Linda, The answers to your query are in the Orchid Archives. I posed
the same Question in December and got some excellent replies.
Here is the info I found most useful… Bob Williams
 Moissanite Website is: www.moissanite.com
 Response by Francoise Jones:
It is Professor Henri Moissanite that first discoveredmoissanite in
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 occur
only in small grains ( around 1mm ). 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
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 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.
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.
 Reply by Oya Borahan:
Hello Bob Williams, You will find an article about Moissanite in
Winter 1997 issue of Gem & Gemology of GIA publication. I am writing
these from G&G:
What does anyone know about the following : Chemical Composition :
Silicon Carbide (SiC)
Crystal System : …different crystal structures found having
cubic, hexagonal, rhombohedral symmetries. This complexity results
from the existence of polytypes, which represent different stacking
sequence of hexagonal layers of atoms.
Refractive Index: 2.648-2.691 Birefringence: 0.043 (moderate) Specific
Gravity: 3.22 (syntetic moissanite will float in methilene iodide (SG
3.32) diamond will sink. Hardness : 9 1/4 Thermal Conductivity: The
termal properties of moissanite is very close to those of diamond that
is why the termal probe reacts as if it were a diamond. Electrical
Conductivity: Variable with some speciments which displays electrical
conductivity Fluorescense: LW inert to orange Who makes or mines it?
Syntetic moissanite is a manmade product produced by C3 Inc. What is a
typical price to the trade ($/ct.)?: I wanted to take photographs of
the inclusions and structure of moissanite. A friend has brought me
from Far East a half carat stone for 50$. That is all I know about
its price. Kind regards from Istanbul, Turkey Oya Borahan