Pearl, a concretion, consisting chiefly of carbonate of lime, found in several bivalve mol-lusks, but especially in the avicula rnargari-tifera (meleagrina margaritifera, Lamarck), or true pearl oyster, and among fresh-water bivalves in the unio rnargaritiferus. Pearls are usually spheriform and yellowish or bluish white. The purest white pearls are most valued in Europe and America, while those of a yellowish hue are preferred by the Hindoos and Arabs. The pearl is rather harder than calcareous spar, but it has the same chemical composition, with the exception that it has in addition, between the many layers of mineral deposit of which it is made, films of animal membrane, which becoming dry give it its hardness. The substance of the pearl is normally deposited upon the interior surface of the shell in the form of a slimy secretion of the exterior of the mantle. Grains of sand or other foreign bodies, lodging between the mantle and the shell, produce an irritation of the delicate tissues which causes the deposition of pearly matter around them for protection. Advantage is taken of this by man, and by the introduction of different foreign bodies pearls of various shapes and dimensions are made to grow.
In this way the Chinese compel one species of fresh-water mussel, unio hyria, to produce pearls. A plan of making pearls was suggested to the Swedish government by Linnaeus. He bored a hole through the shell, thus easily reaching the exterior of the mantle. He was rewarded with £450 for the plan, but it was not found practically successful. The peculiar iridescence of the pearl is of the same nature as the colors of thin plates. (See Light, vol. x., p. 444.) The mother of pearl on the inner side of the shell has the same structure. - From a very early period pearls have ranked among gems, and been highly esteemed as ornaments. The book of Job refers to their great value, and frequent allusions are made to them in other parts of the Scriptures. The Greeks and Romans used them in profusion, and even decorated their feet with pearls. Pliny, after referring to the prodigal display of pearls in his time, adds: " Nay, even more than this, they put them on their feet, and that not merely on the laces of their sandals, but they must needs tread upon them and walk with them under foot as well." He also alludes to the breastplate which Caesar brought home and dedicated to Venus Genetrix, saying it was formed of British pearls; which confirms the statement of Suetonius that pearls were Caesar's chief inducement for his British expedition.
Pearls vary much in size. Those which are about the size of a pea and of good color and form are most valued, except unusually large specimens, which are rare. The most noted was owned by the late Mr. Hope of England. It weighs 3 oz., and is 4 1/2 in. in circumference and 2 in. in length, but irregular and imperfect. Among the Romans enormous prices were paid for fine ones. Strings of pearls were valued as high as 1,000,000 sesterces, or about $40,000. The pearls in the ear drops of Cleopatra, which she proposed to dissolve in vinegar at a costly repast, the subject of a wager, were valued at about $400,000. In the reign of Queen Elizabeth Sir Thomas Gresham is said to have imitated this feat with a pearl valued at $75,000. - The pearl oyster, from which almost all the pearls of commerce are obtained, is a bivalve of nearly circular form, slightly convex, and sometimes 12 in. in diameter. It is met with in different parts of the world, especially in the Indian ocean and the northern Pacific. Like the common oyster, pearl oysters congregate in large numbers on banks, and are obtained year after year from the same localities. Where the water is shallow, they are sometimes dredged, but they are generally taken by divers.
The most noted pearl fisheries are near the coasts of Ceylon, Japan, Java, and Sumatra, and in the Persian gulf. The coasts of Colombia, including the bay of Panama, were long since remarkable for their product of pearls, and they have furnished large amounts of them, but generally of inferior value to the oriental pearls. Still, one possessed by Philip II. of Spain, obtained in 1574 from Margarita, weighed 250 carats, and was valued at $150,000. The Spaniards who first visited the American continent found the natives decked with necklaces and bracelets of pearls, and Montezuma is described in his first interview with Cortes as wearing garments adorned with this precious ornament. In the trade in pearls from the Spanish American coast which soon sprung up, the islet of Cubagua became famous for abundant supplies. On the W. coast of Central America pearls are still procured, which are of fine lustre, but of irregular forms. Small vessels from Mazatlan and Acapulco are employed in this business. Besides the crew, they carry Indian divers, called luzos, who receive one fifth of the profits, the remainder being equally divided between the government and the owner of the vessel.
Humboldt remarks with surprise that he had never heard of pearls found in the fresh-water shells of South America, though several species of the unio genus abound in the rivers of Peru. Pearls of large size were found in the streams of New Jersey near Salem in 1858, and one more than an inch in diameter was sold in Paris for more than $2,000. - Among the most famous pearl fisheries are those of Ceylon and Coromandel, now controlled by the English government. From the time of Pliny, when the Romans obtained their pearls from the same region, Ceylon has always been celebrated for its pearls and pearl divers. The divers are natives trained to this pursuit, and accustomed to descend to depths of 6 or 8 fathoms 40 or 50 times a day. They take down a large stone to hasten their descent, and a bag in which they place the oysters, as they tear them off from the rocks. They remain under water from a minute to a minute and a half. The fishing season begins in March or April, and continues about a month. A single shell often contains from 8 to 12, and in some instances it is said even 20 pearls. The usual dimensions of good oriental pearls are from the size of a pea to about three times that size. Those smaller are called ounce pearls from being sold by weight, and the smallest seed pearls.
The pearl fisheries of the Bahrein islands in the Persian gulf are said to yield annually from $1,000,000 to $1,500,000. - Pearls are valued as well for the purity of their lustre as for their size. The smaller ones are worth from 50 cents to $3 each; single fine pearls are worth $5 and upward; and a handsome necklace of pearls as large as peas is worth from $500 to $15,000. Pearls in commerce are classed as oriental and occidental, or Indian and Pacific, and divided into round, pear-shape, and baroque; when smaller than 1/16 of an inch in diameter, they are termed seed pearls. Mother of pearl is familiarly known in its applications to ornamental purposes, and thousands of tons of the shells are annually exported from the Indian and Pacific oceans, valued according to quality from $70 to $650 a ton; it is used principally for buttons, knife handles, inlaying of furniture, etc, and is often beautifully carved. - False or artificial pearls were formerly made at Murano, a suburb of Venice, of glass lined with a pearl-colored varnish, or with quicksilver; but the French have been of late years the most successful imitators of the natural pearl.
The artificial pearls are lined with wax and fish scales, which are taken from the body of the fish (roach and dace) while living, in order to preserve the glistening hue. A variety of the smelt, said to be peculiar to the Tiber, has long afforded the Roman jewellers the means of coating waxen beads so that they have a greater resemblance to pearls than either the Venetian or French.
Pearl, a S. county of Mississippi, separated from Louisiana on the west by the Pearl river; area, 520 sq. m.; pop. about 700. It was formed in 1872 from the N. part of Hancock co. and the S. part of Marion co. The surface is undulating and mostly covered with pine forests. The soil is not generally fertile. Capital, Riceville.