Monash University Professor Andy Tomkins (left) with RMIT PhD student Alan Salk and a urilite meteorite sample. Credit: RMIT University
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Exotic diamonds from an ancient dwarf planet in our solar system may have formed shortly after the dwarf planet collided with a large asteroid some 4.5 billion years ago.
A team of scientists say they have confirmed the presence of lonsdaleite, a rare hexagonal form of diamond, in the mantle’s urelite meteorites. dwarf planet.
Lonsdaleite is named after the famous British crystallologist Dame Kathleen Lonsdale, who became the first woman to be elected a member of the Royal Society.
Research group – with scientists from Monash UniversityAnd the RMIT UniversityAnd the CSIROthe Australian synchrotron, e University of Plymouth – I found evidence of how lonsdaleite formed in urelite meteorites. They released their results on 12 September a Proceedings van de National Academy of Sciences (PNAS). The study was led by Monash University geologist Professor Andy Tomkins.
Lonsdaleite, also known as hexagonal diamond in reference to its crystal structure, is a carbon allotrope with a hexagonal lattice, unlike the traditional diamond cubic lattice. It is named in honor of Kathleen Lonsdale, a crystallologist.
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The team predicted that the hexagonal structure of Lonsdalite’s atoms makes it harder than regular diamond, which has a cubic structure, said RMIT professor Dougal McCulloch, one of the senior researchers involved.
“This study conclusively demonstrates that Lonsdalite exists in nature,” said McCulloch, director of the Microscopy and Microanalysis Facility at RMIT.
“We also discovered the largest lonsdalite crystals known to date, measuring down to one micron, much thinner than a human hair.”
Lonsdaleite’s unusual structure could help develop new fabrication techniques for superhard materials in mining applications, the research team said.
What is the origin of these mysterious diamonds?
McCulloch and his Massachusetts Institute of Technology team, PhD students Alan Salk and Dr. Matthew Field, used advanced electron microscopy techniques to capture solid, intact slices of meteorites to create quick snapshots of how diamonds and diamonds formed. ordinary.
“There is strong evidence that there is a recently discovered common diamond and nesadalite formation process that is similar to the supercritical chemical vapor deposition process that took place in these space rocks, possibly on the dwarf planet shortly after a catastrophic collision. “McCulloch said. he said.
“Chemical vapor deposition is one way people make diamonds in a laboratory, mainly by growing them in a specialized room.”
Professor Dougal McCulloch (left) and RMIT PhD researcher Alan Salk with Professor Andy Tomkins of Monash University (right) at RMIT’s Microscopy and Microanalysis Facility. Credit: RMIT University
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Tomkins said the team suggested that lonsdaleite in meteorites formed from a supercritical fluid at high temperatures and moderate pressure, almost perfectly preserving the shape and texture of the pre-existing graphite.
“Later, Lonsdalite was partially replaced by diamond with a cooler environment and lower pressure,” said Tomkins, a prospective ARC fellow at Monash University’s School of Earth, Atmosphere and Environment.
And so nature has given us a process that we can try to replicate in the industry. We believe lonsdaleite can be used to make extra rigid machine parts if we can develop an industrial process that promotes the replacement of preformed graphite parts with lonsdaleite. “
Tomkins said the study’s findings helped solve a long-standing conundrum related to the composition of carbon phases in urelite.
The power of collaboration
dr. CSIRO’s Nick Wilson said the collaboration of technology and expertise from the various institutions involved allowed the team to confidently confirm lonsdaleite.
At CSIRO, a micro-analyzer with an electronic probe was used to quickly map the relative distribution of graphite, diamond and Lonsdalite in the samples.
“Individually, each of these techniques gives us a good idea of what this substance is, but when taken together, it really is the gold standard,” he said.
Reference: “Lonsdaleite Sequencing of Diamond Formation in Ureilite Meteorites Via” At sight Chemical Liquid / Vapor Deposition “by Andrew J. Tomkins, Nicholas C. Wilson, Colin McRae, Alan Salk, Matthew R. Field, Helen E. Brand, Andrew D. Langendam, Natasha R. Stephen, Aaron Turbie, Zanett Pinter and Lauren A. Jennings and Dougal G. McCulloch, September 12, 2022, available here. Proceedings van de National Academy of Sciences.
DOI: 10.1073 / pnas.2208814119
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