Pearls are the only gemstones made by living creatures. Mollusks produce pearls by depositing layers of calcium carbonate around microscopic irritants that get lodged in their shells, usually not a grain of sand as commonly believed.
While any shelled mollusk can technically make a pearl, only two groups of bivalve mollusks (or clams) use mother-of-pearl to create the iridescent “nacreous” pearls that are valued in jewelry. These rare gemstones don’t require any polishing to reveal their natural luster.
Appropriately, the name “pearl” comes from the Old French perle, from the Latin perna meaning “leg,” referencing the leg-of-mutton shape of an open mollusk shell. Because perfectly round, smooth natural pearls are so uncommon, the word “pearl” can refer to anything rare and valuable.
The rarest and most expensive pearls are natural pearls made in the wild, without human interference. The majority of pearls sold today are cultured or farmed by implanting a grafted piece of shell (and sometimes a round bead) into pearl oysters or freshwater pearl mussels.
Pearls are very soft, ranging between 2.5 and 4.5 on the Mohs scale. They are sensitive to extreme heat and acidity; in fact, calcium carbonate is so susceptible to acid that authentic pearls will dissolve in vinegar.
The finest pearls have a naturally reflective luster, making them appear creamy white with an iridescent sheen that casts many colorful hues.
Cultured freshwater pearls can also be dyed yellow, green, blue, brown, pink, purple or black.
Black pearls, which are mostly cultured because they are so rare in nature—aren’t actually black but rather green, purple, blue or silver.
Pearls used to be found in many parts of the world, but natural pearling is now confined to the Persian Gulf waters near Bahrain. Australia owns one of the world’s last remaining pearl diving fleets and still harvests natural pearls from the Indian Ocean.
Today, most freshwater cultured pearls come from China. South Sea pearls are cultured along the northwestern coastline of Australia, the Philippines, and Indonesia.
Pearls have been used as adornment for centuries, at least as far back as ancient Greece, where they believed pearls were the tears of the gods. The oldest known pearl jewelry was discovered in the sarcophagus of a Persian princess who died in 520 B.C.
Ancient Japanese folktales told that pearls were created from the tears of mythical creatures like mermaids and nymphs. Early Chinese civilizations believed that dragons carried pearls between their teeth and the dragon must be slain to claim the pearls, which symbolized wisdom.
Other cultures associated pearls with the moon, calling them "teardrops of the moon." Hindu folklore explained that dewdrops fell from the moon into the sea, and Krishna picked one for his daughter on her wedding day.
Because natural pearls were so rare throughout history, only the richest nobles could afford them. During the Byzantine Empire, rules dictated that only the emperor was allowed to wear these treasured gemstones. Ancient Egyptians were often buried with their prized pearls.
Tudor England was known as the Pearl Age because of the stone’s popularity with the upper class during the sixteenth century. Portraits showed royals wearing pearl jewelry and clothing adorned with pearls.
Pearls became more accessible in the early 1900s when the first commercial culturing of saltwater pearls began in Asia. Since the 1920s, cultured pearls have almost completely replaced natural pearls in the market, making this classic gemstone affordable for nearly any budget.
Pearls make the perfect gift for babies born in June or under the signs of Gemini or Cancer. As ancient symbols of purity and innocence, pearls are traditionally worn by a bride on her wedding day, making pearl jewelry a great gift to celebrate a bride-to-be or a 1st, 3rd, 12th or 30th anniversary.
If you’re shopping for perfectly round natural pearls, you’ll need patience and a large pocketbook. Most pearls on the market today are produced through culturing, giving pearl buyers a wealth of options.
Most freshwater cultured pearls are made in China, while common saltwater cultured pearls include Akoya, white or golden South Sea, and black Tahitian. Colors can range from creamy white to pink, yellow, brown, purple, blue, green, silver or an iridescent rainbow of hues like a peacock.
Pearls are one of few gemstones not measured by carats. Luster is the most important aspect of choosing a pearl. The finest pearls are metallic and reflective like mirrors.
Pearls can range in size from 3mm to 13mm. Because pearls do not require polishing or faceting like most gemstones, finding a pair of pearls that match perfectly in size, color and luster can be more difficult and more expensive. A matched strand of natural pearls may sell for hundreds of thousands (if not millions) of dollars.
Beware of imitation pearls or shell pearls, which are made from conch shells or glass coated with a solution containing fish scales. Rubbing two pearls together will reveal if they are smooth imitation stones, or if they feel gritty from the nacre that comprises natural and cultured pearls.
Expert gemologists can distinguish natural pearls from cultured pearls by using gemological X-ray equipment. Natural pearls consist entirely of concentric growth rings, while cultured pearls have a solid nucleus of the bead or shell that was implanted to stimulate pearl production.