Clarity, the second of the 4 Cs, measures the absence of unique birthmarks found within each stone. Birthmarks located internally are referred to as inclusions, while those that reach a diamonds external surface are called blemishes. The GIA clarity scale is as follows:
Flawless (FL) - No birthmarks are visible under 10x magnification. Stones falling under this classification are exceptionally rare!
Internally Flawless (IF) - Only blemishes, not inclusions, are visible under 10x magnification.
Very, Very Slightly Included (VVS1 and VVS2) - Birthmarks are difficult for a skilled grader to see under 10x magnification
Very Slightly Included (VS1 and VS2) - Birthmarks can be identified under 10x magnification with effort, but are characterized as minor
Slightly Included (SI1 and SI2) - Birthmarks are noticeable under 10x magnification
Included (I1, I2, and I3) - Inclusions are obvious under 10x magnification and may affect transparency and brilliance