Check with the National Association of Jewelry Appraisers (NAJA) for
a member near you. You can also look for an American Gem Society
(AGS) member jewelry store. Membership in both organizations requires
that there is a GIA Graduate Gemologist (GG) on staff. They will be
able to grade your diamonds. Whether any of them will do it for a
trade I don't know, but it's worth asking. Most will be happy to help
you figure out whether what you have is genuine or not and whether
it's worth appraising for insurance or not at no charge.
In the Northern Hemisphere, the type of light used for color grading
diamonds is called 'natural northern daylight'. It's the reason most
diamond wholesalers' offices are in spaces with windows that face
north; they get natural northern light with no direct sunlight. Such
a space is ideal for buying and selling diamonds. A professional
grading lab will have an artificial lighting system that meets the
standards of 'natural northern daylight'. Some can cost well well
into the thousands of dollars. Some of the less expensive ones look
similar to desk lamps or lighting fixtures that you can get at Office
Depot, but they are actually quite different.
Accurate color grading also requires comparison with diamonds of
known grades because the eye isn't capable of consistently discerning
very slight differences in color without having something to compare
to. These sets of comparison stones are very expensive as well. Most
gemological equipment is very expensive, there's a lot of it and the
training isn't cheap either and can take years. That's the main
reason that appraisers charge what can seem to be a lot. Their
investment of both time and money is substantial, so give them a
break if they aren't all that interested in grading your diamonds for
little or no money. Like I said though, most will give you an idea of
whether it's worth paying for an appraisal or not for no charge.
Here's a little peak behind the appraisal curtain. One of the things
we hear from time to time that makes my wife, the GG roll her eyes
and chuckle is "I don't need a written appraisal, I just want to know
what it's worth." It makes her want to respond - "What do you think
an appraisal is?" Valuation is the most risky, difficult and time
consuming part of almost any appraisal and is entirely dependent on
doing all of the measuring, weighing, figuring and grading first.
Putting it in writing is the easy part.
There are also several different types of values, depending on
whether they're buying it, selling it or insuring it, and they're all
figured differently. There's a lot more to answering "how much is it
worth" than it might seem at a casual glance. "I won't hold you to
it" doesn't make it any easier to figure out either.
It's kind of like the one we've all heard at one time or another
concerning resetting a stone that's fallen out of a mounting - "I
don't want all that work done on it, can't ya just take a minute or
two and pop it back in there?"
Hope this is helpful.