Petrified wood is a kind of fossil. When plant material is protected from decay due to organisms and oxygen and buried by sediment this is formed. Groundwater rich in solids is dissolved then gushes through the residue, substituting the original plant material with a new inert material such as opal or calcite, silica, or pyrite. The original woody material’s fossil is the result of this process. It often exhibits sealed details of the wood, bark, and cellular structures.

What is Petrified Wood

Some samples of petrified wood are such precise preservations that people do not understand they are fossils and are shocked by their weight when they pick them up. Near-perfect specimens are unusual; however, samples that show evidently identifiable woody structures and bark are very common.

Petrified wood is not unusual. It is found at many locations worldwide in sedimentary rocks and volcanic deposits. Where there is volcanic bustle, enclosed plant material is sometimes found with mudflows, ash, or pyroclastic debris. It is also found where wood formed from sediment deposited by air or water is replaced by minerals deposited from groundwater. It is particularly found around coal joints, although many of the wood specimens in these locations are moulds and casts rather than petrifications.  

Petrified wood and its many other names

Petrified wood is known by a wide variety of names. A general term for wood that has been preserved or petrified by other methods of fossilization is called “Fossilized wood”. Petrified wood that has been replaced by opal, a shapeless form of silica, is called “Opalized wood”. Wood that has been replaced by agate, a form of chalcedony or microcrystalline quartz, is called “Agatized wood”. Wood that has been replaced by any form of silica is Silicified wood.

Uses of Petrified Wood

In lapidary work petrified wood is often used. It is cut into shapes for making jewellery. To make bookends it is sawn into blocks; to make table tops it is sawn into thick slabs; and for clock faces it is sawn into thin slabs. It can be used for many other crafts. It can be cut into cabochons or used to make tumbled stones. To make tumbled stones small pieces of petrified wood are placed in a rock tumbler.

For lapidary work only a small part of petrified wood is suitable. Those with lots of gaps, poorly preserved specimens, or closely-spaced fractures break while being worked or do not polish well. Specimens with spectacular colour or with no voids or fractures are highly prized for lapidary work.

Petrified wood can be collected only from private property with the landowner’s permission, or from government lands, but only in small quantities. You need to get permission and collecting rules from the owner of private property before you start collecting.