[Rockhounds] Weird Hexagonal Diamonds Came From an Asteroid-Dwarf Planet Smashup

[Kreigh Tomaszewski]

New research indicates that a rare form of diamond may originate in the
burbling cores of distant worlds, arriving on Earth thanks to violent
cosmic collisions.

According to a team of scientists in Australia, the mineral lonsdaleite—a
type of diamond with a hexagonal crystal structure—can be found in
meteorites that were likely created when an asteroid collided with a dwarf
planet billions of years ago. They investigated 18 ureilite fragments using
advanced electron microscopy, to better understand how the lonsdaleite
within the space rocks formed. Their research is published
<http://dx.doi.org/10.1073/pnas.2208814119> today in PNAS.

“This study proves categorically that lonsdaleite exists in nature,” said
study co-author Dougal McCulloch, director of the Microscopy and
Microanalysis Facility at RMIT in Australia, in a university release
<https://www.rmit.edu.au/news/all-news/2022/sep/space-diamonds>.

Lonsdaleite has previously been found in meteorites, including the Diablo
Canyon meteorite, a fragment found in Arizona’s famous Meteor Crater
<https://earthobservatory.nasa.gov/images/148384/arizonas-meteor-crater>.
The mineral has also been created in lab settings, but otherwise is
vanishingly rare on Earth. The mineral differs from usual diamonds in its
crystal structure, which is hexagonal (ordinary diamonds have a cubic
crystal structure.) Separate research earlier this year
<https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.L100101> indicated
that lonsdaleite’s structure makes it harder than other diamonds.

https://gizmodo.com/hexagonal-diamonds-lonsdaleite-meteorites-1849524782