# Popular Science Monthly/Volume 49/July 1896/Pearls and Mother-Of-Pearl

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* PEARLS AND MOTHER-OF-PEARL.
By CHARLES STUART PRATT.
AMONG the picturesque industrial possibilities of our southern Pacific coast is the artificial production of pearls. By this is meant, not the manufacture of artificial pearls, but the artificial growing of real pearls; that is, instead of the haphazard pearl-fishing of the present, the establishment, on the southern California coast, of oyster ranches, where the pearl-producing bivalves shall be scientifically directed and assisted in growing both gem pearls and mother-of-pearl.
This is hardly more visionary than was the recent establishment of ostrich ranches just inland from this same Pacific coast. A glance at the natural process of pearl-making will throw some interesting light on these oyster ranches-to-be. Mother-of-pearl is the natural product of the wild oyster, if we may so designate the bivalve of the unfenced sea bottoms. To secure a smooth surface for the contact of its soft, sensitive body, the oyster lines its coarser, rougher shell with a substance named nacre—which is simply carbonate of lime, with a trace of organic matter. This nacre is secreted and deposited in successive layers of filmy thinness and of marvelous smoothness of surface; the result is the lustrous, iridescent mother-of-pearl.
Unlike mother-of-pearl, the gem pearl, round or otherwise, is an unnatural product of the oyster. The gem pearl is an accident, almost a disaster, to its creator. In fact, a healthy, undisturbed oyster never produces a pearl. But if a sharp grain of sand finds its way inside the shell, the disturbed oyster protects its tender, sensitive flesh from the irritation of this offending substance by depositing about it smooth coatings of the nacre with which it has already formed or deposited the mother-of-pearl ​lining of its shell. Layer after layer is added, until finally we have the round, lustrous gem for brides' fingers and the throats of queens.
It is possible that in some cases a wound throws off bony particles which become the nucleus of the pearl; or, in place of sand, the foreign substance may be a minute parasite, or a morsel of seaweed, or one of the tiny siliceous vegetables known as diatoms, or even one of the eggs of the oyster itself. Some such encysted particle, though perhaps of microscopic size, lies at the center, and was the cause, of every pearl. So the pleasure-giving gem is really the outgrowth of pain.
Now, it has been discovered that, instead of waiting the accidental intrusion of the alien particle into the shell of the oyster, grains of sand, or other objects, for the nucleus of the pearl, may be deliberately inserted by the hand of man, and that the oyster will at once set to work at pearl-making. It is known that the Chinese, from a remote period, have ingeniously taken advantage of this singular self-defense of the oyster. In the month of May the river mussels are taken from the water, and small pellets of clay, and even tiny images of the gods, are slipped inside the shells. The mussels are then replanted and left half a year. In November they are taken up again, and, while some of the shellfish die, most have coated the clay pellets and little metal gods with nacre, producing real pearls and genuine mother-of-pearl deities.
These mother-of-pearl Buddhas are in great demand with the curious and the devout, but there is no evidence that any of the priceless pearls of the world have been so produced. And yet surely the results obtained suggest great possibilities for the enterprising man who shall establish the oyster ranches already mentioned, and who shall add to the ingenuity of the Chinese all the resources of modern science.
The thin layers of nacre are always deposited thicker in depressions than over elevations; hence uneven surfaces become level, and small particles of whatever form gradually become spherical. The perfect round pearl, however, can only result when the nucleus penetrates the soft body of the oyster, or remains unattached to the shell. Often it does become so attached, and when removed has a defect on one side, and can only be used in settings where that side is hidden; such pearls are called boutons or button pearls; odd, irregular shapes are called baroques. Large or heavy intruding objects are quite likely to become attached to the lower half of the shell. Such objects often, in the course of years, are buried from sight under successive layers of nacre. Some Chinese Buddhas thus imbedded in the flat or lower halves of the bivalves are to be seen in London museums, and they ​illustrate the curious fact that the oyster has the habit of forcing intruders out, not manlike through the door, but through the walls of its house. The way of it is this: while the successive coverings of nacre are deposited on the inside of the shell, the outside of the shell is gradually decaying and crumbling away, so that as the wall inside the alien object becomes thicker, the part outside becomes thinner, till finally the intruder reaches the surface—is literally forced through the shell of the oyster.
The pearl is the one gem that comes to us perfect from the hand of Nature, and to this its great antiquity as a gem is largely due. Precious stones whose beauty and brilliance depend on polishing and cutting would naturally be discovered and utilized later. The discovery of the diamond, for instance, probably dates within historic times. Though known earlier, it was not generally included among the gem treasures of royalty even as late as the seventh century. The modern cutting of diamonds in regular facets was invented as recently as 1456. Indeed, it is quite probable that the pearl was the first gem known and treasured by prehistoric man—since the search for food must have been the first occupation of the earliest of the race, and the shining pearl would thus have been discovered in river mussels if not in marine oysters. Certain it is that the Old Testament and the, most ancient written histories allude to pearls, and that remoter evidence is found in the tombs and excavated cities of still earlier eras. The Egyptians, Babylonians and Assyrians held the pearl in an esteem verging on reverence.
Not only were pearls known and prized as the most precious of gems, but they were gathered and treasured in astonishing quantities by the early Oriental potentates. Many relics and records of those days remain. The crown of the Khan of the Tartars, captured on the Oxus by the Persians in the fifth century, was decorated with several thousand pearls. The famous crown of Chosroes, made in the sixth century, and which was strangely concealed for a thousand years in an obscure fortress among the Lauristanian Mountains, till brought to light by Shah Abbas, is incrusted with pearls in conjunction with rubies. In the seventh century the Arabs captured from the Persian nobles fabrics of amazing richness, among which was one marvelous carpet of white brocade, four hundred and fifty feet by ninety feet, with a border worked in precious stones to represent a garden of all kinds of beautiful flowers—the leaves of emeralds and other green gems, the buds and blossoms of pearls, along with rubies and sapphires.
The treasures of the Turkish nobility during some of the more brilliant reigns of the empire seem to belong to fable rather than to veritable history. Sinan Pasha, dying at eighty, left fifteen ​strings of enormous pearls, and of "fine pearls" no less than sixty bushels!—accumulated during campaigns in Europe, Asia and Africa.
Shah Jehan, greatest of Mogul sovereigns after Timour, collected the wealth of India about him at Delhi, including the world-famous diamond known ever since as the Great Mogul. His was the famous peacock throne, the spread tails of the peacocks formed of precious stones to emulate the colors of the living bird, the whole valued at nearly thirty-five million dollars. Its canopy was fringed with pearls. His, too, was the Taj Mahal, the most marvelous tomb ever built, on which twenty thousand men worked for more than twenty years. And this Shah Jehan loved to wear round his neck priceless strings of immense pearls.
The Greeks and Romans rivaled the Orientals in their appreciation of pearls. When Alexander and his eighty companions wedded their beautiful Persian brides at the most famous marriage feast of history, the pearls of the Persian Gulf were the favorite jewels—as they are with brides in this closing decade of the nineteenth century. The Romans sent caravans on yearlong journeys to Ceylon for pearls. And there is evidence that Julius Cæsar really invaded Britain for the sake of expected plunder in pearls. That he was not disappointed is shown by the record that on his return he dedicated to the Venus Genetrix a breastplate of the British gems.
The ancients seem to have had no conception of the real origin of pearls. Even in the days of the Romans they had not advanced beyond the early myths of creation by Vishnu, of angels' tears dropped out of heaven into the gaping mouths of mussels, or the diverse theory that they were as mystically congealed from dewdrops, which with equal mystery, after their ethereal descent, dropped through fathoms of water without commingling—unless, indeed, the shellfish were supposed to come to the surface to receive them. Pliny gravely asserts that "pearls are great or small, better or worse, according to the quantity and quality of the dew they have received. For, if the dew were pure and clear that went into them, then are the pearls fair and orient. Cloudy weather spoils their color, lightning stops their growth, and thunder makes the shellfish eject hollow husks or bubbles" in place of pearls.
Ceylon and the Persian Gulf, which were the chief sources of fine pearls back before the dawn of the Christian era, have retained their supremacy through twenty centuries, though profitable pearling grounds are now worked in Eastern waters off New Guinea and the northern Australian coasts, in the Sulu Archipelago, off Japan, and among the Polynesian islands. In minor quantity, and perhaps quality, pearls are gathered from Western ​waters off the coasts of equatorial South. America, the West Indies, Panama, and southern California. The Aztec kings possessed pearls of great beauty and price, obtained, it is supposed, from Panama. The palace of Montezuma, when despoiled by the Spaniards, is described as "studded with pearls," along with emeralds.
Some fine pearls are produced in inland waters by the freshwater mussel (Unio margaritifera). Most of the river pearls are found in China, though at some periods the pearl industries in England and Scotland have been important. The rivers of Germany and parts of Russia are also pearl-producing. The principal river-pearl fishery in the United States is in the Little Miami in Ohio.
The marine mollusks yielding pearls are the Avicula (Meleagrina) margaritifera, Avicula macroptera, and Avicula fucata.
In the Persian Gulf the Avicula fucata is specially fished for gem pearls, as it produces more and of finer quality than the other varieties, though it is smaller and of less value for the mother-of-pearl lining of its shell. All three varieties mentioned, however, are found on the famous Great Pearl Bank, which lies along the west coast of the gulf. There the pearling industry from remote times has so dominated the people that it has passed into a proverb, "All are slaves to one master. Pearl."
The great Ceylon pearl fisheries are now a monopoly, under the supervision of the British Government, as formerly under that of the Portuguese and the Dutch. The fishing seasons occur at irregular and infrequent periods, only half a dozen having been sanctioned by the inspecting officer in the quarter century between 1863 and 1887. The value of the pearls from these several fishings varied from fifty thousand to three hundred thousand dollars, with a total of about one million dollars. The Ceylon fishing season runs from four to six weeks. The latest of which there is data was that of 1889, when in twenty-two days fifty divers brought up eleven million oysters, which yielded the Government fifty thousand dollars and the divers about fifteen thousand dollars. In Ceylon it is the custom to land the cargoes of oysters on the shore to die and decay. When sufficiently decomposed they are opened and then washed and searched for the more valuable loose pearls, after which the boutons are clipped from the shells, and the larger of the shells themselves selected for their mother-of-pearl.
Diving for pearls is perhaps the most perilous of occupations, with the possible exception of its antithesis—that of aeronautics. There are the terrible physical tortures of the first descents from the pressure of water; the bleeding from nostrils, ears and mouth; the bursting of small blood-vessels in the lungs; and the ​rending of a way from ear to nasal passage. Nearly all divers become partly or totally deaf. Incipient heart and lung troubles are quickly developed to a fatal end. Paralysis is often induced. Sharks occasionally devour the naked natives; such tragedies are not common, however, since the splashing and constant agitation of the water serve to keep them at bay—though, no doubt, the natives themselves would credit their immunity to the shark-charmer who accompanies each boat.
The native crews off Ceylon usually include ten divers, five of whom rest while the other five are diving. Each man has a diving stone, weighing perhaps forty pounds, to which is attached a rope long enough to reach the bottom, and having a loop for the foot. The diver slips his foot into the loop at the sinking stone, inhales a full breath, compresses his nostrils with his left hand, raises his body as high as possible, and sinks swiftly to the bottom, feet foremost. The average depth for native divers is fifty feet, the greatest depth about seventy-five. The naked diver must work with great rapidity, as he can remain at the bottom only about fifty-five seconds. In spite of stories of divers remaining below for three or four minutes, the best divers rarely reach eighty seconds, and few exceed sixty. In this brief period such shells as can be secured are thrust into the shell-bag, net, or basket, the tender in the boat is signaled by the line attached, and the diver assists his own ascent by seizing the bag line as it is drawn up.
In the Persian Gulf the ancient custom of stopping the ears with cotton saturated with oil and closing the nostrils with pincers of tortoise shell is still in vogue. But the primitive method of diving is now being superseded by scientific diving in the modern diving dress. This consists of a rubber-cloth suit in one piece from foot to neck. The hands are bare, the elastic wristbands of the dress hugging tight enough to exclude water. The neck is large, of course, to admit the body after the feet and legs. The diver once in this dress, the neck is fastened between the double rims of a brass corselet, and then a big copper helmet is set over the head and screwed to the corselet. The helmet has glass windows at each side and in front, an air-tube entering at the back through which air is supplied by a pump worked by a couple of men in the boat, and a valve at the side for the outlet of vitiated air. The armored diver wears leaded canvas or leather boots weighing fifteen or sixteen pounds, and a couple of heart-shaped leaden plates over chest and back weighing twice as much more. He has a life-line fastened to his right foot and then by a slip-noose about his waist. This life-line is held by a "tender" in the boat who answers signals: one jerk, pull up; two, more air; three, lower bag.
​The armored divers are mostly white sailors, Germans, Swedes, a few English, and an occasional American; and so great is the advantage of the diving suit that one armored diver is considered equal to a whole crew of natives. Instead of a swift, breathless struggle of fifty or sixty seconds, at a depth of fifty feet or less, with a limit of seventy-five, the armored diver can work for ten minutes at a depth of a hundred feet, while at a depth of thirty he can work for a couple of hours. The deep-sea dangers to which the naked diver is exposed are mostly shared by the armored diver. The protection from the tremendous crushing pressure of the water afforded by the suit and the cushion of inclosed air is offset by the increased pressure at greater depths. The armored diver likewise encounters the venomous stonefish. This little fish punctures the hand reaching for a shell and injects a poison which causes the whole arm to swell, with great pain. The remedy is to remain down, as the pressure of water induces free bleeding at the wound, and the consequent outflow of the poison. If the bitten diver comes to the surface, as the unarmored diver must, the arm swells rapidly, turns black, and is painful for weeks.
Sharks do not attack the armored diver, but he has peculiar perils which the naked native diver escapes. At some great depth the air-pump may not work, or the air-pipe may burst. But there are greater dangers yet. Pearl oysters are not found in beds, like our edible bivalves, but scattered over the sea bottom; hence it is the custom to beat up against the tide or current, and then let the lugger drift, with a drag-anchor perhaps. Yet sometimes the drifting boat is seized by a strong current and whirled along, and then, while the diver hurries on to keep up, his life-line or air-pipe may become fatally entangled in branching coral; or, again, a slack line or pipe may fall into the jaws of the "giant clam," which close over it, and hold the diver prisoner to his death, alone in the dim ocean depths.
The most perfect pearls are found within what is called "the mantle" of the mollusk, an elastic membrane which envelops the oyster, and which is supposed to secrete the nacreous fluid. The finest specimens lie near the lips of the shell, or are imbedded in the softer part of the oyster near the hinge of the shell. The ideal gem pearl is spherical, white, without blemish in texture or "skin," with pure "water" or appearance of transparency—though no pearl is really transparent—and of distinguished lustre or orient. Lustre is the soul of the pearl, as brilliancy is of the diamond. Finely formed drop shapes, and then oval or egg shapes, are but little below the spherical pearls in value, if of equal perfection. The fine gem pearls are the size of peas; very much larger specimens, of twenty-five grains and upward, of perfect quality, are rare, and command corresponding values.
​At the breaking up of the French crown treasury in 1791, a superb spherical pearl of large size sold for forty thousand dollars, and two pear-shaped pearls, weighing two hundred and fourteen grains, were valued at thirty thousand dollars each. The Shah of Persia possesses one of the finest pearls in the world, worth three hundred thousand dollars. The Imam of Muscat has refused one hundred and fifty thousand dollars for one of his famous gems. Perhaps the most extraordinary pearl now known is in Mr. Beresford Hope's collection in South Kensington; it is two inches long, four in circumference, and weighs eighteen hundred grains.
When Rome ruled the world, a wonderful pearl worth four hundred thousand dollars was cut in halves for earrings for the Venus in the Pantheon. The pearl of the Cleopatra legend is said to have been of equal value—though if swallowed it must have been as a pill without sugar coating, since gem experts assert that no acid the human stomach could endure will dissolve a pearl; indeed, the most powerful acids known only discolor and destroy the outer layers of nacre after long immersion. Authorities do not agree upon this point, however.
While the white pearl is really the ideal pearl of all ages, fashion, local in place and time, has favored other colors for the hour. Rose-colored pearls have been the fad in Paris for several seasons, to the enriching of the Scottish fishers. The Chinese prize yellow pearls; and just now black pearls, if of perfect quality, command the highest price. The largest and finest black pearls come from the La Paz pearling grounds off Lower California, which also yield pink pearls.
The color of pearls, as well as the quality and especially the lustre, depends on the peculiar environment of the oyster, the chemical composition of the water. The inky fluid ejected by the great squid is believed to affect the color of pearls. Temperature and the health of the mollusk may modify the nacreous deposits. Be all this as it may, when the oyster ranches already alluded to shall be established on our California coast, we may well expect that, with the co-operation of chemical and biological science, marvelous results will be obtained in both the quality and color of pearls—any color being produced at pleasure. Women of fashion and wealth will then order their pearls a season ahead, to be grown of desired form, lustre, and color, to harmonize with their gowns, as to-day they order in advance the gowns themselves.
Artificial pearls, which only the expert is likely to detect, are made by coating the inside of thin glass spheres with a solution of liquid ammonia and the lustrous coating of the lower scales of the bleak and dace, filling the bulb with melted wax. ​and then subjecting the surface to the action of hydrofluoric acid. This was the invention of Janin, Jacquin, or Jalquin, a rosary-maker in Paris, in 1680. A thousand fish yield less than an ounce of the "pearl essence" which is correspondingly costly. The cheaper so-called Roman pearls have a lustrous coating on the outside, but bear little resemblance to real pearls, or even to the artificial pearls just described.
Considering the vast values in gem pearls obtained from the Eastern fisheries, it is surprising to find that the plain, unromantic mother-of-pearl secured is of even greater worth. Previous to the discovery of the extensive Australian fishing grounds, in 1865, the supply of mother-of-pearl was diminishing, while the demand was increasing. The large-shelled species already mentioned are there found in fine quality. The shells are the size of large soup-plates, weigh a pound each, and are worth about a dollar a pair. An expert diver, in diving dress, will collect three or four hundred pairs in a day. About a hundred gem pearls are found in every ton of these shells.
Beautiful art work in carved and inlaid mother-of-pearl has long been produced in China and Japan. Some idea of the extent of its European use in the arts and manufactures may be had from the fact that eight thousand people are engaged in working mother-of-pearl in Austria, and half that number in France, while the value of the annual import into England is nearly one and a half millions. In the Philippine Islands windows are made of mother-of-pearl; and James Anthony Froude, in his volume of voyaging in Oceana, describes frightful Maori idols with slips of mother-of-pearl glittering in their eye-sockets; while in Cashmere it is the custom to inlay the inscriptions in tombstones with the same exquisite substance. To cap the climax of curious uses of the lustrous nacre, it is said that large quantities of seed pearls are imported into China to be calcined into medicines for the Celestials.