Mechanical properties of lithic raw materials from Kazakhstan: Comparing chert, shale, and porphyry
Namen A. Iovita R. Nickel K.G. Varis A. Taimagambetov Z. Schmidt P.
April 2022Public Library of Science
PLoS ONE
2022#17Issue 4 April
The study of lithic raw material quality has become one of the major interpretive tools to investigate the raw material selection behaviour and its influence to the knapping technology. In order to make objective assessments of raw material quality, we need to measure their mechanical properties (e.g., fracture resistance, hardness, modulus of elasticity). However, such comprehensive investigations are lacking for the Palaeolithic of Kazakhstan. In this work, we investigate geological and archaeological lithic raw material samples of chert, porphyry, and shale collected from the Inner Asian Mountain Corridor (henceforth IAMC). Selected samples of aforementioned rocks were tested by means of Vickers and Knoop indentation methods to determine the main aspect of their mechanical properties: their indentation fracture resistance (a value closely related to fracture toughness). These tests were complemented by traditional petrographic studies to characterise the mineralogical composition and evaluate the level of impurities that could have potentially affected the mechanical properties. The results show that materials, such as porphyry possess fracture toughness values that can be compared to those of chert. Previously, porphyry was thought to be of lower quality due to the anisotropic composition and coarse feldspar and quartz phenocrysts embedded in a silica rich matrix. However, our analysis suggests that different raw materials are not different in terms of indentation fracture resistance. This work also offers first insight into the quality of archaeological porphyry that was utilised as a primary raw material at various Upper Palaeolithic sites in the Inner Asian Mountain Corridor from 47–21 ka cal BP. Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
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Department of Early Prehistory and Quaternary Ecology, University of Tübingen, Tübingen, Germany
Department of Archaeology, Ethnology and Museology, Faculty of History, Archaeology and Ethnology, Al-Farabi Kazakh National University, Almaty, Kazakhstan
Center for the Study of Human Origins, Department of Anthropology, New York University, New York, NY, United States
Applied Mineralogy, Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen, Germany
Competence Center Archaeometry – Baden-Württemberg, Eberhard Karls University of Tübingen, Tübingen, Germany
Institute of Archaeological Sciences, Eberhard Karls University of Tübingen, Tübingen, Germany
National Museum of the Republic of Kazakhstan, Nur-Sultan, Kazakhstan
Department of Early Prehistory and Quaternary Ecology
Department of Archaeology
Center for the Study of Human Origins
Applied Mineralogy
Competence Center Archaeometry – Baden-Württemberg
Institute of Archaeological Sciences
National Museum of the Republic of Kazakhstan
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