Knowra Pearl Pearl A pearl is a layered biomineral structure formed by some mollusks around an irritant or implanted nucleus. Its alternating mineral and organic layers produce its characteristic luster.
Nacre : A composite material of aragonite crystals and organic matrix that lines some mollusk shells. Pearls are built from successive layers of nacre.
Mollusca : A phylum of invertebrate animals that includes snails, clams, oysters, and cephalopods. Only certain mollusks produce pearls of the kind described here.
Pearl culture : The controlled production of pearls by introducing a nucleus or tissue into a mollusk and allowing layers to form. It applies pearl-forming biology to produce pearls commercially.
Natural pearl : A pearl formed without deliberate human implantation of a nucleus or mantle tissue. It contrasts with pearls whose formation begins through cultivation procedures.
Aragonite : A crystalline form of calcium carbonate found in shells, corals, and other biominerals. Its crystals form much of the mineral phase in nacreous pearls.
Mollusk mantle : A tissue layer in mollusks that secretes shell material and encloses the visceral mass. Mantle tissue supplies the cells that form a pearl sac.
Pearl grading : The assessment of pearls by qualities such as size, shape, color, surface, and luster. These traits guide how pearls are compared and valued.
Cultured pearl : A pearl formed after humans deliberately initiate pearl growth inside a mollusk. Its formation is assisted, though the mollusk builds the pearl layers.
Conchiolin : A family of proteins that forms the organic matrix in mollusk shells. Organic matrix between mineral layers helps shape pearl structure.
Mollusk shell : A hard external structure secreted by the mantle of many mollusks, commonly containing calcium carbonate. Pearl layers use biomineralization processes related to shell formation.
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