Petrified Wood Meaning, Properties, Facts and Photos

What is Petrified Wood?

Petrified wood is a type of fossil in which the organic material has been replaced by natural minerals. It forms through a geological process called petrifaction.

Petrifaction begins when ancient trees fall and are quickly buried. Due to a lack of oxygen the plant material is protected from decay.

As groundwater rich in dissolved minerals such as quartz, calcite, pyrite, and occasionally opal flows over the volcanic ash, mud, or sediment, it seeps into pores and cavities of the buried organic material.

When the water dries up, the minerals crystallise creating an internal cast.

Although most original plant material decomposes, cell walls often remain intact and surround the newly formed crystals. The result is a fossil of the original woody material.

In some cases petrified wood can be an almost exact replica of the original organic matter, right down to microscopic levels. It's not unknown for ring patterns, bark and wood grain of the original tree to be clearly visible.

Patterns can occasionally be so precise that the specific variety of tree can be identified.

The colour of petrified wood comes from the various minerals that seeped into the wood during the petrifaction process. Red or pink comes from hematite, shades of yellow, orange and brown come from goethite.

Green comes from chromium, copper or iron compounds, and white is from quartz. Black is carbon or pyrite, and blue and purple come from manganese dioxide.

The process of petrifaction which is very slow, is believed to take around 10,000 years at the very minimum, from start to finish.

Some research suggests that under the right conditions, it may happen over a much shorter period of time. However, what is known for sure is that the slower the process, the more precise the replication.

It's sometimes believed that petrified wood is the original organic matter that has turned to stone, but this is incorrect. The organic matter is always replaced by natural minerals.

The Meaning of 'Petrified' Wood

'Petrified wood' comes from the word 'petrifaction', which is from ancient Greek meaning 'wood turned into stone'.

When someone is petrified, they're paralysed by fear, which causes them to freeze. The word 'petrified', which means to convert or change something into stone, comes from the Latin 'petra' meaning 'rock' or 'stone'.

The suffix 'fied' is believed to come from the Latin 'facere' meaning 'to make'. 

The terms 'fossilised wood' and 'petrified wood' are often used interchangeably. Deciphering the difference between the two is not easy.

This lengthy thread in the Fossil forum from 2012 addresses the matter well. You can read it here.

Petrifaction is a form of fossilisation, but for simplicity, fossilisation tends to be used instead. In the forum thread in the previous link, one thing that's emphasised is that not all fossils are reinforced or replaced with minerals. Those which are seem to be classified as 'fossilised' instead of 'petrified'.

According to the Oxford dictionary, 'fossil' means "the remains or impression of a prehistoric plant or animal embedded in rock and preserved in petrified form." It defines 'petrifaction' as "the process by which organic matter exposed to minerals over a long period is transformed into a stony substance."

Although any organism can be petrified, wood, bone and shell are the most common.

The word 'fossil' comes from the Latin 'fossus' meaning 'dug up' or 'buried'.

What is Peanut Wood?

Peanut wood is a distinctive and unusual type of petrified wood that's not particularly well known.

Around one hundred and twenty million years old, most of the world's current supply of peanut wood started life as conifer trees in Western Australia.

As the trees died, they were carried away by water and ended up in the sea as driftwood. They were then attacked by the teredo navalis also known as the naval shipworm.

This saltwater clam which has an appetite for boring through wood has been an extremely destructive pest for as long as there has been wood in the sea.

Once full of boreholes, the driftwood sank to the ocean floor and the process of petrifaction began.

Peanut wood gets its name from the distinctive round to oval-shaped markings which can resemble peanuts.  

Article Pictures

The petrified wood in the picture at the top of our article and the petrified ammonite are on display in London's Natural History Museum. Photos by Stone Mania.

The second picture is courtesy of Stan Celestian. Clicking this image redirects to more impressive photos of petrified wood.

The petrified wood slices in the third picture are from our collection. With the exception of the peanut wood, all photos are clickable and redirect to the original image.

Pop-up images: Pyrite, hematite, goethite, - Courtesy of Stan Celestian. Chromated petrified wood (petrified wood coloured by impurities of chromium) - Courtesy of Ron Wolf. Graphite (carbon) - Courtesy of James St. John.