A recently published scientific report may contribute to the discovery of new deposits of the world’s most valuable gemstones – pink fancy colour diamonds.
In a paper published in the Nature Communications journal, scientists from Curtin University in Western Australia have suggested that pink diamonds may be older than initially thought.
The study aimed to improve the broader understanding of the geological conditions necessary for the formation of pink diamonds and other colour varieties.
It was previously believed that the pink diamonds discovered in the Argyle Mine were 1.2 billion years old. They are now thought to be at least 100 million years older, based on the study of the age of elements in material recovered from the mine.
Using lasers to analyse minerals and rocks extracted from the Argyle deposit, researchers believe that pink diamonds were formed during the break-up of an ancient supercontinent known as Nuna, approximately 1.3 billion years ago.
The researchers describe three key ‘ingredients’ for the creation of pink diamonds. The first is carbon, sourced from at least 150 kilometres beneath the Earth’s surface.
The second is pressure – otherwise known as non-isotropic stress and plastic deformation – which causes diamonds to change their light reflection and absorption properties.
The third ‘missing’ ingredient is now believed to be a volcanic eruption, which forces diamonds closer towards the Earth’s surface.
“I think using that sort of [diamond-producing] recipe, I think we’ll be able to find more of these pink diamonds, but it’s not going to be easy,” Hugo Olierook, Curtin University geologist, told ABC News.
Put another way, two continental crusts collided around 1.8 billion years ago to form a supercontinent.
The site of this collision is where pink diamonds are discovered today, and the crash itself caused changes in the crystal structure of these diamonds and turned them ‘pink’.
Approximately 500 million years later, the supercontinent broke up. This weakened the region, allowing magma to erupt and carry the pink diamonds closer to the surface.
This is important because the study of mountain belts produced by the supercontinental break-up could lead to the discovery of new pink diamond deposits in Australia, Canada, Russia and southern Africa.
“There’s been at least three supercontinents we know of,” Olierook said.
“So any rocks that were deposited at the time they broke up, those are the ones I’d be looking at.”
The Argyle Mine closed in 2020. The mine was responsible for approximately 90 per cent of the global supply of pink diamonds.
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