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Green diamonds - natural & treated?


#1

Doing an appraisal on a 1.11 ct. “natural green diamond” and am
wondering if any one is familiar with diagnostic inclusions, marks,
etc to separate natural from treated re: the green color (besides the
spectroscope). Also does any one have an idea of price difference
between the two or know of a sure who I can contact for more

Many thanks.
Steve


#2

I wouldn’t touch the natural issue myself on a green diamond. I think
you need to get a gem lab involved. The naturals and treated can look
exactly alike in green diamonds.

Daniel R. Spirer, G.G.
Daniel R. Spirer Jewelers, LLC
1780 Massachusetts Ave.
Cambridge, MA 02140
@Daniel_R_Spirer
www.spirerjewelers.com


#3

Hi Steve,

Naturally colored green diamonds are extremely rare. Because of
that, and the very real possibility of treatment, they are always
regarded with suspicion. Unless you are appraising the Dresden
Green, which is naturally colored throughout, any color displayed by
nearly all natural green diamonds will have the color confined to a
"natural" on the girdle that reflects throughout the stone. In other
words, a diamond that has been irradiated (the only treatment to
create green color in diamond) to a green color will usually have a
uniform color with no zoning, whereas a natural green’s color is
confined to the skin of the rough from which it is cut. That’s why
the color will be confined to a natural on it’s girdle, a sign of a
very skilled cutter. Since you’re appraising the diamond, I’ll
assume you know what a natural is.

Sorry, there are no diagnostic inclusions from irradiation. The only
mark you may find will be the above mentioned natural. Sometimes,
irradiated diamonds will trigger a geiger counter, but most are kept
in storage until their half-life has expired to safe levels for
humans.

The really bad news is that most irradiated green diamonds are
almost impossible for even a well-equipped gemological laboratory to
detect. The reason is that all green diamonds are irradiated, either
in the earth before mining, or by a technician in a laboratory. even
the clues I mention in the first paragraph aren’t totally
conclusive. Unless you’ve had a lot of experience grading green
diamonds, you might consider outsourcing the appraisal to someone
who has.

You’re asking for pricing info, but you don’t list any
characteristics. Most price guides list green diamonds only as
irradiated, which should give you an indication of their rarity. An
IF green diamond over 1ct can wholesale for over $2k, if irradiated.
A natural green diamond is so rare, you can practically name your
price. Many argue that treated stones are worth the same (or more,
because of the costs involved) as natural stones, but, believe me,
you’ll get a LOT more for a (certified) natural green diamond than
an irradiated one.

Finally, I can only assume that, since you’re asking how to separate
treated from natural, that you don’t have a certification from a
reputable gem lab. A stone of that (possible) magnitude should at
least be sent off to a reputable lab (EGL, GIA, etc.) to determine,
if possible, whether it is natural or not. Sure, it costs a good
deal, but if it IS a “natural green diamond” a certificate stating
so will not only remove all doubt, but will increase the value of
the owner’s estate significantly. I would like to know who makes the
claim that the stone in question is natural. That claimant should be
willing to have it certified, if only to get the most for their
money. Then again, a lab still may not be able to tell for sure.
After considering all of the clues, if the possibility exists, I’d
suggest sending it off for evaluation.

James in SoFl


#4

Hi Steve

Natural green diamond is rare and many of the green diamond in the
market are mostly treated. Using basic gemological instrument to
identify the nature of colour is quite difficult, because of
improvement in technique of treatment i.e. irradiation plus
annealing.

I have learned from the Swiss Gemological Foundation Lab (SSEF,
Switzerland) and also Mr. George Bosshart (former chief gemologist
at the Gubelin Gem Lab) that you need to cool your diamond down to
minus 190 degree Celsius and use the UV visible spectrometer to
identify the presence of the presence of irradiated peak around 440
and 250 nm. Reference: Swiss Watch & Jewelry Journal 2/89.

You need to experience the technique involved in identification, it
is fun.

As for pricing, check with Christie’s auction houses, they sold some
green diamond before, quite high price.

Tay