The developing field of petrology in archaeology

This paper traces the development of optical petrology, noting the fields in which it can profitably be employed and what its limitations are. It then discusses the principles behind the use of trace element analysis. Variants of optical emission spectrometry, atomic absorption spectrometry, X-ray fluorescence spectrometry and neutron activation analysis are described and compared in terms of expense, analytical accuracy and possible destruction of the sample, illustrated by some recent attempts to source artifacts of obsidian, flint, sanukite and soapstone.     

Technological Choices in Hand‐Made Indigenous Pottery from Western Mallorca (Balearic Islands,Spain) (C.1200–75 bc): An Archaeometric Approach

This paper addresses the technological choices observed in Mallorca (Spain) for the production of hand‐made pottery during the Late Bronze and Iron Age. We have conducted a diachronic analysis of the ceramic assemblages recovered from two archaeological sites placed in the same territory by means of X‐ray fluorescence and optical microscopy by thin‐section analysis. The archaeometric characterization of the hand‐made vessels allows us to establish several compositional groups related to the use of different raw materials and certain paste recipes associated with the archaeological sites and periods considered. Thus, this study evidences different productive strategies in each site and across time in the same geographical area.     

Considerations on the provenance determination of plant ash glasses using strontium isotopes

Strontium isotopic analysis has been proposed as a suitable method to determine the primary production location of ancient plant ash glasses. The technique is based upon the assumption that Sr enters this glass type with the plant ash used as a flux material, and that the ⁸⁷Sr/⁸⁶Sr ratio of the resulting glass reflects the geological provenance of that flux. In such case, the bulk Sr isotopic composition of the bedrock should be inherited unchanged in the plants growing on that bedrock. Different types of plant ash glasses have been shown to have widely differing ⁸⁷Sr/⁸⁶Sr compositions. In this study, the ⁸⁷Sr/⁸⁶Sr composition of several plant species growing on different bedrock types is measured, and compared to the bulk Sr isotopic composition and petrology of that bedrock. The paper shows that the ⁸⁷Sr/⁸⁶Sr ratio of these plants is a function not only, or even mostly, of the local geology, but also of the Sr isotopic composition of the total water consumed by that plant. This is highly likely to be both plant species dependent and dependent on the small-scale hydrology of the area immediately surrounding the plant. In this way, no definite relation between the isotopic composition of a geological outcrop and the plants growing on this bedrock can be inferred. Hence, the isotopic composition of a plant ash made from such plants is uncertain and moreover species dependent. Though groups of plant ash glasses can certainly be compared in time and space using Sr isotopes, it may prove difficult to ascertain a plant ash glass type to a specific geographical-geological region.