The diamond holds a long-standing reputation as the hardest natural material found on Earth, a fact often interpreted to mean it is indestructible. This perception of ultimate strength stems from its unique atomic structure, which makes it nearly immune to scratching. However, the true measure of a diamond’s resilience involves more than just its scratch resistance. Understanding a diamond’s durability requires separating its remarkable hardness from a different property called toughness. The distinction between these two physical attributes determines how well a diamond survives the wear and tear of daily life.
Defining Hardness Versus Toughness
Hardness describes a material’s resistance to permanent deformation, specifically scratching or abrasion on its surface. Diamonds score the maximum 10 on the Mohs scale of mineral hardness, meaning no other naturally occurring substance can scratch a diamond. This exceptional property allows diamonds to retain their polish and sparkle over long periods, making them ideal for daily wear in jewelry.
Toughness measures a material’s ability to resist breaking, chipping, or fracturing when subjected to a sudden impact or sharp blow. This property relates to the energy a material can absorb before rupturing. Despite their supreme hardness, diamonds exhibit only moderate toughness compared to some other gemstones. For example, glass is hard but brittle, while steel is softer but tough and will bend rather than shatter.
The moderate toughness of diamond means that while its surface resists abrasion, the stone is still susceptible to structural damage. If a diamond is struck with sufficient force and at the right angle, it can chip or cleave. The material is considered brittle, a characteristic separate from its inability to be scratched. This combination of extreme hardness and comparative brittleness defines the diamond’s durability profile.
The Crystal Structure and Cleavage
A diamond’s hardness originates from its internal structure, a dense, three-dimensional lattice of carbon atoms. Each carbon atom is bonded to four others by strong covalent bonds, creating a rigid network that is difficult to disrupt. This uniform structure resists scratching or abrasion.
However, this crystalline perfection introduces planes of relative weakness known as cleavage planes. These planes are directions within the crystal where the atomic bonds are slightly less interconnected. In a diamond, these weaker paths follow the faces of an octahedron, meaning there are four perfect cleavage directions.
When a diamond receives a sharp, focused blow, particularly along one of these cleavage planes, the energy of the impact can be channeled along the weaker bonds. This allows the diamond to split, or cleave, relatively smoothly, resulting in a chip or fracture. This structural vulnerability is the primary reason why a diamond is not unbreakable.
Factors That Can Damage a Diamond
The primary threat to a diamond is mechanical impact, particularly the type that exploits the stone’s inherent cleavage planes. A direct hit to a vulnerable point, such as a thin girdle edge, a pointed culet, or a sharp corner on a fancy shape like a princess or marquise cut, can cause chipping. This damage is a structural failure along the weaker bond lines within the crystal, not scratching.
Another significant threat is high heat exposure, as diamonds are chemically stable but not inert. If a diamond is heated to approximately 1,562 degrees Fahrenheit (850 degrees Celsius) in the presence of oxygen, it will begin to oxidize, effectively burning away. While typical household heat exposure is not a concern, extreme heat sources, such as those used in jewelry repair or house fires, can cause the diamond to turn white, blacken, or even transform back into graphite.
While a pure diamond is chemically resistant to nearly all common household acids and cleaners, the metal setting is not. Harsh chemicals like chlorine bleach or abrasive cleaning powders can corrode gold and other alloys, weakening the prongs that hold the stone secure. Even mild chemicals like soap and lotion can leave a film on the diamond’s surface, dulling its brilliance.
Everyday Care and Practical Durability
Protecting a diamond involves mitigating the risks associated with its moderate toughness and structural vulnerabilities. Selecting a secure setting style can significantly enhance practical durability; for example, a bezel setting fully encircles the girdle, offering maximum protection to the stone’s edges. V-shaped prongs are often employed to guard the sharp corners of stones like princess cuts, which are susceptible to impact.
Safe storage prevents the one substance capable of scratching a diamond from causing harm: other diamonds. Since diamonds can easily scratch each other, storing them separately in a fabric-lined box or soft pouch is prudent. This practice also prevents diamonds from scratching other softer gemstone jewelry.
Routine cleaning is a simple way to maintain the stone’s appearance and security. A mixture of warm water and mild dish soap, applied with a soft toothbrush, can remove the oils and grime that dull a diamond’s sparkle. Regular professional inspections should also be scheduled to ensure the metal prongs remain tight, preventing the stone from loosening or falling out.