Background

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 a new mineral and called it silicon carbide (SiC). The mineral form of silicon carbide was named moissanite in honor of Moissan later on in his life.

Until the 1950s no other source, apart from meteorites, had been found. Later it was found as inclusion in kimberlite from a diamond mine in Yakutia in 1959, and in the Green River Formation in Wyoming in 1958. The discovery in the Canyon Diablo meteorite and other places was challenged for a long time to be carborundum contamination from human abrasive tools. The existence of moissanite in nature was questioned even in 1986 by Charles Milton, an American geologist.

Geological occurrence

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.

Composition

All applications of silicon carbide today use synthetic material, as the natural material is incredibly scarce. Silicon carbide was first synthesized by Jons Jacob Berzelius, who is best known for his discovery of silicon. Years later, Acheson produced viable minerals that could substitute diamond as an abrasive and cutting material. This was possible as moissanite is one of the hardest substances known to man, falling only behind rhenium diboride and diamond in hardness. Acheson mixed coke and silica in a furnace and found a crystalline product characterized by a great hardness, refractability, and infusibility, which was shown to be a compound of carbon and silicon. Since naturally occurring moissanite is so rare, lab-grown moissanite is the only commercially viable version of the mineral.

Structure

The structure of moissanite is one of its greatest properties. Similar to the diamond structure, moissanite's structure gives it great strength, making it useful for testing applications and microelectronics. The crystalline structure is held together with strong covalent bonding that gives moissanite its strength along with other properties that rival diamond. Moissanite has little to no anisotropies occurring with in the crystal structure, thus giving it the ability to withstand high pressures and temperatures. On the Mohs scale of hardness, moissanite is graded at 9.25, second in strength only to diamond. Moissanite is harder than rubies and sapphires which come in at a hardness of 9, and significantly harder than cubic zirconia, which is a brittle material and takes damage relatively easily.