A diamond is not indestructible, despite its reputation as the hardest natural material. While diamonds possess unparalleled resistance to scratching, they are vulnerable to specific types of damage, including chipping, fracturing, and surface alteration. This common misconception leads many owners to believe their gemstone is immune to all forms of harm. Understanding the material science behind a diamond’s durability reveals how this gemstone can be compromised, which is important for proper care and handling.
Understanding Hardness Versus Toughness
A diamond’s ability to withstand damage is governed by two distinct physical properties: hardness and toughness. Hardness refers to a material’s resistance to scratching and abrasion, where diamond excels, scoring a perfect 10 on the Mohs scale. This results from the tightly bonded arrangement of carbon atoms in its crystal structure.
Toughness describes a material’s resistance to breaking, chipping, or fracturing under impact. Diamonds are rated as moderate in this category, meaning they are relatively brittle. The vulnerability lies in the crystalline structure, which features planes of weakness known as cleavage planes.
These cleavage planes are specific directions within the crystal lattice where the atomic bonds are slightly weaker. If a diamond receives a sharp blow aligned with one of these planes, it can split cleanly. This inherent brittleness means a sudden, hard impact can easily cause damage.
Mechanical Damage Chipping and Fractures
The most common forms of severe damage result from mechanical impact that exploits the stone’s moderate toughness. A sudden, sharp force, such as knocking a ring against a hard object, can cause a chip or a fracture. Damage is especially likely to occur in areas where the diamond is thinnest or most exposed.
The girdle, the narrow perimeter dividing the top and bottom of the stone, is the area most susceptible to chipping. Vulnerable impact points also include the culet or the sharp corners of princess, marquise, or pear cuts. A chip is a shallow piece broken off the edge, while a fracture is a deeper break that does not follow a cleavage plane.
A more severe type of breakage is cleavage, where the impact force travels along one of the stone’s internal weakness planes. This action causes a clean split through the diamond, distinct from a random fracture. Diamonds containing internal flaws or inclusions are more susceptible because these imperfections act as stress points where a crack can initiate.
Surface Damage Scratches and Abrasion
While a diamond is the hardest natural substance, its surface is not entirely impervious to damage. Its Mohs 10 ranking means only another material of equal or greater hardness can leave a permanent scratch. In practical terms, only another diamond can scratch a diamond.
This surface damage frequently occurs when diamond jewelry is stored improperly, allowing two stones to rub against one another. Common materials like quartz (Mohs 7) are not hard enough to scratch the surface. However, industrial-grade abrasives utilizing ultra-hard materials can cause surface wear.
Clarity Enhancement Vulnerabilities
A different surface vulnerability is found in diamonds that have undergone clarity enhancement treatments, such as fracture filling. This involves injecting a glass-like substance into surface-reaching fractures to improve visual clarity. The filling material is much softer than the diamond and can be damaged or removed by abrasion, heat, or certain chemicals, revealing the original fracture.
Environmental and Thermal Vulnerabilities
Diamonds are chemically stable and resistant to almost all common acids. However, they are susceptible to damage from extreme temperature changes and very high heat. Thermal shock occurs when a diamond is exposed to a rapid, drastic shift in temperature, such as moving from a hot environment directly into cold water.
This rapid change causes internal stress that leads to the expansion of existing internal flaws, resulting in new fractures or cracks. Exposure to extremely high temperatures in the presence of oxygen can cause the diamond’s surface to oxidize. When heated to approximately 700° Celsius (1,292° Fahrenheit) in air, the carbon atoms on the surface convert into graphite or carbon dioxide.
This process results in a white, cloudy, or blackened, pitted appearance on the diamond’s facets. While the diamond crystal is largely unaffected by most common household cleaning agents, specific chemical vulnerabilities exist for treated stones. Harsh chemicals, particularly strong acids, can degrade or dissolve the glass-like filler material used in fracture-filled diamonds.