Diamonds present in 4 meteorites in north-west Africa most likely got here from an historic dwarf planet, and they’re anticipated to be tougher than Earth diamonds


12 September 2022

Electron microscope image of hexagonal diamond in a meteorite

Electron microscopy has revealed hexagonal diamonds (the darkish space close to the center of the image) in meteorites present in Africa

Alan Salek/RMIT

Mysterious hexagonal diamonds that don’t happen naturally on Earth have been found in 4 meteorites in north-west Africa.

“It’s actually thrilling as a result of there have been some folks within the area who doubted whether or not this materials even existed,” says Alan Salek at RMIT College in Melbourne, Australia, who was a part of the group that discovered them.

Hexagonal diamonds, like common diamonds, are fabricated from carbon, however their atoms are organized in a hexagonal construction somewhat than a cubic one.

Also called lonsdaleite, hexagonal diamonds had been first reported in meteorites within the US and India within the 1960s. Nonetheless, the beforehand found crystals had been so small – solely nanometres in dimension – that it was laborious to substantiate whether or not they had been actually hexagonal diamonds.

To hunt for bigger crystals, Salek and his colleagues used a robust electron microscope to look into 18 meteorite samples. One was from Australia and the remaining had been from north-west Africa.

They discovered hexagonal diamonds in 4 of the African meteorites, with some crystals measuring as much as a micrometre in dimension – about 1000 occasions greater than earlier discoveries. This allowed the group to substantiate the weird hexagonal construction.

“It’s an essential discovery as a result of now now we have bigger crystals, we are able to get a greater thought of how they shaped and perhaps replicate that course of within the lab,” says Salek.

Primarily based on the chemical composition of the meteorites that introduced them to Earth, the hexagonal diamonds seem to have shaped inside dwarf planets, says Andy Tomkins at Monash College in Melbourne, who led the analysis.

The group’s evaluation suggests the crystals had been created by a response between graphite – which is fabricated from carbon atoms layered in sheets – and a supercritical fluid of hydrogen, methane, oxygen and sulphur chemical compounds that most likely shaped when an asteroid crashed into the dwarf planet and broke it into fragments that ultimately fell onto Earth.

“When the planet broke aside, it was like taking a lid off a Coke bottle – it launched the stress and that drop in stress mixed with excessive temperatures led to the discharge of this supercritical fluid,” says Tomkins.

That is much like the method by which common diamonds are made in labs, by heating graphite with gases like hydrogen and methane, suggesting that a number of tweaks might produce lonsdaleite as a substitute, says Salek.

Hexagonal diamonds are predicted to be about 60 per cent tougher than common diamonds based mostly on their construction, and this additional hardness might have essential industrial purposes in the event that they might be made synthetically. For instance, they might doubtlessly be used to make ultra-hard noticed blades or different machine elements, says Salek.

Journal reference: Proceedings of the Nationwide Academy of Sciences, DOI: 10.1073/pnas.2208814119

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