Thermal Alteration of Flint: An Experimental Approach to Investigate the Effect on Material Properties

ABSTRACT

Archaeological lithic assemblages are often affected by burning, as evident from severe thermal damage on these artefacts. In this study, the thermal alteration of four different flint types was investigated by performing controlled heating experiments in laboratory setting. The resulting heat alterations were afterwards compared to heating of flint samples in campfire experiments, as these correspond better to the burning conditions present during prehistoric times. The microstructural and chemical changes occurring in flint during heating were analyzed using different macroscopic (visual observations and color measurements) and microscopic (optical microscopy and non-destructive X-ray micro-CT) techniques. Eventually, the terminology regarding the degree of heat exposure was refined and complemented with temperature ranges and color information for the investigated flint types. In doing so, this study provides criteria for a more objective macroscopic determination of the burning degree of archaeological flint artefacts, that could be useful in a wide range of lithic studies.

KEYWORDS:

• Flint assemblages
• thermal alteration
• burning terminology
• experimental archaeology

Acknowledgements

This project is funded by the special research fund of Ghent University (BOF-UGent, BOF16/IOP/001). BOF-UGent is also acknowledged for the financial support of the UGCT Centre of Expertise (BOF.EXP.2017.0007). Tim De Kock (UGent) was a postdoctoral fellow of the Research Foundation-Flanders (FWO) and UGent (BOF) and acknowledges its support. The two anonymous reviewers are acknowledged for providing valuable comments and suggestions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes on contributors

Géraldine Fiers is a PhD candidate at the PProGRess group in the Department of Geology at Ghent University, supervised by Prof. Veerle Cnudde (Geology) and Prof. Philippe Crombé (Archaeology). Her research focuses on flint characterization and its post-depositional alteration in a context of the preservation of prehistoric microwear traces on stone tools. Therefore she uses a wide variety of techniques for the petrographic, geochemical and structural investigation of flint.

Éva Halbrucker is a PhD candidate at the Prehistory research group in the Archaeology Department at Ghent University. Her work focuses on the microwear analysis of lithic tools from the Mesolithic-Neolithic transitional period in northwestern Belgium. She moreover investigates the effect of patination and burning on the preservation of microwear traces.

Tim De Kock was a research assistant and post-doctoral researcher at the PProGRess group in the Geology Department at Ghent University, where he investigated the properties and degradation of natural stones in a heritage context. He is currently professor at Antwerp Cultural Heritage Sciences (ARCHES), University of Antwerp.

Hans Vandendriessche has been a research assistant and PhD candidate at Ghent University since 2015 and is currently working on a PhD about the lithic technological traditions of the Lateglacial and Early Holocene in Belgium, supervised by Philippe Crombé. After having obtained his MA degree in 2009 and prior to this research project, he worked as a field-archaeologist on several large-scale preventive excavations in the Scheldt basin.

Philippe Crombé is head of the Archaeology Department and professor of Prehistoric Archaeology at Ghent University. He is currently promoter of several multidisciplinary research projects focusing on the Lateglacial and Early Holocene transition and the Neolithization process in the Scheldt basin of northwestern Belgium. Prior to the Kerkhove project, he directed several large-scale excavation projects in the Antwerp-Harbour, which yielded the sites of Verrebroek-Dok and Doel-Deurganckdok and led an interdisciplinary research on the Lateglacial Moervaart palaeolake.

Veerle Cnudde is teamleader of PProGRess (Geology Department, Ghent University) and holds a dual professorship at Ghent and Utrecht University. Within PProGRess, various dynamic processes inside the pore space of geomaterials are studied and imaged. The group specializes in non-destructive imaging of the 3D structure and chemical composition of Earth materials from the nano- to macro-scale and wants to stretch the limits in terms of both temporal and spatial resolution, for real-time imaging of processes in the pore space of Earth materials.

Notes

1 “Fine or coarse-grained” is referred to the archaeological term when describing lithics. Fine-grained flints appear more smooth than coarse-grained flints. It is related to the texture of the flints’ surface (Luedtke, 1992).

Additional information

Funding

This project is funded by the special research fund of Ghent University Special Research Fund (BOF-UGent) [grant number BOF16/IOP/001]. The Ghent University Special Research Fund (BOF-UGent) is acknowledged for the financial support to the Centre of Expertise UGCT (BOF.EXP.2017.007).