Pearls, Coral and Amber: Judging and Care
- Trinket File
- Metals and Stones
- 05 May, 2026
Pearls and other organic jewelry materials get graded in language borrowed from diamonds, which is where the confusion starts. A mineral stone is judged on color, clarity and cut and shrugs off most of daily life. A pearl, a piece of coral or an amber bead is a layered or resinous organic material soft enough to mark with a fingernail. Treat it like a hard gem and it’s damaged quickly; treat it as what it is and it can last generations.
The useful question isn’t which pearl is “best.” It’s whether the nacre is thick enough and the surface sound enough for how you’ll wear the piece.
What a pearl is
A pearl is nacre: thin layers of aragonite platelets bound by a protein called conchiolin. The layers build up inside a mollusk over months and years, each a fraction of a millimeter thick. Nacre thickness, not pearl size, decides how deep the surface looks and how much wear it’ll take.
Cultured pearls come in two constructions. Bead-nucleated pearls (akoya, South Sea, Tahitian) grow around a round shell bead, which the mollusk coats in nacre. Tissue-nucleated pearls, which include most freshwater pearls, have no bead and are solid nacre throughout. That matters once the surface wears: a thin-nacre bead-nucleated pearl can wear through to the bead, while a solid-nacre pearl just loses a little surface.
Because nacre is mostly calcium carbonate, pearls are soft: 2.5–3 on the Mohs scale, per GIA. Quartz dust, a zipper, a metal clasp and a ring are all harder. That’s the whole reason care matters more here than with a diamond.
Luster, overtone and what your eye can judge
Luster is the sharpness and depth of the reflection. Under a bright light, a good pearl throws back a crisp, almost mirror-like highlight; a dull one gives a soft blur. Overtone is the translucent color over the body color, like rose or green over white, or green over dark gray. Judge both by rolling the pearl under neutral light and watching the reflection, not the color.
Check the surface at about 12–16 inches under direct light. A few small marks are normal; no commercial pearl is flawless. What matters is the kind of flaw. A shallow pinprick or smooth bump affects looks; a deep pit, crack or thin chalky patch goes through or near the nacre and shortens the pearl’s life. Shape runs round, near-round, button, drop and baroque, and moves price far more than durability. An off-round pearl with thick nacre and a clean surface is sturdier jewelry than a round one with a thin skin.
Freshwater versus saltwater
| Type | Construction | What to expect |
|---|---|---|
| Freshwater | Tissue-nucleated, solid nacre | Wide range of shapes, usually the most affordable; often off-round or baroque; durable with no bead to expose |
| Akoya | Bead-nucleated | Usually round with sharp, bright luster; nacre varies by grade, thin examples show wear first |
| South Sea and Tahitian | Bead-nucleated | Larger, typically thicker nacre, naturally dark or silver body colors; priced well above akoya |
| Keshi | No intentional bead | Effectively solid nacre, often irregular, used for individual pieces |
Imitations, treatments and drill holes
Imitation pearls are glass, plastic or shell beads coated to look like nacre, and they’re legitimate when sold as such. Under magnification, an imitation surface is smooth with a faint dimpled texture, while real nacre shows a fine, overlapping, almost tile-like structure. Worn imitations show the coating flaking or ringing the drill hole.
Treatments include bleaching, dyeing and sometimes a thin surface coating. They’re common and not automatically a fault, but a coating behaves like plating: it wears at high points and shouldn’t be rubbed or cleaned with anything abrasive.
The drill hole is every strung pearl’s weak point. Drilling can chip the nacre at the exit, and a thin edge there crumbles. Knots between pearls stop them rubbing their neighbors and keep the strand from scattering if the cord breaks. Check that knots are present, the cord is clean and the pearls sit close without gaps.
Organics beyond pearls
Coral is calcium carbonate in a branching skeleton: porous and fairly soft. Some is bleached or dyed, and it reacts to acids and perfume. Amber is fossilized resin, light, warm to the touch and soft enough to scratch with a fingernail. Alcohol, solvents and hairspray attack it, and it can craze in very dry conditions. Jet is a form of lignite, very light and brittle in thin sections; water, dryness and knocks all damage it. All three are set carefully, usually in a bezel or cup that supports the edges instead of gripping them.
Care myths, and the truth
Myth: a quick soak is fine. Never soak. Wipe after wearing with a soft, barely damp cloth, then dry flat.
Myth: pearls go on first, then perfume. The other way round: perfume, hairspray and makeup first, pearls last, because alcohol and oils dull nacre permanently.
Myth: a jewelry box is safe storage. Not loose with other pieces. Use a soft pouch away from metal; a chain in the same compartment scratches pearls and amber.
Myth: pearls keep best stored away. Keep them out of dry heat and direct sun, and wear them; nacre that dries out crazes.
Myth: a silver dip or ultrasonic is a deep clean. Never on pearls. Ultrasonics, steam, acid dips and silver dip attack nacre, and dip dissolves a silk cord.
Myth: restringing means the pearls are poor. It’s routine. Restring when the cord looks soiled or stretched, since the cord is what fails and the knots prevent a scattered loss. Jewelers listing the service typically charge about $4–$8 per inch, Oct 2026.
Counter routine
Roll a pearl or strand on a flat surface to see how round it is and whether the drill hole is centered. Check the reflection under bright light for sharpness. Examine the surface in direct light from about a foot away and decide whether any flaw looks deep or shallow. Look at drill holes for chips and the cord for dirt; on a strand, confirm knots are present and even. Then judge against use: a necklace worn weekly deserves thick nacre and tight knots, while occasional earrings can be thinner and less perfect without risk.
