How a Clarity Grade is Assigned
When a trained diamond grader is evaluating a diamond for its clarity, he or she will view the stone with the naked eye and with 10x magnification to assess the overall impact of the diamond's clarity characteristics. External characteristics do not affect the clarity grade below Internally Flawless (IF). They will, however, factor into the polish grade. There are many types of internal characteristics, but here is an brief explanation of the most common ones you will see:
- Crystal - A foreign crystal trapped inside the diamond during the growth process
- Feather - A break inside the diamond that is caused by blunt force or pressure applied to the stone
- Pinpoint - A tiny crystal that appears literally no larger than a pinpoint when viewed at 10x magnification
- Cloud - A series of pinpoints grouped together
- Needle - An included crystal shaped like a rod
- Indented Natural - A portion of the skin of the rough diamond crystal that falls below the polished surface of the diamond
After identifying all of the inclusions visible under 10x magnification, the grader then assesses the overall impact of the internal characteristic(s) based on five factors:
- Size - How small or large is/are the inclusion(s)?
- Number - How many inclusions are inside the diamond?
- Position - Where are the inclusions located?
- Nature - What type of inclusion(s) is/are present?
- Relief - What is the visual impact of the inclusion(s)?
Once the diamond grader has identified the internal characteristics and assessed their impact on the diamond, he or she determines a clarity grade based on established guidelines set forth by the laboratory.
Reading Clarity on the Certificate
On the grading report for a loose diamond, you will see a single clarity grade assigned to the stone ranging from FL to I3 on the GIA scale. Some labs such as AGS use their own nomenclature. In addition to the clarity grade, the grading reports for most stones above one carat with be accompanied by a "diamond plot," or a map of the external and internal characteristics of the diamond. Inclusions (most properly referred to as "internal characteristics") are found inside the diamond and are marked in red on all major laboratory reports such as GIA, AGS, and EGL. Blemishes (or "external characteristics") are found on the surface of the diamond. Blemishes are only noted on a grading report if the diamond is graded Flawless (FL) or Internally Flawless (FL), and they will be marked in green.
How/Why Clarity Matters
While given the choice, most women would probably want a Flawless diamond, a very high clarity grade is not needed for a diamond to be free of visible characteristics that may detract from the beauty of the stone. Most people cannot see an inclusion with their naked eye until the diamond reaches the SI or I range. That being said, one can still find a diamond that is essentially "eye clean" at SI1 if the stone is selected properly and by a knowledgeable diamond buyer. For a diamond to be brilliant, it must return as much light as possible that enters the stone back to the eye. Inclusions can interrupt the path of light and result in dull, lifeless stones regardless of the precision of the cut. Inclusions can dramatically affect the durability of the diamond depending on their size, type, and location. For example, a feather reaching the girdle of a diamond leaves the stone prone to chipping during the setting process or normal wear. Keep this in mind when considering diamonds in the I range.
To select an eye clean diamond, I recommend purchasing diamonds that are grades VS2 (or perhaps SI1 if well-selected) or higher. This way you can maximize the other three C's and get the most out of your budget.
Originally posted by me to LibertyDiamonds.com on 4/5/2010.