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Synthetic Moissanit


#1

Hello all:

A new diamond imitation, synthetic moissanite (silicon carbide),
is now being produced by C3 Inc. in near-colorless form for jewelry
purposes. With refractive indices of 2.648 and 2.691, a dispersion
of 0.104, a hardness of 9� on the Mohs scale, and a specific
gravity of 3.22, synthetic moissanite is much closer to diamond in
overall appearance and heft than any previous diamond imitation.
The thermal properties of synthetic moissanite are also so close to
those of diamond that the thermal probes currently on the market
react to synthetic moissanite as if it were “diamond.” This new
material can be readily separated from diamond on the basis of its
anisotropic optical character, which produces a doubling in the
appearance of facet junctions. A new instrument manufactured by C3
Inc. solely to distinguish synthetic moissanite from diamond was
also examined for this study.

This was taken from the Gems and Gemology home page.

Michael Mathews Victoria,Texas USA


#2

It appears that C3 is more interested in selling there tester that
product. Most gemologist have a polariscope that will determine if
the mineral is doubly refractive. Cheaper testers are sure to
follow.


#3

Hi Michael,

It is Professor Henri Moissanite that first discovered moissanite
in 1904. Moissanite is the natural hexagonal polymorph of SiC. It
occurs in meteorites, a little gift from above, and also had just
been found in kimberlite rocks from Yakutia in Russia, but they
only occur in small grains (around 1 mm ). The grains can be green,
blue, black, transparent and yellow. It has a hardness of 9.50,
specific gravity of 3.218 and a refractive index of 2.654 - 2.697.
The fracture is conchoidal, cleavage not determined.

There are also an unnamed natural cubic form of SiC and a natural
trigonal form of SiC.

The synthetic form of SiC is called Carborundum and have all the
same properties.

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 9.50,
diamond hardness 10, refractive index 2.65, diamond RI 2.42,
specific gravity 3.21, diamond SG 3.5, this material is the closest
to diamond than any other gem materials. Most jewelers who had the
opportunities to view the material mistakenly identified synthetic
moissanite as diamond !!!

C3 Inc. plans to begin distributing its artificial gemstone in the
first half of 1998, in the US and the Pacific Rim. Also C3 Inc. is
taking a very strong position about the full disclosure of the
qualities of synthetic moissanite.

Three characteristics of synthetic moissanite :

  • it is doubly refractive,
  • it has white ribbon-like inclusions,
  • doesn’t show an absorption spectrum line at 415nm as 95% of the
    natural diamonds do.

Best Regards,

Francoise.


#4

Michael:

Regarding the info on synthetic moissanite, with the large
birefringence and HUGE dispersion, it’s going to be brilliant, but
not look that much like diamond, as far as I can tell from the
numbers. The dispersion is what gives CZ away in many cuts and if
my memory is correct the dispersion of the moissanite is much
higher, so it’s going to look more like a coated rhinestone, no?

It will certainly be a novelty, but I don’t think it will fool
anyone with any savvy at all. The text you quote is part of
someone’s lube job, I think.

Roy (Jess)


#5
    It will certainly be a novelty, but I don't think it will
fool anyone with any savvy at all. 

Hello Jess:

I worry about some of the counter help in stores that only know
that they are supposed to test the diamonds with the tester. I
wonder how many stores have take-in people that could tell the
difference. I’m sure it is a large percentage. I don’t really think
it will be a problem either. As long as diamonds are never
described as diamonds on the take-in ticket, you can usually steer
clear of those out to defraud. I will be interested to see some.

Michael Mathews Victoria,Texas USA


#6

Hi Gang,

There’s a good article on Moissanite in the current (Winter 97)
issue of Gems & Gemology. The article also describes the tester C3
mfgrs to differentiate between diamond & moissanite.

I had the oppourtunity to look a 1 carat moissanite srb at the
Tucson sho w. While the lighting wasn’t all it could have been, it
was possible to dete ct the doubling of facet junctions near the
culet with a 10x loupe. The dispersion was evident, but alot of the
apparent dispersion of a stone can be greatly affected by the
angles used in cutting the crown. The disperssion may help id a
stone as a diamond simulant, but don’t rely on it alone.

Dave


#7

Dave:

I am speaking out of turn as I haven’t seen moissanite, but if you
use visual gemology, I think the dispersion is going to be
unmistakeablely large. CZ is .060 and diamond is .044, but
moissanite is at least .080 (recent message said .100) If you have
a comparison stone it is going to be obvious in looking at the
rainbows, I think. Well, I am going to be looking for some at
this spring’s shows. I think you’re right, the double refraction
is going to be a bigger giveaway.

Roy (Jess)