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Stone ball In archaeology, a stone ball or petrosphere (from Greek πέτρα (petra), "stone", and σφαῖρα (sphaira), "ball") is the name for any spherical man-made object of any size that is composed of stone. These mainly prehistoric artifacts may have been created or selected, but altered in some way to perform their specific function, including carving and painting.  Several classes of petrospheres exist, such as:
Naturally formed stone balls, such as concretions and spherulites, have been at times misidentified as petrospheres. For example, fringe archaeologists and advocates of prehistoric extraterrestrial visitors have repeatedly argued that the stone balls, which range in diameter from 0.61 to 3.35 m (2 ft 0 in to 11 ft 0 in), found around Cerro Piedras Bola in the Sierra de Ameca, between Ahualulco de Mercado and Ameca, in Jalisco, Mexico, are petrospheres[citation needed]. However, these natural stone balls are megaspherulites that have been released by erosion from a 20- to 30-million-year-old ash flow tuff, which originally enclosed them and in which they formed. The proponents of these stone balls being petrospheres base their arguments on the false claims that all of these spheres are perfectly round, that they are composed of granite, and that natural processes cannot produce stone balls[citation needed]. Similarly, cannonball concretions, i.e. those found along the Cannonball River in North Dakota and near Moeraki, South Island, New Zealand, also have been misidentified as petrospheres[citation needed]. Palaeolithic shaped stone balls Shaped stone balls are found at Palaeolithic sites across Africa, Asia, and Europe, associated with Oldowan (c. 2.6 million – 1.7 million years old), Acheulean (c. 1.76 million – 130,000 years old), and African Middle Stone Age (c. 280,000–50,000 years old) stone tool industries.[2] The function of shaped stone balls is still debated. Some archaeologists argue that they were deliberately shaped by humans to use as tools; others that they are byproducts of the use of rocks for other purposes.[2]
See alsoReferences and bibliography
External links Wikibooks has a book on the topic of: A Researcher's Guide to Local History Terminology  Wikimedia Commons has media related to Stone spheres.
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