Opalized Wood: Gemstone, Formation, Where to Find it

What is Opalized Wood

Opalized wood is a type of petrified wood that has been replaced by opal. It is formed when silica-rich water infiltrates the cellular structure of wood and gradually replaces the original organic material with silica. This process can take millions of years.

Opalized wood is often found in sedimentary rocks, such as sandstone and shale. It is most commonly found in Australia, Oregon, Nevada, and Mexico.

How does Opalized Wood Form

The specific steps in the formation of opalized wood are as follows:

1. A tree dies and falls to the ground.
2. The tree is buried in sediment or volcanic ash.
3. The sediment or ash traps oxygen, preventing the wood from decaying.
4. Water seeps through the sediment or ash, carrying dissolved silica.
5. The silica replaces the organic material in the wood, atom by atom.
6. The wood is eventually petrified, forming a solid opal replica of the original wood.

Opalized wood is often found in sedimentary rocks, such as sandstone or limestone. It can also be found in volcanic rocks, such as rhyolite or tuff.

Opalized wood is a beautiful and rare gemstone. It is often used in jewelry and other decorative items. It is also prized for its unique play of colors, which is known as opalescence.

Factors that affect the formation of opalized wood

Here are some of the factors that affect the formation of opalized wood:

• The type of wood: Some types of wood are more likely to be opalized than others. For example, coniferous woods, such as pine and fir, are more likely to be opalized than deciduous woods, such as oak and maple.

• The environment: The environment in which the wood is buried is also important. Silica-rich environments, such as volcanic ash or hot springs, are more likely to produce opalized wood.

• The time: The amount of time that the wood is buried also affects the formation of opalized wood. The longer the wood is buried, the more likely it is to be completely replaced by silica.

The different types of opalized wood

There are two main types of opalized wood: common opal and precious opal.

• Common opal

  Common opal is the most common type of opalized wood. It is characterized by its milky white or translucent appearance. It does not have any play-of-color, which is the characteristic iridescence that is seen in precious opal.

• Precious opal

  Precious opal is a rarer type of opalized wood. It is characterized by its vibrant colors and play-of-color. Precious opal is often used in jewelry and other decorative items.

Properties of Opalized Wood

Opalized wood has a Mohs hardness of 6-7, which means that it is relatively soft. It is also brittle and can easily break if it is dropped or hit.

Opalized wood is often used in jewelry and other decorative items. It can also be used as a gemstone, but it is not as valuable as precious opal.

Precious opal-replaced fossil wood from Nevada, USA Photo: James St. John

Opalized wood is found in many different parts of the world, but the most famous deposits are found in:

Australia: The opal fields of Australia are home to some of the most beautiful and valuable opalized wood in the world. The most famous deposit is the Coober Pedy opal fields, which are located in South Australia. 

Oregon: The United States also has a number of important opalized wood deposits, including the John Day Fossil Beds National Monument in Oregon.  

Nevada: Nevada is home to the Rainbow Ridge opal mines, which are known for their high-quality opalized wood. 

Mexico: Mexico is another important source of opalized wood, with deposits found in the states of Chiapas, Chihuahua, and Sonora.  

Brazil: Brazil is home to some of the most unique and colorful opalized wood in the world. The most famous deposit is the Chapada dos Parecis region, which is located in the state of Mato Grosso. 

Opalized wood can also be found in smaller deposits in other parts of the world, such as Indonesia, Russia, and Madagascar.

How much does Opalized Wood Cost

The value of opalized wood depends on a number of factors, including the color, clarity, and size of the specimen. Precious opal is typically more valuable than common opal.

Opalized wood is a highly prized gemstone, and it can command a high price. However, there are also many affordable pieces of opalized wood available on the market.

Opalized Wood in the Geological Record

Opalized wood is a relatively rare type of fossil, but it has been found in rocks from a variety of geological periods. The oldest known examples of opalized wood come from the Triassic Period, about 200 million years ago. Opalized wood is also found in rocks from the Jurassic, Cretaceous, and Cenozoic periods.

The distribution of opalized wood in the geological record suggests that it was most common in warm, humid climates. This is because silica-rich water is more likely to be present in warm, humid environments. 

Colorful crystal patterns are displayed in a cross-section of petrified wood in the Petrified Forest National Park, located in northeast Arizona. ARTERRA/GETTY IMAGES

How to care for Opalized Wood

Opalized wood is a relatively soft gemstone, with a hardness of 6.5 to 7 on the Mohs scale. It is therefore important to take care when handling opalized wood jewelry or objects.

Opalized wood should be kept away from sharp objects and harsh chemicals. It should also be cleaned with a soft cloth and mild soapy water.

Conclusion

Opalized wood is a beautiful and unique gemstone that is formed when wood is replaced by opal. It is found in many different parts of the world and is often used in jewelry and other decorative items. If you are looking for a unique and special gemstone, opalized wood is a great option.