that has enough cell structure to tell if it represents either a hardwood or conifer it is more valuable than one that doesn't. If it is determined to be a hardwood, it is usually worth more than a softwood (with the exception of pre Tertiary wood). Hardwoods are not nearly as common.
            10. Is it an identifiable hardwood?
                Depending on the interests of the buyer hardwoods that retain enough cell structure to identify as to the family or genus they represent are rare and more valuable. Certain families and genera are more rare than others and the scarcity increases value.

    In general the price of petrified wood depends a lot on where and from whom you buy it. It can sell for as little as 1 cent per pound for a yard full, if it is holding up the sale of a house. Estate sales usually have the cheapest prices.
At a rock shop or rock and mineral show; broken chunks of petrified wood without any additional value characteristics usually sell for $1-3 per pound. Similar material with one to three add on value characteristics sell for $3-5 per pound; more than three features, $5 and up per pound. Cut slabs of petrified tree trunks or limbs sell for from $1 to $100 per inch of diameter measurement depending on the number of additional value characteristics. The value increases log rhythmically as diameter increases.

    My personal experience over the last six years is: The cheapest petrified wood I ever got from another individual was given to me free of charge. The most expensive specimen I ever saw that was for sale and was actually purchased for the asking price was $3,000 for a scientifically identified logette "round" of Ginkgo weighing about 50 pounds.

Many people have E-mailed me asking me to put a value on a piece of petrified wood they have. Some attach photos of the specimens they are inquiring about. Many ask me if I want to buy it or know of someone who might. My answer is always the same.

I cannot give a value to petrified wood from a photo, no matter how many angles or how high the resolution of the image! I can only give a value to specimens that I can personally examine. If you live in my area and want to bring it to my location that is OK, I will value it with no charge . If you want to hire me to travel to your location to inspect your specimen I will do that for time and traveling expenses. Please remember my interest in petrified wood is mostly scientific, I have never paid more than $6.00 for any piece I have purchased. 

The best way to find out how much your piece is worth is to go to a rock shop in your area. You can either show them what you have or compare what they are selling to what you've got. You might want to go to a rock and mineral show instead, to see more variety and get the opinion of more dealers. You might prefer to go to a meeting of your local rock hounding club. There will be people there who collect petrified wood and can help you evaluate your specimen or steer you to a dealer who would be interested.
 

Copyright© 2001, 2002 by Ed Strauss. All  rights reserved.


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