13 Rocks You Won't Believe Aren't Man-Made!

SolarHatch Updated: 2025-10-13

10. Moeraki Boulders

For decades both scientists and tourists have been enthralled with the over fifty spherical stones known as the Moeraki Boulders, which are found on Koekohe Beach on South Island New Zealand. Not merely a monument to the long, patient work of natural processes, but these amazing geological formations—each weighing several tons and some standing more than six feet high—have great cultural value for the nearby Maori people.
On the prehistoric seafloor, huge stones started to develop some 60 million years ago. The region that is currently Koekohe Beach was under a large, shallow sea during this time. Their development began with the collection of sediment around a central core, which might have been a fossil, a bit of shell, or perhaps a particle of sand. Layer upon layer of calcite minerals progressively accumulated around this core over millions of years, much as a pearl forms in an oyster.
Larger concretions stayed buried in the mudstone bottom as they developed. As the shoreline has shifted and sea levels have varied, the surrounding mudstone—which is softer and more prone to erosion—has progressively worn away over millions of years. Gradually revealing the harder, more resistant stones, this erosion process has left them exposed on the beach as we know them now.
The way the Moeraki Boulders were created produces their unusual spherical form. These stones are so unique because the calcite minerals collected around the central core did so uniformly in all directions, producing almost flawless spherical form. Further proof of their concretionary source comes from some of the cracked open stones revealing a hollow interior lined with crystals.
From a geological standpoint, the Moeraki Boulders provide insightful analysis of the past scene of New Zealand. They give hints about the processes of sedimentation and mineral deposition that took place millions of years ago as well as proof of the marine environment that formerly prevailed in this region. Our knowledge of concretion formation and the geological history of the Otago coast has much advanced thanks in great part to the study of these rocks.
Within Maori culture, the stones have particular significance in local folklore and custom. Maori tradition holds that the stones represent the remains of eel baskets, calabashes, and kumara (sweet potatoes) that washed ashore following the fabled canoe, Araiteuru, crashed at adjacent Shag Point (Matakaea). This mythology links the boulders closely to the history and identity of the local Maori people as well as offers a cultural explanation for their existence.
Drawn from all around the world to wonder at their size, form, and mystery of formation, the Moeraki Boulders have grown to be a popular tourist destination. The facility is under great control to strike a mix between public access and environmental preservation. Although visitors are not allowed to climb on or try to remove the rocks, they are urged to see and photograph them so that these geological beauties will stay unaltered for next generations to enjoy.
More stones will probably show themselves over time as sea levels vary and coastal erosion advances. With the possibility for fresh discoveries and landscape modification in the next years, this continuous process of exposure gives the site a dynamic element. The Moeraki Boulders are a potent reminder of the enormous timescales involved in geological processes and the surface of our planet's always shifting character.