Ancient Beads with an Otherworldly Origin
IRA FLATOW, HOST:
Next up, 5,000 years ago, fashion-conscious Egyptians were just like us. They wanted their jewelry to be shiny and heavy. They wanted their bling. But that was 2,000 years before the Iron Age, before the development of iron smelting. So how did they get their iron? The answer came from the sky, literally - meteorites from the sky, to be exact.
In a recent research paper, researchers analyzed iron beads from 3200 B.C. that were created from meteoric iron. How did they do that? Thilo Rehren is an archaeometallurgist at the University of College London at Qatar in Doha, one of the authors of the paper published in the Journal of Archaeology Science. Welcome to SCIENCE FRIDAY.
DR. THILO REHREN: Thank you very much. Good afternoon.
FLATOW: Can you describe for us what these beads were, what they look like, how they were found?
REHREN: OK. They were excavated about 100 years ago by a team of archaeologists directed by the famous Flinders Petrie, who excavated in many, many places in Egypt, from a cemetery containing two or three hundred graves, all of which were excavated.
They look like small bits of iron, about the size of a segment of your little finger, maybe an inch long, a few millimeters, five, eight millimeters thick (unintelligible). But because of the corrosion, the hole - the long axis in the hole, one couldn't see that it was open, actually.
FLATOW: Mm-hmm. And you can...
REHREN: They look - yeah. They look very corroded now.
FLATOW: They're corroded. And you can tell from looking at the beads that there had been iron work done on them, banging, shaping?
REHREN: Yes. It was clear from the beginning, just from looking at some holes -corroded and rusty they are - that they're iron metal, or used to be iron metal. But because of the heavy corrosion, it was difficult to really envisage how they were made.
And these seven, eight, nine beads from that tomb come together with a dozen or two of other beads of very similar shape, of different materials, some of them lapis lazuli from Afghanistan. Some are carnelian or agate from elsewhere in Egypt. And those stone beads were - with a hole had been drilled through it. With the iron beads it was just too corroded to see how they were made.
FLATOW: Hmm. This is SCIENCE FRIDAY from NPR. I'm Ira Flatow, talking with Thilo Rehren. And where did they get the beads from?
REHREN: Well, that's the big question, and that's probably impossible to answer, really, because we can only say they are from the sky, they're meteoritic iron. But meteorites fall wherever they want to fall. And so they could have down everywhere.
On the other hand, if you look where modern meteorite hunters go, one of the - the second-best place to go is the Sahara Desert. And if you're in Egypt, on the River Nile banks, it's not that far to go to that desert and to pick them up.
REHREN: And it's relatively easy because they stand out like dark rocks in a relatively light landscape that's been accumulated for thousands of years. So it's probably reasonable to assume they were from the wider local vicinity.
FLATOW: If this is before the Iron Age, how - would they recognize this as some foreign substance, or would they recognize where it might have come from?
REHREN: They would have recognized that they're different from other stones that scatter the landscape. They're as black as other black stones, but they are three times as heavy. The specific gravity of these metal beads, metal lumps, is that much bigger than stone, and you would immediately notice that when you pick them up.
They would have known that sort of material from copper and gold, which are occurring in Egypt as native metals as well. So they were used to the existence of such dense materials. Whether they knew that they're from the sky that early on, I don't know.
But then if you just remember a few months ago, Siberia, people observed a meteorite strike, and they were able to locate, even in the densely wooded landscape, to locate the impact crater, pick up some of the fragments. Now, if you're in a desert, whatever falls from the sky, you can find that pretty easy. So it's quite easily imaginable. They knew from the beginning that these strange stones were actually falling from the sky.
FLATOW: Have any beads been found in North America like these?
REHREN: Yes. In the - I think in Ohio you have beads which are about 2,000, 2,500 years old, and they were also made from meteoritic iron, bent round, not as thin, as fine works as these Egyptian ones, but as beautiful and the same material and principle, same technology.
FLATOW: Hmm. Is there any way to know if the discovery of meteoric iron led to smelting of iron in the Iron Age? They had this iron around, and it helped them figure out.
REHREN: No, I don't think so because the good thing with the meteoritic iron is that it falls from sky and it's ready for you to work. You don't need to smelt. You don't need to do the chemistry...
REHREN: ...that transforms your ore into metal. That's (unintelligible) they invented - around that time, actually - was copper. And they did copper smelting for a few thousand years until somehow out of that emerged the iron smelting.
REHREN: How exactly that happened we don't know. But the interesting link here is that when you start iron smelting at the late Bronze Age, you create iron metal as a solid metal, in contrast to the previous copper smelting where you had liquid copper.
This solid iron lump that you create in the early iron furnaces is very difficult to work, or so we thought. Now we understand these guys had already 2,000 years of experience working solid meteoritic iron. So when they started smelting iron, it helps them to work that metal.
It didn't help them to make it in the first place.
FLATOW: Dr. Rehren, thank you very much for taking time to be with us today.
REHREN: My pleasure. Thank you very much for having me.
FLATOW: Welcome. Thilo Rehren is an archaeometallurgist at the University College London in Qatar, Doha.