Grading stones for fancy colored diamonds would be nice,
though I suspect that having a set for every color would be VERY
expensive. I have never seen nor heard of sets like this, not for
retail shops anyway.
The only masterstone sets I've seen for sale, even for colorless (D
to Z scale) diamonds, are CZ sets. To my knowledge, the only way to
obtain a set of genuine diamond masterstones for grading any color
is to put the set together yourself and send them off to GIA (or
another reputable gem lab) for certification.
The requirements are: Round Brilliant cut, minimum size .25ct and
all within .10ct of each other. No fluorescence in colors E through
J and no more than Faint to Medium fluorescence in K through Z.
Clarity SI2 or better with no eye-visible inclusions through the
pavilion and no inclusions that affect color or transparency.
Consistent proportions; crowns and pavilions must not be noticeably
shallow or deep, and girdles must be Thin to Thick (cut grading
terms range from Extremely Thin to Extremely Thick). Girdles may be
faceted, polished or bruted, but not heavily bearded, wavy or have
large naturals or extra facets. There must be at least three stones
to a set. Few use more than ten, and a five-stone set is typical.
Requirements for fancy colored diamond masterstone sets are similar.
Looking at the above requirements shows that even a standard set for
colorless diamonds is quite expensive. I don't know what GIA charges
for certifying a set, but anyone may inquire directly to them.
I believe that the GIA terms would be appropriate to use in an
appraisal, and probably the Argyle's term as well, as long as you
could match the color to the term. Have you seen any charts or
photos that describe these colors? In the absence of grading
stones, that may be the only way to attempt to describe color.
Once, I had a flyer with photos of them but I doubt I kept it. As a
GIA alumnus, I usually discard "romantic" color descriptions, but
sometimes keep them around for comparison. I'll look around and, if
I find it, I'll contact you off-list if you want it.
Keep in mind that fancy colored masterstones can be any color. In
fact, each stone in the set can be a different color. They are used
to determine the saturation of the hue, not the specific color. If
it is green, blue, yellow, etc. well, that's the easy part. Whether
the stone is Faint, Vivid, Intense, etc. THAT is the focus of a
colored masterstone set, just as where a colorless stone falls in
the D to Z scale is the focus of the regular set. If an appraiser
isn't even familiar with this entry-level knowledge, they shouldn't
Color grading colorless stones is a tricky business for the
untrained. Grading fancy colored diamonds is even more difficult. I
agree with Richard, a GIA cert should be obtained.
James in SoFl