Last but most defiantly not the least C that needs to be considered – the Certificate. GIA is considered the highest authority in grading diamonds by the trade. EGL is another major laboratory that is vastly used in the US market. EGL is not consistence in the way they grade diamonds around the world.
Cost is considered to be the 5th C. In most cases customers would have a certain price range that they would like to stay in. As a result we should look for most suitable combination of the four C’s for every customer. It is an individual decision, some customers would like to have a higher clarity and give up some color. There is always a trade off between the color clarity and the size (weight) of the diamond.
The clarity of a diamond is based on a scale from FL (flawless) and IF (internally flawless) to I3 (heavily included). FL-IF are clean diamonds and there are no imperfections within the diamond. VVS1-VVs2 (Very, very slightly included) – on those diamonds it would be virtually impossible to see any imperfections under a 10X magnifying glasses. On the larger diamonds, 1.5ct and above, those diamonds would be a good investment with a combination of D-F colors. VS1-VS2 are Very Slightly included diamonds. When you look at the diamond under 10X loop you would find the overall look of the diamond very clean and transparent although there will be some minute imperfections. SI1-S12 are the most saleable diamonds within the U.S. Those diamonds would have some different types imperfections that would be visible under 10X magnifying glasses. Most of the SI stones are eye clean (hard to notice the imperfections to the naked eye).
You should always keep in mind that seeing or not seeing an imperfection is a subjective matter. There are some types of imperfection, mostly black carbon, that might be visible to the naked eye. As a general rule the determination of a clarity grade is based mostly on the ratio of the mass of the inclusion to the mass of the diamond. It is safe to say that a 1 carat (ct) diamond and a 20ct diamond that have the same size imperfection would not be graded the same way. The lowest grade with in the gem quality diamonds are I1 and I2 those are mostly included diamonds. the imperfections of those diamonds are mostly visible to the naked eye. Some of the I1 stones can face up nice if the imperfection is off to the side of the stone making in prongable.
The fewer and less visible these birthmarks are the more valuable a diamond will be. The following chart illustrates the varying grades for Clarity.