Cultured pearl

Cultured pearls are special kinds of pearls that people help to make. They grow inside living molluscs, which are animals that live in water. People put something small inside the mollusc to start the process, and this helps the mollusc make a pearl.

These pearls are the same as natural pearls because they are made from the same material. Cultured pearls can grow in both seawater and freshwater. Today, most of the pearls people buy and use come from this careful process of cultivation. This makes them easier to find and more available for everyone.

Development of a pearl

A pearl forms when the mantle tissue of a mollusk is injured. In response, the mantle tissue makes a substance called nacre, which is made of calcium carbonate and a protein called conchiolin. This nacre builds up in layers and forms a pearl.

Natural pearls happen by chance in nature, but cultured pearls are made by people. They place a piece of tissue from another mollusk inside, which causes a pearl sac to form. This sac then makes calcium carbonate, creating a pearl.

The most common way to make cultured pearls uses shells from freshwater river mussels. These shells are cut into small, round pieces and polished before being used.

Pearl nuclei: the core of modern cultured pearls

A pearl nucleus, or bead, for a cultured pearl is a round or shaped piece made from a shell. It is placed inside a special sac where the mollusk adds layers to form the center of a cultured pearl. Modern pearl growers usually use shells from freshwater bivalves found in the Mississippi River or freshwater bodies in Hunan and Jiangxi provinces in China.

Cultured pearls today are in two main groups. The first group includes beaded cultured pearls like Akoya, South Sea, Tahitian, and large modern freshwater pearls, often called Edison pearls. These pearls grow in the gonad of the mollusk, and usually only one pearl is made at a time. Harvesting happens after about one year for Akoya pearls, 2–4 years for Tahitian and South Sea pearls, and 2–7 years for Edison pearls. This method was first developed by a British biologist who shared the knowledge with two people from Japan.

The second group includes non-beaded freshwater cultured pearls, such as Biwa or Chinese pearls. These grow in the mantle of the mollusk, where up to 25 pieces can be placed at once, making them very common. The quality of these pearls has improved a lot, from small, grain-shaped pieces to nearly round pearls. Recently, large, nearly perfect round pearls up to 15 mm in diameter with a shiny metallic look have been made.

The nucleus bead in beaded cultured pearls is usually a polished sphere made from a freshwater mussel shell. Along with a small piece of tissue from another mollusk, it is placed into the reproductive organ of a saltwater mollusk. In freshwater pearl farming, only the tissue piece is used and placed into the mantle of the host bivalve. Some pearl oysters are given a new, larger bead in the same process and returned to the water to grow for another few years. An experimental method uses a radio-frequency identification nucleus to track where the pearls come from.

History

Song Dynasty (960 to 1279 AD)

Long ago in ancient China, during the Song Dynasty, people began making pearls in a special way. They used a mold to create a tiny buddhist figure from lead and placed it inside a freshwater mussel shell, Hyriopsis cumingii.

Reaching Europe

In 1637, a Chinese book called Tiangong Kaiwu by Song Yingxing described pearls and how they form. This book traveled to Europe along the Silk Road and made scientists curious about pearls.

Formation Theories and Cultivation Research

From the 1500s to the 1700s, scientists in Europe used new tools like microscopes to study pearls. They created many ideas about how pearls form.

The Rise of the Modern Cultured Pearl Industry

In 1916, Mikimoto Kōkichi used new technology to grow pearls in akoya pearl oysters in Japan. Soon after, in 1917, Mitsubishi began growing pearls in the Philippines, Buton, and Palau. Today, most akoya pearls come from a special type of oyster called Pinctada fucata.

Modern industry

Today, growing pearls has made the pearl industry more stable and predictable. Almost all pearls sold worldwide are cultured pearls. Scientists can tell cultured pearls from natural ones by using X-rays. Colored pearls can be made by adding special minerals like cobalt chloride to the shell.