How to spot a fake gemstone listing on Amazon

GuideUpdated November 1, 2026

Most fake gemstone listings fail one of three checks. The label: under the US FTC Jewelry Guides (16 CFR 23.25), a stone that was not mined must have its gem name preceded, just as prominently, by a word such as lab-grown, lab-created, imitation or simulated. The price: it has to fit the material. The numbers: a size in millimetres and a carat weight that you can check against each other when it arrives. A listing is the seller’s own description, so treat every line of it as a claim to check.

Illustration (AI render): read the listing, then check the piece when it arrives.

The three checks

The qualifier word in front of the gem name

The FTC Jewelry Guides make it unfair or deceptive to use an unqualified gem name, such as ruby, sapphire or emerald, for anything that is not a mined stone of that kind (16 CFR 23.25(a)). A lab-made or imitation stone may carry the gem name only when it is immediately preceded with equal conspicuousness by “laboratory-grown”, “laboratory-created”, “[manufacturer name]-created” or a phrase of like meaning, or by “imitation” or “simulated” (23.25(b)). So “Lab-Created Ruby” and “Simulated Emerald” are honest labels for two very different things, while “Ruby Ring” on a cheap listing, or “Faux Emerald”, tells you nothing: the Guides say “faux” is not an adequate disclosure.
A price that fits the material

Lab ruby and sapphire are cheap because flame fusion, in GIA’s words, remains the least expensive and most common way to make synthetic and spinel. Lab emerald is grown by flux or hydrothermal methods, which GIA describes as slow and expensive (flux growth can take up to a year), so it never costs what lab ruby does. A large “natural” ruby or emerald for the price of a meal is not natural, and hundreds of carats of “lab emerald” for pocket money are not emerald. For listings that passed this check, see lab gems worth buying.
A size and a weight you can check

A good listing gives length, width and depth in millimetres and the weight in carats (a carat is 200 milligrams, 16 CFR 23.18). The two numbers together give the stone’s density, and density separates corundum from glass and from cubic zirconia. A listing with no dimensions cannot be checked this way, which is reason enough to skip it. Put the numbers into the weight checker below.

Lab-created, simulated and the other words, defined

Lab-created, lab-grown, [maker]-created, synthetic: The same mineral as the mined gem, made in a laboratory. GIA defines a synthetic gem material as one made in a laboratory, and the FTC lets a seller pair these words with a gem name only if the product has essentially the same optical, physical and chemical properties as the stone named (16 CFR 23.25(c)). A lab-created ruby is corundum, the same mineral as a mined ruby.
Simulated, imitation: A look-alike. GIA describes a simulant as a material that looks like another gem but has a very different chemical composition, crystal structure and optical and physical properties. Glass, cubic zirconia and YAG are the usual ones.
Real, genuine, natural, precious: Never correct on a lab stone: the FTC calls it unfair or deceptive to use these words for anything manufactured or produced artificially (16 CFR 23.27).
Faux: Not an adequate disclosure that a stone was not mined, according to the FTC Jewelry Guides.

Claims you can check at home

925, S925, sterling: look for the stamp inside the band or on the post. Under 16 CFR 23.5, “sterling” means at least 925 parts per thousand silver. More in what metal labels mean.
Size in millimetres: digital calipers. A 6 by 8 mm oval either is or is not.
Carat weight: a carat scale. Check whether the listing gives the weight of one stone or a total for the whole piece.
Diamond vs moissanite: GIA found that thermal diamond testers react to synthetic moissanite as if it were diamond, so a plain thermal tester cannot separate them. Use a tester sold to tell moissanite from diamond, or look through a side facet with a 10x loupe: moissanite shows doubled facet edges. See does moissanite pass a diamond tester?
Certificate included: it is in the box or it is not. A report from GIA or IGI can be looked up; see how to verify an IGI or GIA certificate number.

Claims you cannot check without a lab

D colour, VVS1, Ideal or 3EX cut: on moissanite and small melee these describe a batch, in the seller’s words. Only a laboratory report whose number you look up yourself grades the stone you hold. IGI reports give colour and clarity grades on lab-grown diamonds; since 1 October 2025, GIA describes colourless and near-colourless lab-grown diamonds only as Premium or Standard.
Natural: on a cheap parcel, unverifiable; on a single stone, ask for a report.
No treatment mentioned: the FTC expects a seller to disclose a treatment that is not permanent, that needs special care, or that significantly affects value, and for online sales to say so in the product description (16 CFR 23.24). Only a lab can confirm a stone is untreated. See gem treatments explained.
CVD or HPHT: both make lab-grown diamond. You cannot tell which at home; a laboratory report may state the growth method.

Words that tell you nothing

Grade A+, AAA, AAAAA: a seller’s own scale, not a laboratory grade.
Diamond-level shiny, high purity, luxury: adjectives.
“Sapphire ring” with no carat weight, no origin and no “lab-created”: a sapphire-coloured stone. The same goes for “emerald” and “ruby” in a title at signet-ring prices.
“Green Emerald Cubic Zirconia”: read to the end of the title. The stone is the last noun, so this is a green cubic zirconia, not an emerald; the same goes for the text on the listing photos.
Gold plated, white gold plated, rhodium plated: a thin coat over another metal. See what each metal label means.

Home tests when it arrives

None of these needs a gem lab. Run them inside the return window. For gold, silver, diamond, moissanite, emerald, opal and pearl tests too, see how to tell if it’s real.

Weigh and measure

A carat scale and digital calipers. Measure length, width and depth in millimetres, weigh in carats, and put the numbers in the checker below. Corundum lands near 4.0, ordinary glass near 2.5 and cubic zirconia near 6.

UV torch

Use a torch rated 365 nm: that is the long-wave UV GIA’s laboratories use. GIA recorded a strong red glow under long-wave UV on a flame-fusion ruby (one with a flux-grown overgrowth). A strong red glow fits lab ruby; a “lab ruby” that stays dark deserves a closer look. The glow alone does not prove ruby, so pair it with the weight check.

Lapis: the acetone swab

Rub a hidden spot with a cotton bud dipped in acetone, the solvent in many nail polish removers. GIA’s laboratory tests lapis for dye this way, and found the dye mostly in cracks and porous areas. Blue on the swab means dyed stone. A clean swab is not proof: GIA also saw heavily dyed beads, sealed with paraffin, that the swab test did not reveal as clearly. Real lapis often shows gold-coloured flecks of pyrite and some white calcite.

Jade and other dyed stones: look in the cracks

Shine a torch through the stone and look with a 10x loupe. GIA describes dyed jadeite as showing green concentrated in the boundary gaps between grains. Colour gathered along the grain edges and in cracks, like a web of veins, points to dye. For valuable jadeite, only a laboratory report settles it.

Weight checker

An estimate: cutting proportions vary, so allow about 15 percent either way.

Shape Length mm Width mm Depth mm Weight ct

A result in the corundum range fits lab ruby or sapphire but does not prove it: the heaviest glass weighs as much.

How heavy each material is (specific gravity, water = 1)
Material	Specific gravity	Note
Glass	2.0 to 4.5; ordinary soda-lime glass about 2.5	The most common imitation. The heaviest glass reaches the corundum range, so weight alone never clears a “ruby”.
Quartz	2.65
(emerald)	about 2.7	Almost the same as ordinary glass, so weight cannot catch a fake emerald
Diamond	3.52
Spinel	about 3.6	Also made cheaply by flame fusion
Corundum (ruby, sapphire)	about 4.0	Lab-grown and mined alike
YAG (yttrium aluminium garnet)	4.55 to 4.65	A lab-made diamond imitation
Cubic zirconia	5.5 to 6.0	Much heavier than diamond or corundum

Corundum, beryl, quartz and spinel: Handbook of Mineralogy. Diamond: 16 CFR 23.12. Glass, YAG and cubic zirconia: International Gem Society; ordinary soda-lime glass: Wikipedia.

Listings we leave out

These turned up while we checked listings for lab gems worth buying. We do not link them, and you should read their listings carefully if you meet them.

REAL-GEMS. Ruby listings with no dimensions, so the weight cannot be checked, and “Genuine!” in the title of a lab stone, a word the FTC Jewelry Guides rule out for anything made artificially.
GEMHUB. Sells “natural” rubies of over 1,000 carats for the price of lunch. A natural ruby that size would be a museum piece.
DiamondDream. Copies Gryrigns titles word for word, and sells cheaper.
SEAHAWK19. Sells rough that looks exactly like lab ruby rough as “raw natural ruby”.
Huge, cheap “lab emerald”, “lab topaz” or “padparadscha” rough. Lots of hundreds of carats for pocket money. Lab emerald is grown by the flux or hydrothermal methods, which GIA describes as slow and expensive, so hundreds of carats of it cannot cost that little.
“Nano emerald”, “nano crystal” and “emerald colour”. Glass-ceramic and glass, not beryl.
Cheap “colour-change lab alexandrite”. GIA notes that an inexpensive gem with a strong red-green colour change is likely to be a synthetic or a simulant, and that “alexandrite sapphire” generally means lab-grown sapphire made to change colour. Look for the mineral’s name in the listing.

What to do on delivery

Photograph everything before you wear it, run the checks above, and send back anything that fails them. Your protection is the return window on the listing and, for items from third-party sellers, Amazon’s A-to-z Guarantee, which covers an item that is damaged, defective or materially different from what you ordered once you have asked the seller for a return. Keep photos and any test results as evidence.

Frequently Asked Questions

How do you spot a fake gemstone listing on Amazon?

Run three checks. If the stone was not mined, the gem name should come straight after a word such as lab-grown, lab-created, imitation or simulated, as the US FTC Jewelry Guides (16 CFR 23.25) require. The price should fit the material. And the listing should give a size in millimetres and a carat weight, so you can check one against the other when it arrives.

What is the difference between lab-created and simulated?

A lab-created (lab-grown) gem is the mineral itself, made in a laboratory: a lab-created ruby is corundum, like a mined ruby, and the FTC allows a word such as lab-created next to a gem name only when the stone has essentially the same optical, physical and chemical properties as the gem named. A simulated or imitation stone only looks like the gem and is a different material, such as glass, cubic zirconia or YAG.

Can a seller call a lab-grown stone real, genuine or natural?

No. The FTC Jewelry Guides (16 CFR 23.27) call it unfair or deceptive to describe anything manufactured or produced artificially as real, genuine, natural, precious or semi-precious. On a lab stone, those words are a red flag.

Is “faux ruby” an honest label?

Not on its own. The FTC Jewelry Guides say the word “faux” is not an adequate disclosure that a stone was not mined. An honest label says lab-created, lab-grown, imitation or simulated.

Does a certificate in the box prove the stone is real?

Only if it is a report from an independent laboratory and you look its number up yourself on that laboratory’s own website, then match the weight and measurements to the stone. A card printed for the seller proves nothing. How to verify an IGI or GIA certificate number

What can you do if the stone is not what the listing said?

Use the return window on the listing. For items from third-party sellers, Amazon’s A-to-z Guarantee also covers an item that is damaged, defective or materially different from what you ordered, once you have asked the seller for a return. Keep photos and any test results as evidence.