I like to search the internet for interesting things and share them with my friends. Here is an article I found about the Mother of Pearl(nacre)

Pearl is one of my favorite gemstone.I hope you enjoy reading it.

A pearl is a hard, rounded object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of mollusks, a pearl is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes of pearls occur, see baroque pearl.

The finest quality pearls have been highly valued as gemstones and objects of beauty for many centuries, and the word pearl has become a metaphor for something rare, fine, and admirable.

Nacre is crystalline aragonite or calcium carbonate. Shellfish and mollusks excrete it when they are exposed to a parasite or a foreign body introduced into a shell. Nacre is noted for its shine and iridescence, and its coating on shells is called mother of pearl.

A true pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the shell. A "natural pearl" is one that formed without any human intervention at all, in the wild, and these are very rare. A "cultured pearl" on the other hand, is one that has been formed on a pearl farm. The great majority of pearls on the market are cultured pearls.

Pearl is considered to be the birthstone for June.

Sources: www.pearloasis.com