Moissanite
| Moissanite | |
|---|---|
 |
|
| General | |
| Category | Mineral species |
|
Formula (repeating unit) |
SiC |
| Strunz classification | 1.DA.05 |
| Crystal system | 6H polytype, most common: hexagonal |
| Crystal class | 6H polytype: dihexagonal pyramidal (6mm) H-M symbol: (6mm) |
| Space group | 6H polytype: P63mc |
| Identification | |
| Color | Colorless, green, yellow |
| Crystal habit | Generally found as inclusions in other minerals |
| Cleavage | (0001) indistinct |
| Fracture | Conchoidal – fractures developed in brittle materials characterized by smoothly curving surfaces, e.g., quartz |
| Mohs scale hardness | 9.5 |
| Luster | Adamantine to metallic |
| Streak | greenish gray |
| Diaphaneity | transparent |
| Specific gravity | 3.218–3.22 |
| Refractive index | nω=2.654 nε=2.967, Birefringence 0.313 (6H form) |
| Ultraviolet fluorescence | orange-red |
| Melting point | 2730 °C (decomposes) |
| Solubility | none |
| Other characteristics | Not radioactive, non-magnetic |
| References | |
Moissanite (/ˈmɔɪsənaɪt/) 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 the French chemist Henri Moissan in 1893. Silicon carbide is useful for commercial and industrial applications due to its hardness, optical properties and thermal conductivity. Efforts to synthesize silicon carbide in a laboratory began in the late 1800s.
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. Artificial silicon carbide had been synthesized in the lab by Edward G. Acheson just two years prior to Moissan's discovery.
The mineral form of silicon carbide was named moissanite in honor of Moissan later on in his life. The discovery in the Canyon Diablo meteorite and other places was challenged for a long time as carborundum contamination from man-made abrasive tools.
Until the 1950s no other source, apart from meteorites, had been encountered. Later moissanite was found as inclusions in kimberlite from 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 to meteorites. 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.
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