The Moeraki Boulders are located halfway between Oamaru and Palmerston in North Otago in New Zealand's South Island. The area is well-known for its archaeological treasures, including fossils, ancient geological formations and Māori artwork. Estimated to be 50 - 60 million years old, the Moeraki Boulders are scattered along the shoreline but they aren’t going anywhere. Some weigh up to seven tonnes. These mudstone rocks were formed through a process known as concretion. Here layers of mud, silt and calcite build upon each other, in much the same way a pearl is formed layer by layer over a grain of sand.