An inclusion on a diamond is any characteristic that occurs inside the stone or on its surface that was formed during the diamond’s creation or as a result of external events. These natural fingerprints, which can appear as crystals, feathers, clouds, or even metallic reflections, are the result of the immense heat and pressure required to form carbon into diamond deep within the Earth. While the presence of these features is unavoidable in natural diamonds, their size, location, and visibility play a crucial role in determining a diamond’s beauty, durability, and value.
Understanding Diamond Inclusions
At a fundamental level, inclusions are minerals or structural irregularities trapped inside the diamond as it crystallizes. Unlike a scratch on the surface, which is a blemish, an inclusion exists within the material itself. Gemologists view these features not as defects to be eliminated at all costs, but as natural identifiers and indicators of the diamond’s authenticity. Every natural diamond is unique, and its inclusion pattern is as individual as a fingerprint, making it a primary tool for verification and grading.
Types of Inclusions and Their Impact
The specific type of inclusion dictates how it affects the diamond’s appearance and structural integrity. Some inclusions are benign and have minimal visual impact, while others can significantly alter the way light travels through the stone.
Crystals: These are tiny diamonds or other mineral crystals trapped inside the host diamond. While often transparent, they can sometimes be dark or opaque, creating visible spots.
Feathers: These are tiny cracks or fractures that resemble white wisps or feathers. Depending on their size and location, feathers can compromise the diamond’s durability, especially if they extend to the surface.
Clouds: A cluster of tiny inclusions that can create a hazy or milky area within the diamond. A single tiny cloud is usually invisible to the naked eye, but a large "cloudy" inclusion can diffuse light and reduce sparkle.
Cavities: These are openings on the surface of the diamond that often extend from an inclusion. They can trap oil and dirt, making them appear darker and more noticeable.
The Role of Location
Where an inclusion is located is just as important as what it is. An inclusion positioned directly under the table facet of the diamond, the large flat top surface, will be highly visible and can act as a light barrier, reducing the stone’s brilliance. Conversely, an inclusion located near the girdle—the outer edge—or on the side facets might be easily hidden by the setting or be less detrimental to the light performance. In some cases, skilled cutters may strategically position inclusions to minimize their visual impact.
Inclusions and the Clarity Grade
The diamond grading industry, led by organizations such as the Gemological Institute of America (GIA), has established a clarity scale to standardize the assessment of these internal characteristics. This scale ranges from Flawless (FL), meaning no inclusions or blemishes are visible under 10x magnification, to Included (I), where inclusions are obvious to the naked eye and may affect durability.
