Rare Diamond Reveals Clues About Earth’s Interior

A rare diamond has offered clues about the earth’s interior. Discovered in a Brazilian riverbed, the unusual diamond likely traveled to the Earth’s surface during a volcanic eruption. Research suggests the rock originated in the mantle transition zone, which is 250-400 miles below the surface.

Extensive testing revealed the diamond is actually enclosed in a layer of ringwoodite — a mineral commonly found in meteorites. Live Science reports that the mineral has never been found on the Earth’s surface, suggesting the rock was formed deep within the mantle layer.

Ringwoodite forms under intense pressure, which suggests the rare diamond originated in the mantle approximately 320 miles below the Earth’s surface. The mantle, which is a layer of rock between the Earth’s crust and core, is impossible to reach with current technology.

Scientists have attempted to recreate mantle properties in laboratory settings. Their research suggests the formation of ringwoodite could occur within the mantle. They theorize that ringwoodite is created when the mineral olivine is exposed to extreme and intense pressure.

The rare diamond has provided proof that their theory is valid. The composition of the ringwoodite also suggests that the Earth’s mantle contains a significant amount of water. Researchers determined that the ringwoodite contains 1.5 percent water, in the form of hydroxide ions.

Geochemist Graham Pearson explains the significance of the finding:

“It translates into a very, very large mass of water, approaching the sort of mass of water that’s present in all the world’s ocean.”

Pearson suggests the water was carried into the mantle by slabs of oceanic crust. As the Earth’s plates naturally shift, slabs of the ocean’s crust are forced into the mantle. As the slabs are likely saturated with ocean water, the water becomes part of the mantle.

Although “ultradeep diamonds” have little or no commercial value, Pearson said they are priceless to geologists. Pearson said “they literally look like they’ve been to hell and back.” Unlike gem quality stones, the rare diamonds are usually misshapen and incredibly flawed.

Pearson explains that the diamond was likely expelled from inner earth during a kimberlite volcanic reaction, which is specifically violent:

“The eruption of a kimberlite is analogous to dropping a Mentos mint into a bottle of soda… It’s a very energetic, gas-charged reaction that blasts its way to Earth’s surface.”

Pearson led the research, which was conducted by the University of Alberta in Canada. The findings were published the March 12 edition of the journal Nature.

[Image via Live Science]