Pearls have been extremely valued as gemstones since antiquity, and their charm and beauty have always been expanded by the challenge of obtaining them in early times. Unlike most other gemstones which are minerals, Pearls are organic and are produced by living organisms. They are generally produced within the soft tissue layer of molluscs such as shellfish and mussels. Pearls are made of calcium carbonate (in the form of Aragonite) and organic conchiolin that build up as concentric layers as they are covered by their host.