The first terrestrial discovery of a rare mineral called ringwoodite likely confirms a theory that there are large water reservoirs beneath Earth's surface.

Research was published in the journal Nature this week.

Ringwoodite is a form of the mineral peridot, which many believe existed in large quantities under high pressures in the transition zone, according to a press release issued by the University of Alberta.

Ringwoodite has previously been detected in meteorites, but no terrestrial sample has ever been found because researchers have never been able to conduct fieldwork at such depths before.

After analyzing the mineral, researchers confirmed it contained a significant amount of water, approximately 1.5 percent of its weight, according to the press release.

The mineral was unearthed in the Juina area of Mato Grosso, Brazil, by artisan miners from shallow river gravels in 2008.

It is believed that the diamond was brought to Earth's surface by a volcanic rock commonly referred to as kimberlite, according to the release.

"This sample really provides extremely strong confirmation that there are local wet spots deep in the Earth in this area. That particular zone in the Earth, the transition zone, might have as much water as all the world's oceans put together," said Graham Pearson, a mantle geochemist at the University of Alberta in Edmonton and the lead author of the study.

The discovery was accidental, as scientists had been looking for another mineral, when they paid $20 for a 3- to 5-mm-wide brown diamond.

Ringwoodite is invisible to the naked eye, and it was only discovered after being thoroughly analyzed by team member John McNeill, back in 2009.

"It's so small, this inclusion, it's extremely difficult to find, never mind work on, so it was a bit of a piece of luck, this discovery, as are many scientific discoveries," said Pearson.

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