Diamond Clarity

Because they are formed deep within the earth, under extreme heat and pressure; virtually all diamonds contain "birthmarks"; small imperfections inside the diamond (called inclusions), or on its surface (called blemishes). Clarity refers to the degree to which these imperfections are present. Diamonds which contain numerous or significant inclusions or blemishes have less brilliance because the flaws interfere with the path of light through the diamond.

The position of an inclusion affects how easily it can be seen. Diamond cutters make every effort to cut a stone so that inclusions are not visible through the table of the finished diamond. The preferred position for inclusions is under the bezel facets or near the girdle because they are harder to see there.

Diamond Clarity Scale

  • Flawless:
    No inclusions or blemishes are visible to a skilled grader using 10x magnification.
  • Comments:
    Extremely rare, less than 1 in 5000 jewellery quality diamonds are rated FL.

Diamond Plot
Because a photograph cannot capture the subtleties of clarity, gemologists use a diamond plot to map a diamond's interior and exterior flaws. A diamond plot is a graphic representation of every flaw that affects the overall clarity grade. The flaws are found under 10x magnification by a skilled grader.

Example Diamond Plot: The Key To Symbols section
shows the flaws in order of severity

While the plot shows the type and position of each flaw, the actual visibility of the flaw is communicated in the diamond Clarity Grade itself (i.e. two diamonds may have very similar plots, but very different Clarity grades, reflecting the actual severity and visibility of the recorded flaws).

Besides the plot, there is also a comment section on the certificate where additional clarity characteristics are often noted. These are usually too minor to be reflected in the plot itself. Between the plot and the comment section, all inclusions visible under 10x magnification are accounted for.

A note of caution:
A diamond plot does not reproduce the actual appearance of a diamond. For SI1 or lower grades, do not assume that a relatively clean plot indicates that there are no flaws visible to the naked eye. Often, a plot may carry only one or two markings, but these are so severe that they warrant a lower overall clarity grade.
By the same token, a cluttered plot may not mean the diamond is visually flawed. The diamond may in fact be flawless to the naked eye, since no single inclusion is severe enough to be seen (even though the cumulative effect of the flaws might warrant a lower clarity grade).
When in doubt, speak to a diamond consultant, who will gladly review a diamond on your behalf.

Approximately 1 in 3 diamonds sold has been treated or "enhanced" in some way. A variety of techniques exist to artificially improve the natural clarity of a diamond. By drilling a pathway to an internal inclusion with a laser beam, acid can be poured into the tunnel to bleach the inclusion. The laser tunnel appears as a tiny white dot when viewed from the top of the diamond (where the drilling was performed), but as a long white line when viewed from the side. In addition, fractures in a diamond can be filled with a clear glass-like material, making them less visible. Gemologists will not certify diamonds which have been fracture filled.
While laser drilling and fracture filling are used to improve a diamond's clarity, high pressure / high temperature (HPHT) treatments are used to improve colour by removing brown colorations from the diamond. HPHT involves placing the diamond in a pressure vessel and applying extremely high pressure and temperature. This environment mimics the conditions the diamond crystal was originally formed under. The effects of HPHT are permanent, and the presence of the treatment is very difficult to detect. Gemologists will certify a HPHT diamond, but will note the presence of the treatment on the diamond's certificate. Any treatment or "enhancement" made to a diamond lowers its value.