By Reviewed By Andreas Zabczyk

Mother-of-Pearl Gemstones

Mother-of-Pearl Inside a Shell
Mother-of-Pearl Inside a Shell

Shells have been used as currency and decoration for thousands of years. Some of the earliest jewelry was made from drilled shells that were strung to make necklaces. A beautiful product of some shells that can be used to make gemstones and jewelry is an organic material known as mother-of-pearl or nacre.

Mother-of-pearl has been used for decorative purposes since ancient times, especially as inlay. Mother-of-pearl was found in ancient Egyptian tombs and in the ancient Sumerian Tombs of Ur, dating back to around 2600-2400 BC. These Sumerian burial sites were found in Southern Iraq. One object found containing mother-of-pearl inlay was a decorated ostrich eggshell. The mother-of-pearl formed a mosaic with lapis lazuli stones.

Native American Indians had been using mother-of-pearl for hundreds of years before mother-of-pearl inlay became popular in the West during the Victorian era. Intricate mother-of-pearl inlay work was introduced to the USA and Britain during world industry exhibitions. This included carvings from Palestine and Chinese lacquer furniture with exquisitely detailed mother-of-pearl inlay, going back to the Shang Dynasty. Such beautiful objects led to an explosion of mother-of-pearl products in the West.

Magnified Image Showing the Structure of Mother-of-Pearl
Magnified Image Showing the Structure of Mother-of-Pearl

Although mother-of-pearl has a relatively low level of hardness, making it susceptible to scratches, it is made up of an irregular brick-and-mortar-like structure which gives it great strength. Mother-of-pearl is composed of nacre and conchiolin (a complex substance containing complex sugars and binding protein fibers). Nacre is mostly made up of brittle calcium carbonate crystals, known as aragonite. This brittleness is not favored in the gemstone and jewelry industry. Yet, it seems that the added natural substances along with the growth structure makes nacre an extremely tough substance.

The gemological properties of mother-of-pearl are very similar to those of pearl, since the two materials are composed of the same substance. Therefore, they share the same refractive index (1.53-1.69), density (2.6-2.87) and colors. Pearls are usually the same color as the mother-of-pearl of the mollusk shell and seasonal changes, level of salinity or variation in diet can also affect their color. Like pearls, mother-of-pearl can be white, gray, silver, yellow, blue-green, bronze, pink, red, brown, black or banded.

White, Pink and Golden Pearls
White, Pink and Golden Pearls

White, cream and pink nacre is prized for its purity of color and is used in cosmetics, such as face creams that impart a pearly luster and illuminate the facial skin. The luster of mother-of-pearl is the result of both surface and internal reflection of light. Typically, a thicker layer of nacre produces a more impressive luster, thus, the most valuable pearls have sharp, bright reflections.

Some marine gastropod mother-of-pearl is termed "porcellaneous" and "non-nacreous" because the nacre has a different structure than the usual bivalve mollusk mother-of-pearl. This includes melo and conch mother-of-pearl, which has a unique flamed appearance, as do the pearls produced by them. Arguably the most beautiful mother-of-pearl colors are produced by abalone. These have iridescent and vivid purple, blue and green colors that are highly prized. The iridescence of mother-of-pearl is known as "orient" and is thought to be caused by light interference (interaction of light that is similar in source or frequency) and dispersion (separation of light into its respective colors).

The gemstone and jewelry industry revolves around the use of beautiful natural materials, and mother-of-pearl is no exception. Mother-of-pearl can be used for various jewelry items, such as necklace pendants, inlaid rings, earrings and bracelets. This iridescent organic treasure is appropriate for inlay work, cameos and other carvings. It may also be used as gemstone slices, doublets or triplets.

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