The oyster produces the stone called pearl. At dawn the oyster opens and takes in the rays of the stars, the moon and the sun, and also swallows dew, and from these come the pearl. The agate stone is attracted to pearls and so can be used to find them. Once the king pearl has been captured, the lesser pearls are easy to catch. Pearls can be found in abundance near the island of Taprobane (Ceylon/Sri Lanka).

The pearl represents Mary, who received the words of God (the "heavenly dew"). Philippe de Thaon says that the shell of the oyster, which opens and closes without a break, signifies Mary, who conceived and gave birth in like manner.

Drinking a mixture of pearl and dew will cure any disease, but cannot reverse death.

Thomas of Cantimpré says the pearl has both strength and harmony, and it confers health of mind and body, indeed of the mind because it renders the wearer chaste.