AT JUST a few micrometres across they won鈥檛 be anyone鈥檚 best friend. But the oldest diamonds on Earth will stoke controversy about how the planet鈥檚 surface formed.
Martina Menneken of the University of M眉nster, Germany, and colleagues found the diamonds inside zircon crystals between 3 and 4.25 billion years old. They come from Jack Hills in Western Australia, where the oldest identified fragments of the Earth鈥檚 crust have also been found. This makes the diamonds almost a billion years older than the previous record-holders, from South Africa.
The team say that the diamonds seem to have formed at very high pressures more than 100 kilometres underground. If they were indeed created that way, it means the Earth may have had a thick crust just a few hundred million years after the planet itself formed (Nature, ).
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One theory says that ancient zircon crystals from Jack Hills formed in oceans 200 million years after the Earth formed. But if the diamonds were made more than 100 kilometres underground, how did they get inside zircon crystals formed in water at the surface, says Ian Williams of the Australian National University in Canberra. 鈥淭his new work will really stir the pot,鈥� he says.
