The Use of Trace Element Analysis of Entrapped Slag Inclusions to Establish Ore – bar Iron Links: Examples From Two Gallo‐roman Iron‐making Sites in France (Les Martys, Montagne Noire, and Les Ferrys, Loiret)*

Abstract

Knowledge of the iron trade in ancient times rests on determining the source of the objects recovered during archaeological excavations. Unfortunately, attributing the origin is not always possible using archaeological tools alone. Trace element data of the ore and the archaeological material (reduction and reheating slags, entrapped slag inclusions from the bloom, bar iron and iron blades) from two Gallo-Roman iron-making centres, Les Martys (Montagne Noire) and Les Ferrys (Loiret), were determined using ICP-AES/MS and LA-ICP-MS. The results highlight a continuity of composition that makes it possible to establish a link between the initial ore and the semi-finished iron products.

Slag inclusions in iron objects and the quest for provenance: an experiment and a case study

“…Various studies have investigated whether the geological origin of an archaeological iron artefact can be determined using the chemical composition of the slag inclusions (hereafter, SI) within the object (Buchwald and Wivel, 1998;Coustures et al, 2003;Dillmann and L'Hé ritier, 2007;Hedges and Salter, 1979;Høst-Madsen and Buchwald, 1999). The underlying assumption of earlier studies was that the variability in ore compositions should be reflected in the chemistry of SI (Hedges and Salter, 1979).…”

“…More recently, researchers have began to refine these approaches by noting that other factors such as fuel ash, fluxes and furnace lining, together with variable operating parameters, do contribute significantly to slag formation, and that therefore SI in objects should be related to specific ''smelting systems'' rather than generic geological ores (Dillmann and L'Hé ritier, 2007;Paynter, 2006). This has led some to compare compositional data between SI and smelting slags (rather than ores alone), hoping to identify better matches (Buchwald and Wivel, 1998;Coustures et al, 2003). Most of these provenancing attempts, however, have been unconvincing or only partly conclusive, and their interpretation of the data remains speculative.…”

Role of laser ablation–inductively coupled plasma–mass spectrometry in cultural heritage research: A review

“…Small craters are required not only when causing a minimal damage is mandatory as in the case of a precious ancient object, but also when spatially resolved trace element analysis [42,[97][98][99][100] is necessary. When dealing with extremely rough surfaces (little holes, inclusions etc.)…”

“…In Devos et al [98] one low alloy steel (NIST1262) and a cast iron (ARL1721) were used as external standards, as they show concentration of trace metals very similar to those measured in archaeological samples. In Coustures et al [97], authors employed for calibration the international geostandard BCR2 for quantitative determination of trace elements in iron slags.…”

“…While Devos et al [98] utilized LA-ICP-MS to avoid the analysis of inclusions, more than 30 major elements, trace elements and rare earth in slag inclusions were measured by Coustures et al [97] aiming at establishing a link between the initial ore and the semi-finished iron products. The choice of the analytes was carried out taking into account the behavior of trace elements during the bloomery process (for further details see [98] and references therein).…”