Detecting and Quantifying Heat Treatment of Flint and Other Silica Rocks: A New Non‐destructive Method Applied to Heat‐treated Flint From the Neolithic Chassey Culture, Southern France

Abstract

Heat treatment of lithic raw material is known from the Middle Stone Age to the Neolithic. These findings require archaeometric techniques and methods for detecting the heat-induced effects within lithic artefacts. However, the existing methods are often cost-intensive and time-consuming, and most of them are destructive. Here, we present a new method using the infrared spectroscopic measurement of the strength of H-bonds formed between surface silanole groups (SiOH) and H 2 O molecules held in open pores of the samples. The reduction of H-bond strength in chalcedony is shown to be strongly correlated with the loss of open pores induced by heat treatment. Hence, the method is based on measuring one of the transformations aimed for by the instigators of the heat treatment: the reduction of porosity that modifies the rock's mechanical properties. A first application to heat-treated material from the Neolithic Chassey culture (southern France) shows that flint was heated to temperatures between 200°C and 250°C in this period. This has important implications for the study of the procedures used and the heating environments. Our new method is non-destructive, rapid, cost-effective and allows for detection of the used annealing temperatures.

First evidence of heat treatment during the early Neolithic in northeastern Italy

“…Unfortunately, the taphonomic processes can alter the aspect of artifacts causing the formation of other types of patination/modification and making it difficult to detect possible heat treatments (Crabtree and Butler, 1964;Boix Calbet, 2012;Schmidt et al, 2013a). The debate about the transformations of the rock's proprieties is still open (Domanski and Webb, 1992;Domanski et al, 1994;Schmidt et al, 2012), but several authors proposed different approaches to detect these modifications and verify the usage of the controlled heating in artifact manufacturing (Melcher and Zimmerman, 1977;Griffiths et al, 1986;Borradaile et al, 1993;Schmidt et al, 2013a).…”

“…During the early Neolithic, the use of pre-heated flint cores, in order to improve blade production, is attested in Spain (Perales Barr on et al, 2015). In France, during the Neolithic, the intentional heat treatment has been recognized in various archaeological records of the Chassey culture (Binder and Gassin, 1988;Lea, 2005;L ea et al, 2007;Schmidt et al, 2013a). In northern Italy, only macroscopic evidence of heat treatment has been suggested for the late Neolithic site of Botteghino (Mazzieri and Dal Santo, 2007) and for some Neolithic surface findings of Buttrio (Duches, 2009).…”

In the footsteps of Pliny: tracing the sources of Garamantian carnelian from Fazzan, south-west Libya

“…Stemp et al, 2009); heat treatments (e.g. Schmidt et al, 2012b;2013b); engraving techniques (e.g. Sax et al, 1995Sax et al, , 1998Rosenfeld et al, 2003); mechanical properties by geotechnical tests (e.g.…”

Test, Model, and Method Validation: The Role of Experimental Stone Artifact Replication in Hypothesis-driven Archaeology

“…Heat treatment or damage has also been examined through stone-tool replication as model (Brown et al 2009;Schmidt et al 2013), although there are also examples of heat-treatment studies conducted through replication as test, in which researchers were more concerned with understanding the general process and parameters of the effect of heat on stone (Mercieca and Hiscock 2008;Schmidt et al 2012Schmidt et al , 2013.…”