The famously clear and sparkling Golconda diamonds may originate from volcanic deposits 300 km away from where they are mined.
The Hope Diamond - one of the most famous gemstones in the world. Photo: Telegraph
Researchers may have discovered the true origin of famous Golconda diamonds such as the Hope and Koh-i-noor, Live Science reported on April 21.
Golconda diamonds are unique because they have very few impurities and little nitrogen, making them extremely clear and free of any blemishes that would dull their brilliance. They are also very large. The Koh-i-noor diamond, now part of the British Crown Jewels collection in the Tower of London, weighs 105.60 carats. The Hope diamond, on display at the Smithsonian National Museum of Natural History in Washington DC, USA, weighs 45.52 carats.
These Golconda diamonds were discovered in southern India between the 1600s and 1800s. They were mined in placer mines—shallow pits carved into riverine sediments. But before that, diamonds were brought to the surface in large volcanic rocks called kimberlites, and experts didn’t know where the kimberlites that contained these diamonds came from.
New research published in the journal Earth System Science suggests that Golconda diamonds may have originated in the Wajrakarur kimberlite mine in modern-day Andhra Pradesh, India, about 300 kilometers from where they were mined.
To trace the origin of the Golconda diamonds, geologists Hero Kalra, Ashish Dongre and Swapnil Vyas from Savitribai Phule Pune University studied the chemistry of surrounding kimberlite and lamproite rocks, which form at the base of the Earth's crust and upper mantle, where most diamonds form.
The team found that the kimberlite from the Wajrakarur mine could have been pushed up from the depths where diamonds form and contained minerals that are commonly found with diamonds. They then conducted a survey using remote sensing data such as satellite imagery, vegetation measurements, and moisture content. The survey revealed that an ancient river that had long since dried up may have transported diamonds from Wajrakarur to the Krishna River and its tributaries, where the diamonds were found.
However, this result is not certain, according to Yakov Weiss, a geochemist who studies diamonds at the Hebrew University of Jerusalem. In the new study, the authors studied the geochemical properties of conventional diamonds from the lithosphere—the Earth’s crust and upper mantle—and determined that the Wajrakarur deposit could contain diamonds. However, the Golconda diamonds form at greater depths in the mantle, perhaps in the transition zone near the Earth’s core.
It’s difficult to directly trace the origin of Golconda diamonds because they lack the fluid inclusions from the mantle where they first formed. This makes them beautiful and desirable, but it provides little information for geochemists, Weiss said. So Golconda diamonds will probably always remain a mystery.
Thu Thao (According to Live Science )
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