Pink diamonds take Barbiecore madness to another level, but pink comes at a price. These gems are among the rarest and most valuable diamonds around. And they are far from perfect.
“They are actually damaged diamonds,” said Hugo Olierook, a geologist at Curtin University in Perth, Australia.
The color comes from the deformation of the gemstone’s crystal lattice under intense pressure. While all diamonds are formed under pressure, an even greater force changes once diamonds are colored. Additionally, a light squeeze will turn the color diamond pink and a hard squash will turn it brown.
More than 90 percent of the pink stones ever found came from the Argyle mine in Western Australia, which was one of the most productive diamond deposits in the world until it ceased operations in November 2020. Many Argyle diamonds are chocolate brown or tan in color. But out of every thousand gems, a few would appear in the rarer and more valuable pink.
Now they have Dr. Olierook and his colleagues have a new estimate of when and how these gems arrived on Earth’s surface. In a study published Tuesday in the journal Nature Communicationsreported that about 1.3 billion years ago, reddish and brown rocks were pushed through relatively thin continental margins during the demise of Nuna, one of Earth’s oldest supercontinents. If confirmed, the work suggests the possibility that ancient continental crossroads may harbor more of these colorful gems.
The diamonds that appeared in Argyle formed deep underground, near stable continental roots. When the landmasses broke apart to form Nuna, collisions near Australia’s northwestern edge provided the pressure needed to color the once colorless gems.
In the late 1980s, a team led by Robert Pidgeon, now an emeritus professor at Curtin, discovered that the diamond-studded volcanic rocks of Argyle erupted about 1.2 billion years ago. During that period, there were few obvious tectonic triggers for explosive eruptions that could have brought Argyll’s diamonds up from the depths.
“Australia was happily sailing the oceans at the time,” said Dr. Oil eye.
But Dr. Pidgeon has long questioned his own findings. The eruption that triggered the Argyle diamond haul blew through an ancient lake, altering the rocks, potentially affecting the accuracy of the dating estimate. He mentioned the concern in a casual hallway conversation with the study’s other author, Denis Fougerous of Curtin University, who assembled a team to take a closer look.
Scientists have produced a new estimate of the age of the Argyle rocks using a laser beam finer than the width of a hair. Their analysis suggests that the eruption occurred about 1.3 billion years ago—about 100 million years before Dr. Pidgeon.
The new date coincides with when Nuna began to break up and thin along geological seams where earlier continents collided, said Dr. Oil eye. This thinning likely helped the diamond-encrusted magma to shoot to the surface near the edge of what is now northwestern Australia.
The broad link between continental rifting and diamond deposits is not a new idea, but the details are up for debate. A recent modeling study suggests that the breakup of a supercontinent could trigger eddy currents in the Earth’s mantle that send diamond-rich eruptions piercing its crust.
These currents likely ripple inland over time, which could help explain why most diamond-rich eruptions break through the thick continental interior. The Argyle diamonds, which erupted near the continental margin, may represent an early stage of this process before the eruptions marched inland.
The new study is an important step toward deciphering the “perfect storm of conditions” that helped create the colorful Argyle gems, said Thomas Gernon, a geologist at the University of Southampton in England who has studied how diamonds are shaped by the splitting of supercontinents.
However, some questions remain. “This is the last part of the story,” said Steve Shirey, an isotope geochemist at Carnegie Science in Washington, DC, who was not part of the study team. For example, he questions why so much carbon accumulated for Argyle to create an abundance of diamonds.
David Phillips, a geochemist at the University of Melbourne, points out that the new age range for Argyle could narrow further. “The conclusions of this study may be correct, but in my opinion it remains an open question,” he said.
Dr. Gernon emphasized that understanding such an ancient system is no simple task. And one thing is certain, he said: “Nature always has surprises in store.”