Inclusions are sometimes called flaws by uninitiated, but they are more appropriately known as the natural identifying characteristics found within the mass of nearly every diamond. These characteristics can take on a variety of forms. The chart below includes many and the way they are represented or plotted on lab certificates. On most certificates, inclusions shown colored green are external, that is, on the surface of the diamond. Those drawn in red are internal inclusions.

Feather Surface Graining Crystal Pinpoint Polishing Mark Natural Cloud Nick Cavity Chip Feather Outline Extra Facet Scratch Knot Internal Graining Misc.

The existence of inclusions in the diamond and their number does affect its value. Simply put, the greater the amount of inclusions (or the more defacing the inclusions) the diamond bears, the lower it will rank on the clarity scale. Corresponding to that ranking, its value is diminished by its inclusions.

Bear in mind that the inclusions indicated by clarity grades from flawless to SI-1 are impossible to detect with the unaided eye. But contrary to popular belief, not always are less-included diamonds the more attractive, since diamond color, symmetry and cut influence appearance too.