- F
Flawless: No internal or external flaws. Extremely rare. - IF
Internally Flawless: no internal flaws, but some surface flaws. Very rare. - VVS1-VVS2
Very Very Slightly Included (two grades). Minute inclusions very difficult to detect under 10x magnification by a trained gemologist. - VS1-VS2
Very Slightly Included (two grades). Minute inclusions seen only with difficulty under 10x magnification. - SI1-SI2
Slightly Included (two grades). Minute inclusions more easily detected under 10x magnification. - I1-I2-I3
Included (three grades). Inclusions visible under 10x magnification AS WELL AS to the human eye. We do not recommend buying diamonds in any of these grades.
F-IF | VVS1-VVS2 | VS1-VS2 | SI1-SI2 | I1-I2-I3 |
While the presence of these clarity characteristics (inclusions and blemishes) do lower the clarity grade of a diamond, they can also be viewed as proof of a diamond's identity. GIA certificates include what is known as a "plot" of a diamond's inclusions -- think of it as a "diamond fingerprint." Since no two diamonds are exactly the same, comparing the uniqueness of your diamond's clarity characteristics with the plot provided on the diamond certificate offers assurance that the diamond you pay for is the same diamond you receive.
Source: thediamondbuyingguide.com