Diamond Clarity

Almost all diamonds contain minuscule natural birthmarks called inclusions. To determine the clarity of a diamond, an expert examines it under a 10-power magnification. The conventional clarity scale is comprised of 11 grades. The top 6 grades have no flaws that can be detected with the unaided human eye. That is to say, a flawless diamond is no more beautiful to the naked eye than a grade in the middle of the scale. Extremely subtle differences in clarity are very important in determining the rarity of a diamond, but they affect the overall beauty of a diamond only when the clarity measured is in the very low end of the scale.

Surface irregularities in diamonds are called blemishes. These two categories of imperfections - the internal inclusions and the external blemishes - make up the category of clarity for diamonds.

Several grading systems are used to describe the clarity of a diamond. The most common is the grading system of the Gemological Institute of America.
The scale of the GIA ranks diamonds as:

Flawless (FL): no inclusions are visible under a 10-time magnification.

Internally Flawless (IF): no inclusions visible under a 10-time magnification, only external blemishes are present, which can be removed by further polishing.

Very Very Slightly included (VVS1 and VVS2): very very small inclusions that are difficult to see under a 10-time magnification (by definition, if an expert can see a flaw from the top of the diamond, it is a VVS2, otherwise, if an expert can only detect flaws when viewing the bottom of the diamond, then it is a VVS1).

Very Slightly Included (VS1 and VS2): very small inclusions, which are visible under magnification, but invisible to the unaided human eye.

Slightly Imperfect (SI1 and SI2): small inclusions that are noticeable to the naked eye.

Imperfect (I1 to I3): flaws are noticeable to the naked eye.