June Birthstone Pearl: The Living Gem
Pearl is the only organic gem on the birthstone calendar. It grows inside a living mollusc, in layers of aragonite bound by an organic material called conchiolin, which is why it behaves unlike every other stone on the list.
Cultured pearls are real pearls. The mollusc lays down the same nacre on an implanted nucleus that it would on an accident, and telling natural from cultured takes an X-ray rather than a test you can run at home.
The story that Mikimoto invented the cultured pearl compresses three men's work. His 1890s pearls were hemispherical. The round cultured pearl and its 1907 patent belong to Tatsuhei Mise and Tokichi Nishikawa.
Every genuine Edwardian pearl piece is a natural-pearl piece, because cultured pearls did not reach Western retail until the 1920s. That dates a piece as surely as the metalwork does.
Alexandrite joined June in 1952, not 1912. It looks green in daylight and red-violet under a lamp, and the Ural mines that made it famous were already nearly worked out by 1904.
Pearl is the June birthstone, and it is the only organic gem on the calendar. Every other stone on the list grew in rock. This one grew inside an animal, and almost every practical question about pearls comes back to that.
A pearl is not a mineral with an organic coating. It is layer on layer of aragonite, a form of calcium carbonate, laid down with thin films of an organic binder called conchiolin between them. The binder is what makes a pearl act the way it does. It is why pearl sits at 2.5 to 4.5 on the Mohs scale, the softest material on the birthstone calendar. It is why a weak acid will dissolve a pearl. And it decays over long spans of time, which no sapphire does.
Those facts have uses. A pearl surface cannot be recut, so damage on an old pearl is permanent in a way a chipped faceted stone never is. Natural and cultured pearls are both real, and the difference between them is where the nucleus came from rather than what the pearl is made of. And a pearl piece can be placed within a few decades from its construction alone, because every era held pearls differently.
June's second stone is alexandrite, added to the American list in 1952. It is the opposite object in nearly every respect: a chromium-bearing chrysoberyl at 8.5 on the Mohs scale that turns from green to red-violet when you carry it indoors.
- What Is the June Birthstone, Pearl or Alexandrite?
- What Is the Difference Between Natural and Cultured Pearls?
- What Are the Different Types of Pearls?
- What Makes One Pearl Better Than Another?
- How Can You Tell How Old a Pearl Piece Is?
- Why Are Pre-1920s Natural Pearls Different From Modern Cultured Pearls?
- Are Pearls Durable Enough to Wear Every Day?
- How Do You Clean and Store Pearl Jewelry?
What Is the June Birthstone, Pearl or Alexandrite?
Pearl. It has held June on the American list since 1912, and alexandrite was added forty years later. Both are official. Pearl carries the month.
The list came out of a business meeting. In August 1912 the American National Retail Jewelers Association met in Kansas City and settled a market in which every jeweler promoted a different set of monthly stones. June went to pearl, with moonstone printed beside it as the alternate. Alexandrite was not in the room. The Jewelry Industry Council's 1952 revision put it there, in the same pass that gave November citrine and raised tourmaline to a full partner for October. That revision favored stones a buyer could get and could wear hard, which is a strange thing to say about alexandrite.
One man objected to pearl in print, and he was the most qualified American to do it. George Frederick Kunz was Tiffany's vice president, and his 1891 book Natal Stones is part of why a standard American list was possible at all. In The Curious Lore of Precious Stones (1913) he reprinted the new table and disagreed with it. Pearl, he wrote, "is not a stone in any sense of the word," and "should not appear in the list at all." He meant it literally. A pearl is not a mineral. He allowed one use for it, worn as an emblem of purity.
Every genuine Edwardian pearl piece contains natural pearls
Kunz also recorded the older tradition, and it does not say what the modern one says. In his traditional table June belongs to agate, with emerald as the month's talismanic gem. So calling pearl June's ancient stone is a claim the record will not carry. The pearl birthstone is a twentieth-century arrangement. It is recent enough that the man who made the standard American list possible was still around to complain about it.
Moonstone is June's third stone and it deserves a page of its own rather than a paragraph here. Pearl also marks the thirtieth wedding anniversary. The birthstone jewelry guide lays out all twelve months, and October's opal and tourmaline is the other month that splits its allegiance the same way.
What Is the Difference Between Natural and Cultured Pearls?
A natural pearl forms without anyone's help. A cultured pearl forms around a nucleus a technician placed inside the mollusc. After that the animal does identical work in both cases, and both are real pearls.
This is not the same distinction as a mined stone against a laboratory-grown one, and the difference is worth being clear about because the words sound alike. Nobody grows nacre in a factory. In a cultured pearl, the nacre is laid down by a living oyster or mussel. Same aragonite, same conchiolin, same rate, same concentric layers. What a technician supplies is the starting point.
The natural mechanism was described plainly in Bauer's 1904 gemology. Something irritates the mantle, the tissue lining the inside of the shell. The animal cannot expel it, so it coats it. Only about one mollusc in thirty or forty holds a pearl at all, and the shells most likely to hold one are distorted and bored through by parasites. The grain-of-sand story is folklore. Of fifty-nine pearls the naturalist Mobius opened, not one had a sand nucleus. Most had a nucleus of brown organic matter, probably the remains of intestinal worms.
The origin story of culturing needs a correction too. Nearly every account credits Kokichi Mikimoto with inventing the cultured pearl in 1893. What Mikimoto produced in the 1890s were hemispherical pearls, grown against the shell and cut out, and he patented that process in January 1908. The round cultured pearl belongs to two other men. Tatsuhei Mise was a carpenter with no scientific training. He implanted fifteen thousand molluscs with lead-and-silver nuclei in 1902 and harvested small round pearls two years later. The first Japanese patent for round cultured pearls went to him in 1907. Tokichi Nishikawa, a marine biologist, arrived at a nearly identical gold-and-silver-nucleus method at the same time. The two are remembered together, as the Mise-Nishikawa method. Mikimoto did not adopt it until 1916, and round pearls did not reach the market under his name until 1921. GIA's own historical account sets out that sequence.
The at-home tests you have read about catch imitations, not culturing. Rubbing a pearl lightly against a tooth edge, feeling its weight, noticing that it warms slowly against skin: all of that separates a real pearl from glass or plastic. Bauer describes the best imitation of his day: hollow glass beads coated inside with essence d'Orient, a silvery material lifted from fish scales. Those tests will find that bead. They will not tell you whether a real pearl grew around one.
Natural against cultured is a laboratory question and always has been. X-ray does it, because the two are built differently inside. A bead-nucleated cultured pearl shows a sharp boundary where the shell bead stops and the nacre begins. A natural pearl shows concentric growth rings all the way in, with no such line. For a valuable estate piece that is a lab report, not a judgment you make in good light.
What Are the Different Types of Pearls?
Four names cover nearly everything you will see: Akoya, South Sea, Tahitian and freshwater. They differ by the mollusc and the water, and what you notice in the hand comes mostly from how thick the nacre is.
Akoya pearls are farmed mainly in Japan and China and carry the thinnest nacre of the cultured types, roughly 0.35 to 0.7 mm over a shell bead. That thin, tight layer is why an Akoya has a hard, bright, almost mirrored surface. The Akoya pearl necklace most people picture is this kind of strand, and it is also the type with the least margin for wear.
South Sea pearls carry the thickest nacre of any cultured type, roughly 2 to 4 mm and sometimes more. The light goes deeper before it comes back, so the glow is softer and satiny rather than mirror-hard, and the pearls run larger. Colors run white through silver into gold. Tahitian pearls come from French Polynesia, which sets a minimum nacre thickness of 0.8 mm before a pearl can be exported. They run grey through green-black and bronze, usually with an overtone that shifts as the pearl turns.
Freshwater pearls are the odd one out, because most are solid nacre with no bead inside at all. That is why their shapes wander, and why a good freshwater pearl can outshine its reputation.
Mabe is not a kind of oyster. It is a construction. The pearl is grown as a hemisphere against the inside of the shell, then cut out with a ring of shell around it. The back is filled and capped, and the assembly is set dome-up. That is why mabe pearl earrings, brooches and cocktail rings exist and mabe strands do not.
Two more you will meet in estate cases. A conch pearl is not nacreous at all: it comes from the queen conch, runs pink through salmon, and carries a flame pattern across the surface instead of a luster. Marcus and Co. built a brooch around one about 1900 with plique-a-jour enamel, now at the Metropolitan Museum of Art. Baroque pearls are the irregular ones, and Renaissance jewelers and their Victorian imitators used the shape as sculpture. Reinhold Vasters made a mermaid pendant between about 1870 and 1895 whose whole torso is a single baroque pearl, also at the Met. Seed pearls are the ones no bigger than a pinhead. They sat at the bottom of an old trade vocabulary that ran from paragon-pearls the size of a walnut down to dust-pearls the size of a millet grain. Filigree's pearl jewelry spans Akoya strands, mabe studs, seed pearl work and conch.
What Makes One Pearl Better Than Another?
Luster, and by a wide margin. Surface, shape, color, size, nacre thickness and matching all count, and the modern trade grades all seven. Luster is the one you register from across a room.
The old jeweler's word for it is orient, and Bauer treats it as pearl's answer to a diamond's fire. He also explains where it comes from, which is more useful than the term. Nacre is built of aragonite laminae that overlap like roof tiles, each separated from the next by a film of conchiolin. Those laminae are always slightly curved, and they meet the surface as fine striations about one three-thousandth of an inch apart. Light diffracts off that ruling. The thinner the laminae, the better the luster.
So luster is structural, the way play-of-color in opal is structural, and it cannot be added later. This matters when someone offers to polish a dull pearl. Polishing a pearl removes nacre, and there is only ever a fraction of a millimetre of it on an Akoya.
Color is next, and it is partly fashion. Bauer's own hierarchy put silvery, milk-white pearls of the finest water at the top. His description of one is hard to improve: it rolls on white paper "like a globule of quicksilver." Gulf pearls ran yellower. Asian buyers prized them for that. Modern taste is broader than either, and overtone matters as much as body color.
Surface, shape and matching finish the picture. A clean surface beats a pitted one, though small marks near the drill hole are normal and not a fault. Round ranks first, then pear, then oval, then baroque, and baroque is a design decision rather than a defect. Matching is the quiet one. Finding seventy pearls that agree on size, shape, color and luster is harder than finding one good pearl. A matched strand is a different kind of object from a parcel of loose pearls. Treatments belong in the same conversation, stated plainly. Light bleaching is routine on Akoya, and a pre-treatment called maeshori is standard practice for bringing up luster. Dyeing exists too, and it should be disclosed.
How Can You Tell How Old a Pearl Piece Is?
Look at how the pearls are held, not at the pearls. Construction dates a pearl piece within a few decades. The pearls themselves usually date nothing.
One warning before the walkthrough. Pearls get replaced more often than any other stone in an old piece, because they wear out and because they are simple to swap. A mount can be a hundred and forty years old with pearls from the 1970s sitting in it. Date the metal first, then ask whether the pearls agree with it.
Georgian (1714 to 1837). Seed pearls, drilled and threaded on horsehair or fine wire, then woven into flat panels and dimensional forms. The Smithsonian holds a matched brooch, hair ornament and bracelet from about 1830, worked in seed pearls, mother-of-pearl, gold and fiber. That is the technique at full stretch: thousands of pinhead pearls doing textile work. The threading is the tell. Horsehair and silk go brittle with age, and genuine period panels carry small hand-worked irregularities that a modern copy does not.
Victorian (1837 to 1901). Seed pearl work carried straight through the early decades. A Met necklace made between 1845 and 1850 is built from seed pearls, mother-of-pearl, horsehair, silk and yellow gold. The pearls form the fabric of the piece rather than sitting on top of it. Then mourning convention gave pearl a second job. Under the codified rules of Victorian mourning dress, only unpolished jet, onyx, pearls or diamonds in black settings were permitted through the first year. Within mourning symbolism, a pearl stood for a tear. Tiffany and Co.'s 1868 brooch of gold, pearls, black enamel and hair, at the Met, is that convention built as an object. Victorian jewelry covers the period's construction vocabulary in full.
Edwardian (1901 to 1915). Pearl was one of exactly two stones that built this era, alongside diamond, with platinum as effectively the only metal. Dog collars, sautoirs and negligee pendants, all white, set into openwork that was sawn and filed out of solid platinum sheet rather than cast. Edwardian pearl work also hands you the single most useful dating fact here. Cultured pearls did not reach Western retail until the 1920s, so a genuine Edwardian pearl piece is a natural-pearl piece by definition.
Art Deco (1920 to 1935). Pierced filigree in white gold and platinum. Bows and geometric plaques with a single pearl at the center, and lines of seed pearls set against small old-cut diamonds. This is also the decade the ground shifts under the last paragraph. Cultured pearls arrive in Western retail during it, so a Deco pearl may be either, and the metalwork will not tell you which.
Retro and Mid-Century (1935 to 1970). Mabe comes forward. Oversized studs, bold cocktail mounts with one dome and a ring of brilliants, novelty charms with a pearl worked in. The hand-knotted Akoya strand becomes an ordinary object in these decades rather than a rare one. South Sea pearls turn up in geometric gold mounts with real diamond weight behind them.
Four physical checks narrow a date once the style has given you a range. Drill holes. An old hand-drilled hole is slightly irregular and often shows thread wear at the rim. Knotting. Knots between pearls keep a break from scattering a strand and keep the pearls from grinding, and an unknotted strand of any age will have bunched. Clasps. Barrel, fishhook and box clasps with safeties each belong to periods, and a modern clasp on an old strand usually means a restringing. Nacre. A thin-nacre pearl worn through near the drill shows the bead beneath as a dull grey ring. That tells you the pearl is cultured and has been worn hard. Filigree's pearl jewelry runs Victorian seed pearl through mid-century mabe and modern strands, which is the whole span in one place.
Why Are Pre-1920s Natural Pearls Different From Modern Cultured Pearls?
Supply, and it is not a small difference. A natural pearl came out of a fishery that no longer runs at anything like its old scale. A cultured pearl comes off a farm.
Bauer's account of the Gulf of Manar fishery off Ceylon describes a six-week season in March and April. It drew fifteen to twenty thousand people to Kondachchi. Up to three hundred boats worked it, ten divers each, averaging twenty thousand oysters per boat per day. Banks were then rested six or seven years, which is roughly a pearl oyster's life.
The Persian Gulf ran on the same arithmetic and harder terms. Divers went down on a single breath to six or twenty metres, the strongest to twenty-six. Their kit was a nose clip, leather finger guards and a stone weight. Thirty to fifty dives in a day. Accounts of the labour describe conditions that were effectively unfree for the Indian and Arab divers who did the work.
Then the market turned inside a decade. On October 1, 1917, Pierre Cartier closed a trade with Morton and Maisie Plant. He gave up a two-strand natural pearl necklace of a hundred and twenty-eight pearls, plus cash. He got the Italian Renaissance mansion at Fifth Avenue and 52nd Street. It is still Cartier's New York address. Maisie Plant had wanted the necklace. Within a few years, round cultured pearls were selling in London under Mikimoto's name. By 1935 Japan had roughly three hundred and fifty pearl farms, producing about ten million cultured pearls a year. The Gulf and Ceylon fisheries collapsed through the 1920s and 1930s. Three pressures did it at once: cultured competition, the Depression, and the discovery of Gulf oil, which pulled labour and capital away from diving. Bahrain's pearl economy never came back.
The second difference belongs to the material rather than the market. A pearl is the one gem substance that does not keep. Perspiration dulls luster with contact, and Bauer is blunt that an old, much-worn pearl never has the freshness of a newly fished one. The conchiolin eventually goes altogether. He records pearls from the grave of Stilicho's daughter, buried in 400 and opened in 1544, falling instantly to dust when the tomb was opened. By that account, eleven centuries was enough.
Which is why condition on a pearl is permanent. A scuffed sapphire can be recut and repolished. A pearl cannot, because the surface is the gem. Bauer describes an old trick of peeling the outer layer to find a smaller sound pearl underneath. It takes a skilled hand and seldom fully works. Buying an old pearl piece means buying the pearl's last hundred years along with it.
Are Pearls Durable Enough to Wear Every Day?
Yes, with more care than any other birthstone asks for. Pearl sits at 2.5 to 4.5 on the Mohs scale, the softest thing on the calendar, and it is the only birthstone a weak acid will dissolve.
The acid behaviour is worth understanding because it explains the daily rules. Bauer put pearl's hardness at 3 to 4. He also recorded that a pearl effervesces in acid, even acetic acid. What is left is a soft scaly mass of conchiolin still holding the pearl's shape. He also thought the Cleopatra story apocryphal on exactly those grounds: table vinegar is too weak to take down even a small pearl over the course of a banquet. The everyday version of that chemistry is skin and cosmetics. Perspiration, perfume, hairspray and cleaning products all work on the conchiolin at the surface, and the result is a slow loss of luster rather than a visible mark.
Nacre thickness is the durability number that matters, and it is the one nobody quotes. A thin-nacre Akoya has a few tenths of a millimetre between its surface and the bead, and once that is gone the bead shows through as a grey ring. A South Sea pearl with two to four millimetres has room to spare. A freshwater pearl with no bead is nacre the whole way through and has nothing to wear down to.
Construction matters as much as the pearl. Mabe is assembled and hollow-backed, which puts it in earrings, brooches and pendants rather than on a working hand. A bezel that wraps the pearl protects the point of contact. Victorian and Edwardian rings often prong-set a pearl, or drilled it and pinned it on a post. That sits high and looks correct for the period. It also takes every knock the hand takes.
So the practical guidance runs by category. Earrings and pendants go decades without trouble, because they never hit anything. A brooch is safe for the same reason. A strand is fine and needs restringing on a schedule. A ring is the hardest test in the case, and it is still entirely wearable, provided it comes off before the gym and the garden. The jewelry care guide covers handling by stone type.
How Do You Clean and Store Pearl Jewelry?
Wipe them with a soft damp cloth every time you take them off. Nothing else touches them. No ultrasonic bath, no steamer, no jewelry cleaner, no toothbrush.
Last thing on, first thing off is the whole discipline in one line. Perfume, hairspray and lotion go on before the pearls, and the pearls come off before anything else at the end of the day. A wipe after wearing removes the skin oils and salts that do the long-term damage, and it takes about five seconds.
If a wipe is not enough, use warm water with a trace of mild soap on a soft cloth, work quickly, then dry the piece flat on a towel. Drying flat matters for a strand, because a wet silk thread stretches under the weight of its own pearls and stays stretched.
The two machines are the real hazard, at any age. An ultrasonic bath drives rapid pressure change through a laminated organic structure, which can separate nacre layers and loosen the cement in an assembled mabe. A steamer adds heat on top of that. Neither belongs anywhere near a pearl.
Restringing is maintenance, not repair. Silk stretches and takes up oils, and knots between pearls do two jobs: they stop a break from scattering the strand, and they keep pearls from grinding against each other. Once every year or two is reasonable with regular wear, sooner for a strand worn against skin most days.
Storage is the part people get wrong with good intentions. Pearls want their own soft pouch, away from harder stones, because a diamond or a sapphire in the same compartment will mark a pearl in a week of jostling. They also do not want a sealed dry safe or a sunny windowsill, since both pull moisture out of the nacre and out of the silk. A pouch in a drawer is better than a vault. The jewelry care guide has the rest.
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Pearl Jewelry
June's stone across every era Filigree carries, from Victorian seed pearl work to mid-century mabe and modern Akoya strands.
Browse Pearl Jewelry →Caring for Your Jewelry
Cleaning and storage stone by stone. Pearl is the entry that matters most, because nacre is the one surface that cannot be repolished.
Read the Care Guide →Birthstone Jewelry Guide
The complete birthstone calendar with Filigree's pieces for every month of the year.
View the Guide →The softest birthstone gem
Pearl is the one gem on the birthstone calendar that was alive. That single fact drives the softness, the acid sensitivity, the permanence of a scratch, the reason care matters more in June than in any other month, and the reason a natural pearl from before 1920 is a different object from a cultured one grown last decade.
It drives the design history too. Seed pearls threaded on horsehair, mourning brooches where a pearl means a tear, Edwardian platinum built around exactly two stones, mid-century mabe domes in cocktail mounts: each era held pearls in a way that tells you when it worked. The full span of pearl work is in Filigree's pearl jewelry.
Ready to Find Your June Stone
From Victorian seed pearl earrings and Edwardian natural pearls to mid-century mabe and modern Akoya strands, the collection carries pearl across every era.
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What is the pearl wedding anniversary, and why 30 years?
The thirtieth. Assigning materials to anniversary years began in the Holy Roman Empire with silver at twenty-five and gold at fifty, and the Victorians expanded that into a full year-by-year system, attaching pearl to the thirtieth. Kunz records pearl at the thirtieth year in his 1913 tables.
Can you wear pearls in the shower or while swimming?
No. Soap film dulls luster over time, chlorine attacks the conchiolin directly, and a silk thread that gets soaked stretches under the weight of its own pearls and stays stretched. Take them off first.
Is alexandrite a good stone for an engagement ring?
On durability, yes. At 8.5 on the Mohs scale it handles daily wear as well as a sapphire. The catches are supply and cutting: fine natural material is genuinely scarce, and a shallow stone will show a weak color change no matter how good the rough was.
How do gemologists tell a natural pearl from a cultured one?
With an X-ray. A bead-nucleated cultured pearl shows a sharp boundary where the shell bead ends and the nacre begins. A natural pearl shows continuous concentric growth rings with no such line. Film microradiography did this for most of the last century, and real-time X-ray microradiography and X-ray computed microtomography do it now.
Why is moonstone not covered here?
Moonstone is June's third stone, printed as the alternate on the 1912 list. It deserves its own page rather than a paragraph at the end of a pearl article.
