Rules for Clarity Grading

[Caratz]

I have read quite a few online tutorials on clarity grading, but none of them get into the details of how to actually assign a clarity grade. I realize that the size, number, placement and coloration of the inclusions affects a clarity grade, but how is the actual grade assigned?

It seems to me that clarity grading would be the most subjective grade of all. What is the real difference between a VS1 and a VS2? When looking at a stone graded VS1, what would a gemologist see that may lead him to conclude that the stone should have been graded VS2 (or VVS2) instead????

Perhaps one of the experts could post a photo of a stone on a borderline grade that could be one or the other, and explain why. This would be quite helpful!!!

 

[dimonbob]

Caratz
Good question, but no real good answers.
I was once a diamond grader at GIA in Santa Monica so you would think I could answer that question. Some time later I worked for a wholesale diamond dealer where one of my duties was grading diamonds before we sent them to the GIA lab to be graded. We would send out 25 or 30 at a time. Did I second guess GIA right every time...not a chance, sometimes I was high othertimes I was low. Those "split" grades are hard to predict. Who was right? Who knows, but GIA has the power, and that makes me wrong.

 

[oldminer]

WIth the assumption made that the GIA is always correct, a legitimate and experienced grader will be able to mimic the GIA grading within a grade high or low over and over and over again. A two grade discrepancy would be very rare.

You have to keep in mind a few things. The GIA is a human enterprise and not divine. They do occasinally err. They just don't have to admit it like regular folks.

A grader who, on average, calls the clarity grade correctly, is an okay grader. One who is usually too high or too low, needs experience, fine tuning and a supervisor with a better track record. It takes time to be a good, overall grader of clarity.

Labs that consistently grade too high know what they are doing and intend to mislead the public. Their defense is the subjectivity of grading. While it is an excellent defense, it is not a completely honest one in every case.

Diamonds are graded by people at this point in time. It is not a black and white subject in every respect. Thos who do an honest job are often confronted by those who look honest, but who really are not. A little trickery and loose grading goes a long way to increasing the profits on diamonds.

 

[Caratz]

The answers so far remind me of Supreme Court Justice Potter Stewart's comment that went something like: "I cannot define what pornography is, but I know it when I see it."

It sounds like there is no real way to know where to draw the line between a VS1 or a VS2, but "you know it when you see it" . . .