Metal provenance of Iron Age Hacksilber hoards in the southern Levant

Hacksilber facilitated trade and transactions from the beginning of the second millennium BCE until the late fourth century BCE in the southern Levant. Here we demonstrate the use of new, data-driven statistical approaches to interpret high-precision Pb isotope analysis of silver found in archaeological contexts for provenance determination. We sampled 45 pieces of Hacksilber from five hoards (Megiddo Area H, Eshtemoa, Tel Dor, ʿEn Gedi, and Tel Miqne-Ekron) and combined our data with recent literature data for the same hoards plus five more (Beth Shean, Ashkelon, Tell Keisan, Tel ʿAkko, and ʿEn Ḥofez) thus covering silver from the Late Bronze Age III (c.1200 BCE) to the end of the Iron Age IIC (586 BCE). Samples were taken by applying a new minimally destructive sampling technique. Lead was extracted using anion-exchange chromatography, and Pb isotopic compositions were measured by MC-ICP-MS. Data were treated using a new clustering method to identify statistically distinct groups of data, and a convex hull was applied to identify and constrain ore sources consistent with the isotopic signature of each group. Samples were grouped by minimizing variance within isotopic clusters and maximizing variance between isotopic clusters. We found that exchanges between the Levant and the Aegean world continued at least intermittently from the Late Bronze Age through to the Iron Age III, demonstrated by the prevalence of Lavrion (Attica), Macedonia, Thrace (northern Greece), southern Gaul (southern France), and Sardinia as long-lived major silver sources. Occasional exchanges with other west Mediterranean localities found in the isotopic record demonstrate that even though the Aegean world dominated silver supply during the Iron Age, exchanges between the eastern and the western Mediterranean did not altogether cease. The mixture of silver sources within hoards and relatively low purity of silver intentionally mixed with copper and arsenic suggest long-term hoarding and irregular, limited supply during the Iron Age I.