There are ten minerals in Mohs scale, talc, gypsum, calcite, fluorite, apatite, feldspar, quartz, topaz, corundum, and for last and hardest, diamond. Because the Mohs scale was made long ago, it is not exactly correct - for example, several minerals are now known to be harder than the diamond.
Then, is Diamond still the hardest material?
But cubic boron nitride is still, at best, just the world's second hardest material with a Vickers hardness of around 50 GPa. Its hexagonal form (w-BN) was initially reported to be even harder but these results were based upon theoretical simulations that predicted an indentation strength 18% higher than diamond.
Are carbon nanotubes harder than diamond?
Chemists have calculated that chains of double or triple-bonded carbon atoms, known as carbyne, should be stronger and stiffer than any known material. The sixth element, carbon, has given us an amazing abundance of extraordinary materials. Once there was simply carbon, graphite and diamond.
Is a diamond harder than steel?
Imagine a material that is just one atom thick, 300 times stronger than steel, harder than diamond, a fantastic conductor of heat and electricity and super-flexible to boot. This might sound like the stuff of science fiction, but believe it or not, such a material already exists.