The Basic Methods of Pearl Farming: A Layman's Manual - CTSA

A short history of pearl cultureA short history of pearl culturePearls were the first gems discovered by man thousands of years ago. Since that time, people of manycultures have recognized the beauty and value of pearls. Pearls are the only organic gems and requireno processing to reveal their natural beauty. At first, people relied on the chance finding of naturalpearls in a variety of species of marine bivalves and freshwater mussels. Natural pearls are rare asperhaps maybe 1 in 2,000 pearl oysters contain a natural pearl. Natural pearls are formed when thepearl oyster reacts to an irritant by coating it with nacre, the shiny iridescent material found on the innersurface of the shell. Natural pearls are usually small, of various colors and irregular in shape. The highvalue of natural pearls led to the creation of pearl fisheries in nearly every part of the world where pearlproducingmollusks were found. Most of these pearl fisheries were short-lived because the fisherssoon over-exploited the natural stocks.Prompted by the high value and scarcity of naturalpearls, Japanese researchers developed methods thatbrought pearl production under the control of humansin the early twentieth century. These “cultured pearls”are generally larger and of a more consistent size andcolor than natural pearls. Producing cultured pearlsdepends on a surgical procedure called grafting,which entails surgically implanting an artificialnucleus (shell bead) into the tissue of a pearl oyster.The oyster then secretes nacre around the nucleus.After several years of caring for the oysters, the culturedpearls are harvested.Figure 1. Black-Lip pearl oyster in its natural habitat,a coral reef of the Cook Islands.(photograph: Maria Haws).Several species of pearl oysters are cultivated for pearlproduction. This manual focuses on the Black-Lip pearloyster (Pinctada margaritifera). Black-Lip pearl oystersare the most common species of pearl oyster foundin the South Pacific islands (Figure 1). The Black-Lippearl oyster is distinguished from other species by thedark, iridescent nacre found on the inner shell.Figure 2. Black pearls resting on the shell of aBlack-lip pearl oyster (Pinctada margaritifera).(photograph: Maria Haws)Pearls produced by Black-Lip pearl oysters are knownas “black pearls” or “Tahitian black pearls” (Figure 2).Black pearls are large, usually over 7 mm (0.28 in) indiameter and may be as large as 22 mm (0.8 in). Note:Pearls are always measured in millimeters within thePage 5