Natural vs Synthetic Gemstones
Tick what you can see through a 10x loupe and learn what it may indicate about origin and treatment, and which questions only a laboratory can answer.
What do you see under magnification?
This helper is educational and is not a lab verdict. A single feature can be misleading, and some synthetic and treated stones imitate natural features. A recognised gemological laboratory report is the only proof of origin and treatment.
Synthetic, imitation and treated: three different things
- Natural: formed in the earth. It may or may not have been treated.
- Synthetic (lab-grown): made in a laboratory with the same chemistry and crystal structure as the natural stone. It is real material, but it is not natural.
- Imitation: a different material that only looks similar, such as coloured glass or plastic.
- Treated: a natural stone enhanced by heating, oiling, filling, irradiation or diffusion.
Common synthetic types and what to look for
| Type | How it is made | Typical clues |
|---|---|---|
| Flame fusion (Verneuil) — ruby, sapphire, spinel | Powder melted in an oxyhydrogen flame | Curved growth lines (striae) and round gas bubbles |
| Flux-grown — ruby, sapphire, emerald, spinel | Crystals grown from a molten flux | Wispy flux veils, flux fingerprints, tiny metallic platelets |
| Hydrothermal — emerald, quartz | Crystals grown in hot pressurised water | Nailhead spicules and chevron growth patterns in emerald |
| CVD and HPHT — diamond | Carbon grown in a chamber or high-pressure press | Not visible with a loupe; needs laboratory spectroscopy and imaging |
What a phone or loupe cannot tell you
Modern lab-grown diamonds and some advanced treatments leave no clues a loupe can show. Even for stones with clear clues, one feature can be misleading, so gemologists combine several observations with measured properties. You can measure two of them yourself: refractive index with the Gemstone Identifier, and density with the Specific Gravity Calculator. Compare look-alikes with the Gemstone Comparator.
Buying a gemstone safely
- Ask for a report from a recognised gemological laboratory and check the report number matches the stone.
- Ask whether the stone is natural or synthetic and what treatments it has had, and get the answer in writing.
- Be careful when a large, flawless, richly coloured stone is offered at a very low price.
- Buy from sellers who supply verifiable certificates. You can check AA Gems & Jewelry certificates on the certificate verification page.
Frequently asked questions
Can I tell natural from synthetic with a phone camera?
No. The differences between natural and synthetic stones are microscopic, so they need at least a 10x loupe, and for some stones laboratory instruments. A phone photo cannot settle the question.
What is a synthetic gemstone?
A synthetic gemstone is made in a laboratory and has essentially the same chemical composition, crystal structure and properties as its natural counterpart. It is different from an imitation, which only looks similar, such as coloured glass.
Is lab-grown the same as fake?
A lab-grown stone is real in material terms, but it is not natural, and it must be sold as lab-grown or synthetic. Selling a synthetic as natural is misrepresentation. An imitation is a different material altogether.
What magnification do I need to check a gemstone?
A 10x loupe is the basic tool and reveals many clues. A gemological microscope with dark-field lighting shows far more. Some stones, especially lab-grown diamonds, cannot be separated from natural diamonds even under a microscope.
What is a flame-fusion synthetic?
Flame fusion, or the Verneuil process, melts powder in an oxyhydrogen flame and lets it crystallise as a boule. It is the oldest and cheapest way to make synthetic ruby, sapphire and spinel, and typically leaves curved growth lines and round gas bubbles.
How do treated stones differ from synthetic stones?
A treated stone is natural but has been enhanced, for example by heating, oiling, filling or diffusion. A synthetic stone is made entirely in a laboratory. A stone can be treated or synthetic, but a natural stone can also be untreated.
How can I be sure a gemstone is natural?
Only a report from a recognised gemological laboratory is proof. Ask for a lab report and check that the report number matches the stone. At AA Gems & Jewelry, certificates can be checked online on the main site.
Looking for natural, certified gemstones?
Shop Natural Gemstones