Pearls are the odd stone out. Almost every other gem on the TJC shelf was pulled from a rock. Pearls came from an animal, grown slowly over years inside the body of an oyster or a mussel. The British shopper who inherits a strand from a grandmother almost never knows whether it is natural, cultured, or imitation, and the honest answer carries a tenfold price swing. This guide covers the biology of a pearl, the Mikimoto breakthrough and the Japanese inventors who worked alongside him, the real difference between freshwater and saltwater, how to spot a fake, and the indicative price bands you should expect in UK retail in 2026.
At a Glance
| Material | Nacre (CaCO₃ + protein) |
| Mohs hardness | 2.5 - 4.5 |
| Formation time | 6 months - 7 years |
| UK price band (indicative) | £30 - £15,000 |
| Birthstone month | June |
Pearl Types Compared
| Type | Mollusc / source | Typical size | Common colours | Indicative UK price |
|---|---|---|---|---|
| Freshwater | Hyriopsis cumingii mussels, Chinese lakes | 6 - 11 mm | White, pink, peach, lavender | £30 - £400 per strand |
| Akoya | Pinctada fucata oyster, Japan / China (saltwater) | 2 - 10 mm | White with pink or silver overtone | £180 - £2,500 per strand |
| Tahitian | Pinctada margaritifera, French Polynesia | 8 - 18 mm | Grey through peacock-green to aubergine | £400 - £5,000 per strand |
| South Sea | Pinctada maxima, Australia / Indonesia / Philippines | 9 - 20 mm | White, silver, warm gold | £1,500 - £15,000 per strand |
Prices are directional UK retail per-strand ranges; stone size, lustre, surface, matching and metal all move individual pieces up or down.
What a Pearl Actually Is
A pearl is nacre, the same material a mollusc uses to line the inside of its own shell. Chemically it is calcium carbonate (aragonite crystals) stacked in thin plates bonded by a protein called conchiolin. The light that bounces off those plates interferes with itself, giving the pearl its characteristic depth and glow. That optical effect is called lustre, and it is the single most important quality metric for any pearl.
Mohs hardness for pearl sits between 2.5 and 4.5, which makes it one of the softest materials you will find in a mainstream UK fine-jewellery shop (amber, at Mohs 2 to 2.5, is softer still). Pearls scratch on contact with harder gemstones, which is why they live in a separate pouch in a jewellery box, not jumbled with rings.
How a Natural Pearl Forms
The common story is that a grain of sand gets into the oyster and the pearl grows around it. The real story is slightly different. An irritant does enter the mollusc (more often a parasite than a sand grain), but what triggers the pearl is a tiny piece of the mollusc's own mantle tissue breaking free. That tissue, now floating in the body of the mollusc, continues to secrete nacre. Over months and years, layer on layer builds up around it.
Natural pearls are the pearls that formed this way without any human help. They are rare; the figure often cited is that fewer than one in 10,000 wild oysters produces a gem-quality natural pearl, though exact yields vary by species and bed. For most of history they were the only pearls on the market, and good matched strands commanded extraordinary prices in the early 20th century. The most-cited example is Cartier's 1917 acquisition of its Fifth Avenue mansion in New York in part exchange for a natural-pearl necklace valued at the time at around $1 million. Most natural-pearl supply came from the Persian Gulf; the industry collapsed in the 1930s when cultured pearls arrived and the Gulf oyster beds were separately exhausted. Fine matched natural strands at auction today can reach six figures and beyond, with exceptional pieces at specialist sales going further.
How a Cultured Pearl Is Grown (Mikimoto, 1893 and 1916)
A cultured pearl is grown deliberately. For saltwater pearls (Akoya, South Sea, Tahitian), a pearl farmer surgically inserts a small bead nucleus (usually cut from freshwater mussel shell) together with a tiny graft of donor mantle tissue into the body of a host oyster. The mollusc treats the bead as the irritant and the graft as part of itself; the graft begins secreting nacre over the bead. One to seven years later, the farmer harvests the pearl.
Most Chinese freshwater pearls are produced differently: they are tissue-nucleated, with pieces of mantle tissue inserted on their own without a bead, which is why a single freshwater mussel can grow 20 to 40 pearls at once. These pearls are nearly solid nacre rather than a bead with a nacre coat.
The history is often shortened to 'Mikimoto 1893', but the full story is a sequence of related Japanese breakthroughs. Kokichi Mikimoto produced the first cultured half pearls (mabe) in 1893. The technique for cultured round pearls was developed in the following years with important contributions from Tatsuhei Mise and Tokichi Nishikawa, and Mikimoto's patent on round cultured pearls was granted in 1916. By the 1950s cultured pearls were the mainstream market globally; by the 1980s almost every pearl in UK high-street retail was cultured. 'Cultured' does not mean fake. The pearl is grown by a real oyster or mussel using real nacre; the only difference from natural is that a farmer places the irritant (and, for bead-nucleated pearls, the bead) rather than nature.
Freshwater vs Saltwater: Akoya, Tahitian, South Sea
Four types of cultured pearl cover almost all UK retail.
- Freshwater - Grown in Chinese Hyriopsis cumingii mussels in lakes and rice-paddy ponds. Typically tissue-nucleated (no bead), which is why one mussel can grow 20 to 40 pearls per crop. Shapes are often slightly irregular; colours include white, pink, peach and lavender. Indicative UK price: £30 to £400 for a standard 7-9 mm strand. This is the main entry-level pearl.
- Akoya - Grown in Japanese and Chinese Pinctada fucata oysters in saltwater. One oyster usually grows one pearl per cycle, perfectly round, 2 to 10 mm. The classic 'pearl necklace' aesthetic. UK price band: £180 to £2,500 for a strand.
- Tahitian - Grown in Pinctada margaritifera (black-lip oyster) in French Polynesian lagoons. 8 to 18 mm, naturally dark grey through to peacock-green and aubergine. UK price band: £400 to £5,000 per strand or £300+ per single pearl.
- South Sea - Grown in Pinctada maxima (gold-lip or silver-lip oyster) in Australian, Indonesian and Filipino waters. 9 to 20 mm, the biggest cultured pearls, white or warm gold. UK price band: £1,500 to £15,000 per strand.
Our pearl Gemopedia page has side-by-side images of each type. Pearl is one of June's birthstones alongside moonstone and alexandrite; our Birthstones by Month UK guide has the full twelve-month list. Pearl is also the traditional 30th wedding anniversary gem.
What 'Lustre' Means and Why It Matters
Lustre is the deep inner glow a good pearl shows when you turn it in the light. It is caused by light passing through the thin nacre layers and reflecting back from the ones underneath; the thicker and better-stacked the nacre, the richer the lustre. A low-lustre pearl looks chalky and matte; a high-lustre pearl looks like it has a tiny light bulb inside it.
There is no single universal pearl grading standard. The A to AAA scale commonly seen on freshwater and Akoya pearls is a retailer convention rather than an official grading system, so two shops may use the labels slightly differently (broadly, AAA for sharp mirror-like lustre, AA for good lustre with slight haze, A for duller or chalkier material). Top-end freshwater pearls can reach the AAA end of the scale, though Akoya is the type most often graded that way. Tahitian pearls use an official A to D system from French Polynesia. Ask the seller which scale they are using and get the grade in writing before you spend over around £200 on a strand.
Imitation Pearls: Glass, Shell and Plastic
Three fakes you will meet on the UK high street.
- Majorica (glass) - Glass beads dipped in a 'pearl essence' made from fish scales. Spanish, famous since 1890. Honest at the price (£25 to £120 a strand) but not pearl in any meaningful sense.
- Shell pearls - Ground mollusc shell reformed into bead shapes with a glossy coating. Heavier than freshwater pearls, cold to the touch, under £30 a strand.
- Plastic - Lightweight, warm to the touch, often matte or chalky-shiny. Common in costume jewellery under £15.
How to Spot a Real Pearl at Home
Four tests, no tools needed.
- The tooth test - Rub the pearl gently against the biting edge of your front tooth. Real pearl feels slightly gritty, like fine sandpaper. Glass and plastic feel smooth and squeaky. It is one of the quickest first-pass checks used in the UK antiques trade.
- The weight test - Pick up a single strand. Real cultured pearls feel similar in weight to glass beads and noticeably heavier than plastic beads for the same size. Shell pearls feel cold and oddly heavy.
- The drilled hole - Look at the drilled hole with a 10x loupe. Real pearls show the nacre layers as faint concentric rings, often slightly rough at the edge. Imitation pearls show a smooth painted-looking hole.
- The surface under light - Real pearls show very slight imperfections (tiny bumps, faint growth lines) under raking light. Imitation pearls look uniformly perfect.
For anything over around £300, ask the UK seller for a Gem-A or GIA report; prices for a report vary by lab and service level, so get the fee quoted upfront. A report settles any doubt about natural, cultured or imitation.
Caring for Pearls
Pearls are the one gemstone where our standard warm-water-and-soap routine does not work. Nacre is acidic-sensitive and detergent-sensitive. The rule we give customers: wipe each pearl with a damp soft cloth after every wear to remove skin oil and perfume, then dry on a cotton cloth. Store flat in a cotton pouch or cloth bag. Avoid plastic ziplock bags for long-term storage; they trap moisture.
Perfume, hairspray, lemon juice, vinegar, alcohol, nail-polish remover and most skincare products damage pearls. The British dressing-table rule applies in capital letters: fragrance first, pearls last. Never use a silver-dip solution on a pearl-set piece either, because the acidic chemistry attacks nacre on contact. Our how to clean silver jewellery UK guide covers safer alternatives for pearl-and-silver pieces. Re-string knotted strands every three to five years if worn weekly, less if only on occasions.
Shop Pearl Jewellery at TJC
Our pearl jewellery collection is indicatively priced from around £40 for freshwater pendants up to the heirloom end for fine South Sea and Tahitian strands (prices are directional and vary with current stock). For specific types, freshwater pearls are the everyday choice; South Sea pearls are the heirloom step up. UK delivery, returns and warranty terms are set on the main site; please check the live policy pages at checkout, and note that pierced earrings may have hygiene-based returns exclusions.
