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Traces of salt trapped in many diamonds finally proved an old theory
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New research, led by geoscientists from Macquarie University, Australia and published in the latest issue of Science Advances, reveals a new and surprising origin of diamonds. According to the study, most diamonds are actually made of seabed cooked deep in the Earth.


The Salt in Diamonds


Dr. Michael Förster, Professor Stephen Foley, Dr Olivier Alard, and colleagues at Goethe Universität and Johannes Gutenberg Universität in Germany conducted experiments that recreated the extreme pressures and temperatures found 200 kilometers underground. These experiments found that “seawater in sediment from the bottom of the ocean reacts in the right way to produce the balance of salts found in diamonds“.


In other words, the traces of salt found to be trapped in many diamonds indicate that they are “formed from ancient seabeds that became buried deep beneath the Earth’s crust”.


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How Diamonds Grow


Diamonds are brought to the surface of the Earth in volcanic eruptions of a special kind of magma called kimberlite; naturally, geologists do not have access to the Earth mantle, so the true formation of diamonds has remained an unanswered question for many years.


According to Dr. Michael Förster, the theory that salts trapped inside diamonds came from marine seawater isn’t new – it just couldn’t be tested. The experiments that he and his peers conducted, simulating a high-pressure, high-temperature environment, showed that they came from marine sediment.


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“We knew that some sort of salty fluid must be around while the diamonds are growing, and now we have confirmed that marine sediment fits the bill,” said Förster, adding: “The products of our experiments also resulted in the formation of minerals that are necessary ingredients for the formation of kimberlite magmas, which transport diamonds to the Earth’s surface”.

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