A team of scientists discovered lonsdaleite, a rare hexagonal type of diamond that may be stronger than normal diamonds, in ureilite meteorites formed in the mantle of a distant dwarf planet. The research was published in the Proceedings of the National Academy of Sciences by scientists from Monash University, RMIT University, CSIRO, the Australian Synchrotron, and Plymouth University (PNAS).
Rare Diamonds In Meteorite
In a news release, RMIT Professor Dougam McCulloch, a member of the team, stated that the hexagonal structure of the atoms in lonsdaleite might possibly make it tougher than normal diamonds, which have a cubic structure.
Scientists believe the lonsdaleite was produced around 4.5 billion years ago when the dwarf planet collided with a huge asteroid. "This work establishes unequivocally that lonsdaleite exists in nature." We also identified the biggest lonsdaleite crystals known to date, which are up to a micron in size - much, much thinner than a human hair," said McCulloch, director of the RMIT Microscopy and Microanalysis Facility.
The study found strong evidence that lonsdaleite was generated on the dwarf planet through a supercritical chemical vapour deposition process that occurred quickly after a "catastrophic collision." Surprisingly, this chemical vapour is employed in the production of "lab-grown" diamonds.
The team hypothesises that lonsdaleite originates in meteorites from a supercritical fluid at high temperature and moderate pressure. The original form and textures of the pre-existing graphite would have been retained during the process. Later, when the atmosphere cooled and pressure dropped, the lonsdaleite may have been largely replaced by the typical diamond identified in the meteorite.
