The mystery behind pink diamonds just got some more clarity

The dramatic break up of an ancient supercontinent could be behind the planet’s cache of rare pink diamonds. A group of geologists and geoscientists in Australia have found that this shake-up 1.8 billion years ago was one of the key geological ingredients needed for the Earth to produce pink diamonds and why so many have been found in one particular spot in Western Australia. The findings are described in a study published September 19 in the journal Nature and could help the hunt for more deposits of these candy colored minerals.

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Diamonds are crystals of the element carbon that form deep within the Earth, where they are exposed to immense pressure and heat. They are generally brought to the Earth’s surface through magma during eruptions. Scientists believe this process takes millions and even billions of years. The Gemological Institute of America estimates that all of the Earth’s diamonds are billions of years old. 

For diamonds to turn pink, they must be subjected to the force generated by colliding tectonic plates, which bends and twists their crystal lattices the same way that it does to brown diamonds. This new study found that pink diamonds generally are found in locations where the Earth’s continents were ‘stretched’ when they began to break up hundreds of millions of years ago.

A team of researchers from Curtin University in Perth, Australia examined the diamond-rich rocks from the Argyle volcano in the western region of the continent. A closed mine near the Argyle volcano has been home to 90 percent of the world’s pink diamonds, according to mining company Rio Tinto. The stretching of landmasses when an ancient supercontinent called Nuna created gaps in the Earth’s that enable the magma carrying diamonds used to rise to the surface about 1.8 billion years ago.

“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,” study co-author and Curtin University geoscientist Hugo Olierook said in a statement. 

Argyle is located right where the rest of northern Australia and the country’s Kimberly region crashed together and that collision created a scar in the Earth that will never completely heal, according to Olierook.

The team used laser beams on rocks from the Argyle deposit and found that the rocks are 1.3 billion years old, or about 100 million years older than they previously believed. 

[Related: Diamonds contain remnants of Earth’s ancient atmosphere.]

“Knowing the Argyle volcano’s age, at 1.3 billion years old, and situated where some of Earth’s earliest continents fragmented, we have significant further insights into the formation of these diamonds,” Murray Rayner, a study co-author and principal geologist at Rio Tinto, said in a statement. 

The team believes that new deposits of pink diamonds could exist as long as the three crucial ingredients of deep carbon, continental collision, and then stretching are present. 

“Most diamond deposits have been found in the middle of ancient continents because their host volcanoes tend to be exposed at the surface for explorers to find,” said Olierook. “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.”