Petrified wood is essentially mineralized wood; it’s the fossilised remains of wood, sometimes found in the tree’s original shape.
Petrified wood is the remains of trees which have been fossilised over thousands of years. During this fossilisation process, the remains of the wood are replaced by minerals meaning fossilised wood is a mineral build-up which has replaced the original wood.
Very occasionally, petrified wood specimens are found that look so much like the tree they have been formed from that it is hard to tell them apart from actual wood by sight alone.
The main giveaway with these examples is the weight of the fossils, being significantly heavier than the wood they were formed from. It is unusual to find examples with this level of near-perfect preservation, but many specimens have clearly recognisable bark and woody structures.
How do you get petrified wood?
For wood to become petrified, it must be buried quickly under mud, silt or volcanic ash before any rotting can set in.
It must remain buried in this sediment for thousands of years.
The ground where the wood is buried has to be incredibly well compacted to prevent decay.
Less well-compacted wood would allow oxygen or bacteria to get to the wood, and the wood would begin to decay.
When the conditions are just right, the organic material becomes fossilised. During this mineralisation process, groundwater flows through the dead tree, and its wooden remains are replaced over time by the dissolved mineral solids in the water.
The result is a fossil of the original woody material that often exhibits preserved details of the bark and wood but is made entirely of minerals, including silica, calcite, pyrite and, occasionally, other inorganic materials, such as opal.
What is the difference between wood and petrified wood?
Wood is an incredibly versatile and beautiful material we are all used to seeing and using.
Wood is harvested from trees and used widely in all kinds of construction projects, from whittled spoons to enormous ships, buildings, and everything in between.
Although called petrified “wood”, petrified wood is not wood at all. It doesn’t share any of the qualities which make wood such a valuable mainstay of the industry.
As petrified wood is a mix of minerals which have replaced the wood that was once there, it is more closely related to stone than wood. Unlike wood, it is inflexible, difficult to work with, can shatter, and is incredibly heavy.
Despite the differences between wood and petrified wood, in some cases, petrified wood can be, visually, an almost replica of the original wood.
The original tree’s ring patterns, bark and wood grain are usually clearly visible.
Patterns are occasionally so precise the specific variety of trees can be identified from a sample of petrified wood.
Is petrified wood rare?
In many parts of the world, petrified wood is not rare.
Petrified wood is often found where volcanic activity has covered plant material with lava and ash or where a mudflow had occurred in the past.
Petrified wood is especially abundant around coal reserves, too.
Many of the world’s most famous petrified wood localities are in exposed sedimentary rocks that were once ancient floodplains or lake systems where low dissolved oxygen levels prevented decay.
While it takes between tens of thousands and millions of years for petrified wood to form in the natural world, scientists have discovered ways to replicate the necessary processes and can now artificially create petrified wood in days making it less rare now than it was previously.
Is petrified wood a rock?
Because the word petrified means ‘turned to stone’, it is sometimes believed petrified wood is the original organic matter that has turned to stone, but that’s not the case.
In petrified wood, minerals have replaced all of the original organic matter from the tree over thousands of years.
It would be more accurate to say petrified wood is a mineral compound than a rock, though it shares more qualities with rocks than wood.
What is petrified wood used for?
Petrified wood is solid and polishable to a high shine.
Because of its polishable surface and its beautiful colours and patterns, petrified wood is used as a semi-precious gemstone in jewellery.
It can also be used alongside wood as an ornamental stone in trinkets, ornaments, furniture and clocks.
Summary
- Petrified wood is formed over thousands of years when minerals from water replace wood from dead trees.
- Petrified wood is not wood, and it is not rock.
- Petrified wood can look just like wood but is made of minerals.