Here's a breakdown:
* Oysters: The most well-known pearl producers. They create pearls when a foreign object, like a grain of sand, gets lodged inside their shell. The oyster coats the irritant with layers of nacre, which is the iridescent substance that makes pearls beautiful.
* Mussels: Similar to oysters, mussels can also produce pearls, though they are generally smaller and less valuable.
* Conch: Some conch species can create pearls, although they are less common than in oysters.
* Abalone: While abalone are known for their beautiful shells, they don't typically produce pearls.
It's important to remember that not all mollusks create pearls, and even within species, pearl production can vary.