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Petrified Wood Properties Facts and Photos

small trunk section of the mineral petrified wood
Contents

1. What is Petrified Wood?
2. Meaning of Petrified Wood
3. What is Peanut Wood?
4. Article Pictures
5. Shop for Petrified Wood

What is Petrified Wood?

Petrified wood is a type of fossil in which the organic material has been replaced by natural minerals.  The original cell structure however has remained largely intact.

Petrified wood forms through a geological process called petrifaction.  This takes place when fallen trees and plants become buried under volcanic ash or sediment.  Due to lack of oxygen they're protected and preserved.

As groundwater rich in minerals such as quartz, calcite, pyrite and occasionally opal flows over the organic matter, it fills pores and cavities.  When the water dries up the minerals crystallise which creates an internal cast.

Although most of the original organic matter decomposes, the cell walls often remain intact and surround the newly formed crystals.

petrified wood mineral in a museum display cabinet

The colours of petrified wood are caused by the different minerals.  Red or pink comes from hematite, shades of yellow, orange and brown comes from goethite.  Green comes from pure reduced iron also known as native iron and white comes from quartz.  Black is carbon or pyrite and blue and purple come from manganese dioxide.

The process of petrifaction is extremely slow.  It's believed to take around 10,000 years at the very minimum from start to finish.  There is some research to suggest under the right conditions it may take place over a much shorter period of time.  What is known for sure is the slower the process the more precise the replication.

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

It's sometimes believed petrified wood is the original organic matter that has turned to stone but that's not the case.  The organic matter is always replaced by natural minerals.

three slices of polished petrified wood

Meaning of Petrified Wood

The word petrifaction comes from Ancient Greek and means 'wood turned into stone'.  The word 'fossil' comes from the Latin 'fossus' meaning 'dug up' or 'buried'.

In English 'petrified' describes a situation where someone is paralysed by fear which causes them to freeze.  The word 'petrified' means to convert or change something into stone.  It comes from the Latin 'petra' meaning 'rock' or 'stone'.  The origins of 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.

A thread from 2012 that I discovered makes interesting reading and addresses the matter well.

Petrifaction is a form of fossilisation but for the purpose of simplicity, fossilisation tends to be used instead.  In the forum thread in question, 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 as opposed to 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. 

Petrified ammonite fossil on display in London's Natural History Museum

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 has an appetite for boring through wood.  It 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.  

Peanut wood mineral specimen

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 non-compressed image.

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