Strange hexagonal diamonds may have been jettisoned into space when a dwarf planet collided with a large asteroid around 4.5 billion years ago.
New research has identified hexagonal diamonds, also called lonsdaleite, in a rare class of meteorites which could come from the mantle of a dwarf planet. Like graphite, charcoal and diamond, lonsdaleite is a special structural form of carbon. Where the carbon atoms in diamond are arranged in a cubic shape, the carbon atoms in lonsdaleite are arranged in hexagons.
“This study is categorical proof that lonsdaleite exists in nature,” Dougal McCulloch, a microscopist at RMIT University in Australia, said in a statement. statement. “We also discovered the largest lonsdaleite crystals known to date, up to a micron in size – much, much finer than a human hair.”
Lonsdaleite was first discovered in the Canyon Diablo meteorite in 1967 and was named after the British crystallographer Lady Kathleen Lonsdale. The new research predicts that the hexagonal shape of lonsdaleite makes it harder than regular diamonds with a cubic structure, which could lead to new manufacturing techniques for making ultra-hard materials.
Researchers studied lonsdaleite in ureilite meteorites, a rare class of space rock that scientists believe may contain material from the mantle of dwarf planets. The team analyzed slices of these meteorites under a microscope to identify lonsdaleite and predict its origins, and also studied the regularly shaped diamonds found in the rock.
“There is strong evidence that there is a newly discovered formation process for lonsdaleite and ordinary diamond, which resembles a supercritical chemical vapor deposition process that took place in these space rocks, probably on the dwarf planet shortly after a catastrophic collision,” McCulloch said. . “Chemical vapor deposition is one of the ways people make diamonds in the lab, basically by growing them in a specialized chamber.”
Scientists believe that the lonsdaleite contained in the meteorites formed from a supercritical liquid at high temperatures and under increased pressures. This extreme environment allowed lonsdaleite to retain the shape and texture of graphite. Eventually, as the environment cooled and the pressure decreased, the lonsdaleite was partially replaced by diamond.
The team thinks industry could mimic the process of producing this unusual mineral.
“So nature has provided us with a process to try and replicate it in industry,” Andy Tomkins, team leader and geologist at Monash University in Australia, said in the same statement. “We believe lonsdaleite could be used to make tiny, ultra-hard machine parts if we can develop an industrial process that promotes the replacement of preformed graphite parts with lonsdaleite.”
The team’s research was published Monday, September 12 in the Proceedings of the National Academy of Sciences.