In a Bronze Age settlement in Mörigen, Switzerland, archaeologists have discovered a real rarity: an arrowhead made of meteorite iron that is around 2,900 years old. However, as comparative analyzes revealed, this iron does not come from the nearby Twannberg meteorite strewn field, but from a surprisingly distant impact site. The chemical-isotopic composition matches that of a large iron meteorite that hit Estonia a good 3,500 years ago.
In Central Europe, the Iron Age began around 800 BC. Around this time, the people of this region developed technologies to extract iron from ore. But even before this time there were isolated objects made of iron. These were made from rare finds of meteorite iron and were considered extremely rare and precious. They were mostly reserved for rulers and other members of the elite. So far, archaeologists have found only 55 such meteorite iron objects across Eurasia and Africa. 19 of them alone, including an iron dagger, come from the tomb of the Egyptian pharaoh Tutankhamun.
Rusty arrowhead from Bronze Age stilt houses
Given the rarity of such finds, a team led by Beda Hofmann from the Natural History Museum in Bern has been looking for other Bronze Age objects made from meteorite iron. They chose a Bronze Age pile-dwelling settlement in Mörigen, Switzerland, on Lake Biel as a potentially promising location for this. This around 900 to 800 BC. The settlement that was inhabited between the 4th and 6th centuries BC is only a few kilometers away from the strewn field of the so-called Twannberg meteorite. This chunk, which belongs to the rare group of nickel-poor iron meteorites, struck about 160,000 years ago and left a field of fragments about five kilometers long.
It therefore seemed quite obvious that the inhabitants of the settlement could have discovered and processed scattered pieces of iron from this meteorite. Hofmann and his colleagues therefore searched the finds made in Mörigen over the past 150 years for metallic objects that could consist of this meteorite iron. They struck gold with an almost four centimeter long, heavily corroded arrowhead from the Bronze Age settlement: it appeared to be made of iron. In order to confirm this and learn more about the origin of this metal, the scientists subjected them to extensive analyzes using light microscopy, scanning electron microscopy, X-ray tomography, X-ray fluorescence, muon-induced X-ray spectrometry (MIXE) and highly sensitive gamma spectrometry.
Iron is of "heavenly" origin
The analyzes confirmed that the material of the Mörigen arrowhead must be of "heavenly" origin. This was proven, among other things, by the detection of the isotope aluminum-26 – a variant of aluminum that only occurs under the influence of hard cosmic rays. "We were thus able to provide unequivocal proof that the material is a meteorite that was exposed to cosmic radiation in space for a long time," explains co-author Marc Schumann from the University of Freiburg. So this arrowhead must be made of meteorite iron. Evidence of such early use of meteoric iron is extremely rare, archaeologists report.
Given this finding, it would seem plausible that the material came from the nearby strewn field of the Twannberg meteorite. But when the scientists compared the chemical composition of the arrowhead with that of Twannberg meteorite fragments, clear differences became apparent. At around 8.3 percent, the nickel content of the arrowhead was almost twice as high as in the Twannberg meteorite. In addition, a relatively high content of germanium and a lower content of aluminum-26 indicated that the iron in the arrowhead had to come from a large iron meteorite of the IAB type, weighing at least two tons - this does not fit the Twannberg meteorite.
Iron meteorite from Estonia as originator
But where did the arrowhead meteorite iron come from then? "Among the large IAB iron meteorites in Europe, only three have a chemical composition that matches the Möringer Pfeilspitze: Bohumilitz in the Czech Republic, Retuerte de Bullaque in Spain and Kaalijarv in Estonia," explain Hofmann and his colleagues. "Of these three impacts, Kaalijarv is the most likely candidate because the impact occurred in the Bronze Age." The iron meteorite, weighing several hundred tons, struck between 1870 and 1440 BC. B.C. in Estonia, leaving craters several hundred meters wide and an extensive strewn field. However, this is 1600 kilometers away from Mörigen.
How the meteorite iron got from Estonia to Switzerland in the Bronze Age is still unclear. "One possibility is that fragments of this meteorite were traded and transported along the same routes as Baltic amber," suggest Hofmann and his colleagues. They hope there may be other Bronze Age objects made from the iron of the Kaalijarv meteorite that still lie unrecognized in Europe's archaeological collections.
Source: Natural History Museum Bern, specialist article: Journal of Archaeological Science, doi: 10.1016/j.jas.2023.105827