A collection of 18 rare diamond-bearing meteorites from around the world came from an ancient dwarf planet that smashed into a giant asteroid 4.5 billion years ago, according to new research.
The specimens contain lonsdaleite – an unusual hexagonal super-hard form of the precious gemstone. The discovery could hold the key to creating indestructible drills for mining.
The fragments fall into a category of space rocks called ureilites, which account for fewer than 1 percent that fall to Earth.
A study of the meteorites may yield benefits to industrial processes.
“Nature has thus provided us with a process to try and replicate in industry,” said lead author Professor Andy Tomkins, a geologist at Monash University in Melbourne, Australia.
“We think lonsdaleite could be used to make tiny, ultra-hard machine parts if we can develop an industrial process that promotes the replacement of pre-shaped graphite parts by lonsdaleite.”
Diamonds are formed from the same carbon atoms that make up soft graphite in the center of pencils. The only difference is the arrangement.
Graphite is formed from flat sheets held together by weak attractive forces between each layer.
In diamonds, however, the carbon atoms are bound in an extremely rigid “tetrahedral” shape. Combined with the strong bonds it makes them extremely hard.
Yet it does break and crumble at high enough pressures. Tiny flaws in a crystal can also weaken it, making the diamond vulnerable to disintegration.
This does not happen with lonsdaleite in ureilite meteorites from the mantle of the dwarf planet. The hexagonal structure makes it potentially harder than regular diamonds, which are cubic.
“This study proves categorically that lonsdaleite exists in nature,” says senior author Professor Dougal McCulloch of Melbourne’s RMIT University. “We have also discovered the largest lonsdaleite crystals known to date that are up to a micron in size – much, much thinner than a human hair.”
The international team said their strange formation opens the door to dramatic improvements in manufacturing.
They used state-of-the-art electron scanners to capture solid and intact slices – providing “snapshots” of how lonsdaleite and regular diamonds formed.
“There’s strong evidence there’s a newly discovered formation process for the lonsdaleite and regular diamond,” McCulloch said.
It’s believed lonsdaleite formed at high temperature and moderate pressures – almost perfectly preserving the shape and textures of the pre-existing graphite.
“Later, lonsdaleite was partially replaced by diamond as the environment cooled and the pressure decreased,” Tomkins said.
It sheds light on a long-standing mystery regarding the emergence of carbon phases in ureilites.
The study suggests all ureilite meteorites are remnants of the same proto-planet. It also boosts the theory that today’s planets were forged from the leftovers of these early worlds.
Lonsdaleite is named after pioneering British crystallographer Dame Kathleen Lonsdale, the first woman fellow of the Royal Society, a collective of notable scientists.
The study was published September 12 in the Proceedings of the National Academy Sciences journal.
Produced in association with SWNS Talker.
This story was provided to Newsweek by Zenger News.