Pearls are naturally occurring gemstones formed within the soft tissue of certain living shelled molluscs, otherwise known as oysters. Non-cultured pearls created without human aid are extremely rare, especially when found in a well-shaped spherical form. For this reason, most pearls on the market are cultured pearls. Cultured pearls are formed when one places an irritant, such as a grain of sand, a small organism or a tiny particle inside the mouth of a mollusc. The mollusc, detecting this irritant, then deposits layers of calcium carbonate to coat it, thereby neutralising the intruder and creating a pearl.
Pearls vary in size, colour and shape according to their place of origin. Different molluscs, native to specific waters, create different pearls. There are four main types of cultured pearls on the market today, each exquisitely unique in character: Akoya, Tahitian, South Sea and Freshwater.
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Akoya pearls are the most popular and classic of white pearls. They are the also most lustrous of all cultured pearls and boast the greatest shine. Akoya pearls are cultured from saltwater molluscs in Japan and China called Pinctada Fucata. They can range from 2mm to 11 mm in diameter, though the average size is 6-7mm. An Akoya pearl larger than 7mm is considered extremely rare and jumps significantly in price. Akoya pearls can display a rose, gold or blueish hue, but are typically white with a rose overtone. Overall, Akoya cultured pearls are the most even in size, colour and shape, which is why they are such popular fine jewellery adornments.
Tahitian pearls are known for their unique dark colour and large size. They are typically cultured in either the French Polynesian lagoons or the Cook Islands. Tahitian pearls are produced by the large black-lipped variety of the Pinctada Margaritifera oyster. Although they are frequently referred to as black pearls, Tahitian pearls come in a wide array of dark purple, green, grey, silver and blueish hues. Ranging in size from 8-16mm in diameter, the average size of a Tahitian pearl is 9-10mm, making it a bit smaller than the South Sea pearl, but larger than the Akoya.
South Sea pearls are cultured in the northern waters of Australia, South-east Asia, Indonesia and the Philippines. These pearls are produced by the silver-lipped or gold-lipped variety of the Pinctada Maxima oyster. South Sea pearls have the largest range of colour, with the silver-lipped oysters producing pearls with overtones of silvery white or bluish white and gold-lipped oysters producing pearls with overtones of gold, cream or silver. They are also the largest variety of cultured pearls, ranging from 9-20mm in diameter, with an average size of 11-13mm. In addition to their size, they are also notable for their smooth, round form. Due to their remarkable size and shape, their beautiful satin finish, the rarity of the Pinctada Maxima oyster, and the sensitivity of these oysters during harvest, the South Sea pearls are the most expensive cultured pearls on the market.
While most pearls are cultured in oysters that live in salty sea water, freshwater pearls are cultivated in mussels that live in the freshwater lakes, ponds and streams of China. Freshwater pearls are typically not as round, lustrous or shiny as other cultured pearls, however, they are considerably more durable. Using a special harvesting process, a number of pearls can be produced by a single mussel. Depending on the mussel, what the mussel is fed, and the minerals in the local water, freshwater pearls can vary in colour from white, purple, lavender and pink, to peach, plum and tangerine. Ranging in size from 2-16mm in diameter, their average size is 7-8mm. Due to the irregularity in their colour, shape and size, freshwater pearls are the least expensive of all cultured pearls and quite popular for the very same reason. For excellent value, look for well-formed freshwater pearls .