5,000-year-old ‘slag’ reveals earliest metal working processes with CT scanning method

MIT has discovered a new way to penetrate the layers of time using CT scans to uncover how the earliest civilizations of the past worked with metals. Metallurgy, or the use of metals, revolutionized the world as a practice when human beings began extracting and processing metals. Gaining deeper insights into this elusive practice, due to how ancient it is, would reveal their technological abilities. “The goal is to understand, from start to finish, how they accomplished making these shiny metal products, MIT researchers told MIT News.

However, little evidence exists that would enable researchers to glean any insights into their production methods. But, in a new study, MIT researchers and professors employed a known technology to innovate their own processes. They demonstrated how CT scanning could enhance and refine traditional methods of studying ancient artifacts, revealing new and stunning insights into the earliest acts of metallurgy on Earth.

The revolutionary CT approach they developed opens up new avenues of research. CT scans employed to study metals For the study, MIT researchers took a slag sample from an ancient site in Iran called Tepe Hissar. After all, the first metallurgists came from Iran, according to MIT News. They began extracting copper from the rock about 5,000 years ago.

Effectively reaching for the source, the region in Iran is regarded as one of the earliest places where evidence of copper processing and object production might have happened, MIT researchers explained. The slag had already been analyzed and determined to belong to 3100 to 2900 BCE. In what has been called the first attempt to study ancient slag with CT scanning, they acquired an industrial CT scanner to perform their experiment, along with a regular CT scanner already at their disposal on campus.

Slag, MIT News explains, is produced when ores are heated to produce metal, so it’s a molten hot liquid that solidifies like lava as it cools. “Slag waste is chemically complex to interpret because in our modern metallurgical practices it contains everything not desired in the final product…” “There’s always been a question in archaeometallurgy if we can use arsenic and similar elements in these remains to learn something about the metal production process.” Even if arsenic runs the risk of dissolving.

In addition to CT scans, researchers used conventional methods such as X-ray fluorescence, X-ray diffraction, and optical and scanning electron microscopy. But it was the CT scans that provided a detailed overall picture of the internal structure of the slag and the location of pores and traces of other materials.

New way of studying early metal production Already, the CT scans led researchers to discuss how metal was processed in ancient times. Disagreements have even been sparked amongst them about the role of arsenic in early metal production, so their work has inspired new questions. “Moving forward,” MIT concludes, “…CT scanning could be a powerful tool in archaeology to unravel complex ancient materials and processes.” “This should be an important lever for more systematic studies of the copper aspect of smelting, and also for continuing to understand the role of arsenic,” MIT News concludes.

“It allows us to be cognizant of the role of corrosion and the long-term stability of the artifacts to continue to learn more. It will be a key support for people who want to investigate these questions.”