Mother of Pearl

Article | Updated 7 years ago

Many cultures of the world share a sense of mystery and fascination with pearlshell and pearls as objects of desire, wealth, magic and power. In Asia, Europe, Africa, the Americas and Oceania, mother of pearl has featured as a prestige material for thousands of years. In many cultures it continues to do so today.

The shining scales of the serpent-like being Aalingoong are connected with mother of pearl and power. The association between dragons and mother of pearl is not unique to the West Kimberley, but can also be found in a number of Asian mythologies.

The iridescence of mother of pearl is beguiling, but more significant is the widely held belief in a link between lustre and rainbows, rain, and water, the essence of life.

Nacre: An Event of Light

When you look at nacre (mother of pearl or MOP) from the side, the iridescence is not visible. Its surface appears dull. But when you look at it from the top, it becomes a shimmering reflective surface that seems to radiate rainbow-like light. This is because the iridescence is not a static feature of the nacre but rather the result of a dynamic interaction that occurs when light falls on the shell.

Examining a piece of fractured nacreous shell under a scanning electron microscope reveals that nacre is made up of layers of platelets formed from aragonite. Aragonite is a type of calcium carbonate, the substance found in familiar products such as chalk and sodium bicarbonate. A protein can be observed between the layers of aragonite, and this helps to make the resulting substance strong, yet flexible and porous.

Nacre appears iridescent because the thickness of the aragonite is close to the wavelength of visible light; thus the surface appears to change colour as the angle of view changes. When light hits the interior surface of the shell, it refracts as it penetrates the surface, and what we see is the reflected iridescent light.

Recently, scientists have modelled artificial bone and hardened glass on the structure of nacre because it combines the qualities of strength, porosity and flexibility.