The GIA clarity Scale includes eleven diamond clarity grades.  The scale narrows at the top because there are very few diamonds in the higher clarity grades.

1. Flawless – A flawless diamond shows no inclusions or blemishes under 10X magnification when observed by an experienced grader.  There are only three exceptions to this rule.  A diamond can still be considered FLAWLESS if it has small extra facets on the pavilion, as long as they can’t be seen face-up.  Or it can have small naturals, as long as they are confined to the girdle and don’t distort its outline.  Or it can have internal graining, as long as it’s not reflective, whitish, or colored, and does not significantly affect the diamond’s transparency.
2. Internally Flawless (IF) – An IF diamond shows no inclusions when examined by an experienced grader using 10X magnification.  It does, however, have some minor blemishes, such as surface grain lines, naturals, and extra facets.  Except for surface grain lines, the blemishes can often be removed by having the diamond repolished.  This increases an IF diamond’s clarity grade to Flawless, but it’s rarely done.  Flawless and IF diamonds are extremely rare.  You will hardly ever see one in a jewelry store.
3. Very Very Slightly Included (VVS1 and VVS2) – VVS diamonds contain minute inclusions that are difficult even for experienced graders to see under 10X magnification.  In VVS1, they are extremely difficult to see in the face-up view, or small and shallow enough to be removed by minor repolishing.  In VVS2, they are very difficult to see.  They might be pinpoints, tiny feathers, internal graining, a bearded girdle, or tiny cavities.
4. Very Slightly Included (VS1 and VS2) – VS diamonds contain small or minor inclusions observed with effort under 10X magnification.  VS diamonds typically have small included crystals, small clouds, or small feathers. Because of the rarity of Flawless and Internally Flawless diamonds, the highest grades carried by most fine retail stores are in the VVS to VS ranges.
5. Slightly Included (SI1 and SI2) – SI diamonds contain inclusions that are noticeable to an experienced grader under 10X magnification.  Typically, these are clouds, included in crystals, knots, cavities, and feathers.
6. Included (I1, I2 and I3) – Diamonds that fall in the I range contain inclusions that are obvious under 10X magnification.  They might contain large feathers or large included crystals.  In some cases the inclusions affect transparency and brilliance. There is certainly a market for I1 and I2 diamonds, and they’re carried in many retail stores.  They are especially attractive to someone who wants the largest stone possible and is willing to compromise on clarity to get it.  Diamonds in the I3 category are less popular.  They often lack transparency and durability.

INTERNATIONAL CLARITY TERMS