Harder Than Diamond: Is There Any Material That Is Stronger Than the Precious Crystal?

Diamonds can serve a lot of purposes due to their hardness. In jewelry, they can last for generations and can resist scratches from day-to-day wear. As drill bits or blades, they can penetrate almost anything without breaking. Diamonds can polish gemstones, metals, and other materials as a powder.

How Do Experts Measure Hardness?

A person wearing a diamond ring can attest to the durability of this crystal, but the concept of "hardness" means something particular to scientists. Hardness is sometimes confused with other qualities, such as stiffness or strength, but they do not always correlate.

Diamond, for instance, is tough but is only moderately stiff. It is surprisingly easy to break, shattering easily along its crystal faces. This is why gem cutters can create beautiful, multifaceted diamonds that sparkle.

Scientists, in various ways, measure hardness. Geologists rely on a comparative metric called the Mohs hardness scale, which identifies minerals in the field based on their ability to scratch each other. Diamond is at the top of the scale at 10, meaning it can scratch almost anything.

In the laboratory, materials scientists rely on a more precise measurement known as the Vickers hardness test. It determines the hardness of a material based on the force needed to indent it with a pointy tip.

Is There Anything Harder Than a Diamond?

Diamond comprises carbon atoms arranged in a cubic lattice and held together by short, strong chemical bonds. This lattice structure is responsible for the famous hardness of the crystal. Most materials that claim to be more complex than diamonds resulted from slightly changing the classic diamond crystal structure or swapping out some carbon atoms with those of boron or nitrogen.

A major contender for a material that is harder than diamond is lonsdaleite. Like diamonds, this material is made of carbon atoms but arranged into a hexagonal crystal structure instead of a cubic pattern.

Geochemist Paul Asimow from the California Institute of Technology described lonsdaleite as puzzling. It used to be found in tiny quantities, usually inside meteorites, and it was not clear if it was counted as a stand-alone material or just a defect in the standard diamond crystal structure.

Recently, a team of scientists has found micron-sized lonsdaleite crystals in meteorites. Although it is very tiny, it is much bigger than the previous finds, giving more credibility to the mineral. Other scientists have also reported creating lonsdaleite in the laboratory, but it existed for only a fraction of a second.

Lonsdaleite might be intriguing, but it won't replace diamond for applications such as polishing, drilling, and cutting anytime soon. Meanwhile, in its many forms, the diamond still rules the roost regarding hardness, but it might face other challenges in holding its record. Most scientists are not pursuing superhard materials just to set records; they are trying to create something useful.