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A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle) of a living shelled mollusk or another animal, such as a conulariid.Just like the shell of a mollusk, a pearl is composed of calcium carbonate (mainly aragonite or a mixture of aragonite and calcite) [1] in minute crystalline form, which has been deposited in concentric layers.
More than a decade ago the freshwater pearl industry of China shifted production from the cockscomb pearl mussel to the triangle shell mussel (Hyriopsis cumingii). The triangle shell produced fewer pearls, accepting only 12–16 grafts per valve for a total production of 24 to 32 pearls, but produced pearls of better quality.
A black pearl and a shell of the black-lipped pearl oyster. The iridescent colors originate from nacre layers. All shelled mollusks can, by natural processes, produce some kind of "pearl" when an irritating microscopic object becomes trapped within its mantle folds, but the great majority of these "pearls" are not valued as gemstones.
An iridescent ammonite from Madagascar Map of North America highlighting the shallow inland sea present during the mid-Cretaceous period. Ammolite comes from the fossil shells of the Upper Cretaceous disk-shaped ammonites Placenticeras meeki and Placenticeras intercalare, and (to a lesser degree) the cylindrical baculite, Baculites compressus.
The iridescent nacre inside a nautilus shell Nacreous shell worked into a decorative object. Nacre (/ ˈ n eɪ k ər / NAY-kər, also / ˈ n æ k r ə / NAK-rə), [1] 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.
Main pearling areas in Western Australia Early diving recompression chamber at Broome, used to treat the Japanese divers for decompression sickness.. 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 death knight is the first "hero class" introduced in World of Warcraft, and would be the only one available until the introduction of the demon hunter in Legion.Hero classes are those that start the game at a higher level than the regular level 1.
Iridescence is also found in plants, animals and many other items. The range of colours of natural iridescent objects can be narrow, for example shifting between two or three colours as the viewing angle changes, [5] [6] An iridescent biofilm on the surface of a fish tank diffracts the reflected light, displaying the entire spectrum of colours ...