When the nucleus of a pearl is large and very irregular, it necessarily follows that the deposited nacre roughly assumes the irregular outline of the inclosed object. This is strikingly shown in pearls covering a minute fish, a crayfish, or a small crab. Several specimens have been found in which the species could be identified by examination through the nacreous coating.
In the American Unios there is a strong tendency to produce elongated pearls near the hinge of the shell, which are consequently known as “hinge pearls.” The occurrence and form of these suggest that their origin may not be due to nuclei, but that they result from an excess of carbonate of lime in the water, and that the animal stores a surplus of nacre in this convenient form. There are several standard forms of these hinge pearls. Many are elongated or dog-toothed, some are hammer-shaped, others resemble the wings of birds, the petals of flowers, the bodies of fish, and various other objects. A large percentage of the pearls found in Unios of the Mississippi Valley are of these types.
Some irregular pearls or baroques are very large, weighing an ounce or more. A well-known example is the Hope pearl, described on page 463, which weighs three ounces. These monster pearls sometimes assume odd shapes, such as clasped hands, the body of a man, lion, or other animal, etc.
Although baroques may have a pearly luster, they are not highly prized unless unusually attractive, and they have little permanent value, apart from their estimation in the eyes of admirers of the curious and unique. They are used largely in l’art nouveau, and in forming odd and fanciful objects of jewelry, the designer taking advantage of the resemblance which they bear to common objects of every-day life, and by additions of gold and other ornaments completing the form which nature had merely suggested.
Some remarkable examples of baroque mountings have been produced, and a few are to be found in most of the large pearl collections. In a single case in the Imperial Treasury at Vienna are baroques forming the principal parts or figures of a horse, stag, lamb, tortoise, lizard, cock, dragon, butterfly, gondola, hippopotamus, female bust, and three mermaids. Other well-known collections are those of the royal family of Saxony in the Grüne Gewölbe at Dresden; those in the Palace of Rosenberg at Copenhagen; in the Waddesden (Rothschild) collection of the British Museum; among the jewels in the Louvre in Paris; with the treasures of the Basilica of St. Mark in Venice; and in the museum of the University of Moscow.
A remarkable pearl-like ornament more common in Asia than in the Occident, is the coque de perle, which is an oval section of the globose whorl of the Indian nautilus. The exterior or convex surface is highly lustrous, but the material is very thin. It is commonly provided with a suitable filling or backing of putty or cement to impart solidity, and is used like a blister pearl. Sometimes two perfectly matched coques de perle are filled and cemented together, giving the appearance of an abnormally large oblong or nearly spherical pearl.
The color of pearls has no connection with the luster. In general it is the same as that of the shell in which they are formed. Black pearls are found in the black shells of Mexico, and pink pearls in the pink-hued Strombus of the Bahamas. Ceylon pearls are seldom of any other color than white, and Sharks Bays are almost invariably quite yellow or straw-colored, while those of Venezuela are commonly yellowish tinged. But from other localities, pearls simulate every tint of the rainbow, as well as white and black. The most common, as well as the most desirable ordinarily, is white, or rather, silvery or moonlight glint,—“la gran Margherita,” as Dante calls it; but yellow, pink, and black are numerous. They may also be piebald—a portion white and the rest pink or brown or black. Some years ago there was on the market a large bean-shaped pearl of great luster, one half of which was white and the other quite black, the dividing-line being sharply defined in the plane of the greatest circumference. The pearls from Mexico, the South Sea islands, and the American rivers are especially noted for their great variety of coloration, covering every known tint and shade, and requiring such a master as Théophile Gautier to do justice to them.
Many theories have been advanced to explain the coloration of pearls. When the old idea of dew formation prevailed, it was considered that white pearls were formed in fair weather, and the dark ones when the weather was cloudy. It was further considered that the color was influenced by the depth of the water in which they grew: that in deep water they were white, but where it was so shallow that the sunlight easily penetrated, the pearls were more likely to be dark in color. Tavernier curiously explained that the black pearls of Panama and Mexico owed their color to the black mud in which the pearl-oysters of those localities lived, and that Persian Gulf pearls were more inclined to yellow than those of Ceylon, owing to the greater putrefaction of the flesh before they were removed therefrom.[[77]] Two centuries ago the color of a pearl was attributed to that of the central nucleus, and it was concluded that if the nucleus was dark, the pearl would be of a similar hue.[[78]] This theory has also been upset, for pearls are found white on the exterior and quite dark within, and also with these conditions reversed.
GRAY PEARLS IN THE POSSESSION OF AN AMERICAN LADY AND BROOCH FROM TIFFANY & CO.’S EXHIBIT, PARIS EXPOSITION, 1900