Everyone knows that diamond is hard. But were you aware that Lonsdaleite, a similar (although much rarer) mineral (and one of the hardest materials on Earth) is even harder? Or that spider silk, weight for weight, is stronger than steel? How about graphene, which shows extreme strength despite being only one atom thick?
But before anyone can talk about hard materials, they will first need to ask themselves, what makes a material hard? Glass, for instance, will neither bend nor deform but is prone to breaking, so it is durable but not strong. Metals like aluminum or steel will stretch and bend but will be extremely difficult to break, thus they are strong but not durable. And when referring to hardness, are you considering size and weight?
For the sake of this list, hardness will come down to a balance of strength and durability while taking into account the material’s mass. So, without further ado, here is the countdown of ten hardest materials on Earth, from weakest to strongest.
#10. Spider Silk
Spider silk possesses a rare balance of strength and durability. It owes that quality to the thousands of small strands that comprise it, courtesy of the spiders’ diligence. The only factor keeping it in check is the diminutive size of its architects. In fact, if spider silk were as thick as an average human being, it would be able to catch jets mid-fight.
#9. Silicon Carbide
Originally invented in an attempt to make artificial diamonds, silicon carbide was a failure in that regard. It sits at a 9 on the Mohs scale of mineral hardness, just under the maximum rating of 10, which is reserved for actual diamonds. A material only one-third as hard as diamond, however, is still extremely hard in comparison to almost anything else. Today it is mostly used for composite armor on tanks and other armored vehicles, as well as in the construction of abrasive and cutting tools.
Developed by Israeli scientists, the self-assembling nanospheres form the stiffest organic material known to man. In tests, it has displayed extreme levels of hardness, as only a diamond-tipped probe was able to make a dent in it. Even more impressively, the material is quite cheap to make and can even be 3D-printed. The list of potential applications for nanospheres seems endless, from lightweight, printed body armor, to orbital elevators.
As the hardest naturally-occurring material on earth, diamond even owes its name to the word “unbreakable.” As you’ve probably guessed by now, it doesn’t exactly live up to it. Even though only other diamonds or harder substances can cut or scratch a diamond, once you’ve successfully done so, it will become rather easy to break. And after a diamond loses its integrity, even a strong hammer strike can shatter it into pieces, precisely because it won’t bend or deform.
#6. Wurtzite Boron Nitride
A rare mineral that comes into being when a volcano erupts, this material is assumed to be 18% harder than diamond, at least according to its molecular structure. Owing to the flexible bonds between its atoms, it may also be more resistant to heat and shattering. Unfortunately, no one can properly test that theory, as there isn’t that much of the stuff to go around. Still, you wouldn’t be wrong in calling it one of the hardest materials on Earth.
This extremely rare material sometimes forms when a meteorite containing graphite crashes into Earth. Going by its composition, scientists currently assume it to be 58% harder than diamond. Like with #6 on this list, though, there simply isn’t enough of it to put that theory to the test. If the theory proves true, though, it would make Lonsdaleite the hardest natural material known to humankind.
According to the company that invented it, this super-strong polyethylene is the strongest fiber in the world. Considering the fact that it’s proved to be 15 times stronger than steel, they’re probably telling the truth. It is also so light that it won’t sink if you throw it into water; it’ll just float. It’s no wonder that it’s used in the making of modern bulletproof vests.
#3. Metallic Glass
Strength and durability are often mutually exclusive, but that is simply not the case with metallic glass. The name is misleading, though, as the material has little to do with actual glass, aside from its internal structure. As it turns out, when you layer palladium, silver, and other metalloids in a manner similar to that of glass, it results in a material with the advantages of both. Metallic glass is thus as strong and break-resistant as metal, but as durable and hard as glass.
This is where the list heads out into sci-fi territory. Buckypaper is an extremely thin (50,000 times thinner than a human hair) paper-like material, made with compressed carbon nanotubes. In layman’s terms, that means that despite being 10 times lighter than steel, buckypaper is 500 times stronger. No, that wasn’t a typo, and you’ve read it right.
If it ever becomes worthwhile to mass-produce, buckypaper might become the go-to material for military-grade personnel and vehicle armor in the future. That alone should be impressive enough, but the material also has a long list of other possible uses, from fire protection to growing living tissue.
Despite being only one carbon atom thin (the thinnest material in existence!), graphene is insanely strong. In fact, it is 200 times stronger than steel while being lighter than paper and as pliable as rubber. You can stretch it to 120% of its width and length and nothing will happen, and if you drop it it will fall as slowly as a leaf.
It is still not perfect, however, and a study has shown that once torn, it will become as brittle as ceramic. For as long as it keeps its integrity, though, graphene will resist pretty much all attempts to damage it. If scientists find a way to layer it, it could form the basis of something truly indestructible. Even in its basic state, though, it remains one of the hardest materials on earth, and — taking weight into account, is certainly the hardest.