Pearl is a smooth, lustrous, chiefly calcium carbonate organic gemstones. Natural pearls are nearly 100% nacre, a protective mother of pearl coating that is secreted to protect the organism for a foreign body that has entered the shell. Natural or real pearls come mainly from oysters, although there are other bi-valve molluscs which can produce them. Almost any species of bivalve or gastropod is capable of producing pearls. However, only a few species, such as the famous pearl oysters, can create pearls which are highly prized. Cultured pearls are produced by artificially introducing a foreign object into the fleshy part of oysters, which become coated with nacre in a similar manner to natural pearls. Imitation pearls, simulated pearls, have been produced for many years. Pearls are found in the regions of Japan, China, Tahiti, Australia, Indonesia, Philippines, USA and Burma.

 
Hardness : 3.5-4

 
To test if a pearl is natural, rub across your across the edge of your teeth; real pearl feels rough, simulated feel smooth. 
Pearls symbolize wisdom acquired through experience. They are believed to attract wealth and luck as well as offer protection. Known for their calming effect, pearls can balance one's karma, strengthen relationships, and keep children safe. The pearl is also said to symbolize the purity, generosity, integrity, and loyalty of its wearer.