A weapon as legendary as the dagger of King Tutankhamun needs an epic backstory, and last year X-ray analysis showed that the iron in the ancient blade had come from meteorites. Now, a French study has found 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 was categorized by the widespread use of bronze in weapons, tools and decorations. Made by smelting copper and mixing it with tin, arsenic or other metals, bronze was durable and relatively easy to come by, and as such it remained the top choice until it was supplanted when the Iron Age began some 2,000 years later.

That's not to say that iron wasn't 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. The trouble was, most of the metal was locked in ore and needed to be smelted at extremely high temperatures, which was beyond the technological capabilities of the time. So where did those early iron artifacts come from?

It's 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 advanced smelting techniques had been developed, and whether or not their owners knew that the metal was not of this planet, iron would have been prized for its relative rarity.

To determine whether these 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 several Bronze Age samples. Along with 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 beads from Gerzeh, Egypt, which stretch right back to 3200 BCE, just after the Bronze Age began.

Jambon used a portable X-ray fluorescence spectrometer, an instrument that can determine the elements that make up a sample of rock or metal without damaging the target. Using this, Jambon could tell from 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 due to the tendency for nickel to drift towards the molten core of a planet.

Sure enough, all of the tested samples had levels of nickel and cobalt that lined up with those seen in iron meteorites. Jambon concluded that essentially all iron items from the Bronze Age would therefore be made of meteoric iron, until the development of the smelting process that marked the beginning of the Iron Age from about 1200 BCE.

The research was published in the Journal of Archaeological Science.

Source: CNRS