In parts of South Africa, especially near the town of Klerksdorp, miners have uncovered strange stone objects that look almost man-made. These objects are smooth, rounded, and sometimes nearly perfect spheres. Known as Klerksdorp spheres, they have puzzled observers for decades because of their symmetry and polished appearance.
Despite early speculation, these spheres are not artefacts or fossils. They are natural geological formations called concretions. Concretions form when minerals accumulate around a central core within soft sedimentary rock. Over long periods, dissolved minerals in groundwater begin to crystallise and grow outward evenly in all directions.
The rock layers around Klerksdorp are extremely old—more than 2.5 billion years in age. When these layers were still soft mud or volcanic ash, mineral-rich water moved through them. Iron compounds and other minerals slowly bonded together, hardening into compact masses. Because the minerals spread outward at similar rates, the growing stones naturally took on spherical or oval shapes.
As surrounding rock eroded over millions of years, the harder concretions remained intact while softer material wore away. This process gradually exposed the spheres, leaving them sitting loose within mines or embedded in rock faces. Some spheres also show shallow grooves or ridges caused by differences in mineral composition during growth.
Their smooth surfaces are not the result of rolling or polishing. Instead, they reflect uniform internal growth and long-term stability within the rock. What appears perfectly shaped is simply the outcome of slow, consistent mineral processes acting under the Earth’s surface for immense spans of time.