Monash University Professor Andy Tomkins (left) with RMIT PhD scientist 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 crystal expert Dame Kathleen Lonsdale, who was the first woman to be elected a member of the Royal Society.
The research team – with scientists from Monash UniversityAnd RMIT.UniversityAnd CSIROAustralian synchrotron e University of Plymouth – I found evidence of how lonsdaleite formed in urelite meteorites. They released their results on 12 September a Prosidente 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, as opposed to the traditional cubic diamond lattice. Named in honor of Kathleen Lonsdale, a crystal expert.
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The team estimates that Lonsdalite’s hexagonal atomic structure makes it harder than ordinary 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 found the largest lonsdalite crystal known to date, which is up to one micron in size, much thinner than a human hair.”
According to the research team, the unusual structure of lonsdaleite could help develop new fabrication techniques for superhard materials in mining applications.
What is the origin of this mysterious diamond?
McCulloch and his team at the Massachusetts Institute of Technology, PhD students Alan Salk and Dr. Matthew Field, used state-of-the-art electron microscopy techniques to capture solid, intact slices of meteorites to create quick snapshots of how diamonds form. and ordinary diamonds.
“There is strong evidence that there has been a formation process for the newly discovered nesadalite and ordinary diamond, which is similar to the supercritical chemical vapor deposition process that occurs in these space rocks, possibly on a dwarf planet shortly after. cataclysmic collision, “McCulloch said.
“Chemical vapor deposition is one of the ways people make diamonds in the laboratory, especially by growing them in special rooms.”
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 supercritical fluids at high temperatures and moderate pressures, almost perfectly retaining the shape and texture of the pre-existing graphite.
“So, Lonsdalite has been partially replaced by diamond with a cooler environment and lower pressure,” said Tomkins, a prospective researcher at ARC at Monash University’s School of Earth, Atmosphere and Environment.
And nature has given us processes to try and replicate in industry. We believe lonsdaleite can be used to make extra rigid machine parts if we can develop industrial processes that encourage the replacement of preformed lonsdaleite graphite parts. “
Tomkins said the research findings help solve a long-standing conundrum about the carbon phase composition in urelite.
The power of collaboration
CSIRO’s Dr Nick Wilson said the technological collaboration and experience of the various institutions involved allowed the team to confidently confirm lonsdaleitis.
At CSIRO, electronic probe microanalysis is used to quickly map the relative distribution of graphite, diamond, and Lonsdalite in samples.
“Individually, each of these techniques gives us a good idea of what this substance is, but put together – it’s really the gold standard,” he said.
Reference: “Lonsdaleite Sequencing of Diamond Formation in Ureilite Meteorite via OK Liquid / Chemical 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. Prosidente National Academy of Sciences.
DOI: 10.1073 / pnas.2208814119
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