Pearls have been used as adornment for 6000 years and we know for example, that a substantial pearl trade existed in China as early as 2500 BC. Their natural beauty which precludes any need for processing, has made them an enduring symbol of love, virtue and purity.
A pearl, whether natural or cultured, is formed when a mollusc (usually an oyster) forms a protective layer around an intrusive object - perhaps a grain of sand - which has somehow lodged within it. This layer is made up of a substance called nacre, and is the same iridescent 'pearly' substance that lines the inside of the shell. In chemical terms, this material is calcium carbonate in the form of aragonite crystals.