Transcript:

ambience: Grinding stone

That's the sound of two stones being ground together -- two stones that were used thousands of years ago to grind grain in Mesopotamia. But their age is not the only remarkable thing about these particular rocks. They also happen to be artificial. I'm Jim Metzner and this is the Pulse of the Planet, presented by DuPont.

"What I have in my hand at the moment is a chunk of one of the big blocks. They would then use a little hand stone of the same material, and simply grind the grain around."

Anthropologist Elizabeth Stone is a professor at the State University of New York. While excavating a four-thousand-year old city in what's now southern Iraq, she and her team made a remarkable discovery . They uncovered what at first appeared to be pieces of basalt, a black, volcanic rock that the Mesopotamians imported for their grinding stones. But there was something rather odd about this stone.

"It was something where you would look at and say this doesn't look like a natural stone. We kept on having this consistent material that seemed to have two original surfaces, one of which was kind of bubbly in a sense, and then the bottom surface was dead flat, and they were all about the same thickness. And, I mean, what was really striking about them was their consistency. And Mother Nature isn't consistent like that."

Well, the slabs of supposed stone turned out to be an artificial product that was apparently manufactured by firing dirt at very high temperatures, and then cooling it slowly. Scientists believe that Mesopotamian potters could only have developed this process by working together with metalsmiths -- a rare collaboration between tradespeople at that time. The artificial stone is considered a remarkable example of ancient technology.

"You cannot have produced this stuff without a lot of trial, error, and experimentation."

Pulse of the Planet is presented by DuPont, bringing you the miracles of science, with additional support provided by the National Science Foundation.