Carved stone balls
They are usually round and rarely oval, and of fairly uniform size at around 2+3⁄4 inches or 7 cm across, with anything between 3 and 160 protruding knobs on the surface.
As objects they are very easy to transport and a few have been found on Iona, Skye, Harris, Uist, Lewis, Arran, Hawick, Wigtownshire and fifteen from Orkney.
A single example was found in Norway in a medieval cairn; it is thought most likely that this had been acquired and carried home by a Norseman on an expedition to Scotland.
Balls of plain sandstone with the facets from shaping still clearly visible were found at Traprain Law in East Lothian.
[7] In 2013, archaeologists discovered a carved stone ball at Ness of Brodgar, a rare find of such an object in situ in "a modern archaeological context".
[8] Early, undecorated, polished stone balls have also been found 'in-situ' inside a 5,500 year-old tomb at Tresness on Orkney by Professor Vicki Cummings.
[9] Many balls are said to be made of "greenstone", a general term for all varieties of dark, greenish igneous rocks, including diorites, serpentinite, and altered basalts.
[citation needed] The decoration used falls into three categories: More than one design is used on the same ball and the standard of artwork varies from the extremely crude to the highly expert which only an exceptionally skilled craftsman could have produced.
[13] Spirals or plastic ornament which is similar to Grooved Ware is found on the Aberdeenshire examples, this being a type of late Neolithic pottery not known in the north-east but common in Orkney and Fife.
The carving does not appear to have any practical purpose in general, however it has been suggested that one type, with very distinct knobs, was used for processing copper ores (see under 'Function').
[11] Many of the late Neolithic stone balls have diameters differing by only a millimetre, suggesting that uniform size was important for their purpose.
By mapping find-sites in Aberdeenshire, Scotland, it can be shown that often these small stone spheres were found in the vicinity of Neolithic megalithic circles.
To test the proposal, experimental archeologists built a model system, substituting hard wooden balls made to the same size.
The balls were placed into grooves cut in parallel longitudinal wooden 'sleepers'; these supported an overlying carrying-board that the giant test stone rode on.
