Previously found only in meteorites, ringwoodite is a form of the mineral peridot, believed to exist in large quantities under high pressures in the so-called transition zone – 410–660 kilometres beneath the Earth’s surface, 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,’ said Graham Pearson of the University of Alberta, who led the study. ‘That particular zone in the Earth, the transition zone, might have as much water as all the world’s oceans put together.’
Artisan miners unearthed the commercially worthless brown diamond that contained the ringwoodite in 2008 in river gravels in the Juina area of Mato Grosso, Brazil. The scientists had been looking for another mineral when they purchased the three-millimetre-wide diamond. Pearson’s graduate student, John McNeill, discovered that it contained ringwoodite. Further analysis confirmed that the sample contained water.
‘One of the reasons the Earth is such a dynamic planet is the presence of some water in its interior,’ Pearson said. ‘Water changes everything about the way a planet works.’
This story was published in the May 2014 edition of Geographical Magazine
