Carved stone balls are petrospheres dated from the late Neolithic, to possibly as late as the Iron Age, mainly found in Scotland, but also elsewhere in Britain and Ireland. They are usually round and rarely oval, and of fairly uniform size at around inches or 7 cm across, with anything between 3 and 160 protruding knobs on the surface. They range from having no ornamentation (apart from the knobs) to extensive and highly varied engraved patterns. A wide range of theories has been produced to explain their use or significance, with none gaining very wide acceptance.
They are not to be confused with the much larger smooth round stone spheres of Costa Rica.
Age and distribution
Carved stone balls date as old as 5,200 years old, coming from the late Neolithic to at least the Bronze Age.
Nearly all have been found in north-east Scotland, the majority in Aberdeenshire, the fertile land lying to the east of the Grampian Mountains. A similar distribution to that of Pictish symbols led to the early suggestion that carved stone balls are Pictish artefacts. The core distribution also reflects that of the Recumbent stone circles. 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. Outside Scotland examples have been found in Ireland at Ballymena, in England at Durham, Cumbria, Lowick, and Bridlington. A single example was found in Norway in a medieval cairn. Recent theory is that the Norway example was carried home by a Viking from an expedition to Scotland. The larger (90mm diameter) balls are all from Aberdeenshire, bar one from Newburgh in Fife.
By the late 1970s, a total of 387 had been recorded. Of these, by far the greatest concentration (169) was found in Aberdeenshire. By 1983 the number had risen to 411 and by 2015 over 425 balls had been recorded. A collection of over 30 carved balls from Scotland, Ireland and northern England is held by the British Museum.
Archaeological context
Many of the balls have not had their discovery site recorded and most are found as a result of agricultural activity. Five were found at the Neolithic settlement of Skara Brae and one at the Dunadd hillfort. The distribution of the balls is similar to that of mace-heads, which were both weapons and prestige objects used in ceremonial situations. The lack of context is likely to distort the interpretation. Random finds are only likely to have been picked up and entered a collection if they were aesthetically appealing. Damaged and plain balls were less likely to find a market than decorated examples so some more decorated examples might be fraudulent.
Balls of plain sandstone with the facets from shaping still clearly visible were found at Traprain Law in East Lothian. A significant number have already been found here and are known from other southern Scottish Iron Age sites. They may date from the fourth to third centuries BC. These balls are not ornamented and do not have knobs.
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". 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.
Physical characteristics
Materials
Many balls are said to be made of "greenstone", but this is a general term for all varieties of dark, greenish igneous rocks, including diorites, serpentinite, and altered basalts. Including Old Red Sandstone, 43 are sandstone, 26 greenstone, 12 quartzite, and 9 were serpentinite; these had been carved. Some were made of gabbro – a difficult material to carve. Round and oval natural shaped sandstones are sometimes found.
Examples made from hornblende gneiss and granitic gneiss were noted, both very difficult stone to work. Granitic rocks were also used; and the famous Towie example from Aberdeenshire may be serpentinised picrite. The highly ornamented examples were mainly made of sandstone or serpentine. A significant number have not as yet been fully inspected or tested to ascertain their composition.
Experimental archaeology
Full replicas have been made using authentic manufacturing techniques (pecking and grinding) by A.T. Young. It was shown that they could be made using prehistoric technology with no recourse to the use of metal tools.