© University of AlbertaThe diamond is pitted from its violent journey, which ended with the stone shooting up through the Earth's crust at around 70km/h.
A small, battered diamond found in the gravel strewn along a shallow riverbed in Brazil has provided evidence of a vast "wet zone" deep inside the Earth that could hold as much water as all the world's oceans put together.
The water is not sloshing around inside the planet, but is held fast within minerals in what is known as the Earth's transition zone, which stretches from 410 to 660km (250-400 miles) beneath the surface.
"It's not a Jules Verne-style ocean you can sail a boat on," said Graham Pearson, a geologist who studied the stone at the University of Alberta. The water-rich zone could transform scientists' understanding of how some of the Earth's geological features arose.
Tests on the diamond revealed that it contained a water-rich mineral formed in the zone. Researchers believe that the gemstone, which is oblong and about 5mm long, was blasted to the surface from a depth of about 500km by a volcanic eruption of molten rock called kimberlite.
The battle-scarred gem has a delicate metallic sheen, but is pitted and etched from its violent journey, which probably took several days and ended with the stone shooting up through the Earth's crust at a speed of about 70km/h (40mph).
"It's a fairly ugly diamond. It looks like it's been to hell and back," said Pearson, adding that the gem was worth about $20 at most. The stone was found in 2008 by artisan miners working the Juína riverbeds in Mato Grosso in western Brazil.
