Cultured Pearls, also called cultivé pearls, are cultivated by man in a pearl farm that is partly in the water where the shellfish are kept. Cultured Pearls started in China around 500 BC. There Buddha dolls of mother-of-pearl were found (in fact semi-pearls) together with the molds that were used. In the 19th century, the cultivation of pearls was rediscovered by the Japanese Kokichi Mikimoto. At the word pearl, most think of an iridescent ball that requires a lot of money to be deposited. Nothing seems less true. In contrast to a century ago, when the pearl industry was still in its infancy, pearls are no longer exclusive and for wealthy people. Chinese rice pearls are available for small prices. A classic pearl necklace can no longer be thought out of the jewelry box, but are the beads naturally formed, cultured or imitation pearls?
What are Pearls?
Pearls are balls made from the inner shell of a shellfish. A pearl is made when a foreign body becomes attached to the tissue of a shellfish. This could for example be a worm, a piece of seaweed or a stone. The shellfish tries to spit out this object, but if that does not work then she encapsulates the object so that further irritation is prevented. Encapsulation does the animal with the innermost layer of her shell. The most famous pearls are made by bivalves (living in salt or fresh water) that generally have a mother-of-pearl layer on the inside of their shells. Less known are pearls that have no shiny surface and are often made by snails. In nature pearls are a rare phenomenon and 1 in 15,000 wild shellfish is a pearl. The largest natural pearl that is up to the present (2017) found is 'the pearl of Lao Tzu'. This comes from the Philippines, weighs 6.4 kilos and is 24 centimeters in diameter. The Japanese Kokichi Mikimoto started experimenting in 1893 with the insertion of various materials, such as plastic, pieces of shell and wood where the shellfish started to form a layer. In the 1920s he had complete control of the technique and the production of Cultured Pearls started on a large scale.
Cultivé pearls aka Cultured Pearls
The wide range of Cultured Pearls is classified by shape and color. The shape and color that the pearl has, is provided to the shark species that has been used for the breeding process.
Saltwater Cultured Pearls
Saltwater Cultured Pearls are formed in saltwater shellfish and have a shiny mother-of-pearl layer. They are generally round in shape, often harvested when they are about 1.5 centimeters in diameter and appear in a wide range of colors.
Akoya Cultured Pearls
Akoya Cultured Pearls are made by the saltwater oyster Pinctada imbricata fucata (Gould, 1850). This nine centimeter-sized species lives buried in the soil and is collected at a depth of five meters in the area of the Tropic of Cancer to the Tropic of Capricorn. Since 1980 Japan is no longer the only producer of the Akoya pearl, but the pearls are also grown in China, Australia, Hawaii, Indonesia and Vietnam. The pearls are harvested when they have reached a size of eight millimeters in diameter. Akoya pearls are the most common pearl of pearl necklace. They are cream, silver, pink and sometimes yellowish in color.
Silver-lip and gold-lip Cultured Pearls
Silver-lip and gold-lip Cultured Pearls are formed by the same shellfish, namely the Pinctada maxima (Jameson, 1901). This is a saltwater oyster that lives in the area of the Tropic of Cancer to the Tropic of Capricorn at thirty to ninety meters depth. The species can grow up to 30 centimeters high and reach a weight of 6.3 kilograms. Most P. maxima have a mother-of-pearl layer that is white or silver-gray (silver-lip variation). Only a few have a golden mother-of-pearl layer. Silver-lip and gold-lip Cultured Pearls can be up to twenty centimeters in diameter, but generally the pearls are harvested when they have grown to nine to fourteen millimeters. Most pearl nurseries of this type of pearl are located in Japan and also in China, Indonesia, Australia, Cambodia, Korea, Myanmar, Thailand, Vietnam, the Philippines, the Seychelles and the Solomon Islands. The gold lip variation is mainly in the Philippines and can have a diameter of 25 centimeters. Gold-colored pearls are therefore slightly smaller than the silver colored ones and are at most thirteen millimeters. Because of their rarity they are very expensive.
Tahiti Cultured Pearls
Tahiti pearls originate from Pinctada margaritifera (Linnaeus, 1758), a salt water oyster that can grow to 25 centimeters. They live en masse in coral reefs up to 75 meters deep in the waters of Tahiti, where most pearl farms of the Tahiti pearl are located. Since the 1960s they have also been cultivated in Japan, French Polynesia, Papua New Guinea, Fiji, Australia, China, Kiribati, the Cook Islands, the Marshall Islands and the Solomon Islands. The pearls are sold in various sizes (many are up to a few centimeters) and are often black, gray or dark blue in color. Rarely, green, blue and red colors occur. The most precious pearls show a combination of blue, green and red colors. These are called peacock pearls.
Half Cultured Pearls
Half Cultured Pearls, also called blisters, are literally half pearls that are largely filled with wax or plastic. They usually have a round or a drop shape and serve as an inlay in jewelry, such as ear studs and brooches. The advantage is that they can be large and still remain lightweight. Since the 1960s, they have been bred by the Japanese in P. maxima and shortly thereafter Thailand and Indonesia also started growing half-pearls in a different species of horsemeat; the Pteria penguin (Röding, 1798). This species is about fifteen centimeters and has a mother-of-pearl layer with various colors; from gray to blue, from green to pink. Over the years the demand for half-pearls has declined, as a result of which producers are increasingly growing whole pearls in these two shellfish.
Freshwater Cultured Pearls
Less common are pearls from freshwater shellfish and these are also characterized by a mother-of-pearl layer. They have a whimsical shape, are offered in various colors and are smaller than saltwater pearls, making them faster to produce and a lot cheaper.
Rice Cultured Pearls
Rice Cultured Pearls are small freshwater pearls, whimsical in shape and about half a centimeter in diameter. They are grown mainly in Cristaria plicata (Leach, 1815), a species that is widespread in freshwater in East Asia. This freshwater mussel can be twelve centimeters high and a whopping 29 centimeters wide, so there is plenty of room for it inserting a core. On average, forty cores are placed in one C. plicata where the shellfish will form a white, pink, orange, purple or blue mother-of-pearl layer. They can be harvested faster than the larger saltwater pearls, making them much cheaper. Ninety percent of the rice pearls come from China.
Unintentionally Cultured Pearls
Baroque Cultured Pearls
Baroque pearls (keshis) occur accidentally when a piece of tissue becomes damaged during the implantation of a core. A layer of mother-of-pearl is deposited around the damaged piece of tissue, creating a small, oddly shaped pearl consisting purely of mother-of-pearl. The larger baroque pearls are processed into bracelets or necklaces that are offered on the market at a low price.
Cultivate Cultured Pearls
Cultivé pearls can only be cultivated when the means are present in a pearl farm. Pearl nurseries are mainly in Asian waters, where American species cannot survive because of the differences in water quality, oxygen content in the water, temperature, et cetera. Anno 2017 no one has studied the production of purple pearls. However, attempts have been made to grow orange and pink pearls from M. melo and S. gigas. After the foreign body was placed in the tissue of these two shellfish, it began to encapsulate the object in a different place than bivalves do. The location where the snail forms its pearl is inaccessible because of its abnormal anatomy as opposed to bivalves.