The 4 Cs

colour
clarity
cut
carat weight

Diamond professionals use these four factors to describe and classify diamonds. When taken together, they help in evaluating the finished diamonds you buy. That's why they are often called value factors. This page considers clarity.

You may wish to view the excellent tutorial on the Gemological Institute of America web site titled How to Buy A Diamond

clarity

Few things in nature are absolutely perfect. This is as true of diamonds as anything else. Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, they’re called clarity characteristics. Clarity is the relative absence of clarity characteristics. Blemishes include scratches and nicks on a diamond’s surface. Inclusions are on the inside (some might break the surface of the stone, but they are still considered inclusions). Sometimes, tiny diamond or other mineral crystals are trapped inside a diamond when it forms. Depending on where they’re located, they might still be there after the stone has been cut and polished.

Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, they're called clarity characteristics. A clarity grade is determined by the relative absence of clarity characteristics.

Clarity Scale  
Flawless (FL): no blemishes or inclusions when examined by a skilled grader under 10X magnification.
Internally Flawless (IF): no inclusions when examined by a skilled grader, and only insignificant blemishes under 10X.
Very Very Slightly Included (VVS1 and VVS2): contain minute inclusions that are difficult for even a skilled grader to locate under 10X. VVS1: extremely difficult to see, visible only from the pavilion or small and shallow enough to be removed by minor re-polishing. VVS2: very difficult to see.
Very Slightly Included (VS1 and VS2): contain minor inclusions ranging from difficult (VS1) to somewhat easy (VS2) for a trained grader to see under 10X.
Slightly Included (SI1 and SI2): contain noticeable inclusions which are easy (SI1) or very easy (SI2) to see under 10X. In some SIs, inclusions can be seen with the unaided eye.
Included (I1, I2, I3): contain inclusions which are obvious to a trained grader under 10X, can often be easily seen face-up with the unaided eye, seriously affect the stone's potential durability, or are so numerous they affect transparency and brilliance.