The flawless grade (FL) is used to describe diamonds in which a skilled observer, under favorable lighting conditions, cannot see any inclusions or surface blemishes, after thorough examination with a binocular microscope at ten power magnification or with a 10x corrected loupe. Small extra facets on the pavilion near the girdle, not visible when viewed from above, are permitted as are small naturals when they are confined to the girdle and do not flatten the girdle outline. Internal graining is permitted provided it does not draw any color or texture and is not observable through crown.
The internally flawless grade (IF) describes diamonds which have no internal chrematistics observable under the same conditions as described, but which have minor surface blemishes that do not penetrate the stone.
Surface grain lines are permanent provided they are not too thick or numerous so as to detract from the beauty of the stone. Internal graining is permitted, provided it does not draw color or texture.
The VVS1 & VVS2 grades (VERY, VERY SLIGHTLY INCLUDED) are used to describe diamonds which have very, very small inclusions which are difficult for a skilled observer to see under the conditions as described. Colored or textured graining is permitted provided it is not observable through the crown.
The VS1 & VS2 grades (VERY, SLIGHTLY INCLUDED) are used to describe those stones with very small inclusions which can be difficult to observe under the conditions as described. Except for larger stones or occasionally with Emerald cut diamonds, these are rarely visible to the unaided eye.
The SI1, SI2 & SI3 grades (SLIGHTLY INCLUDED) are used to describe stones with small inclusions which are usually obvious when viewed under the described conditions.
The P1, P2 & P3 grades (PIQUE) are used to describe stones with medium or large inclusions (Piques) which are usually obvious to a skilled observer with the unaided eye under favorable lighting conditions.
Every diamond is unique � with its own series of internal and external characteristics. The skilled grader takes into consideration the size, nature, location and number of these characteristics to assign each stone its proper grade.