Is There a Material Stronger Than Diamond?

Diamonds have always been regarded as the most hard and durable material on Earth, so much so that it has become a symbol of status and desirability. But it may soon lose its crown, thanks to a rare natural substance that’s 58 percent harder than diamond.

A mineral’s hardness is based on how well it resists scratching or other surface deformations, as measured by its hardness on the Mohs scale. Diamonds are incredibly hard due to their crystalline structure, with five carbon atoms sharing electrons with four other atoms to form a tetrahedral crystal.

There are several other minerals that are also stronger than diamond, including boron nitride and silicon carbide. But both are difficult to create, as they only occur naturally in extreme heat and pressure of volcanic eruptions.

So, if scientists were able to create an artificial material that is 58 times harder than diamond, it would be very exciting! But before that could happen, we would need to understand what makes these materials so hard.

In the case of wurtzite boron nitride, this is because it is made up of different atoms than diamond. Unlike diamond, wurtzite boron can undergo structural phase transformations when under compressive pressures. This conserves volume by flipping its atomic bonds in response to the stress of the compression, says Zicheng Pan at Shanghai Jiao Tong University and colleagues in a study published today in Physical Review Letters.

A similar substance, called lonsdaleite, is even harder than wurtzite boron. It’s also obtained from graphite-rich meteorites and is 58% stronger than wurtzite boron.