The oyster or mussel slowly secretes layers of aragonite and conchiolin, materials that also make up its shell. This creates a material called nacre, also known as mother-of-pearl, which encases the ...

Natural freshwater pearls occur in mussels for the same reason that saltwater pearls occur in oysters. Foreign material ... mottled are usually bleached to make them whiter and more uniform.

Japan's akoya oysters have been preëminent among cultured pearls ever since Kokichi Mikimoto first established the industry in the early part of this century. But since 1994, something has been ...