Lead in Ancient Peru: the Curamba Smelter and Lead Sling Bullets

Abstract

Since the 16th century, the Inca site of Curamba, in southern Peru, has been interpreted as a metallurgical center for processing silver ore. Yet, aside from the many shallow pits, interpreted as hornos for smelting silver, there was no physical evidence for the use of huayras or tocochimbos, which were the structures traditionally used for precontact silver smelting in the ancient Andes. Geochemical analyses (inductively coupled plasma) of scoria excavated from the hornos at Curamba indicate low Ag (<0.3 ppm to 0.4 ppm), Au (<2 ppm), and Cu (18 ppm to 31 ppm) contents, whereas Pb (155 ppm to 234 ppm) and Zn (125 ppm to 259 ppm) contents were high. This suggests that nonargentiferous galena (PbS) was smelted to obtain lead. A lead-zinc signature is also indicated by the presence of As, Ba, Fe, Mn, and V, yet no ore minerals such as PbS or sphalerite [(Zn,Fe)S] have been found at the site. Several precontact lead artifacts from ancient Peru have been described as bars (lingotes) or weights (pesos). However, alternatively, these artifacts might be more accurately described as: (a) biconic to ovoid (30 mm to 60 mm, 30 g to 40 g) or (b) spherical (35 mm, 80 g to 160 g); therefore, in composition, dimensions, form, and weight, these ancient Peruvian lead artifacts from the north coast are strikingly similar to ancient Roman and Celtic lead sling ammunition from first-century BC battle sites, and are herein interpreted to have served a similar function in ancient Andean warfare.