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PETRIFIED WOOD FOR SALE
About Petrified Wood
Around 400 million years ago during the Devonian period, the first woody plants had begun evolving on land, and soon after began to dominate the Earth's surface. Like all life-forms, these first trees left behind fossil evidence of their remains, but because of the distinct cellular structure of fibrous, woody plants, they were able to retain much of their form and shape through the fossilization process. This has led to modern-day discoveries of entire forests buried solidly underground, revealing entire habitats lost to the shifting sands of time.
A slice of 200 million-year0old petrified wood from Arizona with details such as tree rings preserved.
Fossilization occurs most often when an organism dies on or in sediment saturated with water. Soft organic tissue degrades relatively rapidly compared to inorganic compounds like the surrounding sediment. When the organic component of a deceased organism decomposes, it leaves empty space within the compacted sediment that then holds the shape of the organism’s remains. Mineral-rich water is then drawn through this empty space, leaving behind sediment that fills the empty space, which is then compacted. This process, called permineralization, is one of the most commonly observed methods of fossilization, and is the process by which the forests of Earth’s prehistory are preserved and known to us in the present day.
Trees, like all plants, have a different cellular structure from most other organisms on the planet. Uniquely, plants have cell walls, structures surrounding all of their cells made of cellulose, hemicellulose, and lignin. These are complex carbon-based molecules that form, among other things, the majority of the structural elements of wood. The cells that compose wood are by nature structurally boxy and strong. The mineralization process begins on this outermost layer first, while the inner parts of the cell mineralize at a much slower rate. Thus, when the permineralization process affects submerged trees, much of the actual bodily structure of the tree is retained.
It is very important for fossilization that the remains of an organism decompose slowly, over a long period of time. Most known petrified forests were found with evidence that they were buried very quickly all at once, most commonly through volcanic ash, mudslides, or a combination of the two. The ground that they were buried in was saturated with moisture, indicating lower oxygen content and preventing the most common decomposer organisms (bacteria, fungi, subterranean arthropods) from eating away at the trees in great numbers. By preventing decomposers from doing this, much of the decomposition that actually occurs happens over a very prolonged period of time, perfect for fossilization.
Volcanic preservation tends to be the most common method of fossilization for petrified wood, as it is unaffected by climate trends. But it is not the only method of preservation: for example, the wet and warm conditions of the Carboniferous period led to a high amount of forestation across the globe. This, coupled with the high moisture levels in the surrounding sediment, would mean that any trees caught in landslides or mudslides of any kind would be in perfect petrification conditions.
Of the three major components of un-petrified wood (cellulose, hemicellulose, and lignin), lignin is the molecule that endures the longest. Lignin is also the molecule that binds with minerals to form the major structure of petrified wood. Via hydrogen bonding, lignin molecules combine with mineral molecules (predominantly silica-based minerals like opal and quartz) and form the base template from which the petrified tree takes its shape. Because the fossilization occurs on such a minute, cellular level, much of the detail of the original organism is preserved, even microscopically. Scientists can determine a lot about a tree or forest’s physiology, lifespan, and group ecology through the preservation of details found in petrified wood. Evaluating those microscopic structures can even help scientists identify the genera of petrified wood, and sometimes even species.
Much of what comprises the mineral element of petrified wood comes from silica-based minerals. Common minerals that fall under this grouping include opal, agate (chalcedony), and quartz. Less common minerals that help form petrified wood include pyrite and calcite, and overall about 40 different minerals have been known to be found in petrified wood specimens.
Petrified wood is usually found in dusty, earth-toned colors, but can also be found in bright and brilliant tones based on trace amounts of metals present in the mineralizing sediment. Copper, cobalt, and chromium can all lend the fossil a blue or green tone; high carbon content can create a deep black fossil; iron can give the wood a red, yellow, or brown color depending on how oxidized it is; and manganese can create wild arrays of pink and orange.
Some vibrantly colored petrified wood from Arizona. The red, orange, and purple colors are caused by iron oxides present in the silica that replaced the wood.
Rarely, some specimens of petrified wood have been found where they were preserved in silica-rich hot springs. In such cases, the heat of the springs coupled with the existing silica-rich water led to greater preservation of detail, as evidenced by specimens such as plant fossils found in the Rhynie Chert (A Scottish lagerstätte, or fossil site of exceptional preservation), which retain even some cellular details.
In recent decades, some scientists have sought to artificially recreate the petrification process. Using some artificial sources of silica, they have experimented to create artificial petrified wood, both to research the geological process of permineralization and to create petrified wood for use as a ceramic material.
How Much Is Petrified Wood Worth?
In general, petrified wood is a very abundant fossil. Many petrified wood deposits are quite extensive, some covering hundreds and even thousands of square miles! Due to its abundance, most petrified wood has very little if any commercial value. Some private landowners in Arizona sell petrified logs for decorative purposes for around $2 per pound, which includes the labor and heavy machinery needed to extract, load, and transport them.
Only a very small percentage of petrified wood (like what you see for sale on our website) has coloration, detail, and lack of fracturing that makes it suitable for polishing. Even then, the majority of value is not in the rough petrified wood itself, but the labor costs involved in the polishing process. Polishing petrified wood is a very labor-intensive manual process. To give you an idea, some of the better polishers in the US charge $1-2 per square inch for custom polishing work on petrified wood slabs. Thus, like most fossils, the commercial value is not in the fossil itself but the labor that went into extracting it and preparing it.
Notable Petrified Forests
Petrified forests are found all over the world and date back as far as the beginning of the evolution of large land plants in the Devonian period, approximately 390-400 million years ago, to as recently as 15 million years ago. Older fossils give us great insight into the colonization of the land by aquatic organisms that began during the Devonian period, and more recent fossils often have some of their constituent cellulose and hemicellulose structures intact for observation. However, older specimens are quite rare, since fossilized trees from that time would have been smaller and less susceptible to fossilization.
Most petrified forests are found in badlands areas, rocky deserts where wind based-erosion clears away sedimentary rock, leaving the rather hardy and durable petrified wood visible on the surface. Many present-day deserts were once lushly vegetated many millions of years ago, fading away over time due to reduced water levels.
In North America, one of the more notable petrified wood sites is Petrified Forest National Park, a massive petrified forest in eastern Arizona. Its stores of petrified wood date back to the late Triassic period of the Mesozoic era. At least nine extinct tree species have been found in PFNP, and over 200 plant species in total. The preservation here can be attributed to the volcanic ash phenomenon, which layered ash on top of the forest and preserved it for the future.
Petrified logs in the Arizona petrified forest.
Another notable location is the Brazilian geopark Paleorrota (“Paleo route”). This is somewhat older than the Arizonan site, dating to the Permian-Triassic border approximately 250-270 million years ago. In the northern part of the park, the Caturrita formation exquisitely preserves many Triassic conifer species. This geopark is also where the first Brazilian dinosaur species Staurikosaurus was discovered.
Namibia contains the petrified forest of Khorixas, a national monument of Permian period trees that are believed to have been swept away by flooding and embedded in alluvial soil.
In Australia, the petrified forest outside of Chinchilla, Queensland is known for its striking red coloration. This wood dates to the Jurassic period of the Mesozoic era, when dinosaurs were at the top of the trophic ladder.
Asia has no shortage of petrified forests. India contains two famous sites. The National Fossil Wood Park in Tiruvakkarai has fossils dating back to the Miocene, while the older Akal Fossil Wood Park has trees that date back to the Jurassic, showing beautiful contrasting white, brown, orange, and blue colorations. In China, a Devonian-aged fossil forest was just unearthed in the past decade, quite a remarkable discovery considering the rarity of forests dating back to that time!
Other Interesting Facts
Petrified "peanut wood" from Australia. The whitish areas are boreholes left by teredo worms that were then filled in with silica.