A Precambrian Puzzle
In pyrophyllite mines near Ottosdal, South Africa, miners have for decades been finding small, curious objects. These items, known as the Klerksdorp Spheres, are typically spherical or disc-shaped and range from 0.5 to 10 centimeters in diameter. They are recovered from deposits of pyrophyllite, a soft metamorphic mineral with a Mohs hardness of only 3, that formed approximately 2.8 to 3 billion years ago. This places their origin in the Mesoarchaean Eon, long before the appearance of multicellular life.
The composition of the spheres varies. X-ray diffraction analysis shows they are composed of either hematite (an iron oxide) or wollastonite (a calcium silicate) mixed with hematite and goethite. Unweathered specimens found deep in the pyrophyllite consist of pyrite. Many of the spheres feature striking parallel grooves encircling their equator, which makes them look manufactured. Their hardness is also unusual; some are reported to be harder than steel and cannot be scratched by it, unlike the soft pyrophyllite in which they are found. These characteristics have made them subjects for ancient astronaut theorists and proponents of "out-of-place artifacts" (OOPArts), who argue they are evidence of a prehistoric intelligent civilization.