Smith — a senior research scientist at GIA — examined the diamond for inclusions, chemical hitchhikers from our planet’s interior that can reveal how the crystal formed and under what conditions. But working with high-quality diamonds is a tricky business – normally it’s impossible for researchers to get their hands on the largest ones. They are sometimes flown around the world to visit potential clients – sadly never scientists.
Maya Kopylova, a professor of mineral exploration at the University of British Columbia, says it’s difficult to get samples of diamonds and most of the diamonds she works with would otherwise have been thrown away. “Researchers need to have a good relationship with companies and they will never give you valuable samples,” she says. “So they will never give us diamonds that are 6 mm (0.2 in) or larger.”
Even then, getting them is complicated and expensive. First, Kopylova must visit the high-security facilities where diamonds are sorted and identify the ones she wants to study. Once the acquisition is approved, comes the paperwork – all diamonds must travel with a Kimberley Process certificate, which proves provenance and helps prevent conflict or “blood” diamonds from entering the market.Read:Fast radio burst: Studies reveal details about the origin
However, Smith’s situation is different. At GIA, he has access to one of the largest collections of diamonds in the world – millions of gems sent there to be appraised so they can be insured or sold. “If you want to see something rare and unusual, this is the perfect place to go, because diamonds are always passing by here,” says Smith. “Every few days you may be allowed to borrow and study a diamond for a few hours, maybe a day or two.”
A few years earlier, this was exactly what Smith had done. Along with an international team of scientists, he casually requisitioned 53 of the largest, brightest and most expensive available — including some from the same mine as the Cullinan diamond — and took them back to his lab to view them under a microscope.
What Smith discovered was revolutionary. Nearly three-quarters of Clippir’s diamonds contained tiny pockets, or “inclusions,” of metal that had avoided rusting—not something you’d find in ordinary diamonds—while the remaining 15 contained a type of garnet that forms only in the Earth’s mantle, the layer above the molten core.
Together, these inclusions provide chemical clues that the diamonds formed no less than 360 km (224 miles) and no more than 750 km (466 miles) underfoot. In this Goldilocks zone, it is deep enough to account for the metallic inclusions that had not been exposed to oxygen, which is abundant higher up, and it is not so deep that the garnets would have broken down under the immense pressure of the lower mantle. Ordinary diamonds originate beneath the Earth’s crust, just 150-200 km (93-124 miles) down.Read:Video Shows Incredible 3D Animation of Jupiter’s “Frosted Cupcake” Clouds
For his 2020 study — along with Wuyi Wang, vice chair of research and development at GIA — Smith analyzed the 124-carat diamond and found that it had formed at the deeper end of its possible range — at least 660 km (410 miles). ) lower The Earth’s surface.