The Chinese are said to thread upon fine silk, small beads of mother-of-pearl, and ,f4ten them within shells of. pearl oysters when they rise to the surface of • the water at the beginning of summer. The animals are then restored to their bed, where they soon cover the beads with cal careous matter, and thus convert them into pearls. Small figures of Buddha are the stock subjects introduced, and these are highly valued by Buddh ists in all countries. Small pearls which have been immersed in acetone acids, and thus reduced to their membranous constituents, have the ap pearance of being formed of concentric coats of membrane and carbonate of lime, thus resembling in composition the mother-of-pearl with which oyster-shells are lined. Mr. Robert Garner, F. L.S., particularly examined those formed in the mantle of the Conway and Lancashire salt-water mussel ; and he attributes the same origin to all pearls, the oxidation of a minute species of diatoma caus ing their formation, much in the same way that galls are formed in plants.
Sections of pearls show very fine concentric larainm surrounding a grain of sand or other extraneous matter. The nacreous lustre has been attributed to the diffraction of light from the out cropping edges of the lamina; but Dr. Carpenter says it may result from the minute plication of a single lamina.
In whatever way produced, pearls of consider able size, on account of their beauty and rarity, have been valued at enormous prices in past ages, and are still among the choicest objects of the jeweller's art. Their delicate and silvery lustre has been as widely celebrated as the brilliance of the diamond. The Meleagrina margaritifera furnishes the finest pearls and When secreted in the globular form, it is the pearl ; on the inner walls of the shell, it is the nacre.
A pearl, to be pure, should be of perfect white flegt+, lie spherical or of a regular pear shape; those of blue reflection arc less valued, and the yellow pearls still less. Tavernier was of opinion that the yellow colour was a stain from the rotting mollusc.
The pearl mollusc multiplies by means of what is technically called spat or spawn, which is thrown out in some years in great quantities,— perhaps similar to the edible oyster of Britain, which threw much spat in 1849, and not again until 1860, and not then up at least to 1866. The spat floats in and on the water, and attaches itself to anything it comes in contact with, attaining, it is said, the size of a shilling in six months. In its seventh year the pearl mussel attains its maturity as a pearl producer ; pearls obtained from a seven-year mussel being of double the value of those from one of six years of age. In mussels under four years the pearls
are not of any mercantile value, and after seven years the pearls deteriorate. Those from mussels of about four years old have a yellow tinge, and the older kinds a pinky hue ; but pearls of a red and even black, as also with other colours, are like wise met with. Of all the substances used for personal decoration, the pearl alone derives nothing from art. The Baghdad dealers prefer the round white pearl. Those of Bombay esteem pearls of a yellow hue ;and perfect sphericity. According to European taste, a perfect pearl should be round or drop-shaped, of a pure white, slightly transparent, free from specks, spots, or blemish, and possess the peculiar lustre charac teristic of the gem. In India and China, the bright yellow colour is preferred. The rose-tinted pearl of Scotland is in large esteem amongst Paris ladies. The pearls of Scotland of the best 'kind range in price from £5 to £50, but £100 has been paid for a fine specimen. Pearls of the Persian Gulf and Ceylon realize from Rs. 1000 Ito Rs. 1500 a tola of 180 grains.
I A pair of very fine black pearls was recently 'sold to a rich iron merchant in Paris for 500,000 francs. The pink pearl ranks with the clear white pearl in value. Some specimens have been found with purple, cream, and salmon colours.
Pearls arc designated in 'Europe by their colours, white, yellow, or black ; or by their size, as seed-pearl. The best pearls are of a clear, bright whiteness, free from spots or stains, with the surface naturally smooth and glossy. Those of a round form are preferred, but the larger ear - shaped ones are esteemed for ear - rings. are those of the smallest size.
The dealers in Ceylon recognise twelve classes, in none of which is the actual weight taken into consideration 1. Called Ani, comprising those pearls to which Pliny first applied the term unio,' in which all the highest perfections of lustre and sphericity are centred; 2. Anathari are such as fail a little in one point, either in lustre or sphericity ; 3. Sanadayam, and 4. Kayeral, such as fail in both ; 5. 3Iassagu, or confusion; 6. Vadivu, beauty ; 7. .fedangu, bent or `folded' pearls; 8. Kurwal, double pearls ; 9. Kalippu, signifying abundance ; 10. Pcesal, and 11. Ktu-al, misshapen. These find a ready sale in India, all kinds and shapes being indiscriminately used to adorn the roughly made breastplates of gold worn by women of high caste. 12. Thool, literally powder.' These are all easily disposed of in India, where they are some times made into lime to chew with belle.