The process of the formation of pearls, whether natural or cultured, always hides a mysterious charm. The pearl is produced by a natural reaction of the oysters. A foreign body, such as a grain of sand, may enter the oyster shell as a result of human or environmental factors. The oyster, in self- defence, secretes a crystalline substance, covering with layers of pearl the new irritating element. The result is a natural creation of a pearl whose colour, shape and size depends on the area where the shell was found, or on the external agents that have influenced the process.
Akoya Pearls (Japanese pearls), are salt water pearls, cultured in the South Japan bays, and produced by the oyster called Pincatada Martensii. Their size varies from 2 mm to 10 mm of diameter and their color, basically white, may have some cream, rose or silver overtones.
Australian Pearls (South Sea Pearls), are cultured in the water between the Indian and the Pacific Ocean, mainly in Australia, but also in Philippine and Indonesia.
Produced by the Pincatada Maxima – the largest species of pearl oyster – the Australian Pearls can reach even 25 mm in diameter, mostly for the irregular shaped, knowns as “baroque pearls”. The standard diameter ranges from 9 to 20 mm and the color varies from the classic white/silver, to white with rose shades, or to the golden.
Tahiti Pearls (black pearls) are produced in French Polinesia in large black- lips oysters – Pinctada Margatirifera – which connotes their colors.
Actually, Tahiti pearls are rarely black but they have a lot of colors and overtones ranging from silver, dark grey, green blue, brown, up to the sought after “peacock”, for its multicolored iridescent shades, just like the peacock’s feathers.
The size is from 8 to 18 mm.
Fresh water Pearls are formed in freshwater mussels that live in the Chinese lakes, rivers, and ponds.
They are popular for their wide range of the shape, from baroque, to the drop, the oval and the rice, and only rarely they got perfectlyy round shape. Their range of natural colors includes white, pink, and peach colors.
The diamater varies from 2 mm to 15 mm.
The quality and the value of pearls depends on five key factors: shape, size, colour, surface and orient.
Shape: The most precious pearl is the round-shaped one, which evokes the idea of perfection. No less fascinating is Baroque pearl, very popular in pearl jewellery for its particular natural irregularities.
Size: The diameter is a fundamental aspect to grade the value of pearls, considering however that each type of oyster produces pearls of different size.
Colour: The colour of a pearl depends on the type of the oyster which produced it.
The best way to check the colour of the pearls, and its overtones, is to put it on a white surface, illuminated by lamps without UV rays.
Surface: The surface of the pearl should be as much smooth and polished as possible, without blemishes or defects.
Orient: It is a technical parameter that defines the iridescence of the pearl, that is the grade of the luster.