Diamonds that are absolutely clear are the most sought-after and therefore the most expensive. But many diamonds have inclusions — scratches, trace minerals, or other tiny characteristics that can detract from the pure beauty of the diamond. The fewer and smaller the inclusions are, the less likely it is that they will interfere with the passage of light through the diamond, and the more beautiful the diamond will be. The Gemological Institute of America (GIA) uses a detailed system of rules and standards to summarize the number, location, size, and type of inclusions present in a diamond.
FL, IF Diamonds: Flawless: No internal or external flaws. Internally Flawless: No internal flaws. Very rare and beautiful diamonds.
VVS1, VVS2 Diamonds: Very, Very Slightly Included: Very difficult to see inclusions under 10x magnification. An excellent quality diamond.
VS1, VS2 Diamonds: Very Slightly Included: Inclusions are not typically visible to the unaided eye. Less expensive than the VVS1 or VVS2 grades.
SI1, SI2 Diamonds: Slightly Included: Inclusions are visible under 10x magnification, and may be visible with the unaided eye. A good diamond value.
I1, I2, I3 Diamonds: Imperfect: Inclusions are visible to the naked eye.