How to identify real Pearls vs lab-grown ones: Expert identification guide

Pearls are one of the most misrepresented gems. Sellers often use fuzzy terms like “lab-grown,” “shell,” or “synthetic.” Some are real pearls formed in mollusks. Others are man‑made lookalikes. This guide shows you how to tell the difference with simple checks, why those checks work, and when you need a lab report.

What “real” means: natural, cultured, and lab-made

Natural pearls form in wild mollusks with no human help. They are rare and expensive.

Cultured pearls are grown in oysters or mussels with human help (a bead or tissue is inserted). They are still “real” because they are built by a living mollusk with layers of nacre.

Lab-made (imitation) pearls are not grown in mollusks. They are glass, plastic, or compressed shell powder with coatings. Trade names include “shell pearls,” “Majorca/Majorca,” and “synthetic pearls.” They imitate the look, not the structure.

Most people asking “real vs lab-grown” mean “grown in mollusks vs manufactured.” This article uses “lab-made” for imitations and “real” for natural and cultured pearls.

The quick 10-minute ID workflow

• 1) Clean lightly with a soft damp cloth to remove oils. Dirt can mask surface clues.
• 2) Tooth test: Gently rub a pearl against your front tooth. Real nacre feels slightly gritty; most imitations feel slick. Do not scrape hard.
• 3) Luster and depth: Real pearls show sharp, bright reflections and an inner glow (orient). Imitations look glassy or “painted.”
• 4) Magnification (10× loupe): Look for fine, overlapping growth lines and faint irregularities on real pearls. Imitations show a smooth, orange‑peel or “fish‑eye” coating, bubbles, or brush-like swirls.
• 5) Drill-hole check: Real pearls show chalky nacre layers at the hole and maybe a boundary between nacre and a bead core. Imitations show a uniform glass or plastic core and a distinct lacquer ring or peeling.
• 6) Shape and uniformity: Perfectly round, perfectly matched strands at very low prices are usually imitations. Real strands show minor variances.
• 7) Weight and temperature: Glass imitations feel heavy and cold, plastic feels very light and warms instantly. Real pearls feel substantial and warm quickly but not instantly.
• 8) Color and dye: Check for concentrated color at drill holes or near settings. That points to dye. Many real pearls are bleached; heavy dye is more common in imitations and inexpensive freshwater pearls.
• 9) UV light (optional): Under long‑wave UV, many real pearls fluoresce chalky to blue-white. Some imitations do not, or fluoresce oddly. Results vary by species and treatments, so use this only as a clue.
• 10) Stringing clues: Real strands are usually knotted between pearls to prevent rubbing. Cheap fashion strands often are not. Not decisive, but helpful.

How each test works and what to look for

Why the tooth test works: Nacre is stacks of tiny aragonite platelets held by organic material. That microstructure gives a very fine grit. Glass and most coatings are smooth. Caveat: some “shell pearls” (powdered shell with binders) can feel faintly gritty, so confirm with other tests.

Luster and orient: Real pearls build light from within because light bounces between nacre layers. You see strong reflections and a soft, layered glow, sometimes with pink, green, or silver overtones. Imitations rely on surface coatings; the look is mirror‑like but shallow, or plasticky with diffuse reflections. If every pearl shows the exact same shine and color, be skeptical.

Magnification details: With a loupe, real nacre shows:
– Fine, irregular growth lines and unevenness
– Minute pits or ridges
– Natural variation in overtone
Imitations often show:
– Orange‑peel texture (coating ripples)
– Bubbles or grit trapped in lacquer
– Circular flow lines or brush strokes near the drill hole

Drill-hole anatomy: In beaded cultured pearls (e.g., Akoya, South Sea, Tahitian), the drill hole may reveal a boundary between nacre and a round bead (often white). That is normal. Freshwater tissue‑nucleated pearls are usually nacre through and through, so you will not see a bead. Imitations show a telltale lacquer ring, flaking, or a different colored core (glass or plastic).

Candling for nacre thickness: Shine a bright penlight through the side of a pearl in a dark room. On thinly coated beaded pearls, you may glimpse the bead boundary as a shadow; thick nacre looks more uniform. This helps judge quality, not “real vs fake” on its own. Imitations made of glass transmit light very evenly and may reveal a single homogeneous material.

Weight and temperature: Real pearls have density close to 2.7–2.9 g/cm³ but feel lighter than same‑size glass. Plastic imitations are noticeably light. Temperature clues come from thermal conductivity: glass stays cold longer; plastic warms almost instantly; nacre sits between the two.

UV fluorescence: Aragonite can fluoresce due to organic components. Many Akoya fluoresce chalky blue; South Sea and Tahitian are weaker. Dyed or heavily treated pearls can suppress or alter fluorescence. Painted imitations may show a uniform, odd color. Use as a supporting test only.

Dye detection: Real black Tahitian pearls tend to have bodycolor plus subtle overtones; dyed freshwater “black” pearls often show color concentration at the drill hole, bronze or magenta patches, or dye bleeding on thread. A solvent swab can lift dye on imitations, but it risks damaging real pearls. Avoid chemical tests unless the piece is expendable.

Advanced lab methods (when it’s worth it)

X‑ray radiography or micro‑CT: Shows the internal structure. Natural pearls have concentric growth rings with no bead. Beaded cultured pearls show a central sphere with surrounding nacre. Imitations show a homogeneous core with no growth pattern.

Raman or FTIR spectroscopy: Confirms aragonite (real nacre) versus glass, polymer, or resin.

Elemental analysis (e.g., XRF): Helps identify mollusk species and detect certain treatments.

Get a lab report when value or claims are high: natural vs cultured, rare origins, very large sizes, or when buying at auction. Reputable labs list pearl type (natural/cultured), species when possible, and treatments. Examples: GIA, SSEF, and Gübelin. The cost is small compared to the price difference these labels create.

Common tricky cases

• Freshwater pearls without beads: These can be all nacre and still cultured. Drill holes show nacre only. They are real.
• Keshi pearls: All‑nacre byproduct pearls formed without a bead. High luster, irregular shapes. Real and often valuable.
• Shell pearls: Made from crushed shell and resin with coatings. Often perfectly round, perfect color, and very consistent. The tooth test may feel slightly gritty, but drill holes reveal thick coatings that can chip, and a uniform composite core.
• Mabé (blister) pearls: Dome‑shaped cultured composites assembled onto a backing. Real nacre on the surface, but a constructed back. Not fakes; just a different product.
• “Too perfect” bargains: Large (10–14 mm), flawless, perfectly matched “Tahitian” strands for very low prices are almost always imitation. Real Tahitians show slight surface features and natural color spread.

Buying checklist and red flags

• Ask precise questions: Natural or cultured? Saltwater or freshwater? Bead‑nucleated or tissue‑nucleated? Any treatments (bleaching, dyeing, luster enhancement)?
• Request documentation: A lab report for expensive pieces. For everyday buys, at least a written invoice describing the pearl type and treatments.
• Inspect the drill holes: Look for nacre layers, not peeling lacquer. Check thread for dye bleed.
• Check uniformity vs realism: Real strands have tiny differences in shape, luster, and overtone. Total uniformity at a rock‑bottom price is a warning.
• Mind the setting and findings: Ultra‑cheap plated parts with “perfect” pearls are a mismatch; quality pearls are seldom mounted this way.
• Return policy: A no‑questions return window is a good sign. Scammers avoid it.

Caring for pearls during testing

• Use only a soft, damp cloth; no ultrasonic cleaners, steam, or harsh chemicals.
• Avoid scraping or hard rubbing during the tooth test. Touch lightly.
• Keep pearls away from perfume, hairspray, and acids. Wipe after wearing.
• Store strands flat and separate to prevent abrasion.

Putting it all together: a practical example

Suppose you find a 12 mm, perfectly round, “black Tahitian” strand for $60 online. The pearls are identical. The surfaces look glassy, and the drill-hole rims show a sharp lacquer ring. The tooth test is slick. Under a loupe, you see orange‑peel texture and tiny bubbles. Conclusion: lab‑made imitation.

Now consider an 8 mm white strand at a fair price. The tooth test is slightly gritty. Reflections are sharp with gentle pink overtones. Drill holes show chalky layering and a faint bead boundary. Shapes are mostly round with small differences. Conclusion: beaded cultured Akoya—real pearls.

Summary

Real pearls—natural or cultured—are built by mollusks and have layered nacre. Lab‑made pearls are manufactured lookalikes. No single test is perfect, but a few quick checks—tooth feel, luster depth, magnified surface, and drill‑hole structure—will identify most pieces. Use advanced lab methods when the price or claim is high. When in doubt, buy from sellers who disclose type and treatments and who stand behind their goods.