5.5.5 General considerations

All lithic artefact specialists should have a basic geological knowledge of the raw materials used in Scottish prehistory - where they occur and in which periods they were used. However, the acquisition of relevant information for many less common raw materials can be problematic and, in those cases, it is essential that the lithic analyst works with a geologist. It is for example difficult to distinguish between fresh Staffin baked mudstone and the tuffs of eastern Skye (such as, for example, the form recovered from Clachan Harbour on Raasay; Ballin et al. 2010b). The chalcedonic silicas of the Inner Hebrides and west coast (e.g. An Corran and Camas Daraich; Wickham-Jones and Hardy 2004, 20; Saville et al. in press) may also be difficult to deal with, and the striped lithic raw materials (mostly meta-sediments) recovered from the the Southern Hebrides and the Western Isles are notorious (in some of these cases, even the geologists seem to disagree, defining these types of rock as variously either mylonite, baked mudstone, or hornfels).

An expert geological input is also relevant in connection with acquiring an understanding of the appearances and properties of lithic raw materials. Staffin baked mudstone and Lewisian mylonite were probably both more or less unpatterned in their fresh states, and they may have acquired their striking appearances (marked dark-light banding) as part of the weathering process. It is also likely that the appearance of some raw materials (e.g. meta-sediments) as, for example, loose-textured and apparently ill-suited for flaking, is a result of weathering since deposition.  It is worth noting, however, that in many cases the size of outcrop which will spark archaeological interest may be well below that which would register as significant to a geologist.  Issues of scale in fieldwork may have to be resolved.

In cases where geological consultation does not deal with a problem in a satisfactory manner, such as the case of mylonite/baked mudstone/hornfels (above), fieldwork may provide a solution. In this instance, the possibility of the raw material being mylonite could be tested by attempting to find primary outcrops, or even quarries, along the main faultline of eastern Lewis, where mylonite occurrences have been reported (Smith and Fettes 1979, 78).

5.5.4 Procurement sites

The Burnetland Hill chert quarry pit under excavation by Biggar Archaeology Group 2007. Prior to excavation, the quarry pit was visible as a faint oval depression (courtesy of Tam Ward, Biggar Archaeology Group).

Procurement sites, where raw material was either collected or quarried, represent a particular complex set of issues. To a degree, procurement sites form part of raw material exchange sensu largo, representing one end of the chain from source to end-user (see above), but they also need to be examined and analysed in their own right, where the technologies applied to extract the raw material, as well as the  socio-economical organization behind the actual collection or quarrying processes are discussed.

At present, few Upper Palaeolithic or Mesolithic procurement sites are known from Scotland. An undated, but probably post Mesolithic, quartz quarry from Lewis has been discussed in the archaeological literature (Ballin 2004). Chert quarry pits are known from southern Scotland (Warren 2007, 146), but these features are generally undated. However, the fact that some are associated with relatively narrow blades suggests that they were operational by the Late Mesolithic or Early Neolithic periods. At Early Mesolithic An Corran, baked mudstone may have been procured from an exposure immediately above the site (A. Saville, K. Hardy and S. Birch pers. comms.). Rùm bloodstone was probably procured from the scree or beach at the foot of Bloodstone Hill (N. Galou pers. comm.); prehistoric quarries (even in the simple form of quarry pits) have not yet been located on Rùm (Clarke and Griffiths 1990).