Organic Gems: Mother-of-Pearl
Mother-of-Pearl Jewelry
Source: Australia (Broome), Worldwide
Mother-of-Pearl is similar to pearls in chemical composition, but unlike a pearl, which is the result of nacre secretions emitted to protect the mollusk from a foreign irritant entering the shell, mother-of-pearl comes from the actual shell of the animal. This natural secretion of calcium carbonate and aragonite causes the two main visual aspects that define mother-of-pearl: pearly luster and iridescence.
Although far more abundant, and therefor, far less valuable than pearls, mother-of-pearl has been a major component in jewelry and decorative arts for thousands of years. From ancient Egypt and Persia, to ancient China, mother-of-pearl has been a prized semi-precious gemstone throughout human history. From the early 1900s, the coastal region of Broome, in Western Australia has been one of the largest producers of mother-of-pearl, accounting for up to 80% of world supply.
As part of the shell building process, the mollusk will deposit layers of calcium carbonate held together by an organic horn-like compound called conchiolin. This combination of calcium carbonate and conchiolin is called nacre or mother-of-pearl.
Mother of Pearl & Red Coral Brooch by Michael Zobel |
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Wethered Mother-of-Pearl Necklace |
Mother of pearl (nacre) is a naturally-occurring organic-inorganic composite of calcium carbonate, aragonite, and other organic materials. The nacre is secreted by epithelial cells in the mantle tissue of certain mollusk species such as Abalone. In these mollusks, nacre is continually deposited onto the inner surface of the animal's shell. This process creates the iridescent nacreous layer, commonly known as mother-of-pearl.
The iridescent quality of nacre or mother-of-pearl is due to the fact that the thickness of the aragonite platelets are about 0.5 micrometres, which is comparable to the wavelength of visible light. This results in absorptive and reflective effects on different wavelengths of light (pseudochromatic coloration), resulting in different colors of light being reflected when observed at different viewing angles.
Simulated Mother of Pearl
There are simulated mother-of-pearl substitutes which are created with a layered substrate of transparent or translucent plastic which has been pigmented with metal-oxide-coated mica pigment. On one layer of this substrate is a thin, transparent, thermoplastic resinous laminate film of around ten parallel layers, each with a differing in refractive index.
Mother of Pearl Properties
Bibliography and Reference on Mother of Pearl
1. Paul R. Shaffer, Rocks, Gems and Minerals  . Martin's Press
2. Mearl Corp., Simulated Mother of Pearl . www.freepatentsonline.com
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