Moissanite

Moissanite is a trade name given to silicon carbide (chemical formula SiC) for use in the gem business. more...

As a gemstone, silicon carbide is similar to diamond in several important ways: it is transparent and extremely hard (9 1/4 on the Mohs scale, compared to 10 for diamond), with an index of refraction between 2.65 and 2.69 (compared to 2.42 for diamond). SiC has a hexagonal crystalline structure.

Naturally occurring moissanite is extremely rare, as it is not formed naturally in any quantity within the Earth, and thus is found only in tiny quantities in certain types of meteorite and as microscopic traces in corundum deposits and kimberlite. Virtually all of the silicon carbide sold in the world, including moissanite gemstones, is synthetic. Natural moissanite was first found in 1905 as a small component of a meteorite in Arizona by Dr. Ferdinand Henri Moissan, after whom the material is named in the gem market. Synthetic silicon carbide has been known since 1892, when it was first produced by Eugene G. Acheson in his newly invented resistance furnace. Acheson named the material carborundum by analogy to corundum, another very hard substance (9 on the Mohs scale). Moissan's discovery of naturally occurring SiC was disputed at first due to the potential for contamination of his sample by silicon carbide saw blades that were already on the market at that time.

In 1998 C3, Inc. (Charles and Colvard), a subsidiary of Cree Research, Inc., introduced gem-quality synthetic silicon carbide onto the market under the name "moissanite," marketing it as a lower-cost alternative to diamond. For example, a 1 carat moissanite gem sells for about $600 (2005 USD), while a diamond of similar size and color typically runs for upwards of $4500. Synthetic moissonite is approximately as hard as diamond, with a slightly higher index of refraction and greater dispersion; these qualities make SiC a decent and durable diamond simulant. It is interesting to note that the higher dispersion and index of refraction means moissanite has more fire and brilliance than diamond.

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