Diamonds are often believed to be completely indestructible, leading to questions about testing their limits. They are the hardest natural substance known, granting them unparalleled resistance to surface wear and scratching. However, determining if a diamond can be broken requires distinguishing between the different types of strength a material possesses. The answer depends on the physics of how force is applied to the diamond’s unique atomic structure, not the tool used.
Hardness Is Not the Same as Toughness
The diamond’s reputation for strength stems from its exceptional hardness, which is its ability to resist abrasion or scratching. This property is measured on the Mohs scale of mineral hardness, where diamond occupies the top rank of 10. The dense, tetrahedral bonding of carbon atoms makes it virtually impossible for other natural substances to scratch a diamond’s surface.
Toughness, conversely, describes a material’s resistance to fracturing, chipping, or breaking when subjected to impact. While diamonds are the hardest material, they possess only moderate toughness, classifying them as brittle. This means a diamond is resistant to scratching but vulnerable to shattering under a sudden, sharp blow. This difference is similar to glass, which resists scratching but shatters easily when struck.
The Diamond’s Internal Weak Points
The vulnerability of a diamond is rooted in its highly ordered internal structure. Although the carbon atoms are bonded in a repeating cubic lattice, the strength of these bonds is not uniform in every direction. Along specific planes within the crystal, the atomic bonds are slightly weaker than the surrounding structure.
These planes of comparative weakness are known as cleavage planes. When a diamond receives a sharp impact aligned with one of these planes, the force can overcome the weaker bonds, causing the stone to split cleanly. Diamond cutters exploit this phenomenon, using a precise strike to cleave a rough stone along a cleavage plane before faceting.
A diamond typically has four directions of perfect cleavage. Breaking a diamond is not a matter of applying immense force randomly. Instead, it requires a precise, localized force that targets the inherent weakness in the crystal structure.
Why Standard Pliers Fail to Break a Diamond
Standard handheld pliers are designed to apply a crushing or compression force, not a sharp, precise impact. When the jaws of the pliers close on a diamond, the force is distributed across the contact area. This distributed pressure means the force is unlikely to be concentrated enough to initiate a fracture along a microscopic cleavage plane.
Breaking a diamond through pure compression requires an astronomical amount of pressure, far exceeding what a person can generate with hand tools. The diamond’s bulk strength is immense when the force is spread out, allowing it to resist crushing. Pliers cannot generate the necessary localized pressure or the specific sharp energy needed to exploit the diamond’s inherent brittleness. The steel of the pliers would likely deform or break before the diamond does.
Real-World Ways Diamonds Get Damaged
In everyday life, diamonds are damaged by accidental sharp impacts that exploit their cleavage planes, not by crushing. Chipping usually occurs when a diamond’s girdle (the thin edge separating the crown from the pavilion) or a pointed tip strikes a hard surface. An accidental blow against a car door frame or a metal countertop can deliver the sharp, localized energy needed to cause a fracture.
Jewelers must exercise caution when setting diamonds, as applying too much localized pressure or striking the stone from a certain angle can cause chipping. Damage in a setting is often the result of an unintended impact directed precisely onto a vulnerable point. Diamond professionals intentionally cleave stones using a small, sharp hammer and a specialized tool. This highlights that precise application of impact force, not simple pressure, causes a break.