Method Sheds Light on Gems Collected from Historical Site in Iran
Image by Courtesy
04/18/2024
By Brooke Coupal
Once a thriving city in Iran鈥檚 Sistan and Baluchestan Province around 3200 B.C., Shahr-e Sokhteh now stands abandoned.聽
Shahr-e Sokhteh, which means 鈥淏urnt City,鈥� was located at the junction of trade routes crossing the Iranian plateau during the Bronze Age, according to UNESCO, which named the historical site to its聽. Despite the population deserting the city around 1800 B.C., many structures, burial grounds and artifacts remain well-preserved due to the area鈥檚 dry climate. One artifact commonly uncovered by archeologists is gemstones.
A team of researchers from Iran, Italy and the United States set out to discover a minimally invasive way of characterizing Shahr-e Sokhteh gemstones. Their findings, which are published in the Nature Portfolio journal聽, provide a new method for gemstone identification.
鈥淥ur research shows that science can work across borders, across cultures and across time, even with things that are as old as 3200 B.C.,鈥� says聽Noureddine Melikechi, the Kennedy College of Sciences聽dean and a co-author of the paper.
Researchers in Iran gathered gemstones collected from Shahr-e Sokhteh and used a technique known as laser-induced breakdown spectroscopy (LIBS) to measure their elemental composition. The technique involved shooting a laser at the gemstones, which in turn vaporized a tiny portion of the stones that the researchers could then measure.
鈥淭he beauty of LIBS is we need just few nanograms to test a sample,鈥� says Melikechi, who also uses the LIBS technique in his lab and is part of a research team using it to study rocks and soil on Mars. 鈥淭hese gemstones are valuable cultural artifacts, and when the laser zaps them, it makes a small dent that you can鈥檛 even see.鈥�
Image by Brooke Coupal
Ali Safi helped measure the elemental composition of the gemstones while studying at Shahid Beheshti University in Tehran, Iran, before coming to Melikechi鈥檚 lab as a postdoctoral researcher to analyze the measurements.
鈥淚t鈥檚 perfect (working in Melikechi鈥檚 lab),鈥� says Safi, a native of Iran. 鈥淎s a young researcher, I鈥檓 learning every day.鈥�
Safi and Melikechi, along with researchers from Iran and Italy, used machine learning to compare the data collected from the LIBS technique to existing data on gemstones, allowing them to identify the gemstones found in Shahr-e Sokhteh as turquoises, agates, calcites and azures.
The researchers envision jewelers benefiting from their findings.
鈥淯sing this method, they can figure out what type of gems they have with great precision,鈥� Melikechi says. 鈥淥ur work shows, one more time, the power of combining LIBS and machine learning.鈥�
