Diamond clarity is the quality of diamonds that relates to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects, called blemishes. Clarity is one of the four Cs of diamond grading, the others being carat, color, and cut.
Inclusions are solids, liquids, or gases that were trapped in a mineral as it formed. They may be crystals of a foreign material or even another diamond crystal, or may have produced structural imperfections, such as tiny cracks that make a diamond appear whitish or cloudy. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. A clarity grade is assigned based on the overall appearance of the stone under ten times magnification, which is the standard magnification for loupes used in the gem world.
Most inclusions present in gem-quality diamonds do not affect the diamonds’ performance or structural integrity and are not visible to the naked eyes. However, large clouds can affect a diamond’s ability to transmit and scatter light. Large cracks close to or breaking the surface may reduce a diamond’s resistance to fracture.
Diamonds with higher clarity grades are more valued, with the exceedingly rare “Flawless” graded diamond fetching the highest price. Minor inclusions or blemishes are useful, as they can be used as unique identifying marks analogous to fingerprints. In addition, as synthetic diamond technology improves and distinguishing between natural and synthetic diamonds becomes more difficult, inclusions or blemishes can be used as proof of natural origin.
The GIA diamond grading scale is divided into six categories and eleven grades. The clarity categories and grades are:
Flawless category (FL) diamonds have no inclusions or blemishes visible under 10× magnification.
Internally Flawless category (IF) diamonds have no inclusions visible under 10× magnification, only small blemishes on the diamond surface.
Very, Very Slightly Included category (VVS) diamonds have minute inclusions that are difficult for a skilled grader to see under 10× magnification. The VVS category is divided into two grades; VVS1 denotes a higher clarity grade than VVS2. Pinpoints and needles set the grade at VVS.
Very Slightly Included category (VS) diamonds have minor inclusions that are difficult to somewhat easy for a trained grader to see when viewed under 10× magnification. The VS category is divided into two grades; VS1 denotes a higher clarity grade than VS2. Typically the inclusions in VS diamonds are invisible without magnification; however, infrequently some VS2 inclusions may still be visible. An example would be on a large emerald cut diamond which has a small inclusion under the corner of the table.
Slightly Included category (SI) diamonds have noticeable inclusions that are easy, or very easy for a trained grader to see when viewed under 10× magnification. The SI category is divided into two grades; SI1 denotes a higher clarity grade than SI2. These may or may not be noticeable to the naked eye.
Included category (I) diamonds have obvious inclusions that are clearly visible to a trained grader under 10× magnification. Included diamonds have inclusions that are usually visible without magnification or have inclusions that threaten the durability of the stone. The I category is divided into three grades; I1 denotes a higher clarity grade than I2, which in turn is higher than I3. Inclusions in I1 diamonds often are seen by the unaided eye. I2 inclusions are easily seen, while I3 diamonds have large and extremely easy to see inclusions that typically impact the brilliance of the diamond, as well as having inclusions that are often likely to threaten the structure of the diamond.
Diamonds become increasingly rare as clarity increases. Only about 20% of all diamonds mined have a clarity rating high enough for the diamond to be considered appropriate for use as a gemstone; the other 80% are relegated to industrial use. Of that top 20%, a significant portion contains an inclusion or inclusions that are visible to the naked eye upon close inspection. Those that do not have a visible inclusion when the gem is examined approximately 6 inches from the naked eye are known as “eye-clean”, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry. The most expensive gem diamonds fall within the VS and SI grades with FL, IF, and even VVS stones commanding significant premiums. FL and IF stones are sometimes referred to as “museum quality” or “investment grade” to denote their rarity although the term “investment grade” is misleading as diamonds have historically been illiquid and questionable stores of value.