Petrosphere

In archaeology, a petrosphere is the name for any spherical man-made object which is composed of stone of any size. These mainly prehistoric artefacts may have been created and/or selected, but altered in some way to perform their specific function, including carving and painting. Several classes of petrospheres exist, such as the stone spheres of Costa Rica; painted pebbles from Scotland; stone charms from Scotland; sandstone balls from such sites as Traprain LawRees, Thomas & Hunter, Fraser (2000). Archaeoligical excavation of a medieval structure and an assemblage of prehistoric artefacts from the summit of Traprain Law, East Lothian. 1996 - 7. P.S.A.S. 130, P. 413 - 440.] ; the Carved Stone Balls, which are mainly from Scotland, although they have also been found in Cumbria (England), and Ireland; and carved stone shot for cannons and trebuchets. The word comes from the Greek petros ("stone") and sphaira ("ball").

Naturally-formed stone balls, i.e. cannonball concretions and megaspherulites, 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 meters, found around Cerro Piedras Bola in the Sierra de Ameca, between Ahualulco de Mercado and Ameca, in Jalisco, Mexico, are petrospheres. 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, they are composed of granite, and natural processes cannot produce stone balls. 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.

See also

*stone balls
*Stone spheres of Costa Rica
*Carved Stone Balls of Scotland
*Grave orb
*stone round shot (cannonballs)
*spherical stone shot for trebuchets
*lapidary spheres

References and Bibliography

External links

* [http://ads.ahds.ac.uk/catalogue/adsdata/PSAS_2002/pdf/vol_004/4_211_224.pdf Scottish Stone charms]

Stone round shot (cannonballs)

*Ammunition column

*Ruffell, W.L., 1996, [http://riv.co.nz/rnza/hist/gun/smooth4.htm The Gun - Smoothbore Era 1550-1860: Projectiles] Royal New Zealand Artillery Old Comrades' Association, New Zealand.

Stone balls (spheres) of Coasta Rica

*Hoopes, J.W., 2005, [http://web.ku.edu/~hoopes/balls/ The Stone Balls of Costa Rica] University of Kansas, Lawrence, Kansas.

Carved stone balls of Scotland

*Hunterian Museum and Art Gallery, nd, [http://www.hunterian.gla.ac.uk/collections/museum/online_exhibitions/stones/objects/objects.shtml Carved Stone Balls] A gallery of carved stone ball photographs & information
*Marischal Virtual Museum, nd, [http://www.abdn.ac.uk/virtualmuseum/index.php?page=topic&topic=ball,..carved..stone&case=n06&first=7&last=18&roomlocation=ng ball, carved stone] Aberdeen Museum's virtual gallery of their Carved Stone balls
* [http://en.wikibooks.org/wiki/A_Researcher's_Guide_to_Local_History_Terminology A Researcher's Guide to Local History terminology]