Clarity measures the number of blemishes (external flaws) or inclusions (internal flaws) in a diamond. Inclusion include cracks, air bubbles and foreign minerals found in the stone. To ensure the quality of the diamond being purchased, the stone should be certified by either the Gemological Institute of America (GIA) or European Gemological Laboratory (EGL). The GIA and EGL are the two most respected organizations for diamond grading and certification. Grades start at F, completely flawless (internally & externally) and extremely rare down to I3 for diamonds that have visible inclusions.
A diamond's clarity grade impacts its value. Many natural diamonds contain blemishes or impurities called inclusions, many of which can only be seen under 10x magnification. The fewer and less noticeable the inclusions the rarer the diamond and the higher price it commands. The number, size, type and placement of inclusions visible under a jeweler's loupe or microscope determine a diamond's clarity grade. Inclusion under a diamond's table, or top, impact the grade more than an inclusion on the girdle, or side. GIA certificates include a "plot" of a stone's inclusions, similar to a fingerprint for a diamond. No two diamonds are exactly the same, and the plot offers assurance that the diamond you pay for is the one you receive.
The most common type on the market, slightly Included or SI range diamonds include SI2 grade stones. They provide the most value while still offering exceptional clarity to the naked eye. Typical inclusions become visible under 10x magnification. Evaluate SI2 clarity diamonds carefully as some can have visible inclusions.
The GIA and other gemological institutions have yet to recognize or adopt the EGL grade SI3. The GIA would typically grade an EGL SI3 clarity with an equivalent GIA grade of I1. These means SI3 diamonds typically display a flaw visible to the naked eye. SI3 diamonds should follow the same evaluating guidelines as I1 stones and therefore have a lower value than SI2 diamonds.
Included or I1 clarity diamond have a flaw which can be seen with the naked eye, but there should only be one major, not too obvious flaw. Overall the diamond should still look nice, however I1 clarity grades vary so select your diamond carefully. If your budget only allows for the purchase of an SI3 or I1 clarity diamond, examine it thoroughly before purchasing to ensure that the inclusions do not detract from the overall beauty of the diamond.