The visibility of a stone’s inclusions and blemishes under a tenfold magnification is the basis for grading a diamond on the clarity scale. Both inclusions and surface flaws are classified as inclusions on the GIA clarity scale.
Flawless (FL) – No inclusions or blemishes are visible to a skilled grader under 10× magnification
Internally Flawless (IF) – No inclusions; some surface flaws are visible to a skilled grader under 10× magnification
Very, Very Slightly Included (VVS1, VVS2) – Inclusions are difficult for a skilled grader to see under 10× magnification
Very Slightly Included (VS1, VS2) – Inclusions are visible under 10X× magnification but are characterized as minor
Slightly Included (SI1, SI2) – Inclusions are noticeable to a skilled grader under 10× magnification
Included (I1, I2, I3) – Inclusions are obvious under 10× magnification and may affect transparency and brilliance