Monthly Archives: November 2014

Asteroid impacts from space onto Earth make structurally bizarre diamonds

Diamond grains from the Canyon Diablo meteorite are shown. The tick marks are spaced one-fifth of a millimeter (200 microns) apart.image www.worldwidediamonds.info

Scientists have argued for half a century about the existence of a form of diamond called lonsdaleite, which is associated with impacts by meteorites and asteroids. A group of scientists based mostly at Arizona State University now show that what has been called lonsdaleite is in fact a structurally disordered form of ordinary diamond.

The scientists’ report is published in Nature Communications, Nov. 20, by Péter Németh, a former ASU visiting researcher (now with the Research Centre of Natural Sciences of the Hungarian Academy of Sciences), together with ASU’s Laurence Garvie, Toshihiro Aoki and Peter Buseck, plus Natalia Dubrovinskaia and Leonid Dubrovinsky from the University of Bayreuth in Germany. Buseck and Garvie are with ASU’s School of Earth and Space Exploration, while Aoki is with ASU’s LeRoy Eyring Center for Solid State Science.

“So-called lonsdaleite is actually the long-familiar cubic form of diamond, but it’s full of defects,” says Péter Németh. These can occur, he explains, due to shock metamorphism, plastic deformation or unequilibrated crystal growth.

The lonsdaleite story began almost 50 years ago. Scientists reported that a large meteorite, called Canyon Diablo after the crater it formed on impact in northern Arizona, contained a new form of diamond with a hexagonal structure. They described it as an impact-related mineral and called it lonsdaleite, after Dame Kathleen Lonsdale, a famous crystallographer.

Since then, “lonsdaleite” has been widely used by scientists as an indicator of ancient asteroidal impacts on Earth, including those linked to mass extinctions. In addition, it has been thought to have mechanical properties superior to ordinary diamond, giving it high potential industrial significance. All this focused much interest on the mineral, although pure crystals of it, even tiny ones, have never been found or synthesized. That posed a long-standing puzzle.

The ASU scientists approached the question by re-examining Canyon Diablo diamonds and investigating laboratory samples prepared under conditions in which lonsdaleite has been reported.

Using the advanced electron microscopes in ASU’s Center for Solid State Science, the team discovered, both in the Canyon Diablo and the synthetic samples, new types of diamond twins and nanometer-scale structural complexity. These give rise to features attributed to lonsdaleite.

“Most crystals have regular repeating structures, much like the bricks in a well-built wall,” says Peter Buseck. However, interruptions can occur in the regularity, and these are called defects. “Defects are intermixed with the normal diamond structure, just as if the wall had an occasional half-brick or longer brick or row of bricks that’s slightly displaced to one side or another.”

The outcome of the new work is that so-called lonsdaleite is the same as the regular cubic form of diamond, but it has been subjected to shock or pressure that caused defects within the crystal structure.

One consequence of the new work is that many scientific studies based on the presumption that lonsdaleite is a separate type of diamond need to be re-examined. The study implies that both shock and static compression can produce an intensely defective diamond structure.

The new discovery also suggests that the observed structural complexity of the Canyon Diablo diamond results in interesting mechanical properties. It could be a candidate for a product with exceptional hardness.

Henry Sapiecha

pink diamonds line image www.worldwidediamonds.info

Large white RBC 7.36 Carat Diamond Stolen in Geneva Switzerland

Attention sign image www.worldwidediamonds.infoSTOLEN LARGE WHITE DIAMOND IN GENEVAgia-certificate-of-the-stolen-diamond-image www.worldwidediamonds.info

7.36 carat F color diamond of VVS2 clarity has been stolen after being shipped from Moti Kashi Diamonds’ office in Tel Aviv to a client of the company based in Geneva, Switzerland. The client, who is respected and well-known, had received the stone from Moti Kashi Diamonds on consignment.

The diamond, which has Excellent grade in cut, polish, and symmetry, is of medium fluorescence and is certified by the GIA with report number 5161160490, was shipped at the end of September. A few days later, the client informed Moti Kashi Diamonds that he had consigned the diamond to a third party and that it had been stolen.

Moti Kashi Diamonds has requested that the name of the client not be published since they stress that he is an honest dealer and they expect him to take full responsibility for the stolen diamond. Further developments will be published where appropriate, adds Moti Kashi Diamonds, who are requesting to be notified if there is any information about this diamond.

Henry Sapiecha

pink diamonds line image www.worldwidediamonds.info

Chow Tai Fook to Unveil 104-carat Cullinan 1 Heritage diamond on November 28 – 2014

cullinan_507carat_diamond www.worldwidediamonds.info

Hong-Kong based Chow Tai Fook will unveil the 104-carat Cullinan Heritage 1, a diamond cut from an original 507.55 carat Type IIA rough diamond known as the Cullinan Heritage, on November 28, 2014,  Diamond World reports. The company acquired the diamond from Petra Diamonds in an auction for $35.3 million in 2010.

The Cullinan Heritage 1 will be showcased along with other diamonds, also cut from the Cullinan Heritage, on November 28 during a celebration for its 85th anniversary.
cullinan diamond rough diamond ceo image www.worldwidediamonds.info
The piece has been cut and polished by the company’s craftsmen and certified by Forevermark, reports add. Also, the stone will be set into jewellery.

The Cullinan Heritage was discovered in the Cullinan mine in South Africa and is the largest of its grade to have been recovered there since 1986.

Henry Sapiecha

pink diamonds line image www.worldwidediamonds.info