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.
Under 10x magnification, inclusions are not visible, rarest clarity grade
FL: No visible blemishes, < 1% of diamonds
IF: Very slight blemishes, < 3% of diamonds
Under 10x magnification, inclusions are so small, it is difficult to see.
VVS1: Inclusions in bottom-half, pavilion
VVS2: Inclusions in top-half, crown
Under 10x magnification, inclusions are minor, slightly visible.
VS1: Slightly less inclusions than VS2
VS2: Slightly more inclusions than VS1
Under 10x magnification, inclusions are noted, more visible
SI1: Inclusions possibly invisible to the eye
SI2: Inclusions often visible to the eye
Under 10x magnification, inclusions are obvious, visible to the eye
I1: Grade loose diamond are not offered by Buyfinediamonds