How Does Wood Petrify?

Wood must first be covered with such agents as volcanic ash, volcanic lava flow, volcanic mud-flows, sediments in lakes and swamps or material washed in by violent floods – by any means which would exclude oxygen and thus prevent decay. A number of mineral substances (such as calcite, pyrite, marcasite) can cause petrification, but by far the most common is silica. Solutions of silica dissolved in ground water infiltrate the buried wood and through a complex chemical process are precipitated and left in the individual plant cells. Here the silica may take a variety of forms; it may be agate, jasper, chalcedony or opal. The beautiful and varied colors of petrified wood are caused by the presence of other minerals that enter the wood in solution with the silica. Iron oxide stains the wood orange, rust, red or yellow. Manganese oxide produces blues, blacks or purple.

Mineralized fossil bone

Fossil bone can be mineralized in several ways. Permineralized fossils have their original pore space infilled with minerals. Permineralization is commonly confused with petrification, in which the original material of an organism is replaced with minerals, and the pore space is infilled with minerals. In other words, petrification is a combination of permineralization and replacement.

By far, permineralization is the most common type of preservation for most fossil bone, and even when petrification has occurred, there is almost invariably evidence that permineralization occurred first (otherwise, there would be no preservation of the original cavities in the bone!). So, if you are wondering what petrified bone looks like, imagine the bone material being replaced by other minerals, sometimes preserving the fine structure of the bone, sometimes not, and the open pore spaces infilled as seen here. I plan to eventually present some truly petrified bone eventually.

In either case, the boundary between the original, open pore space and the replaced material is quite obvious, because of variations in the shape and orientation of the crystals infilling the pores. In the case of the Haversian canals of bone, this is usually indicated by concentric growth of crystals from the inner surface of the canal towards the interior, often with clear radially-arranged crystals and/or layers of different minerals at early infilling versus later stages.

For more information on bone fossilization processes, including illustrations, see Reid (1996) and Hubert et al. (1996).

‘Instant’ Petrified Wood

‘Instant petrified wood’ — so ran the heading to the announcement in Popular Science, October 1992 [1]. It’s also the reality of research conducted at the Advanced Ceramic Labs at the University of Washington in Seattle (USA).

Researchers have also made wood-ceramic composites that are 20–120% harder than regular wood, but still look like wood. Surprisingly simple, the proces involves soaking wood in a solution containing silicon and aluminium compounds. The solution fills the pores in the wood, which is then oven-cured at 44°C (112°F). According to the lab’s research director, Daniel Dobbs, such experiments have impregnated the wood to depths of about 5 millimetres (0.2 inches). Furthermore, deeper penetration under pressure and curing at higher temperature have yielded a rock-hard wood-ceramic composite that has approached petrified wood. Patent ‘Recipe’ for Petrification

However, priority for the discovery of a ‘recipe’ for petrification of wood must go to Hamilton Hicks of Greenwich, Connecticut (USA), who on September 16, 1986 was issued with US Patent Number 4,612,050. [2] According to Hicks, his chemical ‘cocktail’ of sodium silicate (commonly known as ‘water glass’), natural spring or volcanic mineral water having a high content of calcium, magnesium, manganese and other metal salts, and citric or malic acid is capable of rapidly petrifying wood. But in case you want to try this ‘recipe,’ you need to know that for artificial petrification to occur there is some special technique for mixing these components in the correct proportions to get an ‘incipient’ gel condition.

Hicks wrote:

‘When applied to wood, the solution penetrates the wood. The mineral water and sodium silicate are relatively proportioned so the solution is a liquid of stable viscosity and is acidified to the incipient jelling [gelling] condition to a degree causing jelling [gelling] after penetrating the wood, but not prior thereto. That is to say, the solution can be stored and shipped, but after application to the wood, jells [gels] in the wood. When its content is high enough, the penetrated wood acquires the characteristics of petrified wood. The wood can no longer be made to burn even when exposed to moisture or high humidity, for a prolonged period of time. The apparent petrification is obtained quickly by drying the wood. [3]

The patent indicates that the amount of acid in the solution appears to have a critical effect on the production of the gel phase within the cell structure of the wood, although evaporation also plays its part. Wood thoroughly impregnated, even if necessary by repeated applications or submersions of the wood in the solution, after drying evidently has all the characteristics of petrified wood, including its appearance.

Both Hicks and the researchers at the University of Washington lab have suggested potential uses for such ‘instant’ petrified woods:

* Fireproofing wooden structures such as houses and horse stables (the horses wouldn’t be tempted to chew on the wood either!).
* Longer-wearing floors and furniture.
* Greater strength wood for structural uses.
* Insect, decay and salt water ‘proofing’ wood in buildings, etc.

Rapid Natural Petrification

The chemical components used to artificially petrify wood can be found in natural settings around volcanoes and within sedimentary strata. Is it possible then that natural petrification can occur rapidly by these processes? Indeed! Sigleo [4] reported silica deposition rates into blocks of wood in alkaline springs at Yellowstone National Park (USA) of between 0.1 and 4.0 mm/yr.

From Australia come some startling reports. Writing in The Australian Lapidary Magazine, Pigott [5] recounts his experiences in southwestern Queensland:

‘. . . from Mrs McMurray [of Blackall], I heard a story that rocked me and seemed to explode many ideas about the age of petrified wood. Mrs McMurray has a piece of wood turned to stone which has clear axe marks on it. She says the tree this piece came from grew on a farm her father had at Euthella, out of Roma, and was chopped down by him about 70 years ago. It was partly buried until it was dug up again, petrified. Mac McMurray capped this story by saying a townsman had a piece of petrified fence post with the drilled holes for wire with a piece of the wire attached.

‘Petrified wood thousands of years old? I wonder is it so?’

Several months later Pearce[6] added further to these amazing stories of woods rapidly petrified in the ground of ‘outback’ Queensland:

‘. . . Piggott writes of petrified wood showing axe marks and also of a petrified fence post.

‘This sort of thing is, of course, quite common. The Hughenden district, N. Q. [North Queensland], has . . . Parkensonia trees washed over near a station [ranch] homestead and covered with silt by a flood in 1918 [which] had the silt washed off by a flood in 1950. Portions of the trunk had turned to stone of an attractive colour. However, much of the trunks and all the limbs had totally disappeared.

‘On Zara Station [Ranch], 30 miles [about 48 kilometres] from Hughenden, I was renewing a fence. Where it was dipped into a hollow the bottom of the old posts had gone through black soil into shale. The Gidgee wood was still perfect in the black soil. It then cut off as straight as if sawn, and the few inches of post in the shale was pure stone. Every axe mark was perfect and the colour still the same as the day the post was cut . . . .

‘I understand that down in the sandhill country below Boulia [south-western Queensland], where fences are often completely covered by shifting sand, it’s a common thing for the sand to shift off after a number of years, leaving stone posts standing erect.’

From the other side of the world comes a report of the chapel of Santa Maria of Health (Santa Maria de Salute), built in 1630 in Venice, Italy, to celebrate the end of The Plague. Because Venice is built on watersaturated clay and sand, the chapel was constructed on 180,000 wooden pilings to reinforce the foundations. Even though the chapel is a massive stone block structure, it has remained firm since its construction. How have the wooden pilings lasted over 360 years? They have petrified! The chapel now rests on ‘stone’ pilings![7] Experimental Verification

Of course, none of these reports should come as a surprise, since the processes of petrification of wood have been known for years, plus the fact that the process can occur, and has occurred, rapidly. For example Scurfield and Segnit [8] had reported that the petrification of wood can be considered to take place in five stages:

1. Entry of silica in solution or as a colloid into the wood. 2. Penetration of silica into the cell walls of the wood’s structure. 3. Progressive dissolving of the cell walls which are at the same time replaced by silica so that the wood’s dimensional stability is maintained. 4. Silica deposition within the voids within the cellular wall framework structure. 5. Final hardening (lithification) by Drying out.

Furthermore Oehler [9] had previously shown that the silica minerals quartz and chalcedony critically important in the petrification of wood, can be made, rapidly in the laboratory from silica gel. At 300°C (572°F) and 3 kilobars (about 3,000 atmospheres) pressure only 25 hours was required to crystallize quartz, whereas at only 165°C (329°F) and 3 kilobars pressure the same degree of crystallization occurred in 170 hours (about seven days).

Similarly, Drum [10] had partially silicified small branches by placing them in concentrated solutions of sodium metasilicate for up to 24 hours, while Leo and Barghoorn [11] had immersed fresh wood alternately in water and saturated ethyl silicate solutions until the open spaces in the wood were filled with mineral material, all within several months to a year. Likewise, as early as 1950 Merrill and Spencer [12] had shown that the sorption of silica by wood fibres from solutions of sodium metasilicate, sodium silicate and activated silica sols (a homogeneous suspension in water) at only 25°C (77°F) was as much as 12.5 moles of silica per gram within 24 hours–the equivalent of partial silicification/petrification. As Sigleo concluded,

‘These observations indicate that silica nucleation and deposition can occur directly and rapidly on exposed cellulose [wood] surfaces. [13] Conclusions

The evidence, both from scientists’ laboratories and God’s natural laboratory, shows that under the right chemical conditions wood can be rapidly petrified by silicification, even at normal temperatures and pressures. The process of petrification of wood is now so well known and understood that scientists can rapidly make petrified wood in their laboratories at will.

Unfortunately, most people still think, and are led to believe, that fossilized wood buried in rock strata must have taken thousands, if not millions, of years to petrify. Clearly, such thinking is erroneous, since it has been repeatedly demonstrated that petrification of wood can, and does, occur rapidly. Thus the timeframe for the formation of the petrified wood within the geological record is totally compatible with the biblical time-scale of a recent creation and a subsequent devastating global Flood. References

1. Phil McCafferty, ‘Instant petrified wood?’, Popular Science, October 1992, pp. 56-57.

2 Hamilton Hicks, ‘Mineralized sodium silicate solutions for artificial petrification of wood’, United States Patent Number 4,612,050, September 16,1986, pp. 1-3. As cited by: Steven Austin, CatastroRef–‘Catastrophe Reference Database: Catastrophes in Earth History, Geologic Evidence, Speculation and Theory’, Institute for Creation Research, San Diego. Entry no. 267.

3. Hicks, Ref 2.

4. A.C. Sigleo, ‘Organic geochemistry of silicified wood, Petrified Forest National Park, Arizona’, Geochimica et Cosmochimica Acta, Vol. 42, 1978, pp. 1397-1405.

5. Roy Piggott, The Australian Lapidary Magazine, January 1970, p. 9.

6. R.C. Pearce, ‘Petnfied wood’, The Australian Lapidary Magazine, June 1970, p. 33.

7. Segment on ‘Burke’s Backyard’, Channel 9 TV, Sydney, June 1995.

8. G. Scurfield and E.R. Segnit, ‘Petnfication of wood by silica minerals’, Sedimentary Geology, Vol. 39, 1984, pp. 149- 167.

9. John H. Oehler, ‘Hydrothermal crystallization of silica gel’, Geological Society of America Bulletin, Vol. 87, August 1976, pp. 1143-1152.

10. R.W Drum, ‘Silicification of Betula woody tissue in vitro’, Science, Vol. 161, 1968, pp 175-176.

11. R.E Leo, and E.S. Barghoorn, ‘Silicification of wood’, Harvard University Botanical Museum Leaflets, No. 25, 1976, pp. 1-47.

12. R.C. Mernll and R.W. Spencer, ‘Sorption of sodium silicates and silicate sols by cellulose fibers’, Industrial Engineering Chemistry, Vol. 42, 1950, pp. 744-747.

13. Sigleo, Ref 4, p. 1404.

Trees to Stone

Imagine a large basin area with numerous rivers and streams flowing through lowland. A lush landscape with coniferous trees up to nine feet in diameter and towering almost two hundred feet tall surrounds you. Ferns, cycads and giant horsetails grow abundantly along the waterway, providing food and shelter for many insects, reptiles, amphibians, and other creatures.

During the Triassic Period (200 – 250 million years ago) the Colorado Plateau area of northeastern Arizona was located near the equator and on the southwestern edge of the landmass known as “Pangea”. (Eventually this super-continent separated to create our present continents.) This tropical location resulted in a climate and environment very different from today. Fossil evidence of this ancient land lies in the sediments called the Chinle Formation that is now exposed in Petrified Forest National Park.

Araucarioxylon Arizonicum

Over time, trees died or perhaps were knocked over by floodwaters or wind. Rivers carried the trees into the lowlands, breaking off branches, bark, and small roots along the way. Some trees were deposited on the flood plain adjacent to the rivers and others were buried in the stream channels. Most of the trees decomposed and disappeared. But a few trees were petrified, becoming the beautiful fossilized logs we see today. Most 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 3 species are now extinct.


Some logs were buried by sediment before they could decompose while volcanoes to the west spewed tons of ash into the atmosphere. Winds carried ash into the area where it was incorporated into the deepening layers of sediment. Ground water dissolved silica from the volcanic ash and carried it through the logs. This solution filled, or replaced cell walls, crystallizing as the mineral quartz. The process was often so exact that replacement left a fossil that shows every detail of the logs’ original surfaces and, occasionally, the internal cell structures. Iron rich minerals combined with quartz during the petrification process, creating the brilliant rainbow of colors.

Uplift and Erosion:

Over time, this area has endured many changes. About 60 million years ago, after the Chinle Formation was deeply buried by younger strata, the region was uplifted as part of the massive Colorado Plateau. As time passed, many rivers and storms eroded the land, removing the layers of rock until, again, the Chinle Formation was exposed. Now fossilized logs lie strewn across the clay hills and are exposed in cliff faces. Most logs are broken into segments. Humans did not cut the logs. Because the sections are still in order, we know that the logs fractured after they were buried and the petrification process was complete. Since petrified logs are composed of quartz, they are hard and brittle and break easily when subjected to stress. Earthquakes or the gradual lifting of the Colorado Plateau may have produced such stress.

Petrified wood is found in every state and in many countries, so why was this place made a national park? It was originally established to protect some of the largest and most beautifully preserved concentrations of petrified wood in the world. We now know, however, that few places in the world have a fossil record of the Triassic Period that is so diverse and complete. These things make your park special.

Next here is a website that can be accessed by having the students go to this site to perform some lesson or information search based on what is appropriate for your class room.


How Fossils are Formed

Excerpt from Introduction to Fossil Collecting (C) 1994-2000, Glen Kuban, E-mail: Part of Kuban’s K-Paleo Place home page

When an animal or plant dies, it usually is soon eaten by scavengers or decomposed by bacteria. However, in some cases a flood, mudslide, sandstorm, or other event quickly buries a creature, or it may become entombed in ice, tar, or tree resin. When such an event happens, an organism is largely protected from decay, and may remain buried for millions of years. Through geologic time, and interactions with mineral seepage, pressure, and other factors, the organism or material around it may change in various ways. The changes may involve distortions, infillings, color changes, and the partial or complete conversion to rock (discussed below). Eventually, the specimen may be exposed again (this time as a fossil) through erosion or other factors, including human excavators.

In general, the hard parts of an organism such as teeth, bones, shells, and wood, are more likely to be preserved than soft parts, since hard parts are more resistant to scavenging and decay. Fortunately, well-preserved specimens including soft parts are sometimes found, and missing parts often can be deduced with fair confidence by studying the structures of the existing parts, and by comparisons with similar species living today.

The process by which dead organisms or their parts are transformed into fossils is called fossilization. The study of the factors and conditions that affect the fossilization process is called taphonomy. One of the most common changes fossils undergo through time is the partial or complete conversion to rock. This process (which can happen in various ways), is called petrifaction or petrification. You have probably heard the term “petrified,” meaning “turned to stone.” Certain types of petrification are given special names. If only the open spaces or soft parts of an organism are filled with minerals (such as silica or calcite), leaving the solid parts intact, the process is called permineralization. If an organism’s bones, shell, or other hard parts are dissolved and replaced with other minerals, the process is called replace- ment. Sometimes the original shell or skeleton will remain, but undergo a change in crystal structure called recrystallization. If the entire organism dissolves away, leaving a hollow cavity, the cavity is referred to as a natural mold. If a natural mold is filled with minerals, the infilling is called a natural cast, or if you like fancy words, a pseudomorph. Often molds and casts occur together. Sometimes the area inside the shell of a mollusk (such as a clam) will fill with sediment, after which the shell dissolves away. This internal mold is sometimes called a steinkern, which is German for “stone kernel.”

In some cases an organism’s remains may be preserved through freezing (also called refrigeration), or through drying (desiccation), as sometimes happens with droppings of cave animals. Some fossil plants and insects are compressed into thin carbon films, sometimes called carbonizations, or distillations. Other fossils comprise only the outward impression of an organism or its parts, such as an impression of tree bark. If the impression or trace that records the living movements or functions of an ancient organism (as in the case of animal burrows, trails and trackways), the fossil is called a trace fossil or ichnite. Trace fossils (as distinguished from “body fossils”) also include eggs, tooth marks, stomach contents, and coprolites (fossil excrement), and any other product or trace made while an ancient organism was still alive. Petrifaction

Another common mode of preservation of plants is petrifaction, which is the crystallization of minerals inside cells. One of the best-known forms of petrifaction is silicification, a process in which silica-rich fluids enter the plant’s cells and crystallize, making the cells appear to have turned to stone (petrified). Famous examples of silicification may be found in the petrified forests of the western United States (see Petrified Forest National Park). Petrifaction may also occur in animals when minerals such as calcite, silica, or iron fill the pores and cavities of fossil shells or bones. Recrystallization

Many animal shells are composed of the mineral aragonite, a form of calcium carbonate that breaks down over millions of years to form the more stable mineral calcite. This method of preservation, called recrystallization, destroys the microscopic details of the shell but does not change the overall shape. Snail shells and bivalve shells from the Jurassic Period (205 million to 138 million years before present) and later are still composed principally of aragonite. Most older shells that have been preserved have recrystallized to calcite.

How are Fossils Created?

It’s an exciting feeling to see a fossil in a museum. But how are these fossils formed? What are the different ways that a fossil can be saved for us to see? Well, to answer this, there are four major ways in which a fossil can be preserved. They are: petrification, molds, impressions, amber and sedimentary fossils. Below, find a description of each:


Petrification occurs when a living object is slowly turned to stone of a huge number of years. Petrification is sometimes called “permineralization” because it is brought about mainly by minerals. Minerals seep through the organic matter is an object, filling it completely. Then the organic matter rots away, but a mineral version of the fossil is left. This process usually works best in the fossilization of trees. Some of the most famous petrified trees are in California, and contain huge rings that describe ancient eras.


Molds are literally molds of an animal. Sometimes animals became trapped in mud, dirt or clay. Then their bodies deteriorated, leaving behind their shape and size in the ground. When the hole created by this is discovered, it is known as a mold. A mold can be created in two ways. An organism can deteriorate and leave a hole showing details of its body. Or a hollow object, such as a shell, can become filled with matter. When the object deteriorates, the matter filling it is left behind as a mold.


Have you ever seen a dinosaur’s footprint? These are formed when mud, clay or silt containing an imprint made by an animal turns to stone. This is an example of an impression, or the impression that an animal leaves in soft matter. These fossils are useful in determining weight and structure of ancient animals. Sometimes, even toenails and pores can be seen!


Some fossils are preserved in amber. Amber is a sap-like substance from trees. It is sap that has dried over hundreds of years. Because tree sap is so sticky, it is possible for bugs and even small animals to be trapped within it. In time, the sap hardens to amber and a perfect specimen of the creature is preserved. Amber fossils are plentiful, and are sometimes worn as necklaces and bracelets today!

Sedimentary Fossils

The sea bed contains perhaps the most fossils on the earth. This is because the soft ground under the sea is made of sedimentary rock, or rock that is composed of layers of land. When sea creatures die, they drift to the bottom of the ocean and are covered with a layer of sand. In time, a volcano or mudslide, etc.,may cover the surface under which they are buried. In this way, a new layer is added, and the fossil is preserved in layers of time. Therefore, fossils made in this way are sometimes referred to as “sedimentary fossils.” While there are many of these fossils, they are often very hard to get to. Often, they are dug from ground that was once underwater. In fact, fossils in sedimentary layers are useful in indicating when land was above and below ground.