The term 'coarse stone artefact' is used in archaeological discussion as a blanket description for what is really a wide and disparate range of tools and objects. Many potential functions are represented including butchering tools, grain processors, craft tools of all types, agricultural implements and sculpted pieces. Widely different types of rock were selected and some artefacts were deliberately shaped prior to use whilst others, particularly the cobble tools, were used for jobs which left distinctive task-specific wear traces. These artefacts had many and varied roles to play in prehistoric lifeways and for this reason they must be a valuable component of any research framework.
Most work on stone tools in Scotland has been confined to recording their presence in excavation reports; even that is patchy with no recognised terminology and little discussion of context. Scholarly attention has been paid to individual tool types such as flaked stone bars and ard points from the Northern Isles with attempts to classify them by shape and to date their use (Rees 1979, Rees 1986a, Rees 1986b, Hedges 1986). With the exception of a recent work of synthesis from the Northern Isles (Clarke 2006 and see below) stone tools have never had a role in regional or national discussions of material culture.
Nature and development of the repertoire of stone artefacts over time
Research into use of stone tools in Neolithic Scotland is heavily biased towards the Northern Isles and this is because of the number of research-led excavations, particularly since the 1980s in Orkney, that have produced large assemblages of stone tools from all prehistoric periods. These factors allowed research into the use of stone tools from the Neolithic to the end of the Iron Age which demonstrated how changes in the composition of stone tool assemblages occurred at specific points (Clarke 2006). For example, in Orkney, cobble tools dominated Early Neolithic assemblages whilst flake tools and a narrower range of cobble tool types were more common in Later Neolithic contexts. Various types of ground stone tools were also in use. In contrast, at the same period in Shetland agricultural stone tools such as flaked stone bars and ard points were dominant but these did not appear in Orkney until after the Grooved Ware occupation.
There are therefore clear differences between the material cultures of these two island groups during the Neolithic that have never been addressed - particularly because the emphasis of research on Grooved Ware sites has, in my view, skewed archaeologists' view of the Neolithic. Recent work on St Kilda has demonstrated the presence of flaked stone bars and other stone tools which are dateable, by comparison with assemblages from the Northern Isles, at least to the Bronze Age and possibly earlier (Fleming 2005a and b). This offers a tantalising glimpse of maritime communication routes from the Neolithic onwards.
Elsewhere in Scotland we have very little detail about the use of coarse stone tools. The assemblages are mostly composed of various types of cobble tools and quern stones but we do not know how their use may have changed or developed through time.
Recent excavations of Early Neolithic contexts in Ayrshire indicate the presence of some types of coarse stone tool within Early Neolithic deposits that were also in use during the Late Mesolithic elsewhere in Scotland (Clarke 2008). This raises the question of just how far into the Neolithic these Mesolithic processing strategies continued.
Raw materials and manufacture
A very wide range of raw materials was used for stone tools across Scotland and this reflects the diversity of the local geologies (Clarke 2006). The issue of just where the rock came from and how it was collected has barely been addressed in the literature. A cobble source for many of the tools would suggest local access to beach or river gravels. At a more organised level specific quarries of sandstone have been recorded in Shetland (Calder 1956, 356) and on St Kilda prehistoric quarrying of dolerite was investigated by excavation (Fleming and Edmonds 1999). Also in Shetland evidence for shale quarrying has been identified near Sumburgh (Turner 1998, 32). These were most likely raw material sources for flaked stone bars and probably some other tool types. There is no clear dating evidence to indicate whether these quarries were used in the Neolithic or Bronze Age and there is as yet no demonstrated link between these extraction areas and the tools found on occupation sites. What is apparent is that around the end of the Neolithic and the beginning of the Bronze Age there appear to be different choices made in the use of stone accompanied by some changes in manufacturing methods and a range of new tool types in Orkney and Shetland (Clarke 2006).
Manufacturing was not just confined to the flaking of a blank to shape. For other stone tools grinding was significant, particularly in Orkney.
Though functional terms are given to most prehistoric tools, in reality it cannot be said for certain just what exactly they were used for. In order to investigate the myriad functions of these stone tools, particularly the cobble tools, we need to reproduce the wear traces experimentally and until now there has been no sustainable programme of such work in Scotland. Skaill knives have been assessed for their practicability in butchering (Clarke 1989) and the characteristic wear traces on stone ard points were investigated to determine their function (Rees 1979) but these are isolated instances.
Analysis of wear traces through experimental reproduction is, if done properly, a lengthy scientific process. Key questions need to be formulated before designing the programme and in order to do this we first need to know the range of stone tools present and how they have been deposited - this information is clearly lacking not only in the Neolithic but across the span of prehistory in Scotland.
Not much is known about the use of coarse stone tools across mainland Scotland and the Inner and Outer Hebrides and there is a need to know what there is currently before full advantage can be taken of their potential. A nationwide synthesis of coarse stone tools from the Mesolithic to the end of the Iron Age would provide a valuable corpus of information from existing collections. With this method we can overlap the boundaries of the 'Three Age System' - these are points at which there are significant changes in the production and use of coarse stone tools e.g. Late Mesolithic/ Early Neolithic; Early Neolithic/ Late Neolithic; Late Neolithic/ Early Bronze Age. There is a too much focus on Grooved Ware at the expense of the rest of the Scottish Neolithic - research excavations directed towards the Neolithic of Shetland, Caithness and St Kilda would illuminate the Neolithic of northern Scotland. A programme of experimental archaeology at postgraduate level could attempt to address the range of craft and processing activities that involved these stone tools.