Pink diamonds formed when Earth's earliest supercontinent broke around 1.3bn years ago, says study

Pink diamonds are extremely rare and highly expensive. For years, researchers have been unable to decipher how these gemstones formed and why are they rosy in colour in comparison to other colourless diamonds.

That mystery has now finally been unravelled.

According to a team of Australia-based researchers, the pink diamonds arrived on the surface around 1.3 billion years ago when one of the Earth’s earliest supercontinents, Nuna, fell apart.

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The research published in the journal Nature Communications indicates that ancient continental junctures may be hiding more of these colourful gems.

“While the continent that would become Australia didn’t break up, the area where Argyle is situated was stretched, including along the scar, which created gaps in the Earth’s crust for magma to shoot up through to the surface, bringing with it pink diamonds,” said lead study author Dr Hugo Olierook, a research fellow at Curtin University’s John de Laeter Centre in Perth, Australia, in a news release.

Australia accounts for more than 90 per cent of pink stones formed on Earth. They come from the Argyle mine in Western Australia, which was one of the world’s most productive diamond deposits until it ceased operations in November 2020.

Many of Argyle’s diamonds have a browny hue. But out of every thousand gems, a few would pop up in the rarer and more valuable pink.

Usually, diamonds are found in the middle of ancient continents, within volcanic rocks that have rapidly transported diamonds from deep inside Earth’s interior to the surface.

But the pink diamonds are formed when they are subjected to intense forces from colliding tectonic plates, as they twist and bend their crystal lattices. Most brown diamonds are also formed in this manner.

At Argyle, this process occurred around 1.8 billion years ago when Western Australia and Northern Australia collided, turning the once-colourless diamonds pink hundreds of miles below Earth’s crust.

“Argyle is at the suture of two of these ancient continents, and these edges are often covered by sand and soil, leaving the possibility that similar pink diamond-bearing volcanoes still sit undiscovered, including in Australia,” Olierook said.

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