A diamond is distinguished by its natural characteristics, just as a person would be noted for her blue eyes or his brown hair. Notated as a diamond's clarity, these characteristics can be present on the surface (blemishes) or within the stone (inclusions). The clarity is judged by the number and types of these characteristics and is designated using a scale that runs from Fl, defined as flawless, to I3, defined as inclusions visible with the naked eye. A flawless diamond is truly rare.
Flawless: No internal or external flaws.
Internally Flawless: No internal flaws.
VVS1, VVS2 Diamonds
Very, Very Slightly included: Very difficult to see inclusions with 10x magnification.
VS1, VS2 Diamonds
Very Slightly Included: Inclusions are visible under 10x magnification to a skilled grader.
SI1, SI2 Diamonds
Slightly Included: Inclusions are visible under 10x magnification and may be visible with the unaided eye.
I1, I2, I3 Diamonds
Included: Inclusions are visible with the unaided eye.