Because of its shape and inscrutable luster pearl is true in many cultures as a symbol of eternity, beauty of spirit, wisdom and immortality. They are located on the inside of shells in response to a piece of sand which penetrates the shell. The mollusk then put a layer of calcium carbonate on the sand grain off, in the form of minerals. The layers by a horn-like substance cemented together. It is estimated that 1 in 15,000 wild oysters is a pearl. Therefore, nowadays almost all cultured pearls. For this, put a small grain of pearl in the oyster and the pearl can be harvested after two years.
