Pearl is a smooth, lustrous, variously colored deposit, chiefly calcium carbonate, formed around a grain of sand or other foreign matter in the shells of certain mollusks. Highly valued as the most famed gemstone, pearl is recognized for its beauty and elegance. Pearl is a pathological formation in pearl oyster, formed due to the entrance of a foreign particle into the gap between the body and the shell of the pearl oyster.
The irritation caused by the foreign particle makes the oyster take out a secretion to cover the particle. This when dried, again creates irritation to the animal, so it covers it with its secretion again- the continuous process continues for 3 to 6 years to produce a precious pearl.