Non-destructive analysis of archaeological ochre: a preliminary application to the Middle Stone Age site of Diepkloof Rock Shelter (South Africa)

A number of ochre pieces were found from the Middle Stone Age (MSA) in southern Africa, leading to recent debates about the use of this material. The relevant question behind such a debate lies in the role of ochre in early modern human societies. Technical, socio-economical and symbolic aspects might be associated with ochre processing and use. Ochre pieces showing signs of use-wear found on MSA sites are the main witnesses of such activities. That is why our work has focused on the study of ochre pieces, especially on the issue of the raw material selection. The relevance of non-destructive methods in order to determine the mineralogical nature of ochre is discussed here. Scanning electron microscopyenergy- dispersive X-ray spectroscopy (SEM EDS) and X-ray diffraction (XRD) analyses were used. Based on careful considerations of the association of different features, such as the elementary composition or the fabric, we showed that under certain conditions surface analyses are very useful to assign samples into mineralogical categories.