Meteorites make rare Diamonds!

When a large meteorite collides with the Earth, it can be travelling upwards of 40 Kilometres per second.  This collision releases a huge amount of energy, which can vaporize rocks and create interesting and unique geological structures.

For decades, scientists have been debating the existence of a rare type of crystal called Lonsdaleite, which is associated with impacts.  Strange small crystals were discovered in Arizona in the 1950s around an ancient impact crater called ‘Canyon Diablo.’  It led some scientists to believe that the mineral had mechanical properties similar to diamond, but that it was structurally superior. If it existed in a pure form somewhere, it could have huge industrial applications.  Even though this led to a lot of interest in the crystal, it had never been found or synthesized outside of tiny crystals associated with impacts.

Diamond grains from the Canyon Diablo meteorite. The tick marks are spaced one-fifth of a millimeter (200 microns) apart. Credit: Arizona State University/Laurence Garvie

With new electron microscope technology, researchers from Arizona State University re-examined the tiny crystals and determined that the Lonsdaleite is actually the same as normal diamond, but with small impurities due to shock and heating associated with the impacts.

“Most crystals have regular repeating structures, much like the bricks in a well-built wall,” says Peter Buseck, a researcher with ASU’s School of Earth and Space exploration. “However, 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.”

So it turns out there’s no super-diamond, but once again, science has solved a long standing mystery.

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