Prompt Gamma Activation Analysis, a new method in the archaeological study of polished stone tools and their raw materials

Abstract

Metabasic rocks, particularly greenschists, were very popular raw materials for making polished stone tools by prehistoric man in the Carpathian Basin. The major and trace element compositions of these objects are very helpful in determining the place of origin of the rocks. On the other hand, destruction of the complete object is usually not allowed during the analysis. In this paper we show an application of Prompt Gamma Activation Analyses (PGAA), a relatively new, non-destructive method for investigation of Neolithic stone tools. Twenty-four samples (in the form of greenschist and blueschist polished stone tools from Hungarian Neolithic collections and also greenschists and blueschist from outcrops) were investigated. The aim of this work was to establish a method for distinguishing the different types of greenschists occurring in the Carpathian Basin. PGAA gives reliable data for major and some trace elements of geochemical interest. According to our results, it is possible to distinguish blueschist from macroscopically similar greenschist polished stone tools by PGAA. Three macroscopically different types of greenschist samples form only two groups according to chemical composition, which implies only two different sources of greenschist raw material. We were able to identify one of them as rock from the outcrop of Felsocsatar (Penninic Unit of the Alps in western Hungary). The second source is not yet determined; it requires the study of samples from more outcrops. The investigation of ancient stone tools is only one example of the applicability of PGAA. The advantages of this method can also be exploited in other geochemical research areas.