A Diamond From Deep Beneath Earth's Surface Hides a Rare Mineral

Wednesday, 07 March 2018 - 7:14PM
Earth
Wednesday, 07 March 2018 - 7:14PM
A Diamond From Deep Beneath Earth's Surface Hides a Rare Mineral
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A mineral known as calcium silicate perovskite (CaSiO3) is an unusual mix of highly rare and yet extremely abundant: despite being the fourth most common mineral in the Earth's crust, we've never found one in nature until now.

Traces of the mineral have finally appeared encased inside a diamond found in the Cullinan Mine in South Africa, turning a once theoretical substance into a conclusively real material. The diamond was mined less than one kilometer (0.6 miles) into the mine, but it was likely formed in a much deeper spot in the Earth's mantle.



In fact, due to the nature of calcium silicate perovskite, the diamond has to be what's called a "super-deep diamond", which are formed from 125 - 620 miles (200 - 1,000 kilometers) beneath the surface. This particular super-deep diamond likely came from approximately 430 miles (700 kilometers) beneath the surface.

According to Graham Pearson from the University of Alberta, this discovery is evidence of the recycling of oceanic crust into Earth's lower mantle. He said the following in a press statement:

Opening quote
"Diamonds are really unique ways of seeing what's in the Earth. And the specific composition of the perovskite inclusion in this particular diamond very clearly indicates the recycling of oceanic crust into Earth's lower mantle. It provides fundamental proof of what happens to the fate of oceanic plates as they descend into the depths of the Earth."
Closing quote





The presence of the mineral was confirmed via X-ray by Fabrizio Nestola, a University of Padova professor of geoscience and the lead author of an upcoming paper in Nature on the matter. The discovery will likely have some larger ramifications later down the line, but for now, it's a good reminder that the diamonds found in that mine are useful for more than just fetching a high price.

And even though we have so much invested in discovering more about the other planets in the solar system (and our sun), it shows there's still a lot to learn about what's inside the chunk of rock that we call home.
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