The production of iron from its ore only started in the 2nd millennium BC, but a number of iron artifacts from the preceding Bronze Age are known to exist. According to a new study published in the Journal of Archaeological Science, the composition of all Bronze Age iron artifacts is consistent with a meteoritic origin of the metal.
"The Iron Age began in Anatolia and the Caucasus around 1200 BC, but nearly two millennia earlier, various cultures were already fashioning objects out of iron. These items were extremely rare and always greatly treasured," said study author Dr. Albert Jambon, a researcher at the Université Côte D'Azur and Sorbonne Universités in France.
"So what made these artifacts so valuable? Initial research had shown that some were made with iron from meteorites, which led scientists to wonder how many others were."
"We gathered the available data and conducted nondestructive chemical analyses of samples using a portable X-ray fluorescence spectrometer."
Dr. Jambon examined a series of Bronze Age iron artifacts: iron beads from Gerzeh (Egypt, 3200 BC), a dagger from Alaca Höyük (Turkey, 2500 BC), a pendant from Umm el-Marra (Syria, 2300 BC), an axe from Ugarit (Syria, 1400 BC), several others from the Shang dynasty civilization (China, 1400 BC), and the dagger, bracelet, and headrest of Tutankhamen (Egypt, 1350 BC).
The analyses revealed that all these artifacts were made from meteoric iron.
"When large celestial bodies like Earth are forming, nearly all nickel drifts towards the molten iron core. Thus, it is extremely rare to find nickel on the surface," Dr. Jambon said.
"However, some meteorites are created when celestial bodies are shattered. If these meteorites are composed of core material, they mostly contain iron with high levels of nickel and cobalt. This characteristic makes it possible to identify the source of iron."
"Meteoric iron is also already in a metal state, ready for use, which explains why it went into all Bronze Age iron artifacts."
"In contrast, the iron compounds in terrestrial ores must first undergo the process of reduction, which removes bound oxygen to yield the desired metal. This is the basis of smelting in furnaces, a breakthrough that marked the beginning of the Iron Age."
"With smelting, Iron Age cultures could forget rare extraterrestrial metal and tap into terrestrial iron ores, which were far more abundant and easier to procure," he said.
Albert Jambon. 2017. Bronze Age iron: Meteoritic or not? A chemical strategy. Journal of Archaeological Science 88: 47-53; doi: 10.1016/j.jas.2017.09.008
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