Clarity Grading Philosophy
Clarity grading determines the relative visibility of the inclusions in a diamond and their impact on the overall visual appearance. The importance of clarity in diamond value originates from the notion that as diamond clarity improves, diamonds increase in rarity.
The Clarity Grading Scale
The AGS Laboratories’ reports come with both numeric and verbal descriptors for clarity. The numeric grade corresponds to the AGS Diamond Grading Standards of a 0 to 10 scale, decreasing in clarity as the number grade increases. The verbal descriptors are the industry accepted method of communicating diamond clarity, and AGSL lists grades numerically on our reports while also indicating the corresponding industry standard descriptors:
Flawless/Internally Flawless (0 or 0*)
Flawless and Internally Flawless diamonds contain no internal inclusions when examined by a skilled grader under 10x magnification and in a proper gemological environment. An Internally Flawless diamond may have minor blemishes (marks and features confined to the surface only).
Very Very Slightly Included (1 or 2)
A diamond with a clarity grade of 1 or 2 (VVS1 or VVS2) has minute inclusions that are difficult for a skilled grader to see under 10x magnification.
Very Slightly Included (3 or 4)
Very Slightly Included diamonds with a clarity grade of 3 or 4 (VS1 or VS2) have minor inclusions.
Slightly Included (5 or 6)
Slightly Included diamonds with a clarity grade of 5 or 6 (SI1 or SI2) have noticeable inclusions that are fairly easy to see under 10x magnification. Sometimes, these inclusions can be visible to the unaided eye.
Included (7, 8, 9, or 10)
Included diamonds with a clarity grade of 7, 8, 9, or 10 (I1, I2, or I3), have inclusions that are obvious at 10x magnification. Inclusions can also be obvious to the unaided eye, and at the lower clarities, may have an effect on the diamond’s durability.
The purpose of plotting the inclusions of a diamond is to justify the clarity grade, and to identify the stone at a later date. There is a specific sequence that determines which clarity features are plotted or mentioned as a comment on the report. Plotting is dependent upon the overall clarity of the diamond and the nature of the inclusions.
Read More About The Plot
How Clarity Grades Are Determined
Overall clarity determinations are balanced between the diamond’s appearance face up in the loupe, the microscope at 10x, and eye visibility. Higher power is used to identify inclusions that are otherwise difficult to determine at 10x, which can often include VVS inclusions, however, the final grade is always determined at 10x, in four directions. Factors that graders consider when determining a clarity grade include the size, nature, number, location, and relief of the inclusions. A diamond receives multiple opinions on the clarity grades it receives, so there is a consensus among expert graders as to what the appropriate grade should be. AGSL also has implemented quality control mechanisms to ensure consistency in the diamond grading process.
Diamond Grading Factors
There are five factors that affect how clarity is determined in a diamond, and how inclusions are considered; size, nature, number, location, and relief.
Generally, the larger the inclusion, the greater the impact on the clarity grade. If inclusions are large enough, they can also impact the durability of the stone. The inclusions with the largest impact on the clarity of the diamond and determine the grade are called “grade setters”. Also, the size of the inclusions and their cumulative effect are considered relative to the size of the stone.
The nature of an inclusion refers to the type of inclusion it is, and its relative superficiality or depth. Internal characteristics or characteristics that penetrate with depth into the diamond are called inclusions, and features confined to the surface of the diamond that don’t penetrate into the depth are called blemishes. Inclusions that can have an impact on the durability of the diamond are also considered.
For the most part, the greater the number of clarity characteristics, the lower the clarity grade. However, inclusions are not always judged on the number, but on how readily they are visible.
Location is the position of the inclusion/blemish in the diamond. Inclusions closer to the center of the table tend to have a greater impact on the clarity. Inclusions closer to the girdle (further from the table) are generally more difficult to see, and if they are surface reaching may be at risk for damage. Inclusions that are positioned near the pavilion have the potential to reflect, as the pavilion facets can act as mirrors, reflecting the image of the inclusion. Inclusions that are visible when focusing past the culet have less impact on the clarity grade. In addition, the shape, cutting proportions, and facet arrangement can affect clarity grade by obscuring or emphasizing clarity features.
Relief refers to the distinctness of the inclusion in contrast to the host diamond. The greater the relief, the greater the effect on the overall clarity grade.