Diverse strategies for copper production in Chalcolithic Iberia

Our understanding of early copper metallurgy in the Iberian Peninsula is mostly based on analysis from well-studied regions in the Southeast and Southwest. This paper focuses on two recently recovered Chalcolithic metallurgical assemblages outside these traditional research foci: two slagged crucibles from Lugar Viejo III (Zaragoza) and two large slag cakes from Cueva del Cañaveralejo (Córdoba). Analysis of the compositions and microstructures of the artifacts using optical microscopy and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) suggests they are related to primary copper production, namely smelting in crucible-furnaces under relatively oxidizing conditions, as is standard for this period. The slag layers on crucibles from Lugar Viejo indicate the production of copper with minor amounts of arsenic, also typical for this period. Of special note is the use of organic temper in the crucibles from Lugar Viejo, a practice found at the nearby site of Moncín but rare at other sites in Iberia. However, the slags from Cueva del Cañaveralejo are atypical in their large size (approx. 125 g each), fayalitic composition, unusual efficiency as demonstrated by a low copper content, and lack of arsenic; furthermore, the high sulfur content raises the possibility of the use of sulfidic ores. Results from both sites are compared against published data from well-known sites such as Los Millares, Las Pilas, Almizaraque, and Bauma del Serrat del Pont. The new data from Lugar Viejo and Cueva del Cañaveralejo reinforce the interpretation of metallurgy in the Iberian Peninsula as a low-skilled, conservative technology but also indicate the need for more research into regional variations. (See Supplementary Data 1 for a summary in Spanish)

Caracterización geofísica de técnicas de explotación de nódulos de sílex en el yacimiento de la Leandra (La Muela, Zaragoza).

En el yacimiento de La Leandra (La Muela, Zaragoza) afloran unidades miocenas lacustres que incluyen habituales niveles de especial concentración de nódulos de sílex. Éstos han sido explotados durante varios periodos y, dadas las características climáticas y demográficas, conservan en ocasiones la topografía original desde su explotación. Con el objetivo de evaluar desde el punto de vista geofísico la estructura de una zona explotada del yacimiento, se realizó prospección geofísica por magnetometría, medidas de susceptibilidad magnética de los materiales y prospección geofísica por georradar que fueron integrados en la información obtenida de un vuelo de dron en la zona. La integración de datos obtenida permite identificar una dinámica de explotación a través de pozos verticales, continuidad lateral de las zonas de explotación generando explanadas horizontales cuando existían niveles de interés, o el abandono y posterior relleno de los huecos de explotación generados en el avance de la explotación. El caso analizado permite inferir a partir de los cambios geométricos y estructurales la progresión de las explotaciones de época previsiblemente neolítica y la identificación de una rutina de explotación a modo de minería de transferencia. In La Leandra archaeological site (La Muela, Zaragoza) Miocene lacustrine deposits outcrop and usually present levels with high concentration of silex nodules. These nodules have been exploited during several periods, and due to the weather and demographic characteristics, original topographical features related to their exploitation usually persists. With the aim of evaluating the site exploitation from a geophysical point of view magnetometry, magnetic susceptibility survey and ground penetrating radar were integrated with the obtained information from a drone flight. This analysis permits to identify an exploitation progression from vertical pits, lateral continuity of the excavation when profitable levels were found through horizontal platforms and the later filling of the excavated pits during the excavation progression. The studied case permits to infer from geometrical and structural changes the mining progression from an expected Neolithic quarry and the identification of an exploitation routine through transfer mining

Diverse strategies for copper production in Chalcolithic Iberia

Our understanding of early copper metallurgy in the Iberian Peninsula is mostly based on analysis from well-studied regions in the Southeast and Southwest. This paper focuses on two recently recovered Chalcolithic metallurgical assemblages outside these traditional research foci: two slagged crucibles from Lugar Viejo III (Zaragoza) and two large slag cakes from Cueva del Cañaveralejo (Córdoba). Analysis of the compositions and microstructures of the artifacts using optical microscopy and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) suggests they are related to primary copper production, namely smelting in crucible-furnaces under relatively oxidizing conditions, as is standard for this period. The slag layers on crucibles from Lugar Viejo indicate the production of copper with minor amounts of arsenic, also typical for this period. Of special note is the use of organic temper in the crucibles from Lugar Viejo, a practice found at the nearby site of Moncín but rare at other sites in Iberia. However, the slags from Cueva del Cañaveralejo are atypical in their large size (approx. 125 g each), fayalitic composition, unusual efficiency as demonstrated by a low copper content, and lack of arsenic; furthermore, the high sulfur content raises the possibility of the use of sulfidic ores. Results from both sites are compared against published data from well-known sites such as Los Millares, Las Pilas, Almizaraque, and Bauma del Serrat del Pont. The new data from Lugar Viejo and Cueva del Cañaveralejo reinforce the interpretation of metallurgy in the Iberian Peninsula as a low-skilled, conservative technology but also indicate the need for more research into regional variations. (See Supplementary Information 1 for a summary in Spanish)