Book 6, Question 42
Why Do Some Clams Make Pearls?
Some clams and oysters make pearls by coating something stuck inside them, layer after layer, until it is sealed in.
Some oysters and other mollusks can make pearls. If a bit of grit or a tiny parasite slips inside, the animal coats it with the same shiny material that lines its shell. Layer after layer makes a smooth ball, so the grit stops scratching.
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Quick answers
Is it usually a grain of sand?
No. In natural pearls, the thing inside is usually a tiny parasite, not a grain of sand.
Sources: National Geographic Kids, National Geographic
From the book
Page from A Million Whys Book 6
More fun facts
- A pearl forms when a clam or oyster coats something stuck inside it, layer after layer, until it is sealed in.
- In natural pearls, the thing inside is usually a tiny parasite, not a grain of sand.
- A police officer once found a rare pearl in his bowl of clam stew.
- Long ago, many people thought pearls had magical powers.
- A legend says rich Roman women wore pearls to bed so they would remember how rich they were when they woke up.
Sources: National Geographic Kids, National Geographic
Questions kids ask
Do pearls start with a grain of sand?
Not usually. In natural pearls, the thing inside is most often a tiny parasite.