Iridescent shiny materials are a secretion by a oyster or mollusk on the inside of the shell, this is usually known as nacre or Mother of Pearl. This lining protects the shellfish from abrasions and irritants that can get inside the shell. When a foreign object such as a piece of sand enters the shell, the lining protects the oyster and the nacre begins to build up on the foreign object – as such pearls are formed.

The shiny nacre that develops on the inside of the shell and essentially “gives birth” to a pearl by transferring that nacre to the foreign object is the mother of pearl. The pearl is the shaped nacre formed on the foreign object.

Mother of Pearl is shaped like the shell – and so it can cover larger areas such as watch faces, whereas a pearl is usually shaped round and made into beads etc.

Natural Mother of pearl and natural pearls are always more valuable than manmade.

However Mother of pearl exists in almost all mollusks, but the chances of a particle entering the shellfish and forming a pearl is much more rare and so pearls are more valuable.

For manmade items, pearls are also more valuable because they take much longer to form than the mother of pearl.