1. Mohs Hardness Scale: This measures a material's resistance to scratching. On this scale, diamond is the hardest material at 10, meaning it can scratch all other known materials.
2. Vickers Hardness Test: This measures the resistance to indentation. In this test, the "hardest material" is generally considered to be Lonsdaleite, a hexagonal form of diamond found in meteorites. It's estimated to be around 58% harder than regular diamond, though it's incredibly rare.
Other contenders:
* Wurtzite Boron Nitride (w-BN): While not as hard as Lonsdaleite, w-BN is still incredibly hard and can be synthesized in the lab. It's used in high-tech applications.
* Carbon Nanotubes: These structures have incredible strength-to-weight ratios and can be exceptionally hard in certain configurations.
So, the answer depends on what you mean by "hardness." Diamond is the hardest according to Mohs Hardness Scale, but Lonsdaleite is generally considered the hardest based on Vickers Hardness. However, materials like w-BN and carbon nanotubes also have exceptional hardness properties.
