Science
How does a pearl form?
A pearl works as an oyster's defense: when an irritant slips inside its shell, the oyster coats it in layer after layer of the same smooth material that lines the shell. Over years, these layers build up into a lustrous pearl.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a pearl works.
Step by step
- 1An irritant (like a parasite) gets trapped inside the shell.
- 2The oyster coats it with nacre, the shiny shell-lining material.
- 3Thousands of thin layers build up over months and years.
- 4The layered nacre gives the pearl its glow (iridescence).
- 5Cultured pearls are made by deliberately inserting a tiny bead.
Frequently asked questions
- How does an oyster make a pearl?
- It defends against an irritant by coating it in many thin layers of nacre, the same smooth material that lines its shell, slowly forming a pearl.
- Are natural and cultured pearls different?
- Both are real pearls; cultured ones simply start from a bead a farmer inserts, while natural ones begin from a chance irritant.
- Why do pearls shimmer?
- Light bouncing between the many translucent nacre layers interferes, producing the soft, rainbow-like glow called iridescence.