Clarity Grading of Diamonds

Clarity is one of the 4Cs, the most commonly used attributes to evaluate and price diamonds. It describes how "clean" a diamond is and of the 4Cs is the most complex one. Most diamonds found in nature come with inclusions, defects or any other kind of defects and this in turn affects the diamond's appearance.

To determine the clarity grade of a diamond, a skilled grader is examining the stone under a loupe with 10x magnification. A microscope with higher magnification may be used to find very tiny inclusions but this is only done to aid the grader in finding the areas that need closer inspection. Ultimately, only blemishes that are detectable under 10x magnification are treated as inclusions – anything smaller is discarded. In other words, a "flawless" diamond may as well have inclusions when viewed under higher magnification but they are considered to be too small to affect the diamond's appearance.

On a diamond grading report, the locality and the kind of the inclusion is marked. Inclusions come in many forms and appearances and may look like a bubble, an aglomeration of tiny bubbles, feathers, clouds, cracks, included crystals, etc., to name a few.

The higher the clarity of a diamond – and thus the less visible the inclusions are – the more valuable a diamond is, all other factors being equal. In case of the lowest grades, the inclusions may be so pronounced, that they not only affect the appearance but also the durability of a diamond: A knock on it which would not harm any other diamond can fracture it.

Once grading is completed, a diamond is given its clarity grade. Most commonly used is the grading system by the GIA, the Gemological Institue of America. Other grading scales are very similar in nature and differences are often minuscule. Its scale with a short explanation of each grade is given in the following table:

FLFlawlessNo inclusions or blemishes are visible to an experienced grader under 10x magnification.
Diamonds of this grade are extremely rare.
IFInternally flawlessNo internal flaws are visible to an experienced grader under 10x magnification, but surface blemishes can be detected.
VVS1 & VVS2Very, very slightly includedInvisible by the naked eye and only visible under 10x magnification by a skilled grader.
VVS1 inclusions are normally only detectable from the pavilion whereas VVS2 are seen from the crown.
VS1 & VS2Very slightly includedMinor inclusions that are normally not visible to the naked eye. Only very few untrained examiners may detect a VS2 inclusion under ideal conditions.
S1 & S2Slightly IncludedSI1 is the lowest grade for which inclusions are not visible to the unaided eye under less than perfect conditions.
SI2 inclusions can be seen without a loupe but require careful observation.
I1, I2 & I3IncludedI1 inclusions are almost always visible to the unaided eye. I2 and I3 inclusions are pronounced and in the case of I3 the inclusions can be so severe that the diamond's durability may be affected.

An other, very similar scale comes from the CIBJO (International Confederation of Jewellery Silverware and Diamonds). Both scales are essentially identical, the differences are that the CIBJO does not sub-divide the VVS, VS and SI grades for diamonds under 0.47 carats, both FL and IF grades are called "loupe clean" and the lowest three grades use the letter 'P' instead of 'I', with the 'P' standing for Piqué which is French for "picked".

Further scales were developed by AGS (American Gem Society) using numbers ranging from 0 (flawless) to 10 (included); IDC (International Diamond Council) with a shifted scale to GIA (IF being VVS1, VVS1 being VVS2 and so on); EGL (European Gemological Laboraty) which has the addition of a SI3 grade but otherwise being nearly identical to the GIA scale.

As can be seen above, some of the grade do not differentiate between flawless (FL) and internally flawless (IF) grades. A diamond with an assigned IF grade is a rather superficial grade as such diamonds only have minor blemishes on the surface, for example tiny parallel streaks that come from polishing. In most cases, an IF diamond can be re-polished to achieve the desirable FL grade, whereas any other internal inclusions can not be eliminated without altering the diamond itself.

Any internal inclusions can be removed by re-cutting the stone, subjecting it to treatment or mechanical / chemical removal of the inclusions. All of these methods will either lower the diamond's total weight, introduce other imperfections like a tiny channel in case of laser drilling or reducing a diamond's value due to it being subjected to a treatment process and not being considered purely natural any longer. However, removal of some disturbing inclusions can enhance the diamond's beauty and thus value and re-cutting is an other option that can be considered: A smaller but perfect stone is worth more than a bigger one with unpleasant looks.

We hope that this short introduction to diamond grading provides you with an useful insight. By now, you most likely can appreciate the complexity and care that must be taken when grading a diamond for its clarity.

Further Reading

Grading a diamond for its clarity is one of the 4Cs. Learn more about the other three or go back to the overview of what the 4Cs are by following the links in the list below: