Synthetic moissanite

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Synthetic Moissanite
Chemical composition Silicon Carbide - SiC
Crystal system Hexagonal
Habit Boule plates
Cleavage Weak (good parting)
Fracture Unknown
Hardness 9.25
Optic nature Uniaxial +
Refractive index 2.648 - 2.691
Birefringence 0.043
Dispersion High, 0.104
Specific gravity 3.22
Lustre Sub-adamantine
Pleochroism Unknown

Moissanite is a natural occurring mineral that is named after its discoverer, 1906 Nobel Prize (chemistry) winner Henri Moissan (1852-1907). As a natural source, this mineral is not suitable to be cut into gemstones as it occurs in too small grains.
Synthesizing moissanite has never been a real problem, however at first it was only synthesized for industrial purposes. This material, with a hardness of 9.25 on Moh's scale, is known by many bench jewelers and lapidarists as "carborundum" and is widely used as a sharpening tool for gravers and scrapers. As many who use carborundum can testify, this material is not very attractive as a gemstone.
Around 1987 Cree Research found a method to produce gemstone quality synthetic moissanite, but it was not until 1993 that a near-colorless crystal was obtained. Today this gemstone synthetic is marketed as Charles & Colvard created Moissanite™.

Although a nice synthetic on its own, this material is used mainly as a diamond simulant. Since the arrival of synthetic cubic zirconia in 1976, this is the most convincing diamond simulant, although a trained eye can easily separate synthetic moissanite from diamond.

References