Pearls: Treasures of the Mollusk

For thousands of years, pearls have been the ultimate symbol of beauty, wealth, and mystery – and they come from mollusks. A pearl is born when an oyster or mussel coats a grain of sand or parasite with layers of lustrous nacre, turning a flaw into a gem​.

They are the only gemstone made by a living creature, and perhaps that’s why so many legends and rituals surround them.

The most famous tale is of Cleopatra’s bet: to prove Egypt’s wealth, she dissolved one of her enormous pearls in vinegar and drank it in front of Mark Antony​.

Ancient Egyptians prized pearls so much that pharaohs were buried with them​.

In the Americas, the “Pearl Coast” of Venezuela yielded a pearl that adorned the Spanish crown. European royals like Julius Caesar limited pearls to the nobility by law. By the 1800s, “pearl fever” had divers scouring the Persian Gulf, Red Sea, and Indian Ocean, often risking death to retrieve these ocean treasures. So valuable were pearls that a proverb said, “with pearls on, a lady is never cold.”

Yet, behind the glamour is the mollusk – often a humble oyster working tirelessly undersea. Pearls come mostly from pearl oysters (genus Pinctada) in saltwater and various freshwater mussels in rivers. These mollusks play roles in their ecosystems: oysters filter water (a single oyster can filter tens of gallons a day). For example, freshwater pearl mussels (Margaritifera margaritifera) can live over 100 years and each can filter 50 liters a day, purifying streams​​

The advent of cultured pearls in the early 20th century by Kokichi Mikimoto in Japan revolutionized the pearl world​.

By surgically inserting a bead into oysters and returning them to water, people could induce pearl formation without depleting wild stocks. Today, virtually all pearls sold are cultured, sparing wild oysters from mass harvesting. However, pearl farms still require healthy oysters and clean waters – pollution or disease outbreaks can crash them.