Moissanite is a trade name given to silicon carbide for it's use in the gem business. As a gemstone, silicon carbide is similar to diamond in a few very important ways: it is transparent and extremely hard (9 1/4 on the Mohs scale, compared to 10 for a diamond), with an index of refraction sport ween 2.65 and 2.69 (compared to 2.42 for diamond). Moissanites have 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 moissanite 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 moissanite 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.