Meteorite yields carbon crystals harder than diamond

February 3, 2010 by Lin Edwards report
Nearly octahedral diamond crystal in matrix. Image: Wikimedia Commons

(PhysOrg.com) -- Two new types of ultra-hard carbon crystals have been found by researchers investigating the ureilite class Haverö meteorite that crashed to Earth in Finland in 1971. Ureilite meteorites are carbon-rich and known to contain graphite and diamonds.

The super-hard were created when graphite in the experienced the intense heat and pressure of entering the Earth’s atmosphere and crashing into the ground. The graphite layers would have been heated and shocked enough to create bonds between them, in much the same way as humans manufacture diamonds.

The new carbon crystals were too small to test for precise hardness but they are known to be harder than normal diamonds because the researchers found them by using a diamond paste to polish a slice of the meteorite. The crystals were raised more than 10 µm above the polished surface, which meant they were harder than the diamonds in the polishing paste. The researchers had seen carbon crystals that resisted the diamond polishing in one direction before, but the new crystals were unaffected when polished in every direction.

The scientists then used an array of mineralogical instruments, including , and energy-dispersive among others, to study the structure of the crystals. This allowed them to identify them as representing two new carbon polymorphs or diamond polytypes.

One is an ultra-hard rhombohedral carbon polymorph similar to diamond, while the other is a 21R diamond polytype ultra-hard diamond. The existence of ultra-hard diamonds had been predicted decades ago, but they have never before been found in nature. The novel form consists of fused sheets similar to artificial diamond.

Professor Tristan Ferroir, leader of the research team from the Université de Lyon in France, said the discovery was accidental, but they had thought an examination of the meteorite would “lead to new findings on the carbon system."

Professor Ferroir said there is currently no way to compare the structure of the new to boron nitride and lonsdaleite, the artificially manufactured ultra-hard diamonds, but the findings help scientists gain a better understanding of carbon polymorphs and give them new materials to investigate and perhaps synthesize. They also show the carbon system is more complex than previously thought.

The findings on the new diamond were published in the Earth and Planetary Science Letters journal on February 15.

Explore further: Superconductivity in diamond

More information: dx.doi.org/10.1016/j.epsl.2009.12.015

Related Stories

Superconductivity in diamond

April 10, 2004

As well as holding pride of place as the most sought-after of all precious gemstones, diamond possesses a dazzling array of technologically useful properties. As well as being the hardest, most thermally conducting, and chemically ...

Researchers to Study Properties of the Hope Diamond

August 25, 2005

Since January, scientists from the Naval Research Laboratory's Chemistry Division have been studying the optical properties of the Hope Diamond, at the invitation of the Smithsonian Institution. In collaboration with the ...

Hope Diamond's phosphorescence key to fingerprinting

January 7, 2008

Shine a white light on the Hope Diamond and it will dazzle you with the brilliance of an amazing blue diamond. Shine an ultraviolet light on the Hope Diamond and the gem will glow red-orange for about five minutes. This phosphorescent ...

Scientists Discover Material Harder Than Diamond

February 12, 2009

(PhysOrg.com) -- Currently, diamond is regarded to be the hardest known material in the world. But by considering large compressive pressures under indenters, scientists have calculated that a material called wurtzite boron ...

Diamond is one tough cookie

January 26, 2010

(PhysOrg.com) -- Most people know that diamond is one of the hardest solids on Earth, so strong that it can easily cut through glass and steel. Surprisingly, very little is known about the strength of diamond at extreme conditions. ...

Recommended for you

Brazilian wasp venom kills cancer cells by opening them up

September 1, 2015

The social wasp Polybia paulista protects itself against predators by producing venom known to contain a powerful cancer-fighting ingredient. A Biophysical Journal study published September 1 reveals exactly how the venom's ...

Naturally-occurring protein enables slower-melting ice cream

August 31, 2015

(Phys.org)—Scientists have developed a slower-melting ice cream—consider the advantages the next time a hot summer day turns your child's cone with its dream-like mound of orange, vanilla and lemon swirls with chocolate ...

Antibody-making bacteria promise drug development

August 31, 2015

Monoclonal antibodies, proteins that bind to and destroy foreign invaders in our bodies, routinely are used as therapeutic agents to fight a wide range of maladies including breast cancer, leukemia, asthma, arthritis, psoriasis, ...

3 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Mr_Frontier
Feb 03, 2010
This comment has been removed by a moderator.
danman5000
5 / 5 (3) Feb 03, 2010
It's amazing how many allotropes carbon has, and how very different they are from each other. Graphite, graphene, diamond, buckyballs, and now these two new ones!
Caliban
3.7 / 5 (3) Feb 03, 2010
It would be nice to see what structural properties(in terms of ductility, malleability, and shear-strength, for starters) these materials would have at larger scales. If these properties do scale up, then think of how their use could revolutionize materials science. But more to the point- exploration of the deep oceans and outer space.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.