Nabataean iron picks for copper mining from Nahal ‘Amram, Israel; Chemical, isotopic and production technology analysis

Recent excavations at Naḥal ‘Amram, a Nabataean copper mining center in the Arabah valley, Israel, unearthed for the first time four iron tips of mining picks. The present study undertakes a complex investigation of the picks, including metallographic, indentation hardness, slag inclusions (SIs), metal matrix, and osmium isotopic composition (Os-IC) analyses. The results indicate that the picks were manufactured via similar blacksmithing techniques, using two types of hard alloys: quench-hardened steel and phosphoric iron. A correlation was found between the composition of SIs, metal, and osmium isotopic signature, suggesting that three different ore sources were exploited to produce these picks. The quenched steel likely originated from a single ore source, whereas the two P-rich iron probably provenance from two different, yet geographically close or geologically similar ore deposits. The undertaken study highlights the importance of an integrative provenancing approach, which relies on the analyses of siderophile/chalcophile elements of the metal, lithophile trace elements of slag inclusions, and osmium isotopic analyses. This approach allows the complete characterization of the ore provenance signature of an artefact. However, the final provenance assignment to a specific ore deposit is currently limited, as it depends on our knowledge and familiarity with potential ore sources and on the archaeological evidence of their exploitation.