World’s biggest diamonds may unlock mysteries of Earth’s mantle, say geologists

A new study of the world’s largest diamonds has shown that they’re not only more valuable for jewelers, but also for geologists by offering an invaluable glimpse at the makeup of the Earth’s interior, hundreds of miles below the surface.

Led by the Gemological Institute of America (GIA) and published in the journal Science, the study drew on previous knowledge that larger diamonds are fundamentally different from their smaller counterparts in composition and structure, and explored how and where larger diamonds form that causes them to differ.

“Some of the world’s largest and most valuable diamonds, like the Cullinan or Lesotho Promise, exhibit a distinct set of physical characteristics that have led many to regard them as separate from other, more common diamonds,” Wuyi Wang, GIA’s director of research and development, and an author of the study, said in a press release. “However, exactly how these diamonds form and what they tell us about the Earth has remained a mystery until now.”

Diamonds are formed deep below the Earth’s crust in the mantle and are brought to the surface during volcanic eruptions, bringing with them tiny flecks of metal and minerals trapped inside. While these “inclusions” are cut out to sell the jewels, they offer scientists a unique look at the composition of the Earth’s interior.

“You really couldn’t ask for a better vessel to store something in,” Evan Smith, a diamond geologist at the GIA and an author of the study, told NPR. “Diamond is the ultimate Tupperware.” READ MORE.