Pearl

• 1. Introduction

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  In 1917, the jeweler Pierre Cartier handed over a matched double strand of natural pearls and received a Fifth Avenue mansion in return. The building is now the New York Cartier store. At the time, the pearls were valued at US$1 million. He had been collecting them for years. That trade says something strange about the pearl. It is a small, glistening object grown inside the soft tissue of a living shelled mollusk, and for centuries it could buy a house. Its name has become shorthand for anything rare, fine and valuable. So how does a soft-bodied animal build a gem? Why was a perfect strand so hard to assemble that few exist? And what happened to that value when people learned to coax mollusks into making pearls on demand? The answers run through ancient chronicles, Spanish treasure fleets, a quiet dispute over a patent, and a few pearls that have no business being called pearls at all.

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• 2. Making a Pearl

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  Aragonite is the crystal at the heart of most pearls. A mollusk's mantle, the protective membrane lining its shell, lays down calcium carbonate as aragonite, or as a mix of aragonite and calcite. An organic, horn-like compound called conchiolin holds the crystals together. Aragonite and conchiolin together make nacre, the same material that forms the mother-of-pearl lining the shell.

  The popular story of a single grain of sand is rarely true. Typical triggers are bits of organic material, parasites, or an injury that pushes mantle tissue into the wrong part of the body. The fragile rim of the shell is exposed to crabs and other predators, and worm larvae can also attack it. When such an attack tears loose some external mantle cells, they may survive, tucked into the connective tissue. There they form a small pocket called a pearl sac and keep secreting their natural product, calcium carbonate.

  A cross-section of a natural pearl shows two zones. At the center sits a brown core of columnar calcium carbonate, laid down by young mantle cells in the pearl's early life. Around it lies a yellowish to white shell of nacre. When the sac switches from the first material to the second, the brown pebble gets its pearly coat. The sac never actually travels into the shell. It stays put in the mantle while the shell grows around it. After a couple of years, a pearl exists, and a lucky pearl fisher may find it.

  Light does the rest of the work. A pearl's glow comes from light reflecting, refracting and diffracting through translucent layers. The thinner and more numerous the layers, the finer the luster. Overlapping layers break up incoming light into the shifting iridescence that gem-quality pearls show. The most valuable have a metallic, highly reflective shine.

  That same chemistry is the pearl's weakness. Because a pearl is mostly calcium carbonate, even weak acid attacks it. Vinegar will dissolve one, as acetic acid reacts with the crystals to form calcium acetate and carbon dioxide.

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• 3. Diving for Pearls

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  The ancient chronicle Mahavamsa describes a thriving pearl industry at the port of Oruwella, on the Gulf of Mannar in Sri Lanka. It records that eight varieties of pearls traveled with Prince Vijaya's embassy to the Pandyan king. Pearls also went with king Devanampiya Tissa's embassy to Emperor Ashoka. Pliny the Elder, who lived from 23 to 79 AD, praised that gulf's fishery as the most productive in the world.

  For thousands of years, divers in the Indian Ocean retrieved seawater pearls from the Persian Gulf, the Red Sea and the Gulf of Mannar. Evidence hints that diving there began in prehistory. From the Han dynasty, which ran from 206 BC to 220 AD, the Chinese hunted pearls heavily in the South China Sea, especially around what is now Tolo Harbour in Hong Kong. By the twelfth century, Tanka divers in China tied ropes around their waists so they could be hauled safely to the surface.

  Spanish conquistadors found a new bonanza in the Western Hemisphere. Around the islands of Cubagua and Margarita, some 200 km north of the Venezuelan coast, lay an extensive bed of pearl oysters. One pearl found there, La Peregrina, was offered to Philip II of Spain as a wedding gift for his daughter. The king found it so beautiful that he kept it, and made it part of the Spanish Crown Jewels. Royal inventories listed it for more than 200 years. Garcilasso de la Vega said he saw it at Seville in 1607. He claimed it was found at Panama in 1560 by a slave, who won his freedom, while the slave's owner became alcalde of Panama. Margarita pearls are now extremely hard to find, and are known for a yellowish color.

  The arithmetic of the old trade was brutal. Divers pulled oysters from the seabed or river bottom by hand and checked each one individually. Many hundreds of oysters or mussels had to be opened, and so killed, to find even one wild pearl. In a haul of three tons, only three or four oysters would hold perfect pearls. That scarcity is why pearls fetched such extraordinary prices.

  Britain had its own pearl rush. Pearls were among the attractions that drew Julius Caesar to the island, and they were mostly freshwater pearls from mussels. Scottish Travellers carried on much of the fishing, and learned that pearls differed from river to river. The River Oykel in the Highlands was noted for the finest rose-pink ones. Then came the Abernethy pearl from the River Tay, and publicity about its sale for a substantial sum. During the 1970s and 80s, weekend pearlers heavily exploited the mussel colonies. Pearling was banned in the U.K. in 1998 because river mussels were endangered, and just two firms in Scotland are licensed to sell pearls gathered before that year.

  Today, natural pearling is mostly confined to the Persian Gulf, in seas off Bahrain. Australia keeps one of the world's last fleets of pearl diving ships, though its divers collect South Sea oysters for the cultured pearl industry.

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• 4. The Culture Revolution

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  The year 1916 marks the turning point. That was when Tokichi Nishikawa was granted a patent on a method of culturing pearls. The popular story credits Kokichi Mikimoto, but he did not invent pearl culture. The accepted process was developed by the British biologist William Saville-Kent in Australia. Nishikawa and Tatsuhei Mise brought it to Japan. Nishikawa married Mikimoto's daughter, so Mikimoto was able to use the technology.

  The method was commercial almost immediately. In 1916 it was applied to akoya oysters in Japan, and Mise's brother was the first to produce a commercial crop. In 1917, Baron Iwasaki of Mitsubishi applied it to the South Sea pearl oyster in the Philippines, and later in Buton and Palau. Mitsubishi produced the first cultured South Sea pearl, but the first small commercial crop did not come until 1928. By 1931 the project showed promise, but Mise died. It restarted, then stopped at the start of World War II, before significant production was reached. In the early 1950s, new projects opened at Kuri Bay and Port Essington in Australia, and in Burma, using technicians from the prewar Mitsubishi work. Kuri Bay is now home to a farm owned by Paspaley, the biggest producer of South Sea pearls in the world.

  The technique itself is a small act of surgery. A graft of mantle tissue from a donor shell is placed in a recipient, which forms a pearl sac around it. For most saltwater pearls, a polished bead of mother-of-pearl is implanted too. The oyster coats the bead with nacre, and a harvest can come in as few as twelve to eighteen months. Some South Sea and Tahitian oysters survive the removal of the finished pearl. They are sometimes given a larger bead in the same operation, then returned to the sea for more growth.

  The new pearls caused an uproar. Dealers of natural pearls publicly disputed the authenticity of the cultured ones. Consumers were left uneasy and confused about the much lower prices, and the argument tarnished the image of both kinds. By the 1950s, plenty of women in developed countries could afford their own cultured necklace. Natural pearls shrank to a small, exclusive niche.

  Telling the two apart took new tools. A well-equipped gem laboratory uses X-rays to look at a pearl's center. A natural pearl shows concentric growth rings, with thin layers of conchiolin between the calcium carbonate. A beaded cultured pearl shows a solid center with no rings. A beadless one may show rings, plus a complex central cavity left by the young pearl sac. Imitations are a separate problem. Some are made of mother-of-pearl, coral or conch shell, and others are glass coated with a solution containing fish scales, called essence d'Orient. A microscope exposes them. So does rubbing two pearls together, because real nacre feels slightly gritty and fakes are smooth.

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• 5. Pearls by Water

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  Akoya pearls are the original Japanese cultured pearl. They come from Pinctada fucata martensii, an oyster no bigger than 6 to 8 cm, so akoya pearls over 10 mm are extremely rare and highly priced. They generally run from 2 to 10 millimeters, and are usually cream or white with pink, silver, blue or green overtones. Many were once exported in cans, packed in Nagasaki by the International Pearl Company. In 2010, China overtook Japan in akoya production. Japan has nearly stopped making akoya pearls under 8 mm, yet remains a processing center. It imports most of China's akoya crop, sorts and matches it, relabels it as Japanese, and exports it.

  The South Sea pearl comes from the opposite end of the scale. Its oyster, Pinctada maxima, is the largest pearl oyster, roughly the size of a dinner plate. Pearls of up to 14 mm are not uncommon. They take on the colors of the shell, in white, silver, pink, gold and cream. White and silver ones tend to come from the Broome area of Australia, and golden ones from the Philippines and Indonesia. In 2013, Indonesia Pearl supplied 43 percent of the international South Sea market.

  Tahitian pearls, often called black pearls, come from Pinctada margaritifera, which lives in Tahiti, the Cook Islands, Fiji and other Pacific islands. Their rarity is relative. They are scarcer than Chinese freshwater or akoya pearls, but more common than South Sea pearls, because the black pearl oyster is far more abundant. They are often mislabeled as black South Sea pearls. A related oddity is the keshi pearl, made entirely of nacre. It forms when the grafted mantle slips off the bead, and it is usually small and irregular. For years the industry treated keshi pearls as a drain on production, but today many are intentional. Growers return harvested shells to the water to regenerate a pearl in the existing sac.

  Freshwater pearls tell a different story. In 1914, farmers began culturing pearls in mussels native to Lake Biwa, the largest and most ancient lake in Japan, near Kyoto. Biwa pearls once nearly meant freshwater pearls in general. Production peaked in 1971 at six tons, then pollution all but wiped out the industry. A hybrid mussel tried in Lake Kasumigaura has also nearly stopped producing for the same reason. The Belpearl company in Kobe still buys what remains.

  Japanese producers moved to the Shanghai region, and China is now the largest freshwater pearl producer, at more than 1,500 metric tons per year. Beadless freshwater pearls grow in the mantle, where up to 25 grafts can go into each wing. That volume saturates the market. Quality has improved sharply, from rice-grain-shaped pebbles to near-round pearls, and later round bead-nucleated pearls up to 15 mm with metallic luster.

  The United States joined in during the mid-1960s, led by John Latendresse and his wife Chessy. National Geographic introduced the American cultured pearl in its August 1985 issue. The Tennessee farm is now a tourist destination, but its commercial production has ceased.

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• 6. Strange Pearls

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  In 1934, in the Philippines, someone found the second largest pearl known. The Pearl of Lao Tzu weighs 14 lb, or 6.4 kg, and came from a giant clam. It is a non-nacreous concretion, so its surface is glossy like porcelain instead of pearly. The largest known pearl, the Pearl of Puerto, also came from a giant clam in the Philippines. A fisherman from Puerto Princesa on Palawan Island found it. It is 30 cm wide and 67 cm long, and weighs 75 lb, or 34 kg.

  Almost any shelled mollusk can make some kind of pearl, though most are dull and fragile. They turn up in edible mussels, edible oysters and escargot snails, and are worthless except as curiosities. Gemologists once called these objects calcareous concretions, though a malacologist would still call them pearls. The GIA and CIBJO now use the plain word pearl, or non-nacreous pearl where needed. Under U.S. Federal Trade Commission rules, they may be called pearls without qualification.

  A few species do make gems. The bailer shell Melo, the giant clam Tridacna, various scallops and the pen shells Pinna are among them. In New Zealand, the abalone Haliotis iris yields blister pearls known as blue pearls, admired for bright colors compared to opal. The queen conch, Strombus gigas, a large sea snail from the Caribbean, rarely grows a pink pearl between its mantle and shell. These are a by-product of conch fishing, and the best show a shimmering effect called flame structure. The horse conch Triplofusus papillosus very rarely makes similar pearls in orange. In the Gulf of California, a Mexican farm raises pearls from the rainbow-lipped oyster Pteria sterna, also called Concha Nacar. These pearls fluoresce red under ultraviolet light.

  One producer is no longer alive. The conulariids, extinct cnidarians closely related to stalked jellyfish, also made pearls. Theirs were built of calcium phosphate, which, with their great age and crystal structure, makes them unattractive for decoration.

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• 7. Strands and Measures

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  A single unit, the momme, governs much of the pearl trade. The Japanese government formalized the kan measure in 1891 as exactly 3.75 kilograms. One momme is 1/1000 of a kan, or 3.75 grams. Most pearl dealers still use it to communicate with producers and wholesalers. Silk traders carried the word to the United States during the 19th and 20th centuries, where it became a measure of silk cloth quality. Millimeter size is usually the first factor in a necklace's value, but momme weight tells a buyer whether it is properly proportioned, especially for large South Sea and Tahitian strands.

  Pearl necklaces have their own vocabulary, named by how low they hang. A collar, at 10-13 inches, sits against the throat. A choker, at 14-16 inches, rests at the base of the neck. A princess length, at 17-19 inches, reaches the collarbone or just below. A matinee, at 20-24 inches, falls just above the breasts. An opera length, at 28-35 inches, reaches the breastbone, and a rope runs longer than 45 inches.

  Strands are also graded by size. In a uniform strand of akoya pearls, sizes fall within 0.5 mm, so a strand might run 6.5-7 mm and never a flat 7. Freshwater, Tahitian and South Sea strands are uniform within a full millimeter. A graduated strand typically differs by at least 3 mm from the ends to the center. In the 1950s, American GIs brought home strands of cultured akoya from Japan and popularized them. A graduated strand of 3.5 momme, from 3 mm to 7 mm, cost far less than a uniform one because most pearls were small.

  Shape matters just as much. Perfectly round pearls are the rarest and most valuable. Semi-rounds can pass for round in necklaces. Button pearls are slightly flattened, so they suit earrings and pendants where the back is hidden. Pear-shaped and teardrop pearls suit earrings, pendants and centerpieces. Baroque pearls are irregular and have their own appeal, while circled pearls carry concentric ridges. Jewelers rank luster as the most important quality, and with all else equal, bigger is worth more.

  Color can mislead. White and, more recently, black saltwater pearls are the most popular, but pink, blue, champagne, green and purple exist. Collecting enough of such a shade to make a matched string can take years. Most cheap colored pearls are dyed, often with fabric dye, which only penetrates a layer or two of nacre. Truly valuable pearls are never dyed.

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• 8. Words and Scripture

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  The name Margaret is a distant cousin of the pearl. The English word pearl comes from the French perle, which goes back to the Latin perna, meaning leg, after a bivalve shaped like a ham or mutton leg. The scientific family name Margaritiferidae comes from the Old Persian margarita, meaning pearl, which is also the source of Margaret.

  In the Hindu tradition, the Garuda Purana is the first to document the sacred Nine Pearls. Ayurveda mentions pearl powder as a digestive stimulant and a treatment for mental ailments. Marco Polo reported that the kings of Malabar wore a necklace of 108 rubies and pearls, handed from one generation to the next. Each king had to say 108 prayers every morning and every evening. Until at least the early 20th century, Hindus presented a new, undrilled pearl and pierced it during the wedding ceremony. The pearl is also tied to many deities, most famously the Kaustubha worn on Lord Vishnu's chest.

  The Hebrew Bible uses the word pninim for pearls in several places, including Job 28:18, Proverbs 3:15, and Lamentations 4:7, though its etymology is unclear. In the Christian New Testament, Matthew 13:45-46 compares the kingdom of heaven to a merchant: "Who, when he had found one pearl of great price, went and sold all that he had, and bought it." Revelation 21:21 describes twelve gates, each made of a single pearl, which is the origin of the pearly gates. Matthew 7:6 warns against casting pearls before swine. Revelation 18:16 uses pearls differently, among the finery of a proud and wicked great city.

  The Quran often says that dwellers of paradise will wear pearls. Verse 22:23 describes bracelets of gold and pearls, and 52:24 says they will be waited on by youthful servants "like spotless pearls." Gnosticism has its own pearl in a long poem called the Hymn of the Pearl, respected for its layered theological metaphor. A book of scripture in the LDS Church and some other Latter Day Saint denominations is named The Pearl of Great Price.

  One more work carries the name alone. Pearl is a Middle English religious poem, and it is the natural next stop for a listener who wants to see how far the pearl travelled in language.

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