Petrified wood or also called Petrified Wood or fossil wood can be found all over the world. How is this possible? What causes petrified wood to petrify and how does this petrification process work?

Petrified wood

Before we immediately dive into the depths, first a brief word about petrified wood. Petrified wood can best be described as a fossil imprint of a tree. Due to the petrification process it still looks like a tree, but actually there are only about 10% of the actual tree. The rest has decayed slowly in the millions of years before and minerals have replaced it.

This works the same with the fossils that we still find, with shark teeth or dinosaur bones. The name fossil wood is therefore appropriate.

The petrification process of petrified wood

Ok, now in more depth. To be honest, I myself quickly dropped out of chemistry. With the following I try to explain as well as possible in simple language how the petrification process of petrified wood works.

The petrified wood, the petrified tree or branch and in some cases even the petrified palm tree, are created when it comes to lie under a layer of sediment. This sediment is saturated with minerals. Because the wood hardly comes into contact with oxygen, it decays very slowly. This allows the minerals to replace the cell walls and fill the empty spaces in the wood.

Examples of petrified wood products

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What does wood consist of?

Are you ready for it? It is now getting a bit complicated and technical, but to understand how the petrification process works, it is useful if you know what wood consists of.

Wood mainly consists of holocellulose (cellulose and hemicellulose) and lignin. If you take a normal, dry tree, it consists of 95% of this. Almost half of this is cellulose, cellulose gives wood much of its strength. Cellulose consists of long chains of polymerized glucose arranged in microfibrils that reinforce the cell walls in the wood. Hemicellulose, a branched polymer of several simple sugars, makes up most of the remaining hardwood composition, while lignin, a polymer of phenylpropanes, is more present in softwoods. The hemicellulose and lignin encase and reinforce the cellulose microfibrils.

Decomposition of wood

I hope that the above can be followed a bit, because below you can see why this introduction is important. I am now going to explain to you how wood normally decays.
Dead wood is normally broken down quickly by microorganisms, starting with the holocellulose. Lignin is hydrophobic (water repellent) and decays much more slowly. The rate of decay or rotting is affected by temperature and moisture content, but exclusion of oxygen is the most important factor in preserving wood tissue.
Organisms (bacteria or fungi) that break down lignin need oxygen to survive. As a result, fossil wood older than the Eocene (about 56 million years or older) has lost almost all of its holocellulose, leaving only lignin. In addition to microbial degradation, wood buried in an alkaline environment is rapidly degraded by inorganic reactions with the alkali.

From wood to petrified wood

Wood is protected from decomposition by rapid entrapment in mud, especially mud formed from volcanic ash. The wood is then mineralized, which actually transforms it into stone. Unmineralized wood also exists, but this is very uncommon. The petrified wood is later exposed by the wearing away of the soil around it (erosion). Unmineralized fossil wood is quickly destroyed when exposed by erosion, but petrified wood is durable and therefore remains.

Watch our video about the origin of petrified wood

Minerals in petrified wood

About 40 minerals have been found in petrified wood, but silica is by far the most important. Silica binds to the cellulose in the cell walls and forms a kind of template. Additional silicic acid then replaces the cellulose during decomposition, so that the cell walls are often preserved in great detail.

After this, silicification begins within the cell walls, and the spaces within and between the cells are gradually filled with silicic acid. Over time, almost all of the original organic material is lost and, as mentioned earlier, only 10% of the original tree remains. The other material is almost pure silicic acid, containing only iron, aluminum, and alkali and alkaline earth elements. Iron, calcium and aluminum are the most common.

The colors of petrified wood

Most of the color in petrified wood comes from trace metals. Iron is the most important of these, it can give the wood several different shades, depending on the way it oxidizes (rusts). Chromium produces bright green petrified wood. The differences in color are probably due to the different periods of mineralization.

Curious about our other petrified wood products?

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