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Wondrium is a subscription service  where you find the answers to everything you’ve ever wondered  about, and some things you’ve never imagined you would wonder about! Head to wondrium.com/scishow for a free trial. [♪ INTRO] Even if you didn’t go through a  rocks and minerals phase as a kid, you’ve probably heard some facts  about those sparkly, sparkly diamonds.

Like that they’re the hardest mineral on  Earth, and that they’re a dog’s best friend. No wait, that’s not how the song  goes…Dogs are a girl’s best friend… Anyway, it turns out that first  fact might not be right, either. There’s another naturally-occuring  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. That’s according to the  Mohs mineral hardness scale. And the test behind this scale is really simple.

You drag one mineral across another. If you see a line left behind, whether  with your eye or under a microscope, that mineral is less hard than  the one you scratched it with. The higher a mineral’s Mohs number, the  fewer minerals it can be scratched by.

So with their hardness of 10,  diamonds are nearly unscratchable. They can scratch each other, and while  some synthetic materials might be able to scratch them, we haven’t found  a naturally-occurring mineral that can. But what makes diamonds so hard?

It’s partly due to the fact that  they’re made entirely of carbon atoms. When atoms come together to make minerals, they form a lattice held  together by chemical bonds. Depending on the atoms  involved, these bonds come in two main flavors: ionic bonds and covalent bonds.

In ionic bonds, electrons are  transferred from one atom to another. And ionic bonds can be strong. But they aren’t usually as strong as  covalent bonds, where electrons are shared.

Corundum, the mineral that  makes both rubies and sapphires, has both types of bonds. Its aluminum  atoms will transfer electrons to nearby oxygen atoms to form ionic bonds, and the oxygen atoms will covalently  share electrons between each other. So in the end, it has a Mohs hardness of 9.

Because diamond is pure carbon,  it only uses covalent bonds. But that alone can’t explain why  a diamond is harder than a ruby. Despite looking completely different,  graphite is also pure carbon.

And while diamonds are over here  rocking a 10 in Mohs hardness, graphite ranks about a 1.5. It’s so soft that your fingernail can dent it. So we also have to consider the  shape of the mineral’s lattice.

How the atoms are actually arranged. Graphite atoms come stacked  in two-dimensional sheets. Each carbon atom is bound to  three others in the same sheet.

And while the covalent bonds  within the sheets are strong, the sheets are bound to each other very weakly. When force is applied to graphite,  like you pressing your pencil lead against a sheet of paper, the  structure deforms pretty easily. Meanwhile, a diamond’s atoms are  arranged in a three-dimensional cubic structure, with each carbon  atom bound to four of its neighbors.

Unlike graphite, it resists  force from three dimensions. So hypothetically, if we wanted to  find a mineral harder than diamond, we’d look for something that was still pure  carbon, but had a better lattice structure. Enter lonsdaleite.

Lonsdaleite’s atoms are arranged hexagonally. Each carbon is covalently  bound to six other atoms. These two extra bonds per atom should  produce an even harder mineral.

Unfortunately, scientists have had  a hard time confirming that’s true, because while we’ve known about  lonsdaleite since the 1960s, we haven’t found pure lonsdaleite in  large enough samples to really test it. See, lonsdaleite is natural,  but as far as we know, it doesn’t occur naturally on Earth. The only lonsdaleite we have comes from a special class of meteorites called ureilites.

These are carbon-rich  meteorites that scientists think all come from the same source: a  dwarf planet that was destroyed by a collision very early in  the solar system’s history. And when you crack ureilites open, you  can find some graphite, diamond, and… at least in a few samples…teeny  amounts of lonsdaleite. Sometimes you can even see transition  zones between these different minerals.

That suggests that some kind of  shock forced the carbon atoms to rearrange themselves, and for  some reason, some formed diamond, while others formed lonsdaleite. Researchers are still working  on what that reason is, and on the exact conditions of that shock. But if they can figure it out,  they could maybe find a way to create their own harder-than-diamond mineral.

So far, the science is leaning  toward rapid depressurization. Since ureilites also contain minerals  that exist deep inside the Earth, they all probably started  off under a lot of pressure. But when the dwarf planet got blasted apart, all its insides would have suddenly been  exposed to the near vacuum of space.

One hypothesis proposes that upon  this sudden change in pressure and temperature, the bonds between  some of the carbon atoms could have suddenly shifted and morphed into diamond’s  cubic lattice. Lonsdaleite came later. But a study published in 2022  suggests it’s the other way around.

The ureilite’s carbon atoms were shocked  into forming lonsdaleite first, and most of that lonsdaleite shifted into diamond  when the new meteorite cooled off quickly. So if researchers hope to make  not ju st their own lonsdaleite, but enough that they can run tests  to prove it’s harder than diamond, they need to figure out how  to replicate this process. And to keep their new lonsdaleite warm enough for long enough to not decay into a diamond.

There’s actually been some success, here. Back in 2021, one team claimed  they’d not only made lonsdaleite, they’d also experimentally proven that  their sample was stiffer than diamond. Now, geologically speaking, stiffness and  hardness are two different properties, but you often find that stiffer  minerals are also harder.

So it’s a step in the right direction. Unfortunately, the method they  used was a bit, well, explosive. It destroyed the lonsdaleite they created  almost as soon as they finished testing it.

But if further research backs this study  up, and the team can work out all the kinks, we could eventually have a reliable  way to produce synthetic lonsdaleite. And if it does turn out to be harder  than diamond, industry will love it. Because they’re so hard, diamonds are used for all sorts of cutting,  grinding, and polishing jobs.

An even harder material would make tools  even more effective and last longer. Maybe one day, we’ll all have  lonsdaleite-tipped drill bits. And if we can make them big enough,  people may rock some lonsdaleite bling and write a song about how awesome  this space-based mineral is.

Minerals rock! For more on minerals, you can check  out this video’s sponsor: Wondrium! Wondrium is a subscription service  with videos about everything you’ve ever wondered, and some things you’ve never imagined you would  wonder, kind of like SciShow.

To help you dive deeper, Wondrium has not one, but two programs all about minerals! That’s 36 lectures on the Nature of  Earth as An Introduction to Geology and 24 more lectures on Practical Geology. Through these programs, you’ll learn  tips for collecting minerals and how to identify the minerals you  come across in your daily travels, using color, hardness, and other features.

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