‘Space beads’ push back origins of iron working

Iron beads from jewelry discovered a century ago in an ancient Egyptian grave came from pieces of meteorites that were hammered and heated into ornaments, two new studies find.

Researchers say that techniques employed by Egyptian artisans around 5,200 years ago eventually proved essential for making objects out of iron extracted from ore, a practice that started roughly 1,500 years later in or near modern-day Turkey and 3,000 years later in Egypt.

Hammering relatively soft metals such as copper and gold into thin sheets, which were rolled up to form cylindrical beads, began about 10,000 years ago in Turkey. To do the same with iron lumps from meteorites required impressive blacksmithing skills, says archaeometallurgist Thilo Rehren, who directs a campus of University College London, based in Doha, Qatar.

Chunks of hard, brittle meteorite iron were repeatedly heated to red-hot temperatures and hammered to make tube-shaped beads, Rehren and colleagues report August 20 in the Journal of Archaeological Science.

“We may assume that there was an uninterrupted chain of blacksmiths handing down the skill to work the strange ‘metal from the sky,’ a skill that was necessary later to work with iron smelted from ore,” Rehren says.

Around 2,300 years ago, Egyptian writing incorporated a word meaning “iron (or metal) from the sky” to describe all types of iron.

Analyses—using neutron beams and other noninvasive techniques—of three of nine presumably iron beads from Egypt’s Gerzeh cemetery identified concentrations of nickel, cobalt, phosphorus and germanium, elements characteristic of meteorites containing iron. Intense heating and hammering destroyed the iron’s original crystal structure, the researchers propose.

It’s more likely, however, that preservatives applied by museum curators corroded these beads’ internal structure and turned them black, says planetary scientist Diane Johnson of the Open University in Milton Keynes, England. A light-colored bead discovered at Gerzeh, which bears no signs of chemical treatment, retains a crystal structure typical of meteorite iron, Johnson and her colleagues reported in the June Meteoritics & Planetary Science.

Ancient Egyptians, or people who traded with them, made space beads via careful hammering and heating at lower temperatures than assumed by Rehren’s group, Johnson asserts.

Most important, it’s now clear that ancient Egyptians’ passion for ornaments made out of obsidian, ivory and sea shells included meteorite iron as well, says geologist Timothy McCoy of the Smithsonian Institution in Washington, D.C. Where this material was found and what types of tools were used to make iron beads remain unknown, he says.

Editor’s Note: This story was updated on August 22, 2013 to correct a reference to modern-day Turkey. It was further updated on September 17, 2013, to correct how long beads have been made from cylinders of metal.