The clarity grade is determined by a number of factors: The size of inclusions, the number of inclusions, where the inclusions are located within the diamond, the eye visibility of the inclusions. The fewer the inclusions and the more difficult they are to see under ten power (10x) magnification, the higher the clarity grade.There are many types of inclusions that may be present within a diamond.
Blemishes refer to the exterior features of a diamond and are very small and difficult to view without the assistance of a magnifier. They generally do not affect the beauty of a diamond and are almost always located near the girdle of the diamond. For more information, see the glossary for terms such as natural, extra facet, or blemish.