Raw Material Studies (continued)

General considerations

Obviously, a lithics specialist should have some 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 relating to many less common raw materials can be problematic and, in those cases, it is essential that the lithics specialist works with a geologist. It is for example difficult to distinguish between fresh Staffin baked mudstone and the tuffs of eastern Skye (like for example the form recovered from Clachan Harbour on Raasay; Ballin et al. 2011). The chalcedonic silicas of the Southern Hebrides (eg, Camas Daraich; Wickham-Jones & Hardy 2004, 20) may also be difficult to deal with, and the banded lithic raw materials (mostly meta-sediments) recovered from 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, in some cases, mylonite, and in others, baked mudstone, or hornfels).

A professional 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 (eg, meta-sediments) as, for example, loose-textured and ill-suited for flaking is a result of weathering since deposition.

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 & Fettes 1979, 78).

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Rust-brown/grey chert from Howburn, S Lanarkshire (courtesy of Tam Ward, Biggar Archaeology Group).

Rust-brown/grey chert from Howburn, S Lanarkshire (courtesy of Tam Ward, Biggar Archaeology Group).