Identifying heated rocks through feldspar luminescence analysis (pIRIR290) and a critical evaluation of macroscopic assessment

Abstract

Throughout (pre)history, non-flint rocks have been used to structure fireplaces, to retain heat, to boil liquids, and to cook food. Thus far, the identification of heated non-flint rocks in archaeological contexts largely depends on a visual (macroscopic) assessment using criteria thought to be diagnostic for thermal alteration. However, visual identification can be subject to observer bias, and some heat-induced traces can be quite difficult to distinguish from other types of weathering or discolouration. In this paper, we present feldspar luminescence analysis as an independent, objective way to identify heated non-flint rocks and to evaluate the results against the established visual macroscopic method for the identification of such pieces. This is done by submitting manuported rocks with and without inferred macroscopic characteristics of heating, originating from the Last Interglacial, Middle Palaeolithic site Neumark-Nord 2/2 (Germany), to feldspar luminescence analysis (pIRIR290). Results of the feldspar luminescence analysis are compared with the visual assessments. This proof of concept study demonstrates the potential of luminescence analyses as an independent, quantitative method for the identification of heated rocks—and their prehistoric applications like hot-stone cooking, specifically for cases where macroscopic assessment cannot provide reliable determinations.