Moissanite: The Second Hardest Mineral in Nature after Diamond

Moissanite is a naturally occurring mineral called silicon carbide, but it is so rare that it is almost never found in nature in large enough pieces to be cut into gemstones. For this reason, all of the moissanite used in jewelry is created in a laboratory. Moissanite was first discovered in a meteor crater in Arizona in 1893.

Moissanite is the name given to naturally occurring silicon carbide and to its various crystalline polymorphs. Silicon carbide is useful for commercial and industrial applications due to its hardness, optical properties and thermal conductivity.

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 was named in his honour.

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.
Geology:
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.

The colors seen in moissanite from the Mount Carmel area of northern Israel range from dark blue to light green. Note the broken or rounded morphology. Composite. photo by Aurélien Delaunay.

Formula: SiC
System: Hexagonal
Colour: Green, black, Blue, Colorless, Green yellow, Yellow
Lustre: Vitreous
Hardness: 9½

References:
Gemological Institute of America Inc.
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