Researchers have unveiled a strange ornament-sized rock from near the Arctic that’s red and green and comprised of diamonds. Nearly 30,000 colorless micro-diamonds, to be exact. The findings were presented this week at the American Geophysical Union fall meeting in San Francisco.
The 30-millimeter, 10.5-gram rock was a sparkly donation to science from the owners of Siberia’s Udachnaya diamond mine, which is dominated by volcanic xenoliths (Greek for “foreign rock”) with a few precious “diamondiferous” ones. Among these was a unique diamondiferous xenolith with garnet and olivine to give it those Christmas hues. A team of researchers from the U.S., Germany, and the Siberian Branch of the Russian Academy of Sciences created 2D and 3D images of the strange rock using high-resolution X-ray computed tomography (which is similar to a medical CT scan). These images revealed the relative abundance of its various mineral parts, and diamonds made up 9.5 percent by volume.
The micro-diamonds were between 100 and 700 micrometers in size, and many of them occurred in clusters. With millions of carats per ton, this is the absolute highest yield of diamonds ever in a mantle xenolith, the researchers write. Typical diamond ore averages between 1 to 6 carats per ton (a carat is about a fifth of a gram). But being so tiny, these diamonds weren’t worth much as jewelry.
"The exciting thing for me is there are 30,000 itty-bitty, perfect octahedrons, and not one big diamond," Lawrence Taylor from the University of Tennessee said at the conference. "It's like they formed instantaneously. This rock is a strange one indeed."
Their isotopic carbon concentration suggests that the diamonds come from oceanic crust that was forced deep inside the Earth with the movements of tectonic plates. They likely crystallized from fluids that escaped from subducted crust, Live Science explains.
The chemical reactions that create diamonds are still a bit of an enigma, Taylor tells Live Science. Scientists think they originate in the mantle under crushing pressure, then erupt to the surface during explosive volcanic activities. The process typically destroys a lot of the mantle rocks, but this one somehow survived the trip up.
The work will be published in Russian Geology and Geophysics next month.
Images: Stapanov Alexander via Wikimedia CC BY-SA 3.0 (top), Larry Taylor via Live Science (middle)