Instructional Diamond Grading


Clarity grading
Diamond Clarity Grading involves determining the degree to which a diamond is free of blemishes and inclusions. It is the process of hunting down microscopic imperfections and rating them for difficulty of discovery. The more difficult it is to find inclusions under 10x magnification - using a binocular microscope - the higher the clarity grade. Once these specks are found, their number, size and location all play a role in deciding the final clarity grade.

Gemologists use an 11-grade scale - from 'FL' (Flawless), the highest, to 'I3', very noticeable inclusions - to grade clarity. Each grade down represents increased ease of detection. In short, grades stand for degrees of visibility.

The clarity grading environment
Grading a diamond in a laboratory environment is the ideal way to examine a diamond. Professional diamond laboratories, like GCAL, invest in high quality binocular microscopes, work in quiet darkened environments and have the advantage of examining perfectly clean loose diamonds. Gemologists and appraisers in the field often do not have these advantages.

Diamond clarity grades are always determined by what is visible at 10x magnification, not higher. Professional gemologists first examine the diamond with a microscope and then finalize the grade with a 10x loupe.

Clarity grading procedure
Here we are presenting grading procedures and principals we use every day in our laboratory.

  1. Clean the diamond. Never touch the diamond with your fingers while grading.
  2. With tweezers, hold the diamond in the face up position and examine under 10x microscope. If there are inclusions present, determine if they are VS1 and above, or VS2 and below.
  3. If it is VS1 or above, turn the stone over and check the culet area. Inclusions are commonly missed in this area. Then, hold the diamond in the table-to-culet position and examine the pavilion for inclusions while slowly spinning the diamond. Look through the pavilion 2-3 times, and then once again through the crown.
  4. It is more accurate to keep the diamond stationary (in tweezers or stone holders) and use the focus knob to look in and out of the diamond. The focus knob is much more delicate then your hands moving the diamond. Always be aware of the area coming into view as you concentrate on the area in front of you. And always be aware of the areas that have a black background. If it is VS2 or below, examine the pavilion for surface reaching inclusions.
  5. Once inclusions have been found in the microscope, examine the diamond under a 10x loupe and make a final grading decision.
  6. Always consider these 5 factors when establishing a clarity grade:
    • Size of Inclusion(s)
    • Number of Inclusion(s)
    • Position of Inclusion(s)
    • Nature of Inclusion(s)
    • Color/relief of Inclusion(s)
    • Clarity Grading Tips

The '4-position' method for deciding borderline clarity calls
After viewing the diamond in the microscope for all clarity characteristics, the grader will have an opinion of what the grade will be through the microscope view. This view is just used as a reference.

The final grade will ALWAYS be determined by the way the diamond appears through a 10x power loupe.

  1. Using a 10x loupe, view the grade setting inclusions, in four positions. Twelve o'clock, six o'clock, three o'clock and nine o'clock.
  2. Make four clarity decisions, one for each clock position.
  3. Like in baseball, a tie goes to the runner, meaning a tie goes to the benefit of doubt. The lower grade needs to be the majority look, not an even split. For example, if you see SI2 in two directions and I1 in two directions, then the final grade is SI2.

The 'theoretical grading' method
After locating all the grade setting inclusions, make the grade call that you think is correct. Then look at the grade setting inclusions again and mentally change what you are seeing. Then consider if your grade decision still makes sense. For example, mentally move the crystal from the center of the diamond to the edge, or change a crystal from dark to light, or eliminate some of the inclusions that contributed to the grade.
Consider how you would grade the clarity with the inclusions in a new location, etc. Can you justify your original decision?

How to grade transparent feathers and knots

  1. First, make a determination as to the clarity grade of the feather's size as if size was the only factor, and disregard where it is.
  2. Next view the feather in a face up position, and make a clarity decision based only on the face up view. Forget that it is a feather; just view it as to how bright and how much of it you can see.
    • If you think size is SI2 and the visibility is SI1 or SI2, than the final grade is SI2.
    • If you think size is SI2 and the visibility is VS2 or higher than the grade will be SI1, but never more than one grade higher than the nature grade.
    • This will work with all feathers up to VVS2.

How to Grade High Clarities (VVS2 and better)

  • Always carefully check the culet area for inclusions. Hold diamond girdle to girdle in the tweezers and inspect the culet area from the pavilion side.
  • All possible grade setting inclusions have to be callable with a 10x power loupe. A pinpoint visible with the microscope at 10x but not visible with a 10x loupe is still considered to be Internally Flawless.
  • It does not matter how many pinpoints are callable at 10x through the pavilion for the grade to still be VVS1.
  • A diamond with naturals or extra facets anywhere on the diamond can still receive a grade of Internally Flawless. If a natural is indented, the diamond is graded VVS1 or below.
  • White lines, scratches or pits are often incorrectly called grade setting inclusions that lower a grade below Internally Flawless. The key to making the correct decision is to view the depth or lack of depth from the opposite side of the blemish at 10x power.
  • The most difficult and misunderstood high clarity characteristic is internal graining.

Types of graining

  • Graining is caused by distortions in the atomic crystal structure. Graining is commonly overlooked and misunderstood. It is often the grade setting clarity characteristic in VVS quality diamonds. Remember, to be considered graining, it must be loupe-able just as it is seen in the microscope. Here are some types of graining:
  • Reflective graining looks like a frozen sheet of saran wrap extending into the diamond and is associated with surface grain lines.
  • Surface graining is the easiest to see but will only lower the grade to IF.
  • Colored graining, most commonly brown, pink or green, looks like colored lines running through the diamond and is best seen when viewed in diffused white light.
  • Whitish graining is the most difficult to define, but can be described as white lines, white bands, smoke, rain, or shimmering lines. It usually disappears easily and is best seen at exaggerated viewing angles.

Water Grading

Water grading is a technique that some graders prefer because it quickly removes surface dust and assists looking into the diamond.

  1. To water grade, add a few drops of liquid Joy detergent to a jar of water and use a brush applicator.
  2. The wet brush is used in place of a pointer to remove dust and rotate the diamond in the stone holders.
  3. If you decide to give water grading a try, here are a few things to remember:
    1. Water grading is most efficient for low clarities, but difficult with mounted diamonds
    2. The drying water leaves a film that can interfere with accurately seeing the diamond
    3. It is hard to loupe when using water
    4. High clarity inclusions and polish features are missed when water grading.
    5. Water grading distorts facet shapes when judging symmetry

Clarity grade descriptions
The following are examples of the types of inclusions and comments about each clarity grade.

No internal or external Inclusions at 10 power.
No blemishes, surface graining, extra facets, polish lines, scratches or naturals at 10 power.
Naturals totally confined to the girdle can be Flawless.
Excellent polish does not guarantee Flawless but a Flawless diamond has to have excellent polish.

Internally Flawless
No internal or external inclusions at 10 power.
Any polish grade, symmetry grade, color grade or type of proportion can obtain an IF grade.
Extra facets, naturals, surface grain lines, polish lines, scratches, abrasions, and pits are acceptable.


  • Internal inclusions such as: Pinpoints, clouds, needles, or callable internal graining only visible through the pavilion.
  • Surface reaching inclusions such as: Bruises, chips, feathers and indented naturals not visible face up.
  • Bearding on pavilion side.


  • Inclusions loupe-able face up, such as: Pinpoints, clouds, needles, callable internal graining.
  • Surface reaching inclusions, such as: Bruises, chips, feathers and indented naturals that are loupable face up.
  • Diamond should be louped without exaggerated tilting.


  • Small to very small crystals of a limited number.
  • Small clouds of a limited number. Density matters.
  • Small to medium needles of a limited number.
  • Small feathers of a limited number.
  • Medium sized feathers slightly visible face up.
  • Medium sized bruises of a limited number.
  • Small chips of a limited number.
  • Small indented naturals around the girdle.
  • Usually only white inclusions.
  • Numerous reflecting pinpoints.


  • Small crystals numbering no more than three or four.
  • Medium size individual crystals.
  • Medium size dense clouds.
  • Light clouds throughout, visible face up.
  • Slightly large, thicker needles of a limited number.
  • Medium sized feathers visible face up. Orientation matters.
  • Large feathers not visible face up nearest to the girdle edge.
  • Slightly large sized bruises of a limited number.
  • Medium sized chips of a limited number.
  • Medium sized indented naturals around the girdle.
  • Small black inclusions of a limited number.


  • Medium to slightly large crystals, feathers and needles.
  • Hazy diamonds due to clouds or whitish graining.
  • Slightly large cavities, chips and indented naturals.
  • Numerous VS2 sized inclusions.
  • Numerous reflections of VS2 sized inclusions
  • Very slightly eye-visible after louping and positioning inclusion in brightest location.


  • Large feathers, crystals, black inclusions, numerous twinning wisps, large knots, and large dense clouds.
  • Often look 'busy' with the loupe but when viewed with the naked eye only some/none of the inclusions are noticeable.
  • Eye visibility varies with observer's.


  • Inclusions are easily visible to the unaided eye.
  • Inclusions may affect transparency, brilliance and possibly durability.


  • Very easy to see with the unaided eye.
  • Transparency and brilliance is significantly diminished.
  • Inclusions may impact the durability of the diamond.
  • Approximately ¼ to ½ of the diamond lacks transparency.


  • Extremely visible to unaided eye.
  • Inclusions may significantly impact the durability of the diamond.
  • More than ½ of the diamond lacks transparency.
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Each panel of a GCAL Certificate tells a story to the customer.
  • Panel 1

    Verifies the identification process

  • Panel 2

    Verifies the 4C's quality grading

  • Panel 3

    Illustrates the quality of cutting and proportions revealing the skill of the diamond cutter

  1. 1Gemprint
  2. 2Laser Inscription
  3. 34C's Grading
  4. 4Photomicrograph
  5. 5Hearts & Arrow
  6. 6Optical Brilliance
  7. 7Optical Symmetry
  8. 8Proportion Diagram