Chinese scientists have created a diamond with no Achilles’ heel – one that cannot be broken, even by a hard knock with a hammer – according to a paper published in the peer-reviewed journal Nature Synthesis. While a diamond is the hardest natural material on Earth, it has a major weakness. It is brittle, like glass, and a sharp blow can shatter it. For years, scientists have tried to make diamonds tougher without losing their legendary hardness. The breakthrough material is even tougher than the tungsten alloys used in armour-piercing ammunition, according to the paper, which was published online on July 9.