Nacre

From ArticleWorld


The natural secretions made of both organic and inorganic composites in the internal layers of the mollusk animals is named as nacre or 'mother-of-pearl'. Nacre has natural iridescent properties, changing the appearances that make it unique among the other sea treasures. This nacre is formed by layer after layer of secretions to give birth to pearls.


Contents

Characteristics

Nacre is hard for touch, yet shows beautiful iridescent colour shades from different angles due to the light refractions. Nacre consists about 95% Calcium Carbonate as crystal platelets and trace amounts of fragile ceramics in the form of conchiolin and aragonite and. These tiny fragments are separated by elastic biopolymers and in presence of brittle platelets, nacre becomes strong. However, its strong adhesion property is due to the special arrangement of platelet 'brickwork'. It greatly increases nacre's toughness, making it similar to silicium.

The most interesting feature of nacre is its attractive colour shades or iridescence properties, which is due to the presence of thick aragonite platelets. The thicknesses of these multi-layered platelets look like wavelengths of visible light. This results in continued interference of wavelengths, both constructive or destructive, causes changes in color with movement of the pearl or slight shade.


Origin

Nacre begins as a liquid secretion, becomes as a hard, protective layer with time.

Nacre is a type of secretion from the epithelial cells in the mantle tissue of some species of mollusks, such as oysters. This secretion continuously gets deposited in the innermost layers of the mollusk’s shell. This is to protect it from external invasions, microbial infections, parasites, organisms and decaying waste products. Mother-of-pearl protects the mollusk from external injuries.

Mollusks are marine shells and are sluggish, dwelling near to stony areas and quite bigger to handle with single hand. When some other small unwanted creature, like a parasite or some foreign object enters the body, the mollusk starts secreting nacre in layers, over the irritant. This continued process, known as “encystations” around an irritant result in a small but beautiful mass or pearl. Most of the time, each mollusk forms only one pearl in life.


Sources

A wide range of pearl forming mollusks or Oysters, are seen spread across the globe. Mostly marine, some are found in fresh waters too. Tropical seas in Asia, freshwater rivers in Asia, US and Europe, are main areas where oysters are grown in abundance. There are a variety of species available. Abalones in Japan … are famous pearl forming mollusks. Various aquaculture methods are successfully used to cultivate a variety of pearl oysters to meet the growing needs of the world.


Decorative uses

The oyster pearl variety ‘tesserae’, some times nick-named as ‘mother-of-pearl’ is a hand-cut, attractively edged, is used laminated to ceramic or marbles in house constructions. Since these mother of pearls can be made as fibreglass mesh in place of heavy marbles or tiles, or can be worked out as sheets, for the use as interior decorators, doors and ceilings, exterior and interior attractions.

Its elegant look with iridescent layers are very attractive, they are used in wood furniture, musical instruments like saxophones, guitars, trumpets. They are seen embedded in attractive designs, arrangements, ladies wear etc. Combinations of white and black nacre are used for many architectural decorations, porcelain sinks.


Cultural reference

Nacre is believed to have mysterious properties. It is believed to cool the bodily heat, impart serenity and peace of mind. Some people call it as ‘stone of sincerity’ induces innocence, concentration of mind, faithfulness etc. The wearer of pearl can enjoy the eternal inner calm.