What's Tougher Than Girl's Best Friend? Diamonds versus Boron

You don't often break a diamond. So when in 2003 Dave Mao cracked a tooth of his diamond anvil, he knew something extraordinary must have happened.

Together with his daughter Wendy and other colleagues at the Geophysical Laboratory of the Carnegie Institution for Science in Washington DC, he was using the device to test materials at pressures many millions of times higher than those at the Earth's surface - higher even than in our planet's core - by squeezing them between two tiny diamond jaws.

Behind the glitz, diamond is just a form of carbon. It is, however, by common consent the hardest material known. The substance in the Maos' test cell had also begun as pure carbon.

It was plain old graphite - the soft, slippery stuff that is used for pencil leads and lubricants. Clearly, something had happened in the anvil cell to make it awesomely hard.

It seemed the Maos might accidentally have succeeded where many before had failed. Had they made the first superhard material that matched or even surpassed diamond? Probably not, as it turned out.

Six years and several twists later, though, that feat might at last have been achieved, though not with pure carbon. If the latest reports are right, the hardness crown has changed hands at last.