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” to the rarity of pink diamonds, which are found almost exclusively in Australia, which explains their astronomical price, according to a study published on Tuesday.

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.

Australian team explains in magazine Natural 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.

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 affecting too much.

“Just squeeze a little and it will turn pink.” But press a little more and it turns brown,” explains the geologist.

“Champagne cork.”

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.

The age corresponding to the fracture experienced by the first supercontinent, named indifferently Nuna or Columbia.

In the past, Mr. Oliruk said, “all landmasses were grouped together.” 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.

“Pink Diamond Paradise”

For 200 years, the search for diamonds has been concentrated on continental lands, the scientist notes. However, Tuesday’s discovery could reshuffle the cards in that quest.

The mountain belts created by the breakup of the supercontinent Nuna could become “pink diamonds of heaven,” according to a geologist who names potential areas in Canada, Russia, South Africa and Australia.

According to John Foden, a diamond expert at the University of Adelaide in South Australia, who was not involved in the study, the conclusion may be a bit hasty.

He said the work certainly establishes the age of the Argyle deposit in a “convincing manner”. And suggest a plausible connection between the formation of pink diamonds and the destruction of Nuna.

However, no pink diamonds have been found at other sites associated with this geological event, he notes. This could mean that “the pink character may be an Argyll-specific attribute.”

If this is the case, then the price of pink diamonds can only continue to rise due to the lack of competition at the mine, which closed in 2020 due to economic reasons.

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