That a jewel can begin as an irritant is part of the pearl’s fascination. A grain of sand or a bit of organic matter enters the shell of an oyster and can’t be extruded. Concentric rings of calcium carbonate coating known as nacre build up layer by layer around the foreign body until it is eventually covered. and this creates a pearl. The pearl’s shape may be round, oblong or irregular, and its color range from pale to dark, but most common is a soft, iridescent pastel. The delicate, pristine nature of the pearl has made it an emblem of virginity, purity and youthful love, a gift betrothal and a bridal necklace. In earlier times, it was ground into fine powder for elixirs of healing.