Compositional analysis on lithic beads: The case of the lower Paraná wetland, Argentina

Abstract

Green lithic beads made by Late Holocene hunter-gatherer groups wererecovered from different archaeological sites of the Lower Paraná wetland.Since most of these beads are made of green rocks, they were traditionallyreferred to as copper minerals such as chrysocolla, turquoise andmalachite. The Lower Paraná wetland has no primary lithic outcrops andArgentinean copper quarries are distant. However, there are nearer coppersources in the nearby country of República Oriental del Uruguay.The aim of this paper is to characterize geochemically thearchaeological stone beads recovered in the Low Paraná wetland in orderto determine whether they are copper-rich rocks as traditionally defined, totest their variability and to evaluate the nearest copper sources. For thispurpose, archaeological and geological samples were analysed using ascanning electron microscope coupled with energy dispersive X-rayspectrometry (SEM-EDX) to determine the elemental composition ofmaterials. In the geological samples, results show the presence of copperrocks, possibly chrysocolla. On the other hand, archaeological beads weremade from different lithic sources, most of them, without copper. these preliminary results should be combined with mineralogical information tofully characterize the lithic archaeological assemblage, along with data onadditional geological sources which will contribute to the tracking of theexchange networks of these items