Title: Nacre
Content: Nacre Nacre ( also ), also known as mother of pearl, is an organic-inorganic composite material produced by some molluscs as an inner shell layer; it also makes up the outer coating of pearls. 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. The outer layer of pearls and

Title: Pearl
Content: Pearl 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) in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes, known as baroque pearls, can occur. The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries. Because of

Title: Pearl
Content: from the French "perle", originally from the Latin "perna" meaning leg, after the ham- or mutton leg-shaped bivalve. 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. Nacreous pearls, the best-known and most commercially significant, are primarily produced by two groups of molluskan bivalves or clams. A nacreous pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the

Title: Pearl
Content: tissue. The mollusk creates a "pearl sac" to seal off the irritation. Pearls are thus the result of an immune response analogous in the human body to the capture of an antigen by a phagocyte (phagocytosis). The mollusk's mantle (protective membrane) deposits layers of calcium carbonate (CaCO) in the form of the mineral aragonite or a mixture of aragonite and calcite (polymorphs with the same chemical formula, but different crystal structures) held together by an organic horn-like compound called conchiolin. The combination of aragonite and conchiolin is called nacre, which makes up mother-of-pearl. The commonly held belief that a grain

Title: Lustre (mineralogy)
Content: splendent) minerals have the lustre of polished metal, and with ideal surfaces will work as a reflective surface. Examples include galena, pyrite and magnetite. Pearly minerals consist of thin transparent co-planar sheets. Light reflecting from these layers give them a lustre reminiscent of pearls. Such minerals possess perfect cleavage, with examples including muscovite and stilbite. Resinous minerals have the appearance of resin, chewing gum or (smooth-surfaced) plastic. A principal example is amber, which is a form of fossilized resin. Silky minerals have a parallel arrangement of extremely fine fibres, giving them a lustre reminiscent of silk. Examples include asbestos, ulexite

Question: What is the name of the lustrous substance that forms pearl and mother-of-pearl?
Answer: Nacre