Thanks to Wandrium for supporting this SciShow video! Wandrium is a subscription service where you can find the answers to everything you’ve ever wondered about, and some things you’ve never imagined you would wonder about. Even if you didn’t go through a rocks and minerals phase as a kid, you’ve probably heard some facts about those sparkly diamonds: like that they’re the hardest mineral on Earth. Turns out that might not be right either - there’s another naturally occurring mineral out there that could be harder than diamond, it’s just a little hard to study because it’s only found in rocks that fell from space. When geologists describe a mineral as hard, they aren’t talking about how it feels to the touch - they’re talking about how scratch-proof it is. You may have heard diamonds have a hardness of 10 out of 10. ’s minerals were suddenly exposed to the vacuum of space and the pressure drop might have been enough to force the carbon atoms to rearrange into diamond and lawns Delight
According to the Mohs mineral hardness scale, diamonds, which have a hardness of 10, are nearly unscratchable. This is partially due to the fact that they are made entirely of carbon atoms, which form a lattice held together by covalent bonds. Corundum, which makes both rubies and sapphires, has both ionic and covalent bonds and has a Mohs hardness of nine. Graphite, which is also pure carbon, ranks about a 1.5 in Mohs hardness and is easily dented by a fingernail. The difference in hardness between diamond and graphite is due to the shape of the mineral’s lattice and how the atoms are arranged.
Lonzalite, which has been known since the 1960s, has a lattice structure with each carbon atom bound to six other atoms, and is theorized to be harder than diamond. Unfortunately, pure lonzalite has not been found in large enough samples to test this hypothesis. The only lonzalite found is from a special class of meteorites called eurailites, which are believed to have come from a dwarf planet destroyed by a collision. Researchers are still working to understand the exact conditions of the shock that caused the carbon atoms to rearrange into diamond and lonzalite, and to find a way to create their own harder than diamond mineral.