what is the hardest rock on earth



  1. 0 Votes

    The hardest rock on earth is a diamond.  You may not be thinking of diamond as a rock, but it’s a naturally occurring mineral, so it qualifies!

    Diamond has a bulk modulus (reciprocal of compressibility) of 443 GigaPascals (GPa), which is just a fancy way of saying it’s the hardest rock that naturally occurs in nature.  It also ranks a 10 on Moh’s hardness scale.

  2. 0 Votes

    This depends on how you interpret the question. (“Rock” is a pretty general word.)

    For centuries, the hardest known material was diamond. Cleverly (and luckily), diamond was set up as the hardest thing on the Moh Scale. It is a 10. But the Moh Scale isn’t some natural law such as the speed-of-light, and we know a lot more about the universe, now.

    The hardest material in the universe is the matter in a neutron star (a black hole). Black holes eat diamonds … and everything else.

    Since diamond is very useful as an industrial cutting tool, it’s no surprise that people have been trying to find an even harder substance on Earth. And in that, they had a head-start, because they knew about neutron stars, for example. That lead people to discover Wurtzite Boron Nitride and Lonsdaleite, both much, much harder than diamond. (See links below.)

    But also people wanted to make their own material in any quantity, so Graphene and Buckypaper were developed.

    Except perhaps black hole material (and there’s no way to directly sample that!) there is no theoretical upper limit for hardness, now. (The Moh Scale now goes above 10.) That is, it’s quite possible we haven’t found the hardest material, yet.

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