Natural, Synthetic, and Simulant Categories
A stone can be mined, grown in a lab, or be a different material entirely. The label should say which of the three you are buying.
Every stone in the market falls into one of three categories, and the words used in a listing should tell you which one you are looking at without ambiguity.
Natural
A natural stone formed in the earth without human involvement in its creation. Cutting, polishing, and treatment may still have happened, and a treated natural stone is still natural. Natural does not mean untreated, and it does not mean high quality.
Synthetic
A synthetic stone has the same chemical composition and the same crystal structure as its natural counterpart, grown by people. Synthetic sapphire is corundum. Synthetic emerald is beryl. Lab-grown diamond is diamond, carbon arranged in the same lattice.
The production methods are well established: flame fusion, flux growth, hydrothermal growth, and pulling from a melt, with chemical vapor deposition and high-pressure growth used for diamond. The material is real, durable, and consistent, and it is often a fraction of the price of natural material of the same size.
Using the word synthetic is not an insult. Selling it as natural is the problem, and so is pricing it as natural.
Simulant
A simulant is a different material that resembles the stone it is imitating. It has a different composition and often a different structure.
- Glass is a simulant for nearly everything.
- Cubic zirconia is a simulant for diamond.
- Synthetic spinel is used as a simulant for several colored stones.
- Synthetic moissanite is silicon carbide used as a diamond simulant, and it is a distinct mineral in its own right.
The distinction matters because a simulant has no gemological relationship to the stone it imitates beyond appearance.
Telling them apart
Measurements do most of the work at the simulant end. Glass usually reads a single refractive index near 1.5 with a specific gravity around 2.5. Cubic zirconia reads about 2.16 with a specific gravity near 5.8. Diamond reads 2.417 with a specific gravity of 3.52. Those numbers separate those three quickly.
At the synthetic end the picture changes. Synthetic sapphire has essentially the same refractive index and specific gravity as natural sapphire. Measurements will confirm the species and will not tell you how it formed. Separating natural from lab-grown in those species takes magnification and instruments, looking for growth features: curved growth lines in flame-fusion material, flux residues, or metal platelets.
Some distinctions need a gem laboratory. Lab-grown diamonds are commonly identified by spectroscopy and by growth patterns under magnification, which is why the report matters when the difference in price is large.
A few clues exist for a careful buyer with a loupe. Bubbles in a stone suggest glass or a melt-grown synthetic. Rounded facet edges suggest glass. A perfect, identical pattern of color patches in opal points toward lab-grown material, while natural opal usually shows irregular patches.
What the label must say
In the United States, the Federal Trade Commission's jewelry guidance requires that a lab-grown stone be described with words such as lab-grown, lab-created, laboratory-grown, or synthetic. Calling a lab-grown diamond genuine or real is deceptive, since those words imply mined origin.
One useful exception to keep straight: a cultured pearl is a real pearl, grown in a mollusk with human help, and it is not the same as an imitation pearl, which is glass or plastic coated with a pearl-like finish.
Ask two questions of any listing: what species is this, and was it grown in the earth or in a lab. If both answers are on the page, the category is settled before you look at the price.
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