A Decade of Portable (Hand-Held) X-Ray Fluorescence Spectrometer Analysis of Obsidian in the Mediterranean: Many Advanta
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A Decade of Portable (Hand-Held) X-Ray Fluorescence Spectrometer Analysis of Obsidian in the Mediterranean: Many Advantages and Few Limitations Robert H. Tykot1 1 Department of Anthropology, University of South Florida, Tampa, FL 33620, U.S.A. Email: [email protected] ABSTRACT Starting in 2007, a portable, hand-held X-ray fluorescence spectrometer was used to elementally analyze and determine the geological source of obsidian artifacts in the Mediterranean, effectively replacing the instruments used in my previous research studies INAA, LA-ICP-MS, ED-XRF and an electron microprobe with WDS. Approximately 400 geological obsidian samples from the Mediterranean area, and 8500 obsidian artifacts from prehistoric sites in Italy, France, Croatia, Malta, Tunisia, Greece, Cyprus, Turkey, Israel, and Egypt have been analyzed non-destructively by pXRF. Overall, the pXRF can distinguish all of the individual sources, based on the composition of Fe and trace elements Rb, Sr, Y, Zr, and Nb, as well as assign most artifacts to specific subsources and thus addressing archaeological research hypotheses about trade and exchange in many different time periods. INTRODUCTION Obsidian, a volcanic rock, has been used for making stone tools for nearly two million years. In the Mediterranean, the only geological sources are on the Italian islands of Lipari, Palmarola, Pantelleria, and Sardinia, the Greek islands of Melos and Giali, and in central Anatolia, while by the Neolithic period obsidian artifacts often are found at archaeological sites hundreds of kilometers away (Figure 1). The study of prehistoric trade and exchange, and its implications about socioeconomic practices, transportation capabilities over land and sea, the movement of people and material culture, and how these changed over time, has been a major part of archaeological research for a long time. The development of instrumental methods of elemental analysis first led to studies showing that obsidian sources in the Mediterranean could be distinguished starting in the 1960s [1]. Since then, many different analytical methods have been developed and used successfully on archaeological obsidian [2, 3, 4], with instrumental neutron activation analysis (INAA) [5], electron microprobe analysis (EPMA) [6], X-ray fluorescence (XRF) spectrometry [7, 8, 9], scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS) [10], and laser ablation ICP mass spectrometry (LA-ICPMS) [11, 12, 13] the most commonly used in the Mediterranean. While scientifically sound, there are however four key aspects regarding the analysis of archaeological artifacts: (1) is the analysis destructive to the artifact? (2) where can the analysis be conducted? (3) how much does it cost for the instrument and its use? (4) how much time and labor cost are involved? Most analytical methods are destructive (e.g. taking a powder sample, or a small chip to fit in the instrument chamber), yet more and more countries do not allow destructive analyses and/or for the artifacts to be taken elsewhere for anal
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