Graphite and multilayer graphene detected on ~70,000-year-old stone tools: Geological origin or constituent of hafting resin?

Raman spectroscopy identified graphite and multilayer graphene on ~70,000-year-old stone tools from Middle Stone Age deposits at Sibudu Cave, KZN, South Africa. The graphite/multilayer graphene appeared to be concentrated on the hafting side of the artefacts, suggesting that it was added to the hafting glue. However, graphite/multilayer graphene was only identified on stone tools made of hornfels and not on those made of dolerite and quartzite. A geological origin is therefore not out of the question. In this paper, we present arguments for and against its origin as geological or as constituent of the hafting resin. Our results favour its geological origin and serve as a cautionary tale for interpreting residues on archaeological artefacts without an in-depth study of the raw materials used to produce the tools.