Because of this, pearl has become a metaphor for something rare, fine, admirable and valuable.These wild pearls are referred to as natural pearls.Cultured or farmed pearls from pearl oysters and freshwater mussels make up the majority of those currently sold.A black pearl and a shell of the black-lipped pearl oyster.The iridescent colors originate from nacre layers.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.Freshwater and saltwater pearls [ edit ].Most freshwater cultured pearls sold today come from China.Saltwater pearls grow within pearl oysters, family Pteriidae, which live in oceans.(B) Cross-section showing CaCO3 growth begins onto an organic center.(I) Formation of nacre begins directly on massive aragonite.The combination of aragonite and conchiolin is called nacre, which makes up mother-of-pearl.Typical stimuli include organic material, parasites, or even damage that displaces mantle tissue to another part of the mollusk's body.Natural pearls [ edit ].The mollusk, irritated by the intruder, forms a pearl sac of external mantle tissue cells and secretes the calcium carbonate and conchiolin to cover the irritant.Natural pearls come in many shapes, with perfectly round ones being comparatively rare.The juvenile mantle tissue cells, according to their stage of growth, secrete columnar calcium carbonate from pearl sac's inner surface.Cultured pearls [ edit ].A tiny piece of mantle tissue (called a graft) from a donor shell is transplanted into a recipient shell, causing a pearl sac to form into which the tissue precipitates calcium carbonate.There are a number of methods for producing cultured pearls: using freshwater or seawater shells, transplanting the graft into the mantle or into the gonad, and adding a spherical bead as a nucleus.Most saltwater cultured pearls are grown with beads.Most beadless cultured pearls are mantle-grown in freshwater shells in China, and are known as freshwater cultured pearls.With X-rays it is possible to see the growth rings of the pearl, where the layers of calcium carbonate are separated by thin layers of conchiolin.Value of a natural pearl [ edit ].Fine quality natural pearls are very rare jewels.Origin of a natural pearl [ edit ].Australian pearl divers dive for south sea pearl oysters to be used in the cultured south sea pearl industry.The catch of pearl oysters is similar to the numbers of oysters taken during the natural pearl days.Hence significant numbers of natural pearls are still found in the Australian Indian Ocean waters from wild oysters.Types of cultured pearls [ edit ].Before the days of cultured pearls, black pearls were rare and highly valued for the simple reason that white pearl oysters rarely produced naturally black pearls, and black pearl oysters rarely produced any natural pearls at all.The black cultured pearl is rare when compared to Chinese freshwater cultured pearls, and Japanese and Chinese akoya cultured pearls, and is more valuable than these pearls.However, it is more abundant than the South Sea pearl, which is more valuable than the black cultured pearl.This is simply because the black pearl oyster Pinctada margaritifera is far more abundant than the elusive, rare, and larger south sea pearl oyster Pinctada maxima, which cannot be found in lagoons, but which must be dived for in a rare number of deep ocean habitats or grown in hatcheries.Black cultured pearls from the black pearl oyster – Pinctada margaritifera – are not South Sea pearls, although they are often mistakenly described as black South Sea pearls.South Sea pearls are the color of their host Pinctada maxima oyster – and can be white, silver, pink, gold, cream, and any combination of these basic colors, including overtones of the various colors of the rainbow displayed in the pearl nacre of the oyster shell itself.South Sea pearls are the largest and rarest of the cultured pearls – making them the most valuable. Prized for their exquisitely beautiful 'orient' or lustre, South Sea pearls are now farmed in various parts of the world where the Pinctada maxima oysters can be found, with the finest South Sea pearls being produced by Paspaley along the remote coastline of North-Western Australia.From other species [ edit ].The great majority of mollusk species produce pearls which are not attractive, and are sometimes not even very durable.Before the beginning of the 20th century, pearl hunting was the most common way of harvesting pearls.Not all mussels and oysters produce pearls. They are, for the most part, freshwater pearls from mussels.The first category covers the beaded cultured pearls, including akoya, South Sea and Tahiti.The pearls are usually harvested after one year for akoya, 2–4 years for Tahitian and South Sea, and 2–7 years for freshwater.Along with a small piece of mantle tissue from another mollusk (donor shell) to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad (reproductive organ) of a saltwater mollusk.Mitsubishi was the first to produce a cultured south sea pearl – although it was not until 1928 that the first small commercial crop of pearls was successfully produced.The original Japanese cultured pearls, known as akoya pearls, are produced by a species of small pearl oyster, Pinctada fucata martensii, which is no bigger than 6 to 8 cm (2.4 to 3.1 in) in size, hence akoya pearls larger than 10 mm in diameter are extremely rare and highly priced.Today, a hybrid mollusk is used in both Japan and China in the production of akoya pearls.Timeline of pearl production [ edit ].Mitsubishi commenced pearl culture with the South Sea pearl oyster in 1916, as soon as the technology patent was commercialized. Japan maintains its status as a pearl processing center, however, and imports the majority of Chinese akoya pearl production.South Sea pearls are characterized by their large size and warm luster.Freshwater pearl farming [ edit ].Japanese pearl producers also invested in producing cultured pearls with freshwater mussels in the region of Shanghai, China.Momme weight [ edit ].For many cultured pearl dealers and wholesalers, the preferred weight measure used for loose pearls and pearl strands is the momme.Momme is a weight measure used by the Japanese for centuries.In the United States, during the 19th and 20th centuries, through trade with Japan in silk cloth the momme became a unit indicating the quality of silk cloth.Though millimeter size range is typically the first factor in determining a cultured pearl necklace's value, the momme weight of pearl necklace will allow the buyer to quickly determine if the necklace is properly proportioned.This is especially true when comparing the larger south sea and Tahitian pearl necklaces.Shapes [ edit ].Semi-rounds are also used in necklaces or in pieces where the shape of the pearl can be disguised to look like it is a perfectly round pearl.Pear shaped pearls are sometimes look like as teardrop pearls and are most often seen in earrings, pendants, or as a center pearl in a necklace.They are also commonly seen in necklaces.In general, cultured pearls are less valuable than natural pearls, whereas imitation pearls have almost no value.Lengths of pearl necklaces [ edit ].A uniform strand of akoya pearls, for example, will measure within 0.5 mm.Colors [ edit ].Earrings and necklaces can also be classified on the grade of the color of the pearl: saltwater and freshwater pearls come in many different colors.Religious references [ edit ].Hindu scriptures [ edit ].Additional references [ edit ].References [ edit ].
Edward R. Forte