Diamond clarity refers to the absence of these inclusions and blemishes. Diamonds without these birthmarks are rare, and rarity affects a diamond’s value. Using the GIA International Diamond Grading System™, diamonds are assigned a clarity grade that ranges from flawless (FL) to diamonds with obvious inclusions (I3).
Because diamonds formed deep within the earth, under extreme heat and pressure, they often contain unique birthmarks, either internal (inclusions) or external (blemishes).
Every diamond is unique. None is absolutely perfect under 10× magnification, though some come close. Known as Flawless diamonds, these are exceptionally rare. Most jewellers have never even seen one.
The GIA Clarity Scale contains 11 grades, with most diamonds falling into the VS (very slightly included) or SI (slightly included) categories. In determining a clarity grade, the GIA system considers the size, nature, position, colour or relief, and quantity of clarity characteristics visible under 10× magnification.
Like the colour scale, GIA’s clarity grading system developed because jewellers were using terms that were easily misinterpreted, such as "loupe clean," or "piqué." Today, even if you buy a diamond in another part of the world, the jeweller will likely use terms such as VVS1 or SI2, even if her language is French or Japanese instead of English.