Rare Mineral Hints at Large Source of Water Beneath Earth's Surface

An analysis of a newfound mineral called ringwoodite confirms the theory that there is a large source of water some 410 to 660 kilometers beneath the Earth's crust, according to new research. 

Graham Pearson of University of Alberta and colleagues found that water contributes to 1.5 percent of weight of ringwoodite sample. According to the researchers, the presence of water in this rare mineral shows that there might be a large source of water between the upper and lower mantle.

"This sample really provides extremely strong confirmation that there are local wet spots deep in the Earth in this area," Pearson said in a news release. "That particular zone in the Earth, the transition zone, might have as much water as all the world's oceans put together."

The mineral was found in embedded in a 100 million-year-old kimberlite found in Juina, Brazil, in 2008.    

Kimberlites are igneous rocks that come to surface along with volcanic eruptions. These rocks often contain diamonds.

Ringwoodite is a form of mineral called peridot, which is magnesium-iron rich silicate mineral. This is the first time that ringwoodite has been found on Earth. Previously, ringwoodite was only found in meteorite samples.

Researchers used several techniques including using Raman and infrared spectroscopy and X-ray diffraction to confirm that the mineral was indeed ringwoodite.

The discovery of the mineral not only supports the idea that there is water in the transition zone, but it could change many ideas about rock formation, plate tectonics and volcanism.

 "One of the reasons the Earth is such a dynamic planet is because of the presence of some water in its interior," Pearson said.  "Water changes everything about the way a planet works."

The study is published in the journal Nature.

Pearson said that the research team was quite lucky to have found the ancient diamond in Brazil. The team was actually looking for another type of rock when they bought the brown diamond for $20.

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