Gem and Ornamental

146 G m AND ORNAMHNTAL MATERIAIS OF ORGANIC ORIGIN,-Figure 9,4 Swth Sea nucleatedcultured ged (magn5ed).eentimetres across. The nacre inside the shell is silvery in colour, andin the case of the golden-lipped oyster, it is tinged with a creamy golddour around the edge. It lives in the East Indian Ocean and the westPadie, and is the oyster used in the pearl farming area of north--ternAustralia. It is used to produce South Sea pearls, which arenucleated cultured pearls, measuring 10 to 20 '"' in diameter,and are white to golden in colwr (Fig. 9.4).The black-lipped pesrl oyster, Pincrada ~~, is a littlemder, and measures from 15 to 25 centirnetres across, It, too, hasdvery nacre inside the shell, becoming silvery grey at the edges, whichare surrounded on the lip of the shell by a black border that memblesenamel. The oyster lives in the Indian Ocean and the western andcentral PacXc, especially mund French Polynesia. It is used toproduce the famous Tahitian black peds, which are nucleatedcultured pearls. The nacre secreted by these pearl oysters is naturallycoloured and varies hm light grey to black, with iridescent hints of. .green, purple, pink and blue. The pearls range in size hm 10 to 18mdhems in diameter.The Akoya pearl oyster, Rnctada +a& m d , is again smaller,meas- 8 to 10 eentimetres amoss. It has silvery nacre inside theshell. Ahyas are used in Japan to produce their world-famous nucleatedcultured pearls, and are now also being used in China and otherparts of the Far East. The cultured pearls produced by these oystemvmy in size from 2 to 10 '"' ' s in diameter, and a n white tocream in colour,The black-wiuged p-1 oyster, PEeria paguk, has silvery nacre,a wide black lip md a n m w 'wi& hpe where the shell hinga. It