Diamond Simulants: | Moissanite


Gem-grade Moissanite (Silicon Carbide or Carborundum), manufactured by C3 and Cree Research, was introduced to the jewelry market in 1998. Moissanite was named after French chemist Dr. Henri Moissan (above, left) who won the Nobel Prize in 1906 for his discovery of a new mineral (moissanite-6H) found within meteorite fragments of the ancient Barringer meteor crater (above, center) near Winslow, Arizona. Moissanite, found only in iron-nickel meteorites, is classified as an element rather than a compound.
Moissanite has a hardness of 9.25 on the Mohs scale, while diamond has a hardness of 10. Moissanite is doubly refractive and the refractive index of Moissanite is 2.65 to 2.69. The Toughness of Moissanite is Excellent. Colorless synthetic Moissanite has the appearance of colorless diamond and is more difficult to detect than CZ.

Identifying Moissanite

Due to the anisotropic (doubly refractive) quality of Moissanite, when examining the gem through the kite facets, a doubled image of the opposite facet edges will be visible. Diamond is isotropic (singly refractive) with a refractive index (RI) of 2.417. Moissanite has an RI of 2.670. Moissanite has a very high dispersion index of 0.104 as compared to CZ at 0.060, and diamond at 0.044. Synthetic Moissanite has a thermal conductivity that is very similar to diamond, rendering a thermal conductivity test ineffective
Hodgkinson's 'Visual Optics' Detection

The Hodgkinson technique (aka Visual Optics) was discovered by Alan Hodgkinson with Gem-A in the mid-1970s as a method for differentiating natural diamond from colorless gemstones and simulants. By holding the table or crown very close to your eye while squinting, you look at a single point of light (pen flashlight, candle, etc.) in a dark room. The refraction patterns are distinctly different from material to material.

A small, detailed and sharply focused pattern caused by secondary reflections will be seen when observing a diamond, due to its high refractive index. A similarly sharp, but significantly larger pattern will be visible in Moissanite due to its high RI. Cubic Zirconia's pattern will be more diffused, caused by primary reflections from the pavilion and CZ's low RI.

Moissanite vs Diamond - Detectable to the Naked Eye
  • Dispersion Pattern: Secondary patterns of dispersion due to double refraction
  • Color: Moissanite has a slight yellow color and does not come in grades better than 'J'
  • Lack of Flaws: Moissanite is virtually flawless, most diamonds have some inclusions
Moissanite vs Diamond - Detectable With Testing
  • Double Refraction: Moissanite is double refractive, diamond is singly refractive
  • Refractive Index: Moissanite has a refractive index of 2.670, Diamond's RI is 2.417
Moissanite is double refractive (anisotropic) while a natural diamond is singly refractive (isotropic). You can also Inspect the facet edges with a 10x loupe to look for any chipping or slightly rounded or soft (not sharp) edges that are telltale signs of Simulants.

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