Smith – a senior analysis scientist at GIA – was inspecting the diamond for inclusions, chemical hitchhikers from the inside of our planet that may reveal how the crystal shaped, and below what situations. However working with high-value diamonds is a tough enterprise – ordinarily, it is unattainable for researchers to get their arms on the most important specimens. They’re generally flown world wide to go to potential clients – alas, by no means scientists.

Maya Kopylova, a professor of mineral exploration on the College of British Columbia, says getting samples of any diamonds is difficult, and a lot of the diamonds she works with would have in any other case been thrown away. “Researchers need to have a superb relationship with firms and they’ll by no means offer you useful samples,” she says. “So, they may by no means give us diamonds which can be 6mm (0.2 inches) in dimension or bigger.”

Even then, buying them is convoluted and costly – first, Kopylova has to go to the high-security services the place diamonds are sorted and determine the specimens she’d like to review. As soon as the acquisition has been permitted, then comes the paperwork – all diamonds should journey with a Kimberley Course of certificates, which proves its provenance and helps to forestall battle or “blood” diamonds from coming into the market.

Nonetheless, Smith’s scenario is totally different. At GIA, he has entry to one of many largest collections of diamonds on the planet – hundreds of thousands of gems which were despatched there to be valued, in order that they are often insured or offered. “If you wish to see one thing uncommon and weird, that is the right place to go as a result of there are diamonds coming via right here on a regular basis,” says Smith. “Each few days, you would possibly get to borrow a diamond for perhaps a couple of hours, perhaps a day or two and examine it.”

A number of years earlier, that is precisely what Smith had carried out. Along with a world crew of scientists, he casually requisitioned 53 of the largest, clearest and costliest obtainable – together with some from the identical mine because the Cullinan diamond – and took them again to his laboratory to view below a microscope.

What Smith discovered was revolutionary. Practically three-quarters of the Clippir diamonds contained tiny pockets, or “inclusions” of metallic that had prevented rusting – not one thing you’d discover in bizarre ones – whereas the remaining 15 contained a type of garnet which solely kinds inside the Earth’s mantle, the layer above its molten core.

Collectively, these inclusions present chemical clues that the diamonds may solely have shaped no fewer than 360km (224 miles) and not more than 750km (466 miles) underfoot. On this Goldilocks zone, it is deep sufficient to clarify the metallic inclusions that hadn’t been uncovered to oxygen, which is considerable greater up, and it isn’t so deep that the garnet rocks would have damaged down below the immense pressures of the decrease mantle. Unusual diamonds, in the meantime, originate under the crust, simply 150-200km (93-124 miles) down.  

For his 2020 examine – along with Wuyi Wang, who’s vice presedent of analysis & improvement at GIA – Smith analysed the 124-carat diamond and located that it shaped on the deeper finish of the attainable vary – no less than 660km (410 miles) under the Earth’s floor.