Pearls are one of the few organic precious gemstones, and they begin life as a particle of grit or other debris that becomes embedded inside the shell of a marine or freshwater mollusc such as a clam or oyster. This triggers a defensive mechanism in the mollusc to protects its soft, vulnerable interior and the particle is covered by layers of the substance used normally to coat the inside of the shell which is called nacre (mother of pearl). This process continues until the particle is totally smooth and covered, and results in a beautifully formed circular object called a pearl.
Natural pearls are rare, and so are quite expensive and sold by carat weight. Many of the natural pearls you see on today’s market are in fact vintage pearls, as modern jewelry is usually crafted from the more readily available cultured pearls. Cultured pearls are made by manually introducing a particle of grit to a suitable mollusc, and the shape and size of the pearl can be manipulated by what type of mollusc is used, what water it lives in and also how long the pearl is left before it is harvested. The longer a pearl is left, the harder and thicker the layers of nacre become, and so the larger the pearl generally the higher the quality and expense, and cultured pearls are sold by millimetres rather than karats.
Pearl Shapes
The traditional pearl used in jewelry is spherical in shape, and the rounder and more perfect the sphere the more expensive and desirable the pearl is. You can also get teardrop shaped pearls and baroque pearls, which are those that have an irregular shape, and although these are less expensive they are often very unique and can be very beautiful in their own right.