Pearls are one of the easiest gems to imitate convincingly, and imitation pearls have been made for centuries from glass, shell and plastic. Fortunately, real pearls have a structure that fakes struggle to copy, and several simple checks will tell you a lot. What home tests cannot tell you is whether a real pearl is natural or cultured; that needs a lab. This guide covers both.
Three kinds of pearl
- Natural pearls form in a mollusk without human help, usually around a tiny irritant. They are rare, and most natural pearls on the market today are in antique or vintage jewelry.
- Cultured pearls are real pearls grown with human help. A farmer inserts a bead, a piece of mantle tissue, or both, into a mollusk, which then coats it with nacre over months or years. Almost all real pearls sold today are cultured.
- Imitation pearls are not made by a mollusk at all. They are usually a glass, plastic or shell bead coated with a pearly finish. Some imitations are high quality and marketed under brand names; others are inexpensive costume pieces.
Natural and cultured pearls are both made of nacre: microscopic layers of calcium carbonate crystals. Those layers are what give real pearls their deep luster and slightly gritty surface, and they are the basis of most home tests.
The tooth test
Gently rub the pearl along the edge of your front teeth, or rub two pearls lightly against each other.
- Real pearls (natural or cultured) usually feel slightly gritty or sandy, because of the overlapping nacre crystals.
- Imitation pearls usually feel perfectly smooth or glassy, because the coating is uniform.
Be gentle, and wipe the pearl afterward. This is the most reliable home test, but it is not perfect: some imitations have textured coatings, and a heavily worn real pearl can feel smoother than usual.
Look at the drill holes
Use a 10x loupe or magnifier on the hole where the string enters each pearl.
- Real pearls usually have clean, sharp-edged holes. In bead-nucleated cultured pearls you may see a line where the nacre meets the bead inside, and in thin-nacre pearls you may see that the nacre layer is quite thin.
- Imitation pearls often show chipped, flaking or peeling coating around the hole, a raised rim of coating, or a glass or plastic core with a different color or texture from the surface.
Check luster and surface
Luster is the sharpness of reflections on the surface. Hold the pearl under a light and look at the reflection.
- Fine real pearls show crisp, bright reflections and often a subtle glow, sometimes with soft overtone colors such as rose, silver or green.
- Imitations often look flat, chalky, or uniformly shiny like paint, without depth.
Then look at the surface under magnification. Real pearls almost always have small natural features: tiny spots, ridges, dimples or slight bumps. A surface that is flawless on every single pearl is a reason for suspicion. Imitations, on the other hand, often show wear where the coating has rubbed through to the core, especially around holes and on pearls that touch the neck.
Shape, matching and color
- Shape. Most real pearls are not perfectly round. Even fine round strands show slight variation when you roll them on a flat surface.
- Matching. A strand where every pearl is exactly identical in size, shape and color is more typical of imitation pearls. Good real strands are carefully matched, but not perfectly.
- Color. Real pearls come in white, cream, pink, golden, gray and black, among others. Unusual bright colors, or a color that looks painted on, may mean dye or imitation. Real pearls can also be dyed, so color alone is not proof either way.
Weight and temperature
- Weight. Real pearls and glass imitations both feel reasonably substantial for their size. Plastic imitations usually feel noticeably light.
- Temperature. Real pearls feel cool when you first touch them and warm up slowly against skin. Glass also feels cool, so this mainly helps to identify plastic, which feels close to room temperature from the start.
Neither of these is conclusive on its own, but together with the tooth test and drill holes they build a reliable picture.
Clues from the clasp and stringing
- Fine pearl strands are usually knotted between each pearl, so they don't rub together and so only one pearl is lost if the string breaks.
- The clasp on a fine strand is often gold, platinum or silver with a purity mark. A plated or unmarked base-metal clasp hints at costume, though clasps are sometimes replaced. See the hallmarks guide.
Natural vs cultured: you need a lab
There is no reliable way to tell a natural pearl from a cultured one at home or from a photo. Gemological labs use X-ray imaging to look at the pearl's internal structure: many cultured pearls show a bead nucleus, while natural pearls show concentric growth layers. If you think you might have natural pearls, perhaps in an antique strand with a family history, a lab report from a respected laboratory such as GIA is worth getting, because natural pearls can be worth far more than cultured ones.
A photo cannot test pearls either. It can show shape, color, luster and how a piece is strung and clasped, which helps suggest the likely type and era. AI Jewelry uses those visible details for its description and price range, but it cannot feel nacre, see inside the pearl or confirm whether it is natural, cultured, dyed or imitation.
Freshwater, Akoya, South Sea and Tahitian at a glance
Most cultured pearls fall into four main types. These are typical ranges, and there are exceptions in every category.
| Type | Mollusk and main sources | Typical size | Typical colors | Notes |
|---|---|---|---|---|
| Freshwater | Freshwater mussels, mainly China | About 2–12 mm, larger exist | White, cream, pink, lavender | Often off-round; usually solid nacre; widely available and generally the most affordable |
| Akoya | Pinctada fucata oyster, Japan and China | About 2–10 mm, often 6–8 mm | White and cream, with rose or silver overtones | The classic round white strand; bead-nucleated with sharp luster |
| South Sea | Pinctada maxima oyster, Australia, Indonesia, Philippines | About 8–20 mm | White, silver, cream, golden | Large, with thick nacre and a soft, satiny luster; among the most valuable |
| Tahitian | Pinctada margaritifera (black-lip) oyster, French Polynesia | About 8–18 mm | Gray, black, green, blue, "peacock" | Naturally dark colors; very dark pearls of other types are often dyed |
Professionals judge pearl quality on size, shape, color, luster, surface quality, nacre quality and, for strands, matching.
Tip: if a strand has a broken or loose string, get it restrung by a jeweler before testing or wearing it. Ask for silk with knots between each pearl, and the jeweler can usually tell you on the spot whether the pearls look real.
Caring for real pearls
Nacre is soft and sensitive to acids, so pearls need gentler handling than most gems.
- Put pearls on last, after perfume, hairspray and makeup, and take them off first.
- Wipe them with a soft, slightly damp cloth after wearing. Never use ultrasonic cleaners, steamers or chemical cleaners.
- Store them flat in a soft pouch, away from harder gems that can scratch them, and don't hang strands for long periods.
- Have strands restrung periodically if worn often, since silk stretches and weakens.
If you are sorting a family collection that includes pearls, see what to do with inherited jewelry, and for putting a number on a piece, how much is my jewelry worth?