These are referred to as clarity characteristics in GIA grading reports.
- Bearded Girdle (BG): Usually an effect of the cutting and manufacturing of a polished diamond, these are microscopic feathers, which start from the girdle surface and move on into the interior.
- Cavity (Cv): This imperfection appears when a fragment of the feather breaks off from the diamond. It is seen as a cavity in the form of a crack.
- Cloud (Cld): These are groupings of smaller inclusion in a single area. While hard to discern individually, clouds appear more distinct with each added inclusion in the group.
- Feather (Ftr): This is a white inclusion in the shape of a feather, which is caused by a fracture inside the diamond.
- Knot (K): This characteristic comprises a transparent diamond crystal inside the diamond, and extends to the outer surface after the primary gem has been cut and polished.