A diamond’s clarity is formed over the course of millions of years, deep underground as heat, pressure and volcanic forces shape the carbon atoms into diamonds as we know them.
A human cannot alter clarity, they can merely grade it — typically by inspecting it under 10 power magnification. This process allows the grader to see any blemishes or “inclusions” in the stone, determining its grade. A flawless diamond is the most rare, showing no internal flaws or external inclusions. The fewer the inclusions, the more valuable the diamond.
FL: Flawless. No internal or external inclusions or blemishes.
IF: Internally flawless. No inclusions, only insignificant blemishes.
VVS1/2: Minuscule inclusions, impossible to see with the naked eye and very difficult to see with 10x magnification.
VS1/2: Minor inclusions, that are impossible to see with the naked eye and somewhat difficult to see with 10x magnification.
SI1/2: Small, but noticeable inclusions that are clear with 10x magnification and may also be noticeable to the human eye
I1/2/3: Imperfect. Obvious inclusions that can be seen with the naked eye.
The number after the clarity grade refers to the number, size, nature and position of inclusions. Lower numbers are smaller, whiter and located on the outer parts of the diamond, which makes them harder to see and the diamond more valuable.