You might have already heard about it numerous times, but do you have any idea what mother of pearl exactly is? Technically speaking, this is also another term for the crystalline substance called nacre which makes up the lining of many mollusk species. Incidentally, this same substance makes up a pearl's outer layers and is very well-known to be strong and resilient. Since the thickness of aragonite platelets is very much near the wavelength of visible light, the nacre becomes iridescent – an attribute that gives a particular surface the ability to change color anytime there is a change in the viewing angle.

Whenever a foreign object or an irritant gets inside a mollusk such as an oyster, an organic substance known as nacre is secreted which covers this foreign object in many layers until a pearl is formed. The nacre is actually made up of two substances, namely calcium carbonate and conchiolin. Conchiolin is a natural protein produced by a mollusc in the early stages of pearl development and also serves as an adhesive which will help succeeding layers of nacre to bind together. This dark-colored material is not only limited to a pearl’s initial coating – it may also be seen in other random layers of cultured pearls.

The crystalline calcium carbonate found in nacre is made up of millions of aragonite platelets, as well as silky proteins and very pliable substances like chitin and lustrin. Aragonite platelets are both hexagonal and polygonal in shape, and also microscopic in size (around .35 to .5 microns in thickness and 3-6 microns across); which means you will need the help of a powerful electron microscope if you want to see them. In the initial stages of pearl formation, the crystallized aragonite platelets is a very soft gem, but is made significantly tough and durable by the organic biopolymers and proteins a mollusk secretes.

In forming pearls, mollusks will continuously produce concentric layers of nacre – a process which has no specific pattern, which ultimately results in a unique design made up of swirls and ridges. This is what gives pearls its own fingerprint – a unique identification which separates one pearl from the rest. A pearl’s luster and orient is significantly determined by the distinct shape and size of the aragonite platelets. These platelets also serve as a minute prism, which breaks up the light that comes in contact with it and refracts a faint, rainbow like projection in the pearl’s surface.

The nacre plays an important role in pearl creation. It is a mollusk’s primary defense against the irritation it experiences upon invasion by a foreign object. In essence, the mother of pearl is what actually forms the outer layer of any pearl, which is the result of continuous layering of nacre over the irritant. Mother of pearl has long been considered an object of high value, and widely used not only in pearl jewelry, but can also serve as decoration in clothing, guns, knives and watches. Truly they are nature’s fascinating work of art.