Synthetic, Simulant, Imitation

Grown, not found · Field guide

Vocabulary

These three words are used interchangeably in listings and they mean genuinely different things. Getting them straight is the single most useful thing a beginner can do.

The three words

Synthetic (also lab-grown, lab-created) means the same substance nature makes, made by people instead. Same chemistry, same crystal structure, same hardness and refractive index. A synthetic ruby is a ruby. It is not a fake ruby, and a gemologist will call it ruby — with the word "synthetic" attached, because that fact changes the price by two or three orders of magnitude.

Simulant means something that looks like a given gem but is a different material. Cubic zirconia is not a synthetic diamond; it's a diamond simulant. It's zirconium oxide, a different substance with different hardness, different density, different everything. The only thing it shares with diamond is the appearance.

Imitation is close to a synonym for simulant, and it's the formal term in CIBJO's trade standards: an artificial product that copies a gem's appearance without its chemistry, properties or structure. In everyday use it tends to mean glass or plastic. A doublet, with a thin slice of the real thing on top of something cheap, is its own category: a composite or assembled stone.

The fourth category

Some of the most interesting material on a faceter's bench is none of the above. YAG, LuAG, GGG, lithium niobate and nanosital have no natural counterpart at all. There is no mineral with that formula. Calling YAG "synthetic garnet" is a category error in gem terms: it has the garnet crystal structure but not the chemistry of any garnet nature has ever produced.

These materials are neither synthetics nor simulants when sold on their own merits. Gemologists usually call them artificial or man-made: engineered crystals that happen to be beautiful. More on that distinction here.

What the disclosure words legally promise

In the United States the Federal Trade Commission's Jewelry Guides govern how lab-grown material must be described. The practical upshot for a buyer:

• A lab-grown stone has to be disclosed clearly and conspicuously, using a term like laboratory-grown, laboratory-created, or [maker]-created.
• Cultured is allowed only with a clear qualifier such as "laboratory-grown" beside it. On its own it borrows the pearl trade's vocabulary and implies something biological is happening.
• Synthetic is the precise gemological term, is still what laboratories use, and remains a listed qualifier for colored stones. For diamonds, the FTC dropped it from its examples in 2018 without banning it. You'll see both.
• No qualifier at all — plain "ruby", "emerald" — is supposed to mean natural. In practice, online listings break this rule constantly.

Grown is not the same as treated

A separate axis entirely. Almost all natural sapphire on the market has been heated. Most citrine is heated amethyst. Much blue topaz was colorless until it was irradiated. None of that makes the stone synthetic — it came out of the ground, and it was then improved. A treated natural stone and a lab-grown stone are two different disclosures, and a stone can be both (lab-grown then HPHT-treated is routine in CVD diamond).

Same material, different stone

"Chemically identical" is true and slightly misleading. What separates a natural crystal from a grown one is history, and history leaves marks:

• Inclusions. Natural stones carry other minerals, healed fractures, fluid pockets. Grown stones carry flux droplets, gas bubbles, seed plates, platinum flakes, or nothing at all.
• Growth structure. Verneuil boules show curved striae, because they grow under a curved cap of melt, and pulled crystals can show them too. Nature doesn't grow corundum that way: natural stones show straight, angular zoning.
• Perfection. Grown material is often too clean and too evenly colored. For a cutter that's a feature. For a valuer it's a red flag.

Trade names, decoded

*Trade names get reassigned. Diamonique in particular has referred to more than one material over the decades. Check the stated properties, not the name.

Why a cutter should care

Beyond honesty in resale, the material identity determines everything that happens at the lap. Cleavage decides whether a hard knock ends the stone. Heat sensitivity decides whether you can dop with wax. Birefringence decides whether orientation matters. Hardness decides your lap sequence. Getting the name right is the first step in not ruining the rough. The bench notes page covers this material by material.

A reference to lab-grown gem materials, written for cutters. Values are typical published figures; ranges vary with composition, dopant and measurement wavelength. Nothing here is a substitute for a laboratory report on a stone whose identity matters commercially.