Moissanite is the name given to naturally occurring silicon carbide and to its various crystalline polymorphs. It has the chemical formula SiC and is a rare mineral, discovered by Henri Moissan in 1893, years after it had been synthesized in laboratories.
Mineral moissanite was discovered by Henri Moissan while examining rock samples from a meteor crater located in Canyon Diablo,Arizona, in 1893. At first, he mistakenly identified the crystals as diamonds, but in 1904 he identified the crystals as silicon carbide. The mineral form of silicon carbide was named moissanite in honor of Moissan later on in his life. The discovery in theCanyon Diablo meteorite and other places was challenged for a long time as carborundum contamination from human abrasive tools.
Until the 1950s no other source, apart from meteorites, had been encountered. Later moissanite was found as inclusions in kimberlitefrom a diamond mine in Yakutia in 1959, and in the Green River Formation in Wyoming in 1958. The existence of moissanite in nature was questioned even in 1986 by Charles Milton, an American geologist.
Moissanite, in its natural form, is very rare. It has only been discovered in a small variety of places from upper mantle rock tometeorites. Discoveries have shown that moissanite occurs naturally as inclusions in diamonds, xenoliths, and ultramafic rocks such as kimberlite and lamproite. They have also been identified in carbonaceous chondrite meteorites as presolar grains.
Moissanite was introduced to the jewelry market in 1998. It is regarded as a diamond alternative, with some optical properties exceeding those of diamond. Its lower price, and less exploitative mining practices necessary to obtain it, makes it a popular alternative to diamonds. Due in part to the similar thermal conductivity of moissanite and diamond, it is a popular target for scams; however, higher electrical conductivity and birefringence of moissanite may alert a buyer to fraud. In addition, thermoluminescence is exhibited in moissanite, such that heating it gradually will cause it to change color starting at around 150 degrees Fahrenheit. This color change can be diagnostic for distinguishing diamond and moissanite, although birefringence and electrical conductivity differential are more practical diagnostic differentiators. On the Mohs scale it is a 9.5, with a diamond being a 10. Moissanite is stronger than sapphire or ruby. In many developed countries, the use of moissanite in jewelry has been patented; these patents expire in 2015 for the US, and 2016 in other countries. Moissanite gemstones are sometimes marketed under the trademark Berzelian, a reference to the work of Berzelius on SiC.
Because of its hardness, it can be used in high-pressure experiments, as a replacement for diamond (see diamond anvil cell). Since large diamonds are usually too expensive to be used as anvils, synthetic moissanite is more often used in large-volume experiments. Synthetic moissanite is also interesting for electronic and thermal applications because itsthermal conductivity is similar to that of diamonds. High power SiC electronic devices are expected to find use in the design of protection circuits used for motors, actuators, and energy storage or pulse power systems.
