A multi-technique characterization and provenance study of the pigments used in San rock art, South Africa

During the course of a conservation project at the rock shelter known as RSA TYN2 (Eastern Cape, South Africa), a sample of 33 painted fragments that had become detached from the wall were collected. They have been studied using a multi-technique approach (optical microscopy, SEM-EDS, Raman spectroscopy and FTIR), with the aim of achieving a better understanding of their paint stratigraphy, composition, and provenance. The paintings are on a Clarens Formation sandstone and are embedded in calcium sulphates and oxalates. The red pigments show two different ‘hues’, corresponding to two different compositions. The light red is a red ochre, possibly pure, which is probably a degradation product of the Clarens Formation sandstone. The dark red contains more iron oxides and may be a mixture between the red ochre and pure haematite. Because of the presence of crystals which may be identified as augite we suggest this haematite came from the basaltic upper part of the Drakensberg, at least 4 km away from the rock shelter. The black pigments have been identified as carbon black, that is to say, incomplete combustion products of organic compounds, and are radiocarbon dated to between 2120 and 1890 cal BP, making these samples the oldest directly dated South African rock art.

► First multi-technique study of San rock art. ► Suggests two different provenances for the source of the red pigments. ► Suggests that some form of acidic treatment may have been applied to the rock surface before painting.