Bronze production in the Iron Age of the Iberian Peninsula: The case of El Castru, Vigaña (Asturias, NW Spain)

Abstract

Bronze production during the Iron Age of the Iberian Peninsula is characterised by the use of a relatively simple technology, based on crucible-furnaces. In an area rich in mineral resources, bronze was produced on a small scale and within settlements, to be used for ritual, ornamental and functional objects. Here we present an analytical study of slagged crucibles, small slag nodules and casting spillage from the Iron Age hillfort of El Castru, in Vigaña (Asturias, NW Iberia), with a particular focus on the technology of bronze production. The study sought to contribute to our understanding of Pre-Roman metallurgical activities in the region, as a case in point to discuss broader prehistoric traditions of bronze-making. The results show that the technology and scale of bronze production at this hillfort are coherent with the pattern described for much of prehistoric metallurgy in Iberia, with the-direct production of copper alloys by cementation and co-smelting of mineral ores. The results also illustrate some of the challenges encountered when attempting to identify metallurgical processes through the analyses of crucible residues, and propose some criteria to facilitate future studies.

The Provenance, Use, and Circulation of Metals in the European Bronze Age: The State of Debate

“…The study of European Copper and Bronze Age metal production shows a wide variety of systems operating at different temperatures and redox environments, which would affect metal composition in various ways (e.g., Bourgarit 2007;Höppner et al 2005;Müller et al 2004;Murillo-Barroso et al 2017;Radivojević and Rehren 2016;Rovira 2004). If we focus on bronze specifically, there is widespread archaeological evidence, primarily from the Iberian Peninsula, for the production of the alloy by the co-smelting of copper and tin minerals, or the cementation of metallic copper with cassiterite in crucibles in rather wasteful reactions (i.e., with much tin lost in the slag), and with highly variable temperature and redox conditions within individual crucibles (e.g., Farci et al 2017;Figueiredo et al 2010;Rademakers and Rehren 2016;Rovira 2007;Valério et al 2014). Such conditions are difficult to replicate in a laboratory or model by computing, but the archaeological evidence should at least caution against undue generalizations.…”

El Castru (Vigaña, Balmonte de Miranda, Asturias): un pequeño poblado fortificado de las montañas occidentales cantábricas durante la Edad del Hierro

“…Las actividades metalúrgicas documentadas en la fase 3 constituyen un capítulo destacado en la secuencia del yacimiento, como ya se comentó anteriormente. El análisis de 29 fragmentos de crisol proporciona una interesante lectura de los procesos metalúrgicos desarrollados en la Segunda Edad del Hierro por los habitantes de El Castru (Farci et al 2017). El estudio de la tecnología empleada para la producción de las aleaciones de cobre y el papel de los crisoles en las actividades metalúrgicas han constituido los objetivos centrales de la investigación desarrollada.…”

Traditions and innovations: versatility of copper and tin bronze making recipes in Iron Age Emporion (L’Escala, Spain)

“…Challenging assumptions that the alloying of pure metals would have been predominant in Prehistory, their investigations show that cementation was used in Bronze and/or IA sites in Thailand (Murillo-Barroso et al 2010), the South Caucasus (Erb-Satullo et al 2015), Portugal (Figueiredo et al 2010), Britain (Nothover 1987) and Spain (Rodríguez Díaz et al 2001;Rovira 2007;Renzi et al 2008). Moreover, the combination of different alloying methods in the same site has been documented at LBA Pi-Ramesses (Egypt) and several Iberian sites (Farci et al 2017;Renzi 2013). Also worth noting is the experimental study by Rademakers and Farci (2018), which provides useful reference materials for the identification of archaeological remains.…”

“…However, cosmelting remains common and is not superseded by the new technology. As a peculiar case in point, we can mention the finds from El Castru (Asturias) dated between the fifth and fourth centuries BC (Late Iron Age), where evidence of cosmelting and cementation appeared together in the same production contexts (Farci et al 2017).…”

“…Copper and tin bronze production techniques: Iberia is different A key peculiarity of the Iberian archaeometallurgical record is that, from the beginning of extractive copper metallurgy in the Chalcolithic and until Roman times, crucible smelting is the predominant system. Some examples include the Chalcolithic (third millennium BC) crucible fragments from Almizaraque and Las Pilas (Rovira and Renzi 2017;Müller et al 2004;Murillo-Barroso et al 2017), the samples from several sites reported by Rovira (2007) and dated from the Early Bronze Age (EBA) (2300-1300 BC) to Roman times (first millennium AC onwards), as well as crucibles from the IA hillforts (eighth century BC until Roman times) of La Corona de Corporales, el Castrelín de San Juan de Paluezas and El Castru, among others (Farci et al 2017;Fernandez-Posse et al 1993). There is evidence for the deliberate production of these technical ceramics from the EBA, as shown in the presence of pouring spout and grip handles that are absent in other ceramics (Soriano and Escanilla 2016).…”