The clarity of a diamond is determined by its quantity of inclusions and blemishes. Because diamonds are produced as a result of carbon’s exposure to the heat and pressure deep inside the earth, some damage is bound to occur. Damage on the inside of the diamond is called an inclusion, where damage on the surface of the diamond is called a blemish. A diamond’s clarity is graded then by its number of imperfections, the size of them, their relief, nature, and position. How they impact the stone’s appearance factors into a diamond’s grade.
Inclusions are caused during the formation of a diamond. Crystals get trapped inside of the diamond, and as they grow, the diamond’s atomic structure can be compromised. The less inclusions and blemishes a diamond has, the more it is worth. The growth of a diamond takes billions of years, so as one might imagine, it is extremely rare that they are mined in perfect condition. However, to the naked eye, these imperfections are often invisible. On the other hand, blemishes can be caused both by natural conditions and human interaction with the diamond. It is more often than a diamond’s blemish is caused by its external environment during the cutting and polishing stages than by natural forces during its formation. External flaws include scratches, extra facets, fracture, fingerprints, and nicks, as well as indents and carbon marks from natural causes.
As mentioned, a diamond’s clarity has five determining factors, based on its inclusions and blemishes. The first determining factor for the clarity grade of a diamond is the size of the imperfections. Overall, the bigger an inclusion or blemish, the lower score a diamond will earn on the clarity scale. This size of an imperfection is evaluated relative to the size of the stone, meaning a bigger imperfection on a smaller stone will have a greater impact. This can also impact the durability of the diamond.
The nature of an inclusion is another determining factor of a diamond’s clarity, which refers to the depth of the inclusion or blemish relative to the size of the diamond.
The number of inclusions is the third factor on which a diamond’s clarity is graded; they are judged based on their numerical occurrence as well as their visibility.
The location of imperfections also plays a role in a diamond’s clarity grade. The closer an inclusion to the center of a diamond, the more significantly the diamond is affected by it, thereby lowering its clarity grade. Inclusions close to the girdle are also problematic, though they are harder to see. If they are too close to the surface, the risk of damage increases. As well, inclusions close to the pavilion tend to affect the diamond’s ability to reflect light and can even act as mirrors, which is not ideal for a diamond’s brilliance.
When a diamond has characteristics that contrast with the the host diamond, that is called its relief. A diamond’s relief impacts its clarity grade. Depending on how much the relief is noticeable, which can include color differentiation, its grade is thereby determined.
Diamond clarity has six grades, eleven grades in total including the subgrades. The first is Flawless (FL), which means the diamond has no inclusions or blemishes at 10x magnification. This is extremely rare. The second grade is Internally Flawless (IF). An Internally Flawless diamond has no inclusions at 10x magnification, and only miniscule surface imperfections, or blemishes. A Very, Very Slightly Included (VVS) diamond has tiny inclusions that are hard to spot with 10x magnification. This category has subcategories as well. VVS1 diamonds have a higher clarity than VVS2 diamonds. Next on the clarity scale is Very Slightly Included (VS) diamonds, which have small inclusions that range from difficult to fairly easy to see under 10x magnification. Sometimes, they are even visible with no magnification. This category also has two subcategories: VS1 and VS2.
The fifth clarity grade is Slightly Included (SI), where the inclusions are noticeable, particularly to a trained grader, under 10x magnification. Two subgrades are included in this category, SI1 and SI2. The final grade is Included (I). Their inclusions are completely visible to a trained grader at 10x magnification, and are typically also easily visible without any magnification. Often, their inclusions can affect the diamond’s durability. There are three subgrades within this grade, include I1, I2, and I3. At I3 grade, inclusions are large and noticeable, affecting the diamond’s brilliance and at times putting the structure of the diamond in jeopardy.