Cultured pearl or imitation: how to recognise them and which words to read
Natural pearl, cultured pearl, imitation pearl in glass or plastic: definitions, simple clues such as the tooth test, limits of these methods and the vocabulary used on labels.
Key points
| Material | Nacre: calcium carbonate (aragonite) bound by a protein, conchiolin |
|---|---|
| Mohs hardness | About 2.5 to 4.5 |
| Density | About 2.6 to 2.85 |
| Natural pearl | Formed without any human intervention; now very rare on the market |
| Cultured pearl | Formed after human grafting; the great majority of pearls sold |
| Imitations | Glass or plastic beads coated with “essence d'Orient”; shell beads |
| Fragility | Dissolves in vinegar; sensitive to perfume, sweat and cosmetics |
Three families to tell apart
A pearl forms when a mollusc (oyster, mussel) deposits nacre around a foreign body. Nacre is made of tiny platelets of aragonite, a form of calcium carbonate, bound together by a protein, conchiolin. It is a soft material (2.5 to 4.5 on the Mohs scale) that scratches easily and dissolves in acid, even a weak one such as vinegar.
- A natural pearl forms without any human intervention. Historic fisheries, notably in the Persian Gulf, declined sharply in the early 20th century with the arrival of cultured pearls, and natural pearls have become very rare. In France, decree no. 2002-65 of 14 January 2002 defines a natural pearl as a natural secretion of a wild mollusc.
- A cultured pearl is formed by a mollusc into which a technician has grafted a piece of tissue, sometimes with a shell nucleus. Japanese methods are attributed to Tatsuhei Mise and Tokichi Nishikawa (Nishikawa's patent of 1916); the name of Kokichi Mikimoto remains associated with their spread, but he is no longer considered their inventor. Main types: Akoya (Pinctada fucata, 2 to 10 mm, often white or cream), South Sea (Pinctada maxima, the largest), Tahitian (Pinctada margaritifera, often dark, farmed in French Polynesia) and freshwater (mainly in China, often without a nucleus).
- An imitation pearl is an object made to look like a pearl: a glass, plastic or shell bead coated with “essence d'Orient”, a pearly substance made from fish scales. The name “Majorca pearl” refers to high-quality imitations with a coated glass core.
A cultured pearl is a real pearl: a nacre pearl formed by a mollusc. The difference from a natural pearl is the role of humans, not the nature of the material. What matters is the honesty of the name: in France, natural pearl and cultured pearl are two distinct denominations, and the word “cultured” must appear for a cultivated pearl.
The table of signs
| Sign | Nacre pearl (natural or cultured) | Imitation (glass, plastic, coated) |
|---|---|---|
| Surface to the touch | Slightly gritty when rubbed on the teeth | Very smooth, sometimes slippery |
| Shape and size | Slight differences between pearls on the same necklace | All pearls identical, perfectly round |
| Lustre (orient) | Colour reflections that seem to come from within, pinkish, green or cream tints | Surface shine, uniform, like paint |
| Drill hole | Clean edges, visible layers of nacre, slight ring of nacre | Coating that flakes, paint that comes off, glass or plastic core visible |
| Temperature | Cool to the touch | Glass: cool; plastic: lukewarm |
| Weight | Fairly heavy | Glass: heavy; plastic: light |
The main trap: some modern imitations have an engineered coating that copies the gritty texture, and glass can have the weight and coolness of a pearl. No single sign is decisive.
Simple, safe tests
- The tooth test. After brushing your teeth, rub the pearl very gently along the edge of your front teeth (do not bite it). Nacre gives a fine grainy sensation, like very fine sandpaper; a glass or plastic imitation feels smooth. Rub briefly and without pressing: nacre is soft.
- Rub two pearls against each other, with light pressure: same principle, real ones feel slightly rough, imitations slide.
- Look at the drill hole under a loupe. Flakes of paint or a coating that is coming away reveal a glass or plastic core.
- Compare the pearls with one another. A cultured pearl shows small irregularities of shape, colour and lustre; a row of identical pearls should raise doubts.
- Examine the surface under a loupe. Nacre shows very fine growth lines, like a fingerprint; an imitation may have bubbles or a surface that is too smooth.
Avoid. Do not use vinegar, acid or flame: nacre dissolves or deteriorates in them. Do not scrape the pearl with a metal object.
What these tests do not prove. No home test reliably separates a cultured pearl from a natural one: that requires a laboratory, which uses X-rays (a cultured pearl with a nucleus shows a solid centre without growth rings; a natural pearl shows concentric rings). Almost all pearls on the market are cultured; a pearl sold as “natural” should come with a certificate.
Common treatments on real pearls
Even a real cultured pearl is often treated: bleaching (to even out the tone), dyeing (black, gold, pink or coloured freshwater pearls), irradiation (to darken some pearls), polishing or coating. Decree no. 2002-65, whose scope also covers pearls, requires that dyeing and irradiation be disclosed. Black Tahitian pearls may be naturally dark or dyed: a very deep black with no variation should therefore be questioned.
Other terms to know: a keshi pearl is a cultured pearl without a nucleus, of irregular shape; a mabé pearl forms against the shell, as a half-sphere; a shell pearl usually refers to a nacre bead cut from a shell and covered with a coating: it is an imitation, not a pearl formed by a mollusc.
Care and safety
Nacre is soft and porous: perfume, hairspray, sweat, vinegar and household cleaning products dull it. The jewellers' rule: pearls go on last and come off first. Wipe them with a soft cloth after each wear, store them separately wrapped in cloth, and have the silk thread restrung if the knots loosen. Avoid swimming pools, the sea and ultrasonic cleaners. Imitation pearls with a coating also fear water, which can make the coating peel.
For pearl jewellery, see our page on pearls and beaded stones, as well as the pearl profile or “How to recognise a real pearl”.
The right questions before buying
- Are these cultured pearls (freshwater, Akoya, Tahitian, South Sea), natural pearls, or imitations?
- Has there been bleaching, dyeing or irradiation?
- Are the pearls nucleated or non-nucleated? For nucleated pearls, how thick is the nacre layer?
- Is the thread knotted between the pearls? Are the length and diameter stated in millimetres?
- Is a pearl sold as “natural” accompanied by a laboratory certificate?
See also how to read a label and our commitments.
Frequently asked questions
Is a cultured pearl a real pearl?
Yes. It is a nacre pearl formed by a mollusc after grafting by humans. It differs from a natural pearl, which forms without any human intervention.
How does the tooth test work?
Rub the pearl gently along the edge of your teeth: nacre feels slightly grainy, while glass and plastic are smooth. Some imitations copy this grain, so it is only one clue.
Can you tell a natural pearl from a cultured pearl by eye?
No. Only an X-ray in a laboratory reveals the internal structure. Almost all pearls sold are cultured.
What is essence d'Orient?
A pearly coating made from fish scales, applied in layers to a glass or plastic bead to imitate a pearl.
Can I clean pearls with vinegar?
No. Vinegar dissolves nacre. Use a soft, slightly damp cloth.
Also read
The meanings mentioned belong to tradition and symbolism. They are neither promises of results nor medical advice. Back to Recognizing real stones.