If you give a lump of clay to a child, the first shape they’ll sculpt is likely to be a sphere, or a near-spherical ball.  It’s a shape nature seems to love, and there are complicated reasons for that – explained through Newtonian Physics – but in the hands of a human, a sphere is one of the earliest products of our creative mind.

Humans have been sculpting or shaping stone into roughly spherical shapes for millennia, and any man-made spherical object is called a petrosphere.  There are many examples of petrospheres in our past, and some are quite spectacular.

The creatively named Carved Stone Balls of Scotland, are a particularly interesting example.  These late Neolithic artefacts, attributed to Scotland, but truthfully found throughout Great Britain, are perhaps the most famously known petrospheres.  They are a collection of somewhere near 500 stone balls, carved and shaped by, it is thought, the Pict culture of early Iron Age northern Scotland.  They are mostly spherical balls with anywhere from 3 to 160 protruding knobs on their surface.  Some are ornately carved, while others are worn relatively smooth.

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One of the Carved Stone Balls of Scotland - British Museum

Not a lot is known about them, owing to the manner in which they’re usually found.  Most known examples were uncovered accidentally through agricultural activities, and it is thought that this skews our perspective of their purpose and importance in early cultures, because only the more ornate and aesthetically pleasing ones have found their way into collections, leaving the possibly more common examples lost to the elements.

Leading theories suggest that they were used as weapons, essentially identifying them as components of ancient bolas (throwing weapons) or perhaps ammunition for crude slingshots or similar devices.  This gives you some idea of their size, which is generally 7cm across.  They’re made of a type of basalt stone, sometimes called greenstone, and are quite hard.  Which makes one think it would have been a bad day, were one to have a Carved Stone Ball flung at one’s head.

Of course, not every example of a petrosphere is as easily explained.

Found in the Diquis Delta of Costa Rica are possibly the most enigmatic collection of stone spheres on the planet.  Numbering somewhere near 300 individual spheres, ranging from a few centimeters in diameter to upwards of 2 meters, the Stone Spheres of Costa Rica, also known as the Diquis Spheres and Las Bolas, are a complete mystery.

Carved mostly of gabbro, which is similar to basalt, some of these spheres weigh up to 15 tons, which creates a problem for those trying to explain how they were made and where they came from.  You see, there are no quarries in that region, and since moving one of the heavier examples would be difficult even today, we’re at a loss to explain how they managed to transport them to their current positions.

Costa Rica spheres
Costa Rica stone spheres. (image credit: Antonio Huneeus)

The stones were carved between 200BCE and 1500CE.  They’ve been attributed, alternately, to the Diquis culture and to the Aguas Buenas pre-Columbian culture (200BCE-600CE), but they can’t be dated accurately for various reasons relating to problems inherent in available techniques.

It’s believed that they were carved as a monument to Tara or Tlatchque, the thunder-god of the Bribri culture.  It was said that he used a giant blowpipe to shoot the balls, known to them as Tara’s cannon balls, at the Serkes, or gods of winds and hurricanes, to drive them away.

Some claim that the Diquis Spheres are, or at least most examples are, perfectly spherical, and we’ve heard this claim before.  A large sampling of the Diquis Spheres were measured by Harvard archaeologist Samuel Lothrop in the late 1940’s, and his resulting conclusions, published in his book Archaeology of the Diquis Delta, Costa Rica (1963), offered his assessment of them as impossibly spherical.  That assessment has led several alternate history and ancient alien buffs to proclaim that the Diquis Spheres are an anomaly in our past, possibly attributed to extraterrestrial intervention or a lost advanced civilization.

Later review of Lothrop’s measurement procedures calls his conclusions into question.  Some of the spheres are out-of-round by as much as five centimeters, which pointedly denies them the status of perfectly round.

There are some candidates for petrospheres that aren’t what they appear to be, however.

The Klerksdorp Spheres, named so for the small South African mining town they were found in, were, or are, said to be small metal balls, impossibly round and harder than diamonds.  They’re also said to be somewhere around 3 billion years old.

A typical example of the Klerksdorp Spheres

There are problems with that description though, not the least of which is the fact that they aren’t made of metal.  They aren’t perfectly round either…far from it.

The Klerksdorp Spheres, also known as the grooved spheres, are naturally formed hematite, a type of antiferromagnetic iron ore commonly used in jewellery.  Most of the spheres are actually disk shaped, some with concentric grooves around their circumference.  They formed through a common process known as concretion, and as concretions go they aren’t even the most impressive examples.

The Cannonball Concretions of Cannonball River in North Dakota, the Moqui Marbles of southern Utah, and the Kansas Pop Rocks are particularly interesting examples of natural concretions, and in some cases are better representations of this geological process than are the Klerksdorp Spheres, though some theories are harder to leave behind than others.

One thing is clear through all of this though, and that’s that we humans have an affinity for round shapes.  In terms of modelling clay, a sphere may be one of the easiest shapes to create – though a perfect sphere is notoriously difficult to achieve – but as chiseled sculpture goes, managing to create a ball that is, to the naked eye at least, nearly spherical is a feat worthy of the best Renaissance Masters.  Of course, some say that these ancient cultures had help, whether in the form of an outside influence, or perhaps by way of a special magical or alchemical potion capable of melting and forming stone to their will.  However they did it, it was most certainly done, and we are the beneficiaries of their wisdom, wherever it came from.

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