Bronze Age iron: Meteoritic or not? A chemical strategy.

Abstract

International audienceBronze Age iron artifacts could be derived from either meteoritic (extraterrestrial) or smelted (terrestrial) iron. This unresolved question is the subject of a controversy: are some, all or none made of smelted iron? In the present paper we propose a geochemical approach, which permits us to differentiate terrestrial from extraterrestrial irons. Instead of evaluating the Ni abundance alone (or the Ni to Fe ratio) we consider the relationship between Fe, Co and Ni abundances and their ratios. The study of meteoritic irons, Bronze Age iron artifacts and ancient terrestrial irons permit us to validate this chemical approach. The major interest is that non-invasive p-XRF analyses provide reliable Fe:Co:Ni abundances, without the need to remove a sample; they can be performed in situ, in the museums where the artifacts are preserved. The few iron objects from the Bronze Age sensu stricto that could be analyzed are definitely made of meteoritic iron, suggesting that speculations about precocious smelting during the Bronze Age should be revised. In a Fe:Co:Ni array the trend exhibited by meteoritic irons departs unambiguously from modern irons and iron ores. The trend of Ni/Fe vs Ni/Co in different analysis points of a single object corroded to variable extents provides a robust criterion for identifying the presence of meteoritic iron. It opens the possibility of tracking when and where the first smelting operations happened, the threshold of a new era. It emphasizes the importance of analytical methods for properly studying the evolution of the use of metals and metal working technologies in our past cultures

The Innovation and Adoption of Iron in the Ancient Near East

“…Nevertheless, a suite of recent analyses that address earlier analytical issues strongly suggests that meteorites were used to fashion early iron objects. The meteoritic iron beads from Gerzeh have already been mentioned above (Johnson et al 2013;Rehren et al 2013), while new chemical analysis supports a meteoritic origin for the Tutankhamun dagger (Comelli et al 2016), an ax made of iron, bronze, and gold from Ugarit, and other Bronze Age iron artifacts (Jambon 2017). These recent studies have simultaneously strengthened the case for meteoritic iron and weakened evidence for smelted iron at this early stage.…”

“…More recent analysis of iron artifacts from Kaman-Kalehöyük also shows slag inclusions in iron artifacts from the Old Assyrian Colony period (Level IIIc, 20th-18th centuries BC) and possibly in one heavily corroded iron object from the Early Bronze Age (Level IVa, 22nd-20th centuries BC), though the angular morphology of one putative slag inclusion in the latter artifact is odd (Akanuma 2003(Akanuma , 2008. Though the heavy corrosion necessitates caution, chemical compositions (Ni/ Co and Ni/Fe ratios) of the artifacts are outside the ranges for meteoritic iron defined by Jambon (2017).…”

“…180-181). Corrosion can affect the composition of iron, so measurements must be taken on uncorroded metal, or corrosion must be taken into account in when results are interpreted (Jambon 2017). Analyses show that many early iron artifacts contain nickel (Waldbaum 1980, pp.…”

“…Other scholars, however, doubt that nickel-rich terrestrial ores could explain the chemical composition of early iron artifacts (Jambon 2017, p. 51). The presence of other elements, such as germanium, as well as a Ni/Co ratio of about 18:1, has also been considered diagnostic (Comelli et al 2016(Comelli et al , p. 1306Jambon 2017;Rehren et al 2013, p. 4790). Many of these more recent studies have developed nondestructive approaches that take alteration into account, improving the accuracy of these determinations.…”

Advanced Curation of Astromaterials for Planetary Science

“…Human fascination with the night sky and with celestial objects that fall to the Earth from the sky is as old as our species, and use of these astromaterials as a natural resource occurred at least as early as the Bronze Age (Jambon 2017;McCoy 2018;. However, the initial curation of astromaterials as objects of scientific interest to understand our universe began more recently (Marvin 2006) and in earnest with the curation of meteorite samples in museums starting in the year 1748 at the Natural History Museum Vienna (Brandstätter 2006).…”