Moissanite vs Diamond | Diamond.co.za

Moissanite vs Diamond: quick comparison

These are two different materials, and that is the whole basis of the comparison. A diamond is crystalline carbon. Moissanite is silicon carbide — a different compound, with different optical and physical properties. Almost all moissanite sold is laboratory-created; natural moissanite is vanishingly rare and was first identified in a meteorite crater.

Moissanite is not a fake diamond and not an imitation in any dishonest sense. It is a real gemstone in its own right, sold openly as what it is, and it is durable enough for daily wear. It is only a problem when it is described as a diamond, or when a buyer is not told which one they are getting.

Property	Diamond	Moissanite
Material	Crystalline carbon	Silicon carbide
Mohs hardness	10	9.25
Refractive index	About 2.42	About 2.65 to 2.69
Dispersion (fire)	About 0.044	About 0.104
Optical character	Singly refractive	Doubly refractive
Graded on the 4Cs	Yes	No, different criteria
Origin	Mined or laboratory-grown	Almost always laboratory-created
Price level	Higher	Much lower
Resale market	Established for natural	Minimal

The short answer: if you want maximum sparkle for the least money and are happy that the stone is not a diamond, moissanite is an excellent buy. If the stone being a diamond matters — for its meaning, its grading framework or its resale position — then no amount of brilliance from another material substitutes for it.

Appearance and design differences

Unlike laboratory-grown versus natural diamond, where the stones are visually identical, moissanite and diamond do look different — and the difference is easiest to see in bright, direct light.

Moissanite shows far more fire. Its dispersion is roughly double that of diamond, meaning it splits white light into spectral colours much more strongly. The result is pronounced rainbow flashes. Some buyers love this; others find it reads as obviously not a diamond, and the effect is often described as a disco-ball or oil-slick look.
Diamond’s sparkle is whiter. Diamond returns more white light relative to coloured flashes, producing the crisper, icier scintillation most people associate with a diamond ring.
Moissanite is doubly refractive. Light entering the stone splits into two rays, which under magnification produces a visible doubling of the facet edges. Diamond is singly refractive and shows no such doubling. This is one of the ways a gemmologist tells them apart.
Size perception differs. Because moissanite is less dense than diamond, a moissanite of the same millimetre diameter weighs less. Reputable sellers therefore quote moissanite in millimetres or as a diamond-equivalent weight rather than in carats — if a moissanite is quoted in carats, ask what the actual measurement is.
Larger stones show the difference more. At small accent sizes the two are hard to distinguish; at two carats and above, moissanite’s fire becomes noticeably distinctive.

On design, moissanite imposes no constraints — any setting and metal works, and its hardness is more than adequate for a ring worn every day.

Quality and technical differences: optical differences, hardness, pricing and the distinction between diamond and simulant

Simulant is a precise term

A simulant is any material that resembles a diamond without being one — moissanite and cubic zirconia are both simulants. This is a category distinct from a laboratory-grown diamond, which is diamond: same carbon crystal, same hardness, graded on the same scales. The three-way distinction matters, and conflating them is the most common source of confusion in this whole subject. See lab-grown vs natural diamond for that separate comparison.

Grading works differently

Diamonds are graded on cut, colour, clarity and carat using the scales in GIA’s grading methodology, and issued with independent reports as described in GIA’s guide to report types. Moissanite is not graded on those scales. It is generally described by colour tier and size, and sold with a manufacturer’s certificate or warranty rather than an independent gemmological grading report. That is not a deficiency — it is simply a different product — but it does mean you cannot compare a moissanite’s “grades” against a diamond’s.

Why a diamond tester can mislead you

This is worth knowing. The common handheld testers measure thermal conductivity, and moissanite conducts heat similarly enough to diamond that it can register as diamond on those instruments. Testers that also measure electrical conductivity separate the two, because moissanite conducts electricity and diamond generally does not. So a stone passing a basic thermal tester has not been proven to be a diamond. For a stone of any value, an independent gemmological report is the answer, not a pen tester.

Price and value considerations

Moissanite costs a small fraction of what a diamond of equivalent size costs. That gap is the entire practical argument for it, and it is a strong one.

Size becomes almost unconstrained. A large moissanite is affordable in a way no diamond of the same dimensions is.
The setting becomes the main cost. With an inexpensive centre stone, the metal and labour dominate the quote — so a moissanite ring in platinum with a complex setting is not a cheap ring overall.
There is essentially no resale market. Moissanite is bought to be worn and should be treated as having no meaningful resale value. Neither stone should be bought as an investment — jewellery is not a regulated investment product and we do not give financial advice — but the difference in secondary market is real and worth naming.

If your reason for considering moissanite is purely budget, it is worth comparing against a laboratory-grown diamond before deciding. Laboratory-grown stones have fallen considerably in price, and for some buyers they now occupy the middle ground that moissanite used to own alone — a real diamond, graded conventionally, at a fraction of natural diamond cost. See moissanite vs lab diamond for that direct comparison.

Durability, maintenance or ownership trade-offs

Hardness. Diamond is 10 on the Mohs scale; moissanite is about 9.25. Both are comfortably hard enough for daily wear. In practice moissanite will resist scratching very well, though diamond remains the hardest material used in jewellery.
Toughness. Both can chip if struck at a vulnerable point — hardness resists scratching, toughness resists breaking, and they are different properties. Pointed and cornered shapes need protective settings in either material.
Cleaning. Identical for both, and neither clouds or degrades with normal wear.
Insurance. A diamond of any size should be documented and insured. Moissanite is generally not worth insuring separately, though the setting may be.
Ownership over time. The honest difference is social rather than physical: whether the stone being a diamond matters to you and to the person wearing it, over decades.

Who each option suits

Moissanite suits you if

You want maximum size and sparkle for the least outlay, and you actively like the extra fire.
You want a travel ring or an everyday alternative to a more valuable piece.
You would rather put the budget into the setting, or into something else entirely.
You are comfortable telling people it is moissanite, which you should never have to hide.

A diamond suits you if

The stone being a diamond is part of what the ring means.
You prefer white scintillation to strong rainbow fire.
You want an independently graded stone with a report you can verify.
You expect the piece to be passed on, or want it to hold a position in an established market.

Which option should you choose?

The question is not which stone is better — they are different materials serving different priorities. The question is whether you want a diamond, or whether you want the look of a large bright stone. Both are legitimate answers, and only you can give yours.

If it is the look you want, moissanite delivers it at a fraction of the cost and there is no reason to feel apologetic about the choice. If it is a diamond you want, buy a diamond — and if budget is the obstacle, look at laboratory-grown before you look at a simulant, because that route gives you an actual diamond with an actual grading report.

One firm rule either way: whatever you buy, get it in writing. The material should be stated explicitly on your documentation. A seller who is vague about whether a stone is diamond, laboratory-grown diamond or moissanite is the problem, whichever it turns out to be.

Continue to the relevant buying guide or book expert guidance

If you would like to see the difference rather than read about it, we can show comparable stones side by side so you can judge the fire for yourself. Continue at the diamond buying guide, or browse diamond rings and engagement rings.

Compare moissanite and diamond side by side