|Clarity is a major factor in determining quality and the value of a gemstone. Inclusions not only distract the eye but interfere with the behavior of light in the gem. Clarity also significantly affects brilliancy
However, inclusions that do not affect the durability of colored gems are not nearly as much an issue in determining value as corresponding inclusions in diamonds.
Certain gems are expected to have internal inclusions, especially Emerald and Red Tourmaline. Yet Citrine, Green Tourmaline and Aquamarine are very commonly flawless.
Affect of Inclusions in Grading Colored Gems
- Types of inclusions: Blemishes, cracks, healed fractures and included crystals
- Size designations
- Minute – Very small, pinpoint size included crystals or voids of low contrast observable only in transmitted or reflected light and under careful observation
- Minor – Small included crystals or voids of low contrast observable only in transmitted or reflected light and under careful observation
- Obvious – Included crystal or voids easily observable and of high contrast. Clouds of pinpoint inclusions, clusters of minor included crystals or voids of low contrast
- Prominent – Healed fractures, cracks, clusters of minor included crystals or voids of high contrast that draw the eye
- Contrast/relief/color – The greater the difference in RI between a gem and included crystal, the higher the relief.
- Relief = Greater Contrast = Distraction
- Color contrasts between the gem and host crystal
- Light colored inclusion in light colored gem = Barely Noticeable
- Dark Colored Crystal in light colored gem = Distraction
- Quantity of inclusions
- Individual – pinpoints, included crystals, voids
- Clusters – of included crystals, or voids
- Clouds – of pinpoints
- Degree of distraction is more important that count
- Degree of distraction
- Since the eye tends to focus naturally on the center of a gem, inclusions under the table will be more obvious and distracting than similar inclusions near the girdle
- Dispersion and external reflections will make inclusions under the crown less obvious
- Grade under diffused daylight type lighting
- First, examine the gem with a 10X loupe; then switch to the unaided eye
- Make your final grade assessment without magnification
|Clarity Grade Comparison
||Flawless or Internally Flawless
||Minute, not under table, no affect on appearance
||Minute, under table, little to no effect on appearance
||Minor, not under table, little to no effect on appearance
||Minor, under table, slight effect on appearance, little to no effect on brilliance
||Obvious, not under table, slight effect on appearance and brilliance
||Obvious, under table, significant effect on appearance and brilliance, slight effect on transparency.
||Prominent (draws the eye), under table, significant effect on appearance and brilliance and transparency
||Numerous and Prominent throughout gem, severe effect on appearance, brilliance, transparency, and durability.
||Numerous and Prominent throughout, gem not transparent, shows no brilliance.
Gemstone Clarity Grade
To determine a clarity grade, carefully study a gem. Observing characteristics that distract the eye or could affect durability, transparency, brilliance, scintillation and color. Mentally summarize those observations and ask yourself in which category the gem belongs.
Grading tip: If you notice a minor inclusion, start your grading assessment again with that clarity grade as a minimum.
Most color stone clarity grading is assumed to be with the unaided eye. In one respect we disagree. If your eyesight is below standard, use magnification. A jeweler’s visor may bring you on par with a sharp-eyed grader.
Calibrating your eyes, a.k.a. practicing your opinions compared to experienced graders’ opinions is absolutely necessary. Grading cannot exist in a vacuum
Gemstone Color Zoning
Color zoning doesn’t fit perfectly into color or clarity, but we believe it can best be taken into consideration in the clarity grade.
Color zoning might be described as the uneven distribution of coloring (agents) in a gemstone.
Our illustration is a crude attempt at showing color zoning.
If color zoning is visible to the unaided eye, it should be considered as a having an effect on a gem’s appearance or as a distraction, depending on how prominent the uneven color distribution is.
Consider zoning as an additional inclusion and use the same criterion as any other inclusion. (e.g. minute, minor, obvious, prominent, location, contrast)