The common belief that a diamond is indestructible has been popularized through culture and marketing, giving the impression of an ultimate, unbreakable material. While diamonds are the hardest naturally occurring substance on Earth, they are not immune to damage or destruction. Although incredibly resistant to scratching, a diamond can be broken, chipped, or chemically destroyed under the right circumstances. Understanding a diamond’s vulnerabilities requires examining its physical and chemical properties beyond its celebrated hardness.
Hardness Versus Toughness
A frequent misunderstanding arises from confusing the properties of hardness and toughness in materials science. Hardness refers exclusively to a material’s resistance to scratching or abrasion, a quality where diamond excels with a perfect score of 10 on the Mohs scale. This extreme hardness is why only another diamond can scratch its surface, allowing it to maintain its brilliant polish over time. Toughness, however, measures a material’s resistance to fracturing, chipping, or breaking from a sharp impact or sudden blow.
The diamond’s crystalline lattice structure of carbon atoms makes it highly brittle, giving it only moderate toughness. This explains why an item like a steel beam, which is much softer than a diamond, is far tougher and will bend instead of shatter upon impact. Therefore, while a diamond is the hardest natural substance, it is not the toughest, leaving it susceptible to structural failure.
How Diamonds Mechanically Fail
A diamond’s internal crystalline structure contains specific directions of weakness, known as cleavage planes. These planes are areas where the bonds between the carbon atoms are slightly weaker than in other directions. A sharp, sudden force or impact delivered precisely along one of these cleavage planes can cause the diamond to split cleanly.
This vulnerability to cleavage is the principle that diamond cutters use to shape rough stones, applying a controlled blow to split the diamond rather than grinding away the material. If a finished diamond is struck sharply, perhaps by being dropped on a hard surface or knocked against a metal object, it can fracture along one of these inherent weak points. Damage is particularly likely to occur near vulnerable areas like the sharp edges of a princess-cut stone or the thin girdle that encircles the diamond.
Destruction by Extreme Heat
Beyond mechanical impact, a diamond can also be destroyed through chemical transformation involving extreme heat. Diamonds are composed entirely of pure carbon, which, like coal or wood, is combustible when exposed to sufficient heat and oxygen. When heated to high temperatures, the diamond does not melt but instead undergoes oxidation, effectively burning away.
This process can begin when the diamond is exposed to temperatures around 1,292°F (700°C) in an oxygen-rich environment. At higher temperatures, such as those found in an intense house fire, which can reach 2,000°F (1,100°C), the carbon atoms in the diamond react with the oxygen. The diamond essentially turns into carbon dioxide gas. If the stone was flawless, no residue is left behind, though impurities may result in a small amount of ash.