a pearl shape that is irregular and not symmetrical.

bead-and-tissue-cultured pearls

freshwater or saltwater cultivated pearls whose growth is started by implanting a shell bead nucleus and a donor-mollusk mantle-tissue piece in the mantle, gonad, or other body part of a host mollusk

bead-cultured pearls

freshwater or saltwater cultured pearls whose growth is started by implanting a shell bead nucleus in an existing pearl sac from which a first-generation cultured pearl was removed


a mollusk from the Bivalvia class having a two-part shell attached by a hinge

Biwa pearls

cultured freshwater pearls in Lake Biwa, Japan

black lip oyster

common name of the Pinctada margaritifera

black pearls

pearls of naturally dark colors formed by the Pinctada margaritiferaPinctada margaritiferacumingiPinctada mazatlanica, and Pteria sterna mollusks

black-lipped mollusk

 general name for the Pinctada margaritifera and Pinctada margaritifera cumingi mollusks


refers to any surface defect on a pearl, such as cracks, chips, dull spots, wrinkles, spots, holes, bumps, and pits

blister pearls

pearls attached to the shell of the host mollusk

body color

the aspect of a pearl’s color that is triggered by pigment as conflicting to light interference


 historical Japanese linear measure to designate the diameter of a bead nucleus (bu = 3.03 mm)


 used to drift lines from which mollusks are dangled in net panels or any other holding devices


 a group of thread-like tissue that bivalve mollusks use to anchor themselves to a solid external surface