What Determines A Diamond's Clarity Grade

Author Sue Davidson, G.G.
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Date Oct 24, 2014

What Determines A Diamond's Clarity GradeWhen it comes time to buy a diamond, clarity is one of the all-important "four Cs" you should be paying attention to. But, there are a lot of factors that go into determining a diamond's clarity grade.

In the GIA (i.e., Gemological Institute of America) diamond grading system, clarity is measured based on five factors: the number, size, position, color or relief, and nature of a diamond’s characteristics.

To many people the characteristics inside the diamond are thought of as flaws, but sometimes it is easy to forget that they first came from nature. The characteristics formed within the diamonds become identifiers, like a birthmark, and no two diamonds are the same because they have different characteristics that make each one unique.

The characteristics of a diamond are divided into two categories. Characteristics inside a diamond are called inclusions and characteristics on the outside of a diamond are known as blemishes.

Most people might assume that clarity grading is strictly based on the amount of inclusions in a diamond. The number of inclusions is very important but there are other factors that can easily shift the grade. Find out exactly what goes into determining a diamond's clarity score according to GIA:

Clarity Grading Considerations

All grades reflect the appearance to an experienced grader when viewed at 10X magnification, though viewing from othe angles are used during the grading process.

The grader studies the diamond for internal characteristics and judges them on the basis of the five grading factors: size, number, position, nature and color or relief.

Accurate clarity grading must be done with a “loose” diamond (a diamond not set in a mounting).

GIA 4Cs Clarity

The GIA Clarity Scale contains 11 grades with most diamonds falling into the VS (very slightly included) or SI (slightly included) categories. In determining a clarity grade, the GIA system considers the size, nature, position, color or relief, and quantity of clarity characteristics visible under 10× magnification.

  • Flawless (FL) - No inclusions or blemishes are visible to a skilled grader using 10× magnification
  • Internally Flawless (IF) - No inclusions and only blemishes are visible to a skilled grader using 10× magnification
  • Very, Very Slightly Included (VVS1 and VVS2) - Inclusions are difficult for a skilled grader to see under 10× magnification
  • Very Slightly Included (VS1 and VS2) - Inclusions are minor and range from difficult to somewhat easy for a skilled grader to see under 10x magnification
  • Slightly Included (SI1 and SI2) - Inclusions are noticeable to a skilled grader under 10x magnification
  • Included (I1, I2, and I3) - Inclusions are obvious under 10× magnification and may affect transparency and brilliance

What Determines A Diamond's Clarity Grade

Size

The first clarity factor which is assessed is a clarity characteristic's size. Larger characteristics are typically more noticeable under magnification, thereby placing the diamond into a lower clarity grade.

Number

The second clarity factor which is assessed is the number of clarity characteristics. Generally, the more characteristics, the lower the clarity grade. This assessment is made by judging how readily they can be seen, not by the actual number of characteristics.

Position

The third clarity factor which is assessed is the characteristic's position. When an inclusion is directly under the table of the diamond, it is most visible. An inclusion under the table and positioned close to a pavilion facet will reflect multiple times around the stone, giving this type of inclusion the name "reflector."

Nature

The fourth clarity factor which is assessed is a characteristic's nature. The characteristic's nature determines whether it is internal (extending into the stone) or external (limited to the surface of the stone). Internal characteristics automatically exclude the diamond from the Flawless and Internally Flawless categories. External characteristics exclude the diamond from the Flawless category.

Color or Relief

The fifth clarity factor which is assessed is the color and relief of clarity characteristics. Characteristics that contrast the grade the most, when color tone is involved with the surrounding diamond, are said to have "relief." The degree to which this color and relief is noticeable affects the clarity grade of the diamond.

Colored inclusions invariably show contrast and are more easily seen. A brown feather could be assigned a lower clarity than a white feather. A dark crystal could be graded lower than a white crystal. It is the contrast of the inclusion that will affect its grade.

The location of the inclusion(s) is critical. A dark crystal, which lies right next to the girdle (the outer edge), may be graded SI1 but the exact same crystal in the center may shift it to SI2. A white crystal in the table (the largest facet, the flat surface at the top of the stone) may be assigned SI1 grade but the exact same crystal placed deep in the pavilion (bottom half of the diamond) may have many reflections giving it an SI2 grade.

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