Diamonds are a natural formation and few things in nature are absolutely perfect. This is as true of diamonds as anything else. Natural diamonds are the result of carbon exposed to tremendous heat and pressure deep in the earth. Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, they’re called clarity characteristics. Clarity is the relative absence of inclusions and blemishes.
Among other things, blemishes include scratches and nicks on a diamond’s surface. Inclusions are generally on the inside, and some might break the surface of the stone. Sometimes, tiny diamond or other mineral crystals are trapped inside a diamond when it forms. Depending on where they’re located, they might remain after the stone has been cut and polished, and they can affect a diamond’s appearance.
Clarity characteristics might have a negative influence on a diamond’s value, but they can have positive effects as well. For one thing, they help gemologists separate diamond from imitations. (This is easier with included diamonds than with flawless ones.) And because no two diamonds have exactly the same inclusions, they can help identify individual stones. They can also provide scientists with valuable information about how diamonds form.
Flawless diamonds are very rare—so rare, in fact, that it’s possible to spend a lifetime in the jewelry industry without ever seeing one, and they command top prices.
At the other end of the scale are diamonds with inclusions that can be easily seen by the unaided eye. Between the two extremes are diamonds with inclusions visible only under 10X magnification. Stones in the middle range make up the bulk of the retail market.
There are 11 clarity grades in the GIA clarity grading system. They are Flawless, Internally Flawless, two categories of Very, Very Slightly Included, two categories of Slightly Included, and three categories of Included.
The effect of a clarity characteristic on the clarity grade is based on its size, number, position, nature, and color or relief.
Many inclusions and blemishes are too tiny to be seen by anyone other than a trained diamond grader. To the naked eye, a VS1 and SI2 diamond may look exactly the same, but these diamonds are quite different in terms of overall quality. Sometimes, one factor makes more difference to the clarity grade than the others. But it’s not always the same one. The relative importance of each factor varies from diamond to diamond. For example, an inclusion off to the side of a stone would have less impact on clarity than the same size inclusion located directly under the table. In this case, the position is probably the determining factor. This is why expert and accurate assessment of diamond clarity is extremely important.