Assertion: oyster's pearl | /r/MadeOf | oyster
Facets:
value: by the accumulation of nacre
type: CAUSE
Source sentences:
text: A natural pearl is formed by a mollusk - an animal such as an oyster, clam, conch, or gastropod.
text: Pearls are formed in oysters by the accumulation of nacre, the material lining the oyster shell, around a solid piece of foreign matter that has become lodged inside the shell.