Six-sided diamonds from ancient dwarf planet created by collision
Rare hexagonal space diamonds could be even harder rocks than Earth’s as Aussie study suggests super-strong gemstones formed after large asteroid collided with dwarf planet billions of years ago
READING LEVEL: RED
Strange diamonds from an ancient dwarf planet in our solar system may have formed shortly after the dwarf planet collided with a large asteroid* about 4.5 billion years ago, according to scientists.
The research team confirmed the existence of a rare hexagonal* form of diamond called “lonsdaleite”, after analysing ureilite* meteorites* that came from the dwarf planet.
Lonsdaleite is named after the famous British crystallography* pioneer* Dame Kathleen Lonsdale (1903-1971), the first woman elected as a Royal Society Fellow*.
The team found evidence of how lonsdaleite formed by studying ureilite meteorites that had landed on Earth.
RMIT Microscopy* and Microanalysis Facility director Professor Dougal McCulloch, one of the senior researchers involved, said the team predicted the hexagonal structure of lonsdaleite’s atoms made it potentially harder than regular diamonds, which have a cubic* structure.
“This study proves categorically that lonsdaleite exists in nature,” said Prof McCulloch.
“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 team said the unusual structure of lonsdaleite could help inform new manufacturing techniques for ultra-hard materials in mining applications.
Prof McCulloch and his RMIT team – PhD scholar Alan Salek and Dr Matthew Field – used advanced electron microscopy techniques to capture solid and intact slices from the meteorites to create snapshots of how lonsdaleite and regular diamonds formed.
“There’s strong evidence that there’s a newly discovered formation process for the lonsdaleite and regular diamond, which is like a supercritical* chemical vapour deposition* process that has taken place in these space rocks, probably in the dwarf planet shortly after a catastrophic collision,” Prof McCulloch said.
“Chemical vapour deposition is one of the ways that people make diamonds in the lab, essentially by growing them in a specialised chamber.”
Published in the Proceedings of the National Academy of Sciences (PNAS) journal, the study was led by Monash University geologist Professor Andy Tomkins.
Prof Tomkins said the team proposed that lonsdaleite in the meteorites formed from a supercritical fluid 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,” Prof Tomkins said.
“Nature has thus provided us with a process to try and replicate in industry. We think that lonsdaleite could be used to make tiny, ultra-hard machine parts if we can develop an industrial process that promotes replacement of pre-shaped graphite parts by lonsdaleite.”
Prof Tomkins said the study findings helped address a longstanding mystery regarding the formation of carbon phases in ureilites.
CSIRO’s Dr Nick Wilson said the collaboration of technology and expertise from different institutions allowed the team to confirm the lonsdaleite with confidence, with scientists from Monash University, RMIT University, CSIRO, the Australian Synchrotron and Plymouth University taking part.
An electron probe micro-analyser* was used at CSIRO to quickly map the relative distribution of graphite, diamond and lonsdaleite in the samples.
“Individually, each of these techniques give us a good idea of what this material is, but taken together – that’s really the gold standard,” Dr Wilson said.
GLOSSARY
- asteroid: a small, rocky object that orbits the sun
- hexagonal: a shape with six straight sides
- ureilite: class of asteroid primarily made of minerals olivine and pyroxene, with carbon through it
- meteorites: pieces of debris from space that survive entry into our atmosphere and hit Earth
- crystallography: branch of science dealing with the forms and structures of crystals
- pioneer: person who is among the first to study and develop something
- Royal Society: oldest and most revered scientific organisation in Britain, founded in 1660 by Charles II
- microscopy: using microscopes to view samples and objects that can’t be seen with naked eye
- cubic: having the form of a cube, a solid three-dimensional figure
- supercritical: exceeding critical temperature and pressure until physical and chemical properties change
- vapour deposition: a coating process when a gas at an elevated temperature creates a chemical reaction that leaves a thin layer on a substrate, meaning a foundation or base
- graphite: soft, dark grey form of carbon like that used in pencils
- micro-analyser: very small, sensitive, specialised apparatus for chemical analysis
EXTRA READING
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QUICK QUIZ
- How long ago do researchers think the dwarf planet collided with a large asteroid?
- Who is lonsdaleite named for and why was this particular scientist noteworthy?
- Scientists believe the hexagonal structure of lonsdaleite has what effect compared to the cubic shape of regular diamonds?
- The largest known lonsdaleite crystals are described as much, much thinner than what?
- Prof Tomkins said the team thinks the lonsdaleite could be used to make what?
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CLASSROOM ACTIVITIES
1. Production of lonsdaleite
After reading the Kids News article about lonsdaleite and how it is formed, create a circular flow chart showing the full production process. Try and keep the flow-chart simple by using only key words for each stage of the process.
Time: allow 20 minutes to complete this activity
Curriculum Links: English; Science; Critical and Creative Thinking
2. Extension
If you could design a piece of jewellery using one or more of these lonsdaleite diamonds, what would it be?
Sketch your design below.
Time: allow 15 minutes to complete this activity
Curriculum Links: English; Visual Arts
VCOP ACTIVITY
I spy nouns
Nouns are places, names (of people and objects), and time (months or days of the week).
How many nouns can you find in the article?
Can you sort them into places, names and time?
Pick three nouns and add an adjective (describing word) to the nouns.