It has long been thought that a natural pearl forms when an irritant, such as a piece of sand or small parasite, becomes trapped inside the shell of a bivalve (twoshelled) mollusc, particularly an oyster or mussel, which has its inner shell lined with nacre (mother-of-pearl).
To try to expel the intruder, the mollusc first secretes conchiolin and then nacre to coat the irritant.
Other theories suggest that the pearl is begun by a disease within the mollusc. Layer upon layer of the nacre coating is deposited until a pearl is formed. The process takes several years.
Some of the best natural pearls in the world came from the oysters living in the warm, shallow waters of the Gulf.
The oldest known Gulf pearl was found in Kuwait by archaeologists, is 7000 years old, has a drill hole and was thus probably part of a necklace.
Other examples have been found at Al-Buhais in Sharjah and Al Door a hill-type settlement in Umm Al Qaiwain.
Ancient Mesopotamian texts describe how pearls came from the fabled lands of Dilmun (Eastern Arabia), while greek accounts refer to their beauty.
Pearls came to represent wealth and power from the shores of India to the Mediterranean and beyond.