Scientists said Tuesday they have found the “missing ingredient” for pink diamonds, one of the world’s most expensive stones due to their rarity and beauty, and the discovery could help find more. More than 90 percent of all pink diamonds found were discovered in the recently closed Argyle mine in northwestern Australia.

But exactly why Argyle, which, unlike most other diamond mines, is located on the edge of the continent rather than in its center and produces so many pink gems, remains a mystery. A new study published in the journal Nature CommunicationA team of Australian researchers said pink diamonds came to the Earth’s surface when the first supercontinent broke up about 1.3 billion years ago.

Hugo Oliruk, a researcher at Curtin University in Western Australia and lead author of the study, told AFP that two of the three ingredients that lead to the formation of pink diamonds are already known. The first component is carbon, and it must be in the bowels of the Earth.

Anything deeper than 150 kilometers (93 miles) would be graphite — “the stuff in your pencils, not very good for wedding rings,” Oliruk said.

The second component is the pressure required to damage clear diamonds.

“When you press them a little, they will turn pink. “If you press too hard, they will turn brown,” he said.

He added that most of the diamonds discovered in Argyle were in the less valuable shade of brown.

“Like a champagne cork”

The missing ingredient was a volcanic event that brought diamonds to the Earth’s surface where humans could retrieve them. In the 1980s, it was determined that Argyle diamonds appeared 1.2 billion years ago. But Olieruk said there was no “triggering mechanism” for the growth of rare diamonds at the time, so researchers are trying to establish a more precise timeline.

They used a laser thinner than a human hair to examine tiny crystals in a sample of Argyle rock provided by Anglo-Australian mining giant Rio Tinto, which owns the mine.

By measuring the age of the elements in the crystals, the researchers determined that Argyle is 1.3 billion years old; This means diamonds appeared 100 million years later than previously thought. This coincides with the breakup of the world’s first supercontinent, known as Nuna or Columbia. “Almost every land mass on Earth was crushed together,” Oliruk said around noon.

The enormous pressure that changed the color of the second substance, diamond, occurred 1.8 billion years ago during the collision between Western and Northern Australia. The fact that Nuna began to break up five hundred million years later re-enforced the “scar” from the event, Oliruk said.

He added that magma exploded from this old scar “like a champagne cork popping”, taking the diamonds with it. Study co-author Luc Doucet said such a massive explosion, with diamonds moving at speeds close to the speed of sound, has never been seen in human history.

Where to look next?

For the last 200 years, people have searched for diamonds mostly in the centers of major continents. But knowing the “missing ingredient” of pink diamonds could help future efforts to find rare stones, Oliruk said, adding that discovering more is unlikely to be easy or quick.

Nuna’s ancient mountain belts, which appear to be distributed near the edges of continents, could host a new “paradise of pink diamonds”, he said, citing Canada, Russia, South Africa and Australia as possible locations.

John Foden, a diamond expert from the University of Adelaide who was not involved in the research, told AFP that researchers had “conclusively demonstrated” the age of the Argyle diamonds. But he warned that other diamond-rich states were also linked to Nuna’s collapse and did not produce pink diamonds. This suggests “pinkness appears to be a local feature of Argyll”, he added.

Oliruk said the Argyle mine was closed in 2020 “for various financial reasons”, meaning pink diamond prices could continue to rise as supply dwindles. Source