Lab-Grown Diamonds · Simulants

What Is a Simulated Diamond? Every Type of Fake Diamond Explained (2026)

By Tushar Leclerc · 11 min read

Last Updated: September 3, 2026

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Search for a diamond alternative and you meet a wall of names: faux, simulant, imitation, synthetic, lab-created. Some describe real diamonds, some describe glass. The words get used loosely, and the looseness costs people money when a stone doesn't do what they expected.

Here is the clean version. There is one dividing line that matters, and it is not price or sparkle. It is whether the stone is actually carbon.

What is a simulated diamond?

A simulated diamond, also called a diamond simulant or faux diamond, is any material made or chosen to resemble a diamond while being something else entirely. It mimics the look. It does not share diamond's chemical makeup, its hardness, or the way it handles light.

That last point is what "fake" really means here: not fraudulent, just not a diamond. A cubic zirconia sold honestly as cubic zirconia is a perfectly legitimate stone. It only becomes a problem when it is passed off, or priced, as the real thing.

The word that causes the most confusion is synthetic. Historically it meant lab-made, but because "synthetic" sounds like "fake," many jewellers and the FTC now avoid it for lab-grown diamonds, which are not fake at all. We use "simulant" for the imitations and "lab-grown" for the real diamonds, and keep the two firmly apart.

The main types of fake diamond, ranked

Not all simulants are equal. Each has its own hardness, its own way with light, and its own honest use. Ranked from most convincing to least:

Moissanite

Silicon carbide, discovered by Henri Moissan in a meteor crater in 1893 and now grown in labs. Of all the simulants it is the closest to diamond in both looks and toughness, scoring 9.25 on the Mohs scale, second only to diamond itself. Its one giveaway is too much of a good thing: its refractive index is higher than diamond's, so it throws more coloured flash, the "disco ball" effect a trained eye spots immediately. Durable enough for daily wear, and the only simulant we would call a serious everyday stone.

Cubic zirconia (CZ)

Zirconium dioxide, lab-made since the 1970s and the most common fake diamond by volume. Brand new, a CZ is convincing. But at 8 to 8.5 Mohs it is markedly softer, and over a year or two of wear it scratches, clouds and loses its shine. Fine for costume and occasional pieces; a poor choice for a ring worn every day, unless you accept replacing it periodically.

White sapphire

A colourless corundum, 9 on the Mohs scale, so genuinely hard-wearing. The catch is its light: low dispersion gives it a soft, slightly glassy or milky look rather than diamond's sharp brilliance. Beautiful in a vintage or understated setting, disappointing if you specifically want sparkle.

White topaz

Softer again at 8 Mohs, clear when new but prone to scratching and dulling with wear. Low fire, low brilliance. Best kept to pendants or earrings, which take far less abuse than a ring.

Glass, rhinestone and YAG

The bottom of the range. Rhinestones and Swarovski crystal are cut glass, 6 to 7 Mohs, all surface sparkle and no diamond properties. Yttrium aluminium garnet was an early simulant now largely obsolete. Plain glass, at 5 to 6 Mohs, is the least diamond-like material of all. Fine for fashion, never for a ring meant to last.

Round SolitaireFrom $1,288 Oval HaloFrom $1,530 Oval Three-StoneFrom $1,450 Emerald SolitaireFrom $1,369 Hidden Halo PavéFrom $1,611

Why a lab-grown diamond is not a simulant

This is the distinction the whole subject turns on, and it is worth stating flatly: a lab-grown diamond is not a fake diamond. It is a real diamond.

The Federal Trade Commission confirmed in 2018 that a diamond does not have to be mined to be a diamond; it only has to be carbon in the right crystal structure. Grown in a reactor by the CVD or HPHT method, a lab diamond forms atom by atom in exactly that structure. It has diamond's hardness of 10, diamond's refractive index of 2.417, and diamond's chemistry, because it is diamond. Under a jeweller's loupe it cannot be told from a mined stone; only specialist equipment reading trace elements can separate the two.

A simulant only copies the appearance. Different chemistry, different hardness, different light. That is why a moissanite reads as "not diamond" on a thermal tester and a cubic zirconia clouds over within a couple of years, while a lab-grown diamond lasts for generations exactly as a mined one does.

Every Riona stone is IGI-certified and lab-grown, and arrives with its grading report. On the environmental side, a lab diamond avoids the land disturbance and tailings of mining, though its carbon footprint depends heavily on the electricity used to grow it, so treat any precise percentage, from us or anyone, with caution. Our complete guide to lab-grown diamonds covers how they are made in full.

Mined vs lab-grown vs moissanite

The three stones people actually weigh against each other, side by side. The first two are diamonds; the third is the best of the simulants.

A lab-grown diamond keeps every physical property of a mined stone at a fraction of the price. Moissanite is the strongest choice if size-for-money is the priority and you are happy that it is not a diamond. Our lab-grown versus natural comparison goes deeper on the first two columns.

How to choose between them

Strip away the marketing and it comes down to a short sequence of honest questions.

• Do you want a real diamond, or a stone that looks like one? If owning an actual diamond matters, that is lab-grown. If the look at the lowest possible price matters more, a simulant is legitimate.
• How hard is the piece's life? An everyday ring needs hardness. Lab-grown (10) and moissanite (9.25) shrug off daily wear; cubic zirconia and glass do not.
• What is the real budget? Because lab-grown removed most of the price gap, the old reason to reach for a simulant, cost, is weaker than it was. A 2-carat lab-grown solitaire starts at $1,288 here, against $18,000 or more for the mined equivalent.
• Does certification matter to you? Diamonds, mined or lab, get independent IGI or GIA grading. Simulants get only a brand's own paperwork.

Whatever you choose, insist on independent certification for any stone sold as a diamond. If a seller can't produce it, that tells you what you need to know.

How to spot a simulant yourself

You can't confirm a diamond at home, but you can catch several simulants. These separate the imitations from a real diamond; none of them will flag a lab-grown diamond, because it is a diamond and passes every one.

• The fog test. Breathe on the stone. A real diamond clears almost instantly because it disperses heat; glass and CZ stay fogged a moment longer. Rough, not decisive.
• The sparkle. A diamond returns mostly white light with flashes of colour. If the stone throws constant rainbow fire, it is likely moissanite or CZ.
• Wear and cloudiness. A stone that has dulled or scratched after light wear is almost certainly a soft simulant; a diamond will not.
• A thermal or moissanite tester. The only reliable at-home tools. A basic tester separates diamond from CZ and glass; a dual tester also flags moissanite.

For anything that matters, a jeweller settles it in minutes with an instrument that reads the metal and the stone without harming either.

Heart SolitaireFrom $1,369 Heart HaloFrom $1,530 Oval HaloFrom $1,530 Emerald SolitaireFrom $1,369 Hidden Halo PavéFrom $1,611

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