Rare hexagonal diamonds may have been flung into space when a dwarf planet collided with a large asteroid about 4.5 billion years ago.
New research has identified hexagonal diamonds, also called lonsdaleite, in a rare class of meteorites that could come from the mantle of a dwarf planet. Like graphite, carbon, and diamond, lonsdaleite is a particular structural form of carbon. Where the carbon atoms in diamond are arranged in a cubic form, the carbon atoms in lonsdaleite are arranged in hexagons.
“This study categorically proves that lonsdaleite exists in nature,” Dougal McCulloch, a microscopist at RMIT University in Australia, said in a statement. statement. “We have also discovered the largest lonsdaleite crystals known to date that are down to a micron in size, much, much thinner 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 lonsdaleite’s hexagonal shape makes it harder than normal diamonds with a cubic structure, which could lead to new manufacturing techniques for making ultrahard materials.
The researchers studied lonsdaleite in ureilite meteorites, a rare class of space rocks that scientists believe may contain material from the mantle of Tiny planets. The team analyzed slices of these meteorites under the microscope to identify lonsdaleite and predict its origins, and also studied regular-shaped diamonds found in the rock.
“There is strong evidence that there is a newly discovered formation process for lonsdaleite and regular diamond, which is like a supercritical chemical vapor deposition process that has taken 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, essentially growing them in a specialized chamber.”
Scientists believe that the lonsdaleite in meteorites formed from a supercritical liquid at high temperatures and under high pressures. This extreme environment allowed lonsdaleite to retain the shape and texture of graphite. Eventually, as the environment cooled and the pressure dropped, the lonsdaleite was partially replaced by diamond.
The team believes the industry could mimic the process to produce the unusual mineral.
“Nature has provided us with a process to test and replicate in industry,” Andy Tomkins, team leader and a geologist at Monash University in Australia, said in the same statement. “We believe lonsdaleite could be used to make ultra-hard, tiny machine parts if we can develop an industrial process that promotes substitution of lonsdaleite for preformed graphite parts.”
The team’s research was published Monday (September 12) in the Proceedings of the National Academy of Sciences.