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.
Heavily included diamonds used to be solely for industrial use. In recent years, salt and pepper diamonds have gained increasing popularity.
Inclusions and blemishes
There are several types of inclusions and blemishes, which affect a diamond's clarity to varying degrees. Features resulting from diamond enhancement procedures, such as laser lines, are also considered inclusions or blemishes.
Inclusions
Clouds
Feathers
Included crystals or minerals
Knots
Cavities
Cleavage
Bearding
Internal graining
Pinpoint
Laser lines
Twinning Wisp
Grain center
Laser drill hole
Knot
Needle
The diamond industry uses the term "internal characteristics" instead of "inclusions". For natural diamonds, the "internal characteristics" in the diamond are growth crystals that give the diamond its character and unique fingerprint. When diamonds are graded, they are magnified at 10× power.
Blemishes
Polish lines
Grain boundaries
Naturals
Scratches
Nicks
Pits
Chips
Breaks
Dark spots
Light spots
Abrasions
Clarity grading
Gemological Institute of America grading system
History
In 1952, Richard T. Liddicoat, along with Marquis Person, Joe Phillips, Robert Crowningshield and Bert Krashes began to work on a new diamond grading system which they called the "diamond grading and evaluation appraisal". In 1953, they released their new system which assessed three aspects of diamonds; make, color and clarity. They took terminology used in the industry at the time and refined the definitions to produce a clarity scale by which diamonds could be consistently graded. The system at that time contained nine grades: Flawless, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, and I2. The 'I' of the I1, and I2 grades originally stood for "Imperfect".
During the 1970s, two changes were made to the system. Firstly, the Internally Flawless grade was added, as GIA noticed that many diamonds were being aggressively cut to remove any surface blemishes, and thereby reducing the cutting quality ("make") of the diamonds. The Internally Flawless grade gave diamond manufacturers a choice to leave blemishes on the surface of the stone, and achieve a grade higher than VVS1. The second change made to the grading system was the introduction of the I3 grade. This change was made in response to a growing number of diamonds of very low clarity being cut.
The last change to the clarity grading system took place in the 1990s when the term "imperfect" was changed to "included".