An X-ray analysis of the dagger of King Tutankhamun has shown that the iron in the ancient blade had come from meteorites. A French study has now revealed that the artifact was far from alone as all iron tools dating back to the Bronze Age have otherworldly origins.
Beginning around 3300 BCE in the Near East and parts of South Asia, the Bronze Age came to marked by the widespread use of bronze in weapons, tools and decorations. Produced by the smelting copper and mixing it with tin, arsenic or other metals, bronze was durable and relatively easy to come by, and continued to be the top choice until it was supplanted when the Iron Age began some 2,000 years later.
This does not mean that iron was not used during the Bronze Age, on relatively rare occasions iron artifacts have been found dating back to before the Iron Age, but it was much harder to come by and work with. Extracting the metal from its ore required extremely high temperatures, which was beyond the technological capabilities of the time.
It had long been thought that iron tools of the time were made from meteorites, which would have deposited the metal in an already-workable state on the Earth's surface. The theory would explain the presence of iron in artifacts before the development of advanced smelting techniques.
To determine whether the early iron artifacts were of terrestrial or extraterrestrial origin, Albert Jambon from the the National Center for Scientific Research (CNRS) in France conducted chemical analyses of a number of Bronze Age samples.
In addition to King Tut's dagger, Jambon studied a bracelet and headrest belonging to the Egyptian king in 1350 BCE, axes from Syria and China dating back to about 1400 BCE, a Syrian pendant from 2300 BCE, a Turkish dagger from 2500 BCE, and other artifacts.
He used a portable X-ray fluorescence spectrometer, an instrument that could determine the elements making up a sample of rock or metal without damaging the target. The technique allowed Jambon to tell the iron's impurities whether the metal in the relics came from meteorites or was naturally occurring on earth.
Iron meteorites usually contain higher levels of nickel and cobalt than earthly iron as nickel has a tendency to move towards the molten core of a planet.
The tests revealed that the samples had levels of nickel and cobalt found in iron meteorites. All iron items from the Bronze Age would therefore be made of meteoric iron, until the development of the smelting process marking the beginning of the Iron Age from about 1200 BCE.