The Earth is full of diamonds

Diamonds are forever, especially when it comes to our planet: Earth is probably a veritable diamond factory.

But pump the brakes on your bobcat, because the diamonds we’re talking about are pretty difficult to reach.

Research out of Arizona State University published in Geophysical Research Letters suggests the boundary between the planet’s core and mantle is riddled with diamond and rust.

Working in the Advanced Photon Source at Argonne National Laboratory, the research team determined this by simulating the conditions present at the core-mantle boundary.

At this boundary, temperatures are more than twice as hot as molten lava – enough to release water from present iron minerals to create a rusting effect similar to that which occurs on surface-level iron.

Reactions between water and these minerals are also believed to squeeze-out carbon, which pressures into diamond due to the immense forces acting beneath the surface.

That should excite jewellers the world over, at least those with a drill capable of digging nearly three thousand kilometres beneath the planet’s crust.

“It might have been going on for billions of years”

Earth’s mantle is the mainly solid layer of rock immediately beneath the planet’s crust. By comparison, the outer core is a hellish world of liquefied iron and other elements.

One of those is carbon.

Iron carbon alloy and diamond spots
The iron-carbon alloy reacted with water at high pressure and high temperature conditions related to the Earth’s deep mantle in a diamond-anvil cell / Credit: Arizona State University.

The researchers, led by Arizona postdoctoral researcher Byeongkwan Ko, found that lab-simulated reactions between iron-carbon alloys and water results in diamond production, at least when the temperature and pressure conditions that exist deep below Earth’s surface are recreated.

These reactions may also help push carbon further into the mantle, changing previous understandings of the Earth’s carbon composition.

Previously, carbon was believed to be relatively low in the mantle, compared to levels present in the core.

But the recreation of these carbon processes in the lab may explain that much higher amounts of carbon are fed into the mantle from the liquid iron beneath.

It’s a process that might have taken place for eons.

“The new discovery of a carbon transfer mechanism from the core to the mantle will shed light on the understanding of the carbon cycle in the Earth’s deep interior,” Byeongkwan says.

“This is even more exciting given that the diamond formation at the core-mantle boundary might have been going on for billions of years since the initiation of subduction on the planet.”

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