Ana Luísa Rodrigues and Rosa Marques
The IVORIST project proposes an innovative approach to the study of remarkable artefacts / architectural materials of ivory and schist, using micro and non-destructive analytical methods. For the first time, the analyses will allow the chemical characterization of ivory artefacts and schist architectural materials found in the Perdigões ditched enclosure in funerary contexts, as well as potential raw materials.
The methodological approach to be used aims the determination of the chemical composition of ivory and schist objects / materials by prompt gamma-ray activation analysis (PGAA) and with particle-induced X-ray emission spectroscopy (PIXE). This approach allows quantifying the major, minor and trace chemical elements in the bulk sample, through PGAA, complementing it with the determination of the chemical composition of the surface of the artefacts using PIXE. The achievement of chemical composition on the material surface is important as it may indicate the potential contamination of the artefact by its burial environment. In the case of ivory materials, the chemical composition of surface can be useful to identify differences resulting from heating processes. In selected materials, where destructive techniques can be used, micro sampling will be performed in order to obtain material for neutron activation analysis (NAA). This technique is crucial for a better characterization of materials regarding the trace elements that can be used as geochemical indicators in provenance studies.
In this project, it will be studied: fragments of ivory tusks and fragments of ivory artefacts; schist samples from geological contexts peripheral to Perdigões, and slabs of schist from funerary structures.
Thus, the determination of the chemical composition of ivory artefacts, schist architectural materials and related raw materials will contribute to better understand: i) differences between ivory fragments / artefacts of each structure and ivory tusks (potential raw material), contributing for the discussion of the social role of each funerary structure and for the establishment of the nature and origin of raw materials and artefacts; ii) chemical changes in ivory promoted by heating, post-depositional and taphonomic processes, in order to establish geochemical indicators for ivory changes; and iii) differences between schist slabs of each funerary structure and peripheral geological contexts, contributing to establish the origin of the schist, as well as identify whether in the surrounding territory there were different supply areas for this raw material.