A pearl is a hard object produced within the soft tissue (specifically the mantle) of a living shelled mollusc. a pearl is made up of calcium carbonate in minute crystalline form. The ideal pearl is perfectly round and smooth, but many other shapes of pearls occur. The colour of Pearls can be black, white, pink, pale blue, yellow, green or mauve.
The formation of pearls is very interesting. Oyster, a small sea creature, produces pearls. When a sand particle (grit) gets inside the shell of an oyster, it rubs against the animal’s tender body. To soothe the irritation, the oyster starts depositing layers of pearly nacre on the grit. Nacre, is a pearly layer that lines the inside of its shell. Nacre is made up of calcium carbonate and layering of the grit nacre results in formation of pearl.
Diagram comparing a cross-section of a cultured pearl, upper, with a natural pearl, lower A pearl being extracted from an akoya pearl oyster.
Man has now developed techniques for making cultured pearls. In this method, sand particle is injected into the shell of an oyster and is kept back in water. After a couple of years, the pearl is extracted from the shell.
Pearl of Lao Tze
The Pearl of Lao Tzu (also referred to as Pearl of Lao Tze and previously as Pearl of Allah) is the largest known pearl in the world. The pearl was found in the Palawan sea, which surrounds the island of Palawan in the Philippines, and was found by a Filipino diver. It is not considered a gemstone pearl, but is instead what is known as a "clam pearl" from a giant clam. It measures 24 centimeters in diameter and weighs 6.4 kilograms.