Peanut wood is a variety of petrified-wood that is usually dark brown to black in colour. It is recognized by its white-to-cream-colour markings that are ovoid in shape and about the size of a peanut. It received its name from these peanut-size markings. It is a fossil gem with a very unusual history.
Much of the peanut wood being sold today began its life as a conifer tree on land now known as Western Australia. When these trees died, rivers carried them into a shallow, salty epicontinental sea that covered much of what is now the Australian continent. In the sea this driftwood came under attack from shellfish known as Teredo that would attach themselves & eat the wood, eventually creating bore holes and tunnels. Soon the waterlogged wood would sink to the sea floor. Here the bore holes became filled with a lightly-coloured sediment (& would eventually create the peanut like markings). Over a period of time, the wood became covered in layers of mud and sediment and eventually the petrification process began. The petrification process was believed to have occurred around 120 million years ago.