There is nothing quite like a diamond. For many they are the ultimate “I love you” gift, and jewellers will tell you the ultra-hard stones have unmatched “fire” and “brilliance”. The sentimental and aesthetic value of the gems is matched by their price, which can run to tens of thousand dollars per carat – and even more for coloured diamonds, especially if they are blue, green, violet, orange, red or pink.

But why are diamonds so expensive? How do they form? Do we really find diamonds in volcanoes? What is the link to supercontinents and ancient lifeforms?

In new research published in Nature Communications, we answer some of these questions by studying the world’s largest diamond deposit, Argyle in Western Australia, the source of more than 90% of pink diamonds.

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We found that at Argyle, diamonds crystallised deep in Earth’s interior were brought to the surface when a supercontinent, Nuna, began to break apart. As continents break up, their edges stretch, allowing small pockets of diamond-rich magma to rise to the surface.

Why are pink diamonds so special?

Only about 20% of mined diamonds are of gemstone quality. If you think of diamonds as cars, 80 of every 100 on the road would be old, beat-up rides and 20 would be luxury cars.

One in every 10,000 would be the equivalent of a supercar: a rare and precious coloured diamond.

However, some places in the world are special. Just as you might see a greater proportion of supercars in Monaco or Hollywood, so too do some places produce more coloured diamonds.

When it comes to pink diamonds, one place stands alone. More than 90% of all the pink diamonds ever found come from a single mine in the Kimberley region of Western Australia: Argyle.

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The Argyle mine closed in 2020, and the price of pink diamonds has skyrocketed while the supply dwindles.

While pink diamonds are highly prized, they are also in a sense “damaged goods”.

Diamonds are made of carbon atoms arranged in a compact, regular lattice. Clear, perfect diamonds sparkle because light reflects off their internal surfaces.

However, when diamonds are subject to intense pressure deep inside Earth, the lattice of atoms can twist and bend. This causes small imperfections that diffract light and bring colour to the gem.

Why is Argyle so well-endowed in pink diamonds?

All diamonds are found in pipelike volcanoes, or in their eroded remnants. These volcanoes have deep roots under continents, which is where diamonds reside.

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The roots need to be deep. If they’re shallow, the carbon that might become diamonds will instead be in the form of graphite, which is not nearly as appealing on an engagement ring.

The story of the Argyle volcano begins some 1,800 million years ago, when the continental plate beneath the Kimberley smashed into the rest of WA to form the first supercontinent, Nuna. Five hundred million years later, Nuna ripped apart again while Australia hung together.

Yet old wounds never fully heal. The suture between the Kimberley and the rest of the continent was stretched open as Nuna split up, and the Argyle volcano shot to the surface, bringing pink diamonds with it. The death of a supercontinent gave birth to Argyle.

So what made Argyle’s diamonds pink? The force that damaged the deep diamonds, resulting in their beautiful hue, probably came from the continental collision that formed the supercontinent in the first place. But the diamonds remained deep below this old wound for a long time before being brought to the surface.

Will we find another trove of pink diamonds? With Argyle now closed, the search is on to meet the demand for these illustrious gems.

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The ingredients appear to be continental breakup, the edges of ancient continents and volcanic pipes.

Is carbon recycled in Earth’s interior?

Finding diamonds is no mere quest for glitz and glamour. It’s an exploration of Earth’s deepest history.

Diamonds are ancient time capsules from the depths of our planet. They are relics of a past so remote it challenges comprehension.

We know they are made of pure carbon – but where did this carbon come from?

Most of the carbon is remnants of carbon-rich asteroids that clumped together to form Earth 4.5 billion years ago.

However, some diamonds contain carbon that was once part of living organisms. Organic carbon, from organisms that once thrived on Earth’s surface, got buried deep down by geological processes.

The Argyle diamonds, for instance, hold such organic imprints, like echoes from an ancient world long vanished. In these glimmers of the distant past, we find more than beauty; we find keys to unlock the most profound secrets of our planet’s history.

Around 2,500 years ago, at the western end of the island of Kadavu in the southern part of Fiji, the ground shook, the ocean became agitated, and clouds of billowing smoke and ash poured into the sky. When the clouds cleared, the people saw a new mountain had formed, its shape resembling a mound of earth in which yams are grown. This gave the mountain its name – Nabukelevu, the giant yam mound. Image for Representation.
| Photo Credit: The Hindu

Can you imagine a scientist who could neither read nor write, who spoke their wisdom in riddles, in tales of fantastic beings flying through the sky, fighting each another furiously and noisily, drinking the ocean dry, and throwing giant spears with force enough to leave massive holes in rocky headlands?

Our newly published research in the journal Oral Tradition shows memories of a volcanic eruption in Fiji some 2,500 years ago were encoded in oral traditions in precisely these ways.

They were never intended as fanciful stories, but rather as the pragmatic foundations of a system of local risk management.

Life-changing events

Around 2,500 years ago, at the western end of the island of Kadavu in the southern part of Fiji, the ground shook, the ocean became agitated, and clouds of billowing smoke and ash poured into the sky.

When the clouds cleared, the people saw a new mountain had formed, its shape resembling a mound of earth in which yams are grown. This gave the mountain its name – Nabukelevu, the giant yam mound. (It was renamed Mount Washington during Fiji’s colonial history.)

So dramatic, so life-changing were the events associated with this eruption, the people who witnessed it told stories about it. These stories have endured more than two millennia, faithfully passed on across roughly 100 generations to reach us today.

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Scientists used to dismiss such stories as fictions, devalue them with labels like “myth” or “legend”. But the situation is changing.

Today, we are starting to recognise that many such “stories” are authentic memories of human pasts, encoded in oral traditions in ways that represent the worldviews of people from long ago.

In other words, these stories served the same purpose as scientific accounts, and the people who told them were trying to understand the natural world, much like scientists do today.

Battle of the vu

The most common story about the 2,500-year-old eruption of Nabukelevu is one involving a “god” (vu in Fijian) named Tanovo from the island of Ono, about 56km from the volcano.

Tanovo’s view of the sunset became blocked one day by this huge mountain. Our research identifies this as a volcanic dome that was created during the eruption, raising the height of the mountain several hundred feet.

Enraged, Tanovo flew to Nabukelevu and started to tear down the mountain, a process described by local residents as driva qele (stealing earth). This explains why even today the summit of Nabukelevu has a crater.

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But Tanovo was interrupted by the “god” of Nabukelevu, named Tautaumolau. The pair started fighting. A chase ensued through the sky and, as the two twisted and turned, the earth being carried by Tanovo started falling to the ground, where it is said to have “created” islands.

We conclude that the sequence in which these islands are said to have been created is likely to represent the movement of the ash plume from the eruption, as shown on the map below.

‘Myths’ based in fact

Geologists would today find it exceedingly difficult to deduce such details of an ancient eruption. But here, in the oral traditions of Kadavu people, this information is readily available.

Another detail we would never know if we did not have the oral traditions is about the tsunami the eruption caused.

In some versions of the story, one of the “gods” is so frightened, he hides beneath the sea. But his rival comes along and drinks up all the water at that place, a detail our research interprets as a memory of the ocean withdrawing prior to tsunami impact.

Other details in the oral traditions recall how one god threw a massive spear at his rival but missed, leaving behind a huge hole in a rock. This is a good example of how landforms likely predating the eruption can be retrofitted to a narrative.

Our study adds to the growing body of scientific research into “myths” and “legends”, showing that many have a basis in fact, and the details they contain add depth and breadth to our understanding of human pasts.

The Kadavu volcano stories discussed here also show ancient societies were no less risk aware and risk averse than ours are today. The imperative was to survive, greatly aided by keeping alive memories of all the hazards that existed in a particular place.

Australian First Peoples’ cultures are replete with similar stories.

Literate people, those who read and write, tend to be impressed by the extraordinary time depth of oral traditions, like those about the 2,500-year old eruption of Nabukelevu. But not everyone is.

In early 2019, I was sitting and chatting to Ratu Petero Uluinaceva in Waisomo Village, after he had finished relating the Ono people’s story of the eruption. I told him this particular story recalled events which occurred more than two millennia ago – and thought he might be impressed. But he wasn’t.

“We know our stories are that old, that they recall our ancient history,” he told me with a grin. “But we are glad you have now learned this too!”