A useful measure of the desirability of different raw materials for retouch within and between assemblages: the raw material retouch index (RMRI)

Due to their predictable fracture and the quality of the edge that can be produced on them, fine-grained raw materials such as chert have long been favoured by prehistoric toolmakers for the production of relatively small retouched artefacts. It is common to find far higher frequencies of retouch in such materials than is the case in all other rock types. In order to quantify the desirability of different materials for retouch I propose a simple index relating the frequency of retouched tools in a raw material to the frequency of that material in the entire assemblage. Using the ‘raw material retouch index’ (RMRI) one can compare relative raw material desirability both within and between assemblages.