Pearl
Perhaps the best-loved gems of all time, pearls—both natural and modern cultured pearls—occur in a wide variety of colours. The most familiar colours are white and cream. Black, grey and silver are also fairly common, but the palette of pearl colours extends to every hue. The main colour, or body colour, is often modified by additional colours called overtones, which are typically pink, green, purple or blue. Natural pearls form in the bodies, or mantle tissue, of certain molluscs, usually around a microscopic irritant, and always without human help of any kind. The growth of cultured pearls requires human intervention and care. Today, most of the molluscs used in the culturing process are raised specifically for that purpose, although some wild molluscs are still collected and used.
