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Synthetic Moissanite


#1

Hi

Just read Francois post regarding Moissanite with interest.
Earlier this year I purchased a quantity of synthetic rough,
mostly CZ and Spinel and was offered by the US dealer a piece of
Moissanite. The dealer told me that it was a new material (he did
not say it was synthetic, although to me it would not have made
any difference), anyway he told me it was the closest thing to
diamond yet. His price for a piece that I cut into a 5 mm
brilliant was $17.00.

The dealer had oriented and marked on the rough the location
where the table should be and asked that I not mention his name
as the source of the material. He would however like to hear any
comments I might have. He thought more material would be
available later in the year. I followed his directions and found
that the stone cut rather easily and readily took a good polish.

Conclusion; The cut and polished stone that I have has nowhere
near the brilliance of diamond or CZ, instead it has a whiteish
appearance although it is clear enough. My thoughts are that
somehow the light seems to be trapped inside.

Maybe what I got wasn’t Moissanite at all, maybe the orientation
was wrong. I don’t know the answer and I don’t want to discourage
others from trying out Moissanite when it does become available.

For what it’s worth.

                                        ......Leo

Doucet…


#2

Hi Leo,

It is Professor Henri Moissan that first discovered moissanite
in 1904. Moissanite is extremely rare in nature, specimens that
have been found are too small and too rare, they do not form
naturally in nature so they cannot be mine like other minerals.
Instead they are found in meteorites, a litle gift from above! In
1907 the first application of silicon carbide was produced as an
abrasive and cutting material.Today SiC has been called the
"material for the future" due to its many applications. For people
in the jewellery trade SiC or synthetic moissanite is a very
exceptional good imitator of diamond. Because of its properties
such as high thermal conductivity, hardness (9.5) and refractice
index (2.65) this material is the closest to diamond than any
other gem materials. Most jewelers who had the opportunities to
look at the material mistakenly identified synthetic moissanite
as diamond!!!

A press release dated July 31st, 97 from Cree Research,Inc.
state as follow : “A product release by C3 is scheduled for the
first calender quarter of 1998.”

Also C3 is taking a very strong position about the full
disclosure of the qualities of synthetic moissanite.

Apparently synthetic moissanite will cost more than CZ but much
less than the genuine diamond : $50. TO $7O. per carat ??? The
annual market for CZ at present is over $200.millions !!!

I doubt very much than your piece of rough was synthetic
moissanite, first it is not on the market yet. I also doubt very
much it is natural moissanite, you did cut a 5mm stone out of it,
way too big (if it is you have a museum piece!).Your rough was
easy to cut, synthetic moissanite has a hardness of 9.5 which is
between corundum 9 and diamond 10. Now diamond is 140 times
harder than corundum. What did you cut it with and polished it
with ? Your dealer oriented and marked the rough where to cut the
table, most likely because the stone is doubly refractive and was
trying to minimize the double refraction. Your cut stone lack
brilliance, synthetic moissanite is visually similar to diamond.

Out of curiosity find someone (gemmologist) in your area to find
out what you have been sold (they might be some of that same
stuff in the next parcel you buy, but next time you might not be
told!!!) and run those tests:

  • polariscope, find if your stone is singly or doubly refractive,
  • set it on the refractometer, get an RI,
  • immerse it in a set of SG liquids, find its SG,
  • look at it through a microscope, find the inclusions,

if you can’t get an RI and SG , find what it does under SW/LW/UV
lights see if you can get an AS on the spectroscope.

Have fun with your mysterious stone. Give me the results, may be
we can solve the mystery.

Sincerely.
Francoise.


#3

Hi. I have been able to play with -and photograph- some synthetic
moissanite samples both for C3 and for JCK when I worked there as
an editor. I can tell you that it is a quite convincing simulant at
first sight. I personally could not make out the “doubling” effect
with the naked eye. Even with magnification, I had to strain hard
to see it, though I have seen promotional material prepared by C3
where the “doubling” seems obvious. Remember, the birefringence of
synthetic moissanite is small, and when optimally cut,
birefringence is also minimized when viewed in certain directions.
In tests conducted by C3, approximately 40 jewelers and pawn-shop
owners were fooled because they did the obvious thing: many used a
thermal probe – which hitherto has been a diagnostic tool to
separate diamond from simulants. (Only diamond is thermally
conductive. That is till synth. moissanite showed up. It is also
thermally conductive.) Using a probe was the obvious, routine thing
to do for jewelers, many of whom are not gemologists.

The following is KEY. Don’t throw away your diamond probe. It
will still help jewelers separate diamonds from other simulants. If
you get a “green light,” when using a diamond probe, this now means
that other tests will need to be performed to separate diamond from
synthetic moissanite. If you are gemologically inclined, and don’t
want to spring for the$525 tester C3 has developed, check for
doubling (under magnification) check for bearding (you’ll only see
that in a diamond) and check the girdle. A granular, sugar-like
structure means diamond, (as long as the girdle isn’t polished.)
Also, synthetic moissanite floats in 3.32 specific gravity liquid.
Diamond doesn’t. Under magnification, check for whitish, stringy
or ribbon-like inclusions which are not seen in diamond but do
occur in syn. moissanite. Also remember that for now VERY few
samples are even on the market yet. C3 only just released the
first samples this month (February) and they are under .50 ct in
size.

Best,
Robert