Pearl shell in the context of Composite material


Pearl shell in the context of Composite material

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⭐ Core Definition: Pearl shell

Nacre (/ˈnkər/ NAY-kər, also /ˈnækrə/ NAK-rə), also known as mother-of-pearl, is an organic–inorganic composite material produced by some molluscs as an inner shell layer. It is also the material of which pearls are composed. It is strong, resilient, and iridescent.

Nacre is found in some of the most ancient lineages of bivalves, gastropods, and cephalopods. However, the inner layer in the great majority of mollusc shells is porcellaneous, not nacreous, and this usually results in a non-iridescent shine, or more rarely in non-nacreous iridescence such as flame structure as is found in conch pearls.

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Pearl shell in the context of Pearl fisheries

Pearl hunting, also known as pearl fishing or pearling, is the activity of recovering or attempting to recover pearls from wild molluscs, usually oysters or mussels, in the sea or freshwater. Pearl hunting was prevalent in India and Japan for thousands of years. On the northern and north-western coast of Western Australia pearl diving began in the 1850s, and started in the Torres Strait Islands in the 1860s, where the term also covers diving for nacre or mother of pearl found in what were known as pearl shells.

In most cases the pearl-bearing molluscs live at depths where they are not manually accessible from the surface, and diving or the use of some form of tool is needed to reach them. Historically the molluscs were retrieved by freediving, a technique where the diver descends to the bottom, collects what they can, and surfaces on a single breath. The diving mask improved the ability of the diver to see while underwater. When the surface-supplied diving helmet became available for underwater work, it was also applied to the task of pearl hunting, and the associated activity of collecting pearl shell as a raw material for the manufacture of buttons, inlays and other decorative work. The surface supplied diving helmet greatly extended the time the diver could stay at depth, and introduced the previously unfamiliar hazards of barotrauma of ascent and decompression sickness.

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Pearl shell in the context of Pearling in Western Australia

Pearling in Western Australia includes the harvesting and farming of both pearls and pearl shells (for mother of pearl) along the north-western coast of Western Australia.

The practice of collecting pearl shells existed well before British settlement. After settlement, Aboriginal people were used as slave labour in the emerging commercial industry, a practice known as blackbirding. After 1886, with the rise of 'hard hat' diving, Asian divers from coastal and island regions became most common, leading to the pearling industry being the sole exception to the White Australia Policy of 1901.

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