Peanut wood is a type of petrified wood which is usually black or brown in color. It got its name from the white to cream markings which are about the same size and shape as peanuts. But before we dive into what peanut wood is and how it is formed, it is important to know what petrified wood is.
Petrified Wood
Every often, wood decomposes. But in the case of petrified wood, something which is commonly known as “wood converted into stone” occurs. When a tree turns into a fossil, it converts to a three-dimensional replacement of the plant. This happens when the actual organic matter of the tree is replaced by a silicate such as Quartz. As a result, it turns out that a tree is preserved in its original shape but changes its state and turns to stone.
Petrified wood is not rare. It is often found in sedimentary rocks or volcanic deposits around the world. It is often sold as gemstone and used as decorative material in households. Like all gem material, petrified wood is also associated with many healing properties.
How is Peanut Wood Different from Normal Petrified Wood?
Though peanut wood is a type of petrified wood, it is different from the normal petrified wood. The peanut wood we know today originated in Western Australia as a conifer tree. Over the years, when the trees died, they were carried away by the rivers into the salty sea.
This can be dated back to the Cretaceous time period. Back then, the sea into which the trees were carried was an epicontinental sea. This sea covered most of the continent which we now know as Australia. Also, during that time, there were marine species of clam which survived on wood. As the wood entered the sea, the tiny clam would swim to it and attach themselves over the piece of wood. As it was a source of food, these tiny clams would use their sharp edges of their shell to shave off small particles of wood. Within a few weeks, they could dig many deep tunnels into the wood.
As the tunnels were dug in the tree trunk, it would sink down to the sea floor. Apart from the wood eating clams, other species also survived in the water back in the prehistoric times. One particular species which aided in the formation of peanut wood was radiolarians. These are tiny plankton with siliceous shells which lived above the wood in the water. They generally thrive near the river mouth as they receive a continuous supply of nutrients. As the wood is brought to the sea, the radiolarians continue to live on the wood. But when they die, they usually sink in the water. Since their shells are made up of siliceous elements, they accumulate as a whole sediment.
Deep at the seafloor, there is wood with deep tunnels. Layer after layer, the white sediment from the dead radiolarian accumulates over the wood. Overtime, it enters the holes in the wood log Since the shells are siliceous, some of them get dissolved in the water. This concentrated silica solution enters the cavities of the wood. And then just like normal petrified wood, the organic matter of the tree is replaced with silica. Over a period of time, layers of mud and sand cover the wood and with increasing pressure the process of petrification begins. It is believed that this petrification process occurred around 120 million years ago.
However, peanut wood is different in appearance compared to petrified wood. Unlike normal petrified wood which closely resembles the original tree but is different in texture, peanut wood has white or cream peanut sized markings formed due to radiolarians occupying the bore holes in the tree.
Wood Eating Clams Today
While wood eating clams were common in the Cretaceous period, a few species of wood eating clams still live in the oceans. These wood eating clams are now known as shipworms. These shipworms have posed a threat to wooden boats for quite a long time. As the wooden boat moves around in the sea, these worm-like creatures cling onto the bottom of the boat and create tunnels in the wooden surface. This can cause serious damage especially to smaller wooden boats.
To overcome this problem, shipbuilders started using thin copper sheets to protect their ships from the damage of shipworms. But despite the measures, shipworms continue to cause structural damage to the ship.
How Peanut Wood was Found?
Millions of years ago the process of peanut wood petrification began in the region which we now know as Australia. Back then, the region was covered with sea. The seafloor which contained peanut wood was lithified into sedimentary rocks which were then known as Windalia Radiolarite. As the continental formation changed, these sedimentary rocks rose above the surface of the sea. In these rocks, peanut wood was discovered and classified as a gem material.
As this unique petrified wood was found, it soon became famous due to its distinct appearance. It was then used to make decorative items for households and commercial use.
Today, gem hunters around the world seek to find Windalia Radiolarite. It is widely sold through online auctions and gemstone websites. It is also displayed at gemstone and mineral exhibitions such as Tucson Mineral Shows. Given the easy access, people around the world can buy this surprising and interesting piece of petrified wood.
Conclusion
Peanut wood is a gem material found in the sedimentary rocks called Windalia Radiolarite. It is indeed surprising to see an ancient piece of wood that was bored by clams is now a precious gem material with multiple uses.
