A pearl is a hard glistening object produced within the soft tissue of a living shelled mollusk or another animal, such as a conulariid. Just like the shell of a mollusk, a pearl is composed of calcium carbonate in …
Georgian seed pearl gold ring
A black pearl and a shell of the black-lipped pearl oyster. The iridescent colors originate from nacre layers.
Electron microscopy image of a fractured surface of nacre