Gemstone Final Grade

Now it’s time to put all the grading factors together. If we have followed the procedures faithfully we will have determined grades for the following:

  • Brilliance
  • Saturation & Tone
  • Clarity
  • Cut

So we can add those grades and divide by four to get a Composite.

[Clarity + Brilliance + Saturation & Tone + Cut] / 4 = Composite Score

While this method may seem overly simplistic, there are so many interrelationships that it tends to work.

Our Grade *compared to some other systems.
Composite 1-2 3-4 5-6-7 8-9 10
Asia-Gems.com 1 2 3 4 5
Hughes Poor Fair Good Very Good Exceptional
AIGS 1 2 3 4 5
Common in US Commercial Standard Good Fine Extra Fine
Common in Asia Commercial A AA AAA Gem Quality
Extending The Range of Single Grades
Grades represent ranges. Two gems may fall into the same grade but one, being closer to the top of the range, may be worth more than a gem falling at the bottom of a range.

One way to mitigate this situation is by using a modifier. A gem at the top end of Grade 4 could be designated +4, while a lower end gem would be -4. So we can essentially split each grade into 3 parts (-4, 4, +4).

*approximately and as we understand them

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