Pearls: A Natural Advanced Material

By Huajun Ruan and X.J Loh

Pearl powder is made from freshwater pearls or saltwater pearls below jewellery grade. These are sterilised in boiling water and then milled into a fine powder using stainless steel grinding discs or by milling with small porcelain balls in moist conditions. The powder is sold as such or mixed into creams. Pearl powder is widely believed to help improve the appearance of the skin, and is used as a cosmetic by royal families in Asia. It is also used as a treatment for acne. Some studies have claimed that pearl powder can stimulate the skin's fibroblasts, help regenerate collagen, and accelerate healing of certain skin conditions, wounds, and burns. This book seeks to introduce the benefits of pearl powders and to highlight the potential of this advanced material.

• Language: English
• Publisher: Partridge Publishing Singapore
• Release date: Jan 27, 2020
• ISBN: 9781543753165

Huajun Ruan

Huajun Ruan holds a PhD from Fudan University. He has successfully introduced e-commerce to his pearl farming and processing empire. Now his Fenix pearl powder is a best-seller on the Internet, and has become a dominant online retailer.

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Copyright © 2019 by Huajun Ruan, X. J. Loh.

ISBN:                Hardcover           978-1-5437-5317-2

                          Softcover             978-1-5437-5315-8

                          eBook                  978-1-5437-5316-5

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Contents

Chapter 1   Introduction to Pearls

Chapter 2   Biomineralization of calcium carbonate in pearls

Chapter 3   Osteogenic activity of pearl powder

Chapter 4   Fibroblast regeneration of pearl extracts

Chapter 5   Pearl powder

Chapter 1

Introduction to Pearls

T here are few places on earth as pristine as Australia’s Northwest. The traditional owners of the Kimberley region have cared for this breathtaking coastline from Broome to Darwin for over 50,000 years. The waters of the Timor Sea are teeming with life, including Australia’s South Sea pearl oyster also known as the silver lipped oyster. Although unremarkable in appearance, it produces a highly prized jewel of the sea.. Any mollusk that produces a shell can produce a pearl. That includes abalone, marine snails, clams, mussels and oysters. However, the South Sea pearl oyster produces the pièce de résistance . It is a solitary creature that can grow to around one foot, living for up to forty years. As a result, its pearls are the largest and the most lustrous in the world. An Australian South Sea pearl recently sold for over 1.5 million dollars. The notion that a pearl always forms when a grain of sand enters the creature is a myth. The initiator is usually a tiny organism, such as a parasite that invades the creature and disrupts the cells in the mantle. The oyster defends against this invasion by secreting a smooth, crystalline substance known as nacre to encase the interloper. Nacre or ‘mother of pearl’ is made from calcium carbonate and protein to yield a composite that is both lighter and stronger than concrete. It takes several years for thousands of layers of nacre to build up and create a smooth, iridescent gem. A pearl of value is found in less than 1 in 10,000 wild pearl oysters.

The calcium carbonate of nacre is in the form of the minerals aragonite and calcite. The nacre matrix consists of the proteins conchin and perlucin which form a substance known as conchiolin that glues this layered structure together. Aragonite is crystalline, but conchiolin is porous. These different materials, combined with the slightly translucent nature of the layers, contribute to the pearl’s shimmery/luminous luster. Over time, the oyster will apply several layers of nacre to the foreign body, effectively walling it off from the oyster itself and forming a pearl. The shape of the invading body is a contributing factor to the ultimate shape of the pearl. The internal process of pearl creation is mostly the same whether or not the pearl was created naturally or by cultivation. X-ray analysis can distinguish whether a pearl was cultivated or grown naturally. Natural pearls tend to have microscopic cores and so exhibit concentric growth rings at the center, while cultivated pearls possess a solid core. The rarity of natural pearls makes them more expensive, particularly if they are spherical and so more suited to incorporation into jewelry. Oysters suitable for pearl cultivation are prepared by suspending cages of juvenile oysters in salt or fresh water for two to three years. Saltwater cultivate pearls, are usually initiated with a mother of pearl nucleus prepared from spheres of ground, polished mussel shell measuring between 2.5 mm and 8 mm in diameter. The choice of nucleus is important, not only for maximizing the probability of obtaining a spherical pearl, but also because the core material needs to have similar thermal expansion properties to the nacre. If it doesn’t, the core may expand faster than the outer layers of the nacre coating when heat is applied during the jewelry making process and the pearl may shatter. Beaded nuclei are not usually used for cultivating fresh-water pearls.

When the juvenile oysters are sufficiently mature, they are removed from the water and placed in a dry, shady location for about a half an hour. This generally encourages the oyster to open its shell. Any oyster that doesn’t open I iIs placed back into the water and the pearl farmer will try again later. Pearl farmers will place a wedge in the opened shells to keep them open. The wedged shells may be carefully forced wider to insert the bead. This step must be done carefully because opening an oyster’s shell too far can kill it. The nucleus is inserted in a precise incision in the oyster’s soft body (usually in the gonad), together with a tiny square of living mantle tissue harvested from another oyster. One oyster can provide enough mantle for 15 or so implantations, with the tissue generally staying alive and secreting nacre for a couple of hours. The nuclei and prepared mantle tissue must be in contact with one another to ensure a pearl sack will form. Only a tiny piece of living mantle is inserted in non-beaded shells (usually freshwater).

As many as a couple of dozen non-beaded pearls can be grown at once in a single oyster if multiple implantations are made. Consequently, freshwater pearls are generally cheaper than saltwater pearls, assuming the quality of the end product is similar. Classically, saltwater, beaded pearls tended to produce a higher percentage of spherical pearls, with cultivated freshwater pearls being more rice shaped, but modern cultivating techniques have largely removed this difference. Once implantation is complete, the wedge is removed, and the oyster is placed back into water.

Unsurprisingly, the whole process delivers quite a shock to the oyster. They can take as long as six weeks to recover, or die as