Seawater-Pearls

Akoya-Pearls The oysters (Pinctada Martensii and Pinctada Fucata) are breed in large quantities: They grow up for about 3 years in net-like baskets, that are floating 6 m below the surface. All healthy oysters are used to produce pearls, all others are killed to use their lateral epithelial tissue, that can still produce good quality nacre. A round nucleus of white shell and a piece of epithelial tissue (4 mm2) are implanted into each oyster. The size of the nucleus   may average 7 mm or even 9 mm.   The growth-rate of the nacre varies from 0.15 - 0.30 mm per year and after 3 years the pearls can be harvested. The colours of Akoya-Pearls are white,yellowish or grey.

South-Sea-Pearls The species used in the south-sea are Pinctada Maxima, Pinctada Margaritifera and others.   The oysters live free in bays and creeks 30 - 40 m below the surface and produve both cultured pearls and Mabe-Pearls.   The implanted nucleus may have sizes from 6.5 to 13 mm, the growth-rate of the nacre is about 3.3 mm per year due to higher water temperatures.   The colours of South-Sea-Pearls are bronze,  siver-white (North-Australia) or grey to black (Pinctada Margaretifera from Tahiti), the shapes are oval to baroque.

 

Mabe-Pearls are produced by implanting hemispherical nucleus of plastic, glass or ceramics between the mantle and  the nacreous inner surface of the shell.The oyster now begins to secret nacre over the irritant and cements it to the shell. After the harvest, the nucleus is sawed out and the cavity of the pearl is filled up with a plastic compound and sealed with a round piece of nacre.  The pearls have a size of about 25 mm.