Colorimetric characterization of ochres in a Palaeolithic flint pebble from Maschio dell'Artemisio, Latium, Italy

The flint pebble from Maschio dell'Artemisio, a mountain near Velletri (South-East of Rome), is one of the earliest complex artefacts from the Upper Palaeolithic of the Colli Albani possibly displaying a symbolic/artistic value. It has been used as a stone-striker and retoucher, to create or modify lithic implements. It shows a diffuse and intense ochreous colour on almost half of its surface. Here we discuss the results of an innovative colorimetric approach to define the use of pigments in the area during the Upper Palaeolithic and eventually compare the raw materials with local supplies. Second-derivative diffuse reflectance spectroscopy, a data treatment on colorimetric data used since the 1980s in the characterization of soils, for the first time is here applied to the lithic industry, to characterize and quantify the presence of yellow and red ochres, found in mixture on the surface. We used both a colorimeter and a fibre optic reflectance spectrometer (FORS) and then compared the results to assess their efficiency and define a protocol useful for future investigations on lithic tools. Colorimetric results can lead to an easier estimation of the redness rating, which represents the relative content of hematite and goethite, independently on the level of expertise of the operator. FORS data were more suitable to determine the variation of the inflection point in the reflectance curves. Both techniques showed that in all the points analysed on the flint pebble there is a mixture of yellow and red ochre, possibly reflecting the exploitation of the surrounding area during the Final Pleistocene.