Diamond clarity
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Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal defects 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 may be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can 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 10x magnification.
Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. 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. However, minor inclusions or blemishes are sometimes considered to have some value, 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.
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[edit] 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 and/or blemishes.
[edit] Inclusions
- Clouds
- Feathers
- Included crystals or minerals
- Knots
- Cavities
- Cleavage
- Bearding
- Internal graining
[edit] Blemishes
- Polish lines
- Grain boundaries
- Naturals
- Scratches
- Nicks
- Pits
[edit] Clarity grading
The Gemological Institute of America (GIA), as well as other diamond grading agencies including the European Gemological Laboratory (EGL), American Gemological Society (AGS), and the International Gemological Laboratory (IGL) use a sliding grading scale based on descriptive terms of overall clarity. These grading agencies base their clarity grades on the characteristics of inclusions visible to a trained professional when a diamond is viewed from above under 10x magnification.
The diamond clarity grades in common use are:
- FL - "flawless" in that no inclusions or blemishes are visible under 10 times magnification.
- IF - "internally flawless" with no inclusions visible under 10 times magnification, only small blemishes on the diamond surface.
- VVS1 and VVS2 - "very very slight" inclusions that are difficult to see under 10 times magnification. VVS1 denotes a higher clarity grade than VVS2.
- VS1 and VS2 - "very slight" inclusions and visible under magnification but invisible to the naked eye.
- SI1 and SI2 - "slight inclusions" that may or may not be noticeable to the naked eye.
- SI3 is a grade sometimes used in the industry, originally popularized by the European Gemological Laboratory (EGL). While intended as a range to include borderline SI2 / I1 stones, it is commonly used to mean I1's which are "eye clean", that is, which have inclusions which are not obviously visible to the naked eye. Neither the GIA nor the American Gemological Society (AGS) assigns this grade.
- I1, I2 and I3 - "imperfect", with inclusions clearly visible to the naked eye. For I3, the inclusions impact the brilliance of the diamond and are large and obvious.
All grades reflect the appearance to an experienced grader when viewed from above at 10x magnification, though higher magnifications and viewing from other angles are used during the grading process. In "colorless" diamonds, dark inclusions will tend to create the greatest drop of clarity grade. In other colors pale inclusions may have greater relief (may stand out more) and may cause a greater drop in grade.
Beyond the clarity grading terms, other considerations include the type, size and location of the "inclusion". Inclusions near or on the surface may weaken the diamond structurally. Depending on where the inclusion occurs in the cut diamond and how it is to be used, it may be possible to hide the inclusion behind the setting.
[edit] Rarity and value
Diamonds become increasingly rare when considering higher clarity gradings. Only about 20 percent 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 percent are relegated to industrial use. Of that top 20 percent, 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 are known as "eye-clean" and are preferred by most buyers, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry. The most popular gem diamonds fall within the VS and SI grades with F, IF, and even VVS stones commanding significant premiums, while I stones are shunned by most buyers. F 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.
[edit] Clarity enhancement
Main article: Diamond enhancement
Laser "drilling" involves using a laser to burn a hole to a colored inclusion, followed by acid washing to remove the coloring agent. The clarity grade is the grade after the treatment. The treatment is considered permanent and both the GIA and AGS will issue grades for laser drilled diamonds. Reputable vendors should disclose that laser drilling has been used.
Clarity can also be "enhanced" by filling the fracture much like a car windshield crack can be treated. Such diamonds are sometimes called "fracture filled diamonds". Reputable vendors must disclose this filling and reputable filling companies use filling agents which show a flash of color, commonly orange or pink, when viewed closely. There is a significant price discount for fracture-filled diamonds. The GIA will not grade fracture-filled diamonds, in part because the treatment isn't as permanent as the diamond itself. Reputable companies often provide for repeat treatments if heat causes damage to the filling. The heat required to cause damage is that of a blowtorch used to work on settings, and it is essential to inform anyone working on a setting if the diamond is fracture-filled, so they can apply cooling agents to the diamond and use greater care while working on it.
