World’s biggest diamonds can teach us about the inner Earth

The biggest diamonds ever found aren’t just distinct due to their large size and brilliance, but also because of their origin, according to a new study published in the journal Science.

The study team discovered that these diamonds were popped out of pockets of liquid metal and gas deep within the Earth. The new study is the first to provide evidence of metal being located deep within the Earth’s mantle.

“We usually think of this layer as being just rocky material, but these diamonds are telling us that it’s not just rocks down there,” study author Evan Smith, a research fellow at the Gemological Institute of America, told the Los Angeles Times.

Smith noted that geologists can only access so much of the Earth directly, and so they must study bits of the mantle driven up to the surface by geological forces.

“We can drill holes, but that’s limited to just a few miles,” Smith said. “In terms of getting physical pieces of rock from there, that’s really out of the question.”

Learning From the Deep Earth

Most diamonds type somewhere between 93 and 120 miles below the ground. They develop in the thickest areas of continents, the bottoms of stiff continental tectonic plates. Nearly all diamonds we see come from these locations.

However, the biggest diamonds are very different compositionally from other diamonds. The study team said this indicates they come from much deeper in the Earth, between about 230 to 440 miles underground.

To learn more about the chemical environs of the deep Earth, the researchers looked for small bits of non-diamond material called inclusions that got stuck inside these unique diamonds when they developed.

Most diamond lovers think of inclusions as imperfections, but to Smith they are the most precious part of the stone. By examining inclusions in massive diamonds, the research team was able to determine these precious stones form high temperature, high-stress locations that contained bits of iron and nickel. The presence of these metals is something that had been expected based on theory and study, but until now, there hasn’t been physical confirmation.

Smith said he plans to continue this line of study to determine what other elements might be located at these depths.

“We’re just kind of getting started here,” he said.

—–

Image credit: Robert Weldon and Gem Diamonds Ltd.

The post World’s biggest diamonds can teach us about the inner Earth appeared first on Redorbit.

redOrbit.com
offers Science, Space, Technology, Health news, videos, images and reference information. For the latest science news, space news, technology news, health news visit redOrbit.com frequently. Learn something new every day.”