A pearl CAHIN is a classic jewellery item that has been popular for centuries. It is an eye-catching piece of jewellery, often featuring natural or cultured pearls strung together on a line. Pearl necklaces are available in many styles, ranging from subtle and elegant to bold and dramatic. A smooth, rounded bead formed within the shells of certain mollusks and composed of the mineral aragonite or calcite in a matrix, deposited in concentric layers as a protective coating around an irritating foreign object: valued as a gem when lustrous and finely colored. Compare cultured pearl.