Moissanite — The Silicon Carbide Diamond Simulant
Moissanite — The Silicon Carbide Diamond Simulant
From Henri Moissan's 1893 meteorite discovery to modern laboratory-grown gem material at Mohs 9.25
Moissanite is silicon carbide (SiC), a hard, lustrous, transparent material that has been used commercially as a diamond simulant since 1998. Natural moissanite is exceptionally rare, first identified in 1893 by the French chemist Henri Moissan in fragments of the Canyon Diablo meteorite at Meteor Crater in Arizona; all moissanite used in jewellery today is laboratory-grown, with the principal commercial production developed by Charles & Colvard from the late 1990s onward. Moissanite occupies a distinct position in the diamond-alternative market, distinguished from cubic zirconia by its superior hardness and from lab-grown diamond by its lower cost and its different optical character.
Composition and properties
Moissanite is hexagonal or trigonal silicon carbide, depending on the polytype. Its hardness is 9.25 on the Mohs scale, second only to diamond among common gem materials and well above the durability threshold for daily-wear jewellery. Refractive indices are approximately 2.65 to 2.69, considerably higher than diamond's 2.42 and cubic zirconia's 2.15-2.18, with the result that moissanite returns light efficiently and produces strong brilliance from cut stones. Specific gravity is 3.22, lower than diamond's 3.52 and cubic zirconia's 5.6 to 6.0, which means a moissanite of equivalent measurements weighs less than a diamond.
Dispersion — the property that produces the rainbow-coloured fire of cut stones — is approximately 0.104 in moissanite, well above diamond's 0.044. The result is a stone with substantially more visible fire than diamond, an optical character that some buyers prefer and others find ostentatious. Thermal conductivity is similar to diamond, which means the older single-test thermal-conductivity probes cannot distinguish moissanite from diamond; modern multi-test diamond detectors that combine thermal conductivity with other properties (electrical conductivity, optical refraction) can readily distinguish the two.
Distinguishing moissanite from diamond
Moissanite is doubly refractive, while diamond is singly refractive. Under 10x magnification, moissanite typically shows a faint doubling of facet edges visible through the table, particularly when the stone is examined from oblique angles. Diamond shows no such doubling. The doubling is the most reliable visual distinguisher between the two materials at the bench level, and any properly trained gemmologist can confirm a moissanite identification quickly.
Modern moissanite detectors combine multiple property tests to produce reliable identifications at the retail level. The Presidium MultiTester and similar devices test electrical conductivity, thermal conductivity, and ultraviolet response in combination, producing rapid and accurate diamond-versus-moissanite-versus-CZ classifications. For laboratory-grade identification, infrared and Raman spectroscopy provide definitive separation.
The discovery story
Henri Moissan, the chemist who would receive the 1906 Nobel Prize for his isolation of fluorine, identified silicon carbide in fragments of the Canyon Diablo meteorite while investigating the meteorite's mineralogy in 1893. Moissan initially mistook the silicon carbide for diamond, and the corrected identification took several years to establish. Natural silicon carbide was confirmed in 1905 and named moissanite in honour of its discoverer. Subsequent studies have found small amounts of natural moissanite in a handful of unusual mineral environments, but the natural occurrence is far too rare to support a gem trade.
Synthetic silicon carbide had been produced industrially since 1893, predominantly for use as an abrasive (carborundum) and in semiconductor applications. The development of moissanite as a gem material required a quite different production process — large, transparent, gem-quality single crystals — which was achieved by Charles & Colvard in the late 1990s using a modified Lely sublimation process and proprietary refinements.
Position in the modern market
Moissanite is marketed primarily as a diamond alternative, particularly for engagement-ring buyers who want the appearance of a large, brilliant centre stone at a fraction of the cost of an equivalent diamond. Typical retail pricing for moissanite runs at approximately 10 to 15 percent of the price of an equivalent diamond, though the gap has narrowed substantially since 2018 as lab-grown diamond prices have fallen.
The competitive landscape has shifted significantly with the rise of affordable lab-grown diamond. Where moissanite once enjoyed a clear value proposition as the only durable, brilliant, sub-thousand-dollar diamond alternative, lab-grown diamond now offers actual diamond at competitive prices, and moissanite's market share has correspondingly declined. Moissanite retains advantages in fire (higher than diamond), in price (still lower than lab-grown diamond at equivalent sizes), and in some buyer preferences for the visibly different optical character of the higher-dispersion stone. See also: lab-grown diamond; cubic zirconia; diamond simulant.
Disclosure
Moissanite must be disclosed under Federal Trade Commission Jewelry Guides and equivalent standards in other jurisdictions. Selling moissanite as diamond, or in a manner that creates the impression of natural diamond, is a deceptive trade practice. Reputable retailers identify moissanite explicitly in marketing, sales, and accompanying documentation.