Material analyses of Pre-Columbian metal artwork from Costa Rica: Aspects of technology, provenance and regionality

The wealth of Pre-Columbian gold, guanín (an argentiferous gold-copper alloy, also called tumbaga) and copper objects found in Costa Rica and the country’s abundant ore deposits suggest a rich tradition of local metal artwork manufacturing. However, since the majority of artefacts was unearthed by illicit digging during large-scale infrastructure and construction projects in the 19^th century (primarily of railways and banana plantations), their find context, dating and often also true origin usually are unknown. These circumstances severely limit understanding of e.g., the chronological and regional development of metal use and the differentiation of imports from possible local production, rendering technological and geochemical studies of the objects themselves a major source of insight into these open questions.

Here, we present a study of Pre-Columbian objects of different stylistic and material types, which were found in Costa Rica and are hosted in the collections of the Museo Nacional de Costa Rica (MNCR) and the Museo del Jade in San José/Costa Rica, and the Ethnologisches Museum Berlin. The main element composition of the objects was determined non-destructively by (near) surface analysis performed with portable X-ray fluorescence spectrometry, and their manufacturing techniques were investigated by digital microscopy. Furthermore, detailed metallographic, compositional and isotopic analyses will be carried out on fragments sampled from 30 metal objects from the MNCR. By comparison with data of Pre-Columbian metal objects from neighbouring regions, we discuss craftsmanship techniques, gold-copper supply and technological choices in artefact production, and their possible correlation with areas of origin or different workshops.