Like diamonds and other precious stones, pearls are considered special because they are very pretty and also rare (meaning they are hard to find!).
Pearls come from mollusks, a group of animals that includes oysters, clams, and mussels, among others. Any mollusk that has a shell can make pearls, although the most common pearl-makers are oysters!
Pearls are made when a foreign object like some dirt or a small piece of stray food gets inside the shell of an oyster (or other mollusk) by mistake. To protect itself, the creature covers the intruding object with the same stuff its shell is made of, a mineral known as nacre. The oyster or other mollusk continues covering the object with multiple layers of nacre, eventually forming a pearl!
Further informationIn addition to “natural pearls” (which occur when an object in nature gets into the shell of a mollusk), there are also “cultured pearls.” Cultured pearls are made by the exact same process as natural ones, the only difference is that instead of the dirt or other intruding object entering the mollusk’s shell by chance, it is instead put there on purpose with the intention of making a pearl!
Lots of pearls are nice, round shapes. But some are not! – Pearls that are oval, bumpy, or uneven in shape are called “baroque pearls.”Can you guess how much the biggest pearl ever discovered weighed?? The answer is 14 pounds! Can you think of anything else that weighs that much, like maybe a small dog or a pet cat? Can you imagine a pearl that also weighed that much?!
Sources & links
Bryner, Michelle. “How Do Oysters Make Pearls?” Life’s Little Mysteries. LiveScience.com. 08 Feb. 2010 "pearl." Encyclopædia Britannica. 2010. Encyclopædia Britannica Online. 07 Feb. 2010 “Pearls: Fun Facts.” The Field Museum. 08 Feb. 2010 “Peals and the Biggest Ever.” The Bead Site. 09 Feb. 2010 “What Are Pearls?” Pearls. American Museum of Natural History. 08 Feb. 2010