Inclusions found on a diamond can be considered nature's birthmarks, the distinguishing characteristics that make the stone unique. When grading a diamond, the amount of inclusions and blemishes has a direct impact on its clarity and value. Flawless diamonds containing no inclusions are extremely rare and very expensive. A majority of the commercially sold diamonds contains inclusions that are undetectable to the unaided eye.

A diamond's clarity rating is based on the size, number, and location of internal and external characteristics. Known as inclusions, internal characteristics include crystals, clouds, and feathers. External characteristics, or surface irregularities, are called blemishes. As most inclusions can't be seen by the naked eye, gemologists use a ten-power (10x) microscope to rate a diamond's clarity.