Gemstone used in jewelry, silicon carbide

As a Gemstone used in jewelry, silicon carbide is called Moissanite after the jewel's discoverer Dr. Henri Moissan[7]. Moissanite is similar to diamond in several important respects: it is transparent and hard (9, although a patent states 8.5-9.0,[8][9] on the Mohs scale compared to 10 for diamond), with a refractive index between 2.65 and 2.69 (compared to 2.42 for diamond). Moissanite is somewhat harder than common cubic zirconia. Unlike diamond, Moissanite is strongly birefringent. This quality is desirable in some optical applications, but not in gemstones. For this reason, Moissanite jewels are cut along the optic axis of the crystal to minimize birefringent effects. It is lighter (density 3.22 vs. 3.56), and much more resistant to heat. This results in a stone of higher lustre, sharper facets and good resilience. Loose moissanite stones may be placed directly into ring moulds; unlike diamond, which burns at 800 °C, moissanite remains undamaged by temperatures up to twice the 900 °C melting point of 18k gold.
Moissanite has become popular as a diamond substitute, and may be misidentified as diamond, since its thermal conductivity is much closer to that of diamond than any other diamond substitutes. It can be distinguished from diamond by its birefringence and a very slight green, yellow, or gray fluorescence under ultraviolet light.