Volcanoes and Meteoroids Make Materials Harder Than Diamond

By Adam Hadhazy|Wednesday, June 24, 2009

The reputation of diamond as the hardest material around is under threat. Researchers in China and the United States recently determined that two naturally occurring substances surpass diamond’s resistance to scratching and indentation. They calculated that the mineral lonsdaleite—made of carbon, like diamond—is 58 percent harder than its famous cousin. And wurtzite boron nitride beats diamond’s hardness by about 18 percent after being subjected to pressure, which alters its atomic bonds.

Still, in the short term diamond will continue to dominate in practical applications such as saws, drill bits, and industrial abrasives, since the newly studied materials are extremely rare. Lonsdaleite forms only under the extreme pressure and heat accompanying meteorite impacts, while wurtzite boron nitride is a by-product of intense volcanic eruption. But scientists can create both substances in the lab, says physicist John Janik at the Carnegie Institution for Science. Although producing the conditions required to grow the substances in bulk remains a challenge, Janik and others are working on synthesizing wurtzite boron nitride and lonsdaleite to pave the way for commercial use.

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