Diamonds that are absolutely clear are the most sought-after and therefore the most expensive. Many diamonds have what are referred to as "inclusions" or scratches, trace minerals or other tiny characteristics that can detract from the pure beauty of the diamond. Gemological laboratories such as GIA and EGL use a detailed system of rules and standards to summarize the number, location, size, and type of inclusions present in a diamond. [see Diamond Certification]
Raineri Jewelers suggests an "eye-clean" diamond or gemstone that has no inclusions visible to theunaided or untrained eye. The following categories should serve to educate on the basic criteria for grading a diamond gemstone's clarity:
IF (Internally Flawless)
Both perfect and very rare, these diamonds are the crème de la crème of the diamond world thus the most expensive and difficult to come across. These remarkable diamonds have no internal or external flaws, nor any inclusions visible under 10x magnification.
VVS (Very, Very Slightly Included)
VVS diamonds have minute inclusions that are difficult for a skilled grader to see under 10x magnification. The VVS category is divided into two grades; VVS1 denotes a higher clarity grade than VVS2. VVS diamonds are excellent quality diamonds and thus more costly yet very much worth it in terms of appearance.
VS (Very Slightly Included)
VS diamonds have minor inclusions that are not typically visible to the unaided eye. Divided into two grades; VS1 denotes a higher clarity grade than VS2. VS diamonds are slightly less expensive than VVS diamonds and perhaps the best balance between cost and quality.
(SI) Slightly Included
These diamonds have noticeable inclusions visible to a trained grader when viewed under 10x magnification. SI diamonds may or may not be noticeable to the naked eye. The SI category is divided into two grades with SI1 denoting a higher clarity grade than SI2. Perhaps the best diamond value in terms of cost the SI diamond often still looks quite nice to the untrained eye.
Included diamonds have obvious inclusions that are clearly visible to a trained grader without magnification.