Nacre also known as mother of pearl, is an organic-inorganic composite material produced by some molluscs as an inner shell layer; it is also what makes up the outer coating of pearls. It is very strong, resilient, and iridescent.
 
Nacre is found in some of the more 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.
 
The outer layer of pearls and the inside layer of pearl oyster and freshwater pearl mussel shells are made of nacre. Many other families of Mollusc also have a nacreous inner shell layer, including marine gastropods such as the Haliotidae, the Trochidae and the Turbinidae.

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Abalone, and from the (Rumsen) aulon, is a common name for any of a group of small to very large edible sea snails, marine gastropod molluscs in the family Haliotidae. Other common names are ear-shells, sea ears, as well as muttonfish or muttonshells in Australia, ormer in Great Britain, perlemoen and venus's-ears in South Africa and paua in New Zealand.

The family Haliotidae contains only one genus, Haliotis. That genus contains about four to seven subgenera. The number of species recognized worldwide ranges between 30 and 130 with over 200 species-level taxa described. The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies.

The shells of abalones have a low and open spiral structure, and are characterized by several open respiratory pores in a row near the shell's outer edge. The thick inner layer of the shell is composed of nacre or mother-of-pearl, which in many species is highly iridescent, giving rise to a range of strong and changeable colors, which make the shells attractive to humans as decorative objects, and as a source of colorful mother-of-pearl.

The flesh of abalones is widely considered to be a desirable food, and is consumed raw or cooked in a variety of different dishes.
Decorative items

The highly iridescent inner nacre layer of the shell of abalone has traditionally been used as a decorative item, in jewelry, buttons, and as inlay in furniture and in musical instruments such as guitars, etc.

Abalone pearl jewelry is very popular in New Zealand and Australia, in no minor part due to the marketing and farming efforts of pearl companies. Unlike the Oriental Natural, the Akoya pearl, and the South Sea and Tahitian cultured pearls, abalone pearls are not primarily judged by their roundness. Also, unlike other types of pearls, abalone pearls are not subjected to any type of processing, such as bleaching or buffing. The inner shell of the abalone is an iridescent swirl of intense colours, ranging from deep cobalt blue and peacock green to purples, creams and pinks. Therefore each pearl, natural or cultured, will have its own unique collage of colours.