Clarity refers to the purity of the diamonds, or to the degree to which it is free of blemishes and imperfections. In principal, as the clarity of the diamond increases, its value is enhanced.
The clarity of a polished diamond is affected by both external blemishes and internal imperfections or inclusions, some of which were created in nature when the diamond was formed and others during the cutting and polishing process. Internal inclusions include piqués, or dark spots, gas bubbles or lines, and even tiny crystals. Sometimes cracks in the diamond crystal, or fractures or feathers affect clarity, passing through the interior and sometimes reaching the surface.
Clarity characteristics are what make each diamond unique, since there are no two stones that will have the same exact inclusions in the same locations. Evaluating diamond clarity involves determining the number, size, relief, nature, and position of these characteristics, as well as how they affect the overall appearance of the stone.
The following are the commonly used gemological terms to define clarity:
FL, IF (flawless, internally flawless): A grade given to a polished diamond where no external blemishes or internal inclusions are visible using a standard 10X-magnification loupe. Experienced jewelers seldom see such stones, and some even argue that flawless diamonds simply do not exist.
VVS1, VVS2 (very very slightly included): With VVS1 being the better of the two, such grades are assigned to diamonds in which imperfections and inclusions are very difficult to spot, even under the magnification of a 10X loupe.
VS1 and VS2 (very slightly included): With VS1 being the better of the two, such diamonds appear clean when seen with the naked eye, but the inclusions are relatively easily spotted with a 10X loupe.
SI1, SI2 (slightly included): With SI1 being the better of the two, these diamond’s inclusions can be detected with difficulty with the naked eye, but are quite obvious under the magnification of a 10X loupe. SI3, which is used by certain labs, although not GIA, is a grade slightly lower than SI2.
I1, I2 and I3 (included): With I1 the best of the three, these grades are assigned to diamonds where the inclusions can be seen easily with the naked eye.