Here are different types of cultured pearls Akoya Pearls Pearls more than 7mm in diameter from the akoya oyster are generally from Japan, while smaller ones are more likely to be from China, Hong Kong, Korea or Sri Lanka. They are fairly spherical and range in colour from white, pink and yellow, to green, grey and blue-grey. Keshi pearls are tiny pearls that form as a larger cultured pearl is forming is an akoya oyster. They have not been cultured; they just appear. They have the same colours as akoya pearls, but do not have a nucleus and form as natural pearls with in oyster. Keshi pearls are generally irregular in shape. South Sea and Tahitian Pearls Cultured in the large mollusk pinctada maxima, South Sea pearls are the largest cultured pearls. They have similar colures to the akoya pearls; the white-rose and the gold coloured pearls are particularly popular. Keshi Pearls with a diameter of more than 10mm can appear during the culture of south sea and Tahitian pearls. They are irregular in shape, have no nucleus and may be termed natural; they are referred to as Tahitian or south sea keshi pearls. The only natural black pearls are thise from the mollusk pinctada margaritifera. Pearls may be dyed or soaked in sliver nitrate to appear black.
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Biwa pearls The first freshwater cultivated pearls were produced in Japan’s largest freshwater lake, lake Biwa near Kyoto, and sold commercially in the 1930s. Japanese biwa pearls occur as irregular pearls without a nucleus. Production was interrupted by World War 2. By the 1950s, freshwater pearls were sold in Japan as a less expensive and more colorful alternative to the marine material. Biwa became associated with freshwater pearls and, until recently, all freshwater pearls were sold as biwa.
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Rice Pearls The shape of rice pearls is due to the speed of cultivation, resulting in irregular thickness of the nacre and occasional pitting of the surface. Rice pearls are produced in fresh water – for example, in China. Other names used to sell irregular of fancy shaped pearls include potato pearls, corn pearls, square shaped and lavender button pearls.
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