Physical properties Structure of nacre layers, wherein aragonite plates are separated by biopolymers, such as chitin, lustrin and silk-like proteins Electron microscopy image of a fractured surface of nacre Freshwater pearls grow within certain (but by no means all) species of freshwater mussels in the order Unionida, the families Unionidae and Margaritiferidae.

Saltwater pearls can grow in several species of marine pearl oysters in the family Pteriidae. One family of nacreous pearl bivalves – the pearl oyster – lives in the sea, while the other – a very different group of bivalves – lives in freshwater these are the river mussels such as the freshwater pearl mussel. Cultured pearls are formed in pearl farms, using human intervention as well as natural processes. Many hundreds of pearl oysters or mussels must be gathered and opened, and thus killed, to find even one wild pearl for many centuries, this was the only way pearls were obtained, and why pearls fetched such extraordinary prices in the past. Natural (or wild) pearls, formed without human intervention, are very rare. 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 shell. Nacreous pearls, the best-known and most commercially significant, are primarily produced by two groups of molluskan bivalves or clams. The iridescent colors originate from nacre layers.Īll 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. Definition A black pearl and a shell of the black-lipped pearl oyster. The scientific name for the family of pearl-bearing oysters, Margaritiferidae comes from the Old Persian word for pearl * margārīta- which is the source of the English name Margaret. The English word pearl comes from the French perle, originally from the Latin perna ' leg ', after the ham- or mutton leg-shaped bivalve. Federal Trade Commission rules, and are formed in the same way, most of them have no value except as curiosities. Although these may also be legitimately referred to as 'pearls' by gemological labs and also under U.S. However, almost all species of shelled mollusks are capable of producing pearls (technically 'calcareous concretions') of lesser shine or less spherical shape. Whether wild or cultured, gem-quality pearls are almost always nacreous and iridescent, like the interior of the shell that produces them. They have also been crushed and used in cosmetics, medicines and paint formulations. Pearls have been harvested and cultivated primarily for use in jewelry, but in the past were also used to adorn clothing.

Imitation pearls are also widely sold in inexpensive jewelry. Cultured or farmed pearls from pearl oysters and freshwater mussels make up the majority of those currently sold. These wild pearls are referred to as natural pearls. The most valuable pearls occur spontaneously in the wild, but are extremely rare. Because of this, pearl has become a metaphor for something rare, fine, admirable and valuable. The finest quality of natural pearls have been highly valued as gemstones and objects of beauty for many centuries. The ideal pearl is perfectly round and smooth, but many other shapes, known as baroque pearls, can occur. 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 deposited in concentric layers. Black pearls: commonly pink to orange-red Ī pearl is a hard, glistening object produced within the soft tissue (specifically the mantle) of a living shelled mollusk or another animal, such as fossil conulariids.Yellow and golden pearls: yellow-green, greenish brown to dark brown.White pearls: light blue to light yellow.White, pink, silver, cream, brown, green, blue, black, yellow, orange, red, gold, purple, iridescent

Large preformed pond shells