Fluorecense is definitely a variable and polish can also
affect appearance, but to say that diamonds of the same grade and
cut can be worlds apart is also to say that grading has little
Ron, if by cut, you mean the shape (round, marquise, pear, etc.), I
have to agree. But if you mean finish and proportions, I strongly
disagree. Not to say that ideal cuts may have bad F&P because they
don’t. I mean poorly proportioned stones. After all, if poorly
proportioned diamonds looked as good as ideal cuts, they would cost
For example, I wonder how many of you do appraisals in natural
north light ?
For consistency, I learned to grade all gemstones under a grading
Also, how many appraisers limit their activities to morning
hours when their visual acuity is at its' best.
You’ve got me there, man. Sometimes divorce attorneys, banks and
insurance companies are in a hurry and need it immediately. If they
bring the request at 3:00 p.m., It has to be finished, photos
included, by closing time.
Then again, how does one quantify the effect of the stones
being mounted , or for that matter, how does a mounting compare in
effect between white and yellow metals.?
To clarity grade a mounted diamond, one need only look for
inclusions in facet reflections. This method, taught by GIA and
other schools, works for prong, bezel, pave or any type of mounting.
For color grading, I have one yellow and one white metal temporary
mount for my masterstones. That gets me close enough.
I doubt that appraising will ever be an exact science unless we
develop a machine that performs all the functions of the appraiser
and does so within strict parameters.
I certainly can’t argue with that, Ron. Even gem labs don’t match
each other’s grading reports. I often wonder how many graders a
diamond must be evaluated by at GIA’s Gem Trade Laboratory until the
requisite three people have agreed upon it’s grade so a cert may be
No, it’ll never be an exact science, but once an appraiser has made
enough comparisons of stones to their certs with his/her own
equipment, they can be reasonably accurate. Accurate enough for the
insurance company, anyway.
James S. Duncan, G.G.
James in SoFl