Minerals and Metals in Ancient India v2.c43.s3.t13.1

v2.c43.s3.t13.1

There are many kinds of pearl-like substances in nature, but we are concerned mainly with the pearl produced by the molluscs or oysters Meleagrina margaritifera (fresh water species). The pearl is the response of the mollusc to the stimulus afforded by a local irritation of the mantle. A small foreign body acts as the nucleus, and the concentric material deposited on it are alternate layers of calcium carbonate (as aragonite) and the protein conchiolin both produced and secreted internally by the organism; this is also the constitution of the inner coating of the shells known as the ‘mother of pearl’.