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Aussie scientists find 4-billion-year-old diamonds
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09:01, August 24, 2007

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Scientists in Australia have unearthed diamonds inside zircon crystals that are more than 4 billion years old, almost as old as the Earth.

Found in the Jack Hills region of Western Australia, the gems are considered the oldest terrestrial diamonds every discovered. Researchers think they could give insights into the early evolution of the planet's crust.

"Jack Hills is the only place on Earth that can give us this kind of information about the formation of the Earth," said study team member Alexander Nemchin, a geochemist at Curtin University of Technology, Western Australia. "We're dealing with the oldest material on the planet."

Earth developed from a cloud of dust around a proto-Sun about 4.5 billion years ago. It coalesced into a planet-size body and its surface temperatures probably rose above 10,830 degrees Fahrenheit (6,000 degrees Celsius) during its early formation. When the molten Earth cooled, the liquid lava gelled into rocks. Details about the rocks and when they began to form have been limited by sparse data.

Recent studies of zircons have suggested the Earth might have cooled much more rapidly than previously thought, with the continental crust and oceans forming as early as 4.4 billion years ago.

The diamond find supports this quick-cooling idea, said study team member Thorsten Geisler of the Institute of Mineralogy at the University of Münster in Germany.

The scientists, led by Martina Menneken of the Institute of Mineralogy, ran chemical analyses of the zircons, finding the ancient crystals (and thus the enclosed diamonds) were more than 4 billion years old. That's nearly a billion years older than the previous oldest-known terrestrial diamonds and suggests the diamonds were present in material that crystallized within 300 million years of the formation of Earth, the scientists say.

"I'm quite convinced the Earth must be cooler than previously thought because otherwise we couldn't have found diamonds," Geisler told LiveScience. That's because to form diamonds, heavyweight pressures are required. To reach a pressure in the mantle, we need a relatively thick continental crust. That means we already had rocks [on Earth]."

Source: Xinhuanet / Agencies

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