Revealing the secret of the rarity of pink diamonds
Sciences et technologies

Revealing the secret of the rarity of pink diamonds

Researchers have uncovered the “secret” behind the rarity of pink diamonds, according to a study published Tuesday. They are almost exclusively found in Australia, which explains their astronomical price.

More than 90% of all pink diamonds in existence come from the recently closed Argyle mine in northwestern Australia. But no one really knew why they were found there, on the edge of the southern continent, while most diamond mines are located in continental environments, such as South Africa or Russia.

The Australian team explains in the journal Nature Communications that these rare minerals were formed due to the breakup of Earth’s first supercontinent 1.3 billion years ago. The two “ingredients” needed to create a pink diamond are already known, study first author Hugo Oliruk of Australia’s Curtin University in Perth told AFP.

“Like a champagne cork”

The first ingredient, carbon, is found at great depths. At a depth of less than 150 km, this carbon is ordinary graphite, which is used to make pencil leads, and “which doesn’t look very nice on a wedding ring,” the researcher joked. The second “ingredient”, colossal pressure, is great enough to change the color of a clear diamond, but without too much force.

“Just squeeze a little and it turns pink. But press a little more and it turns brown,” explains the geologist. The Australian team’s discovery helps explain why pink diamonds burst from the Earth’s crust to the surface.

The Argyll mine was originally thought to have formed 1.2 billion years ago, but it was unclear how the diamonds could have made their way back in the absence of a corresponding geological event. The researchers then refined the dating of the deposit by measuring the age of tiny crystalline elements in rock from the mine. And it arrived 1.3 billion years ago.

This age corresponds to the fracture experienced by the first supercontinent, named indifferently Nuna or Columbia. The pressure that colored the diamonds resulted from the collision of the landmass of Western and Northern Australia 1.8 billion years ago.

The mass broke apart 500 million years later, at which point magma rose to the surface, carrying pink diamonds to the surface “like a champagne cork,” according to Mr. Oliruk.

/ATS

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