Notes

Abstract

“CULTURED” pearls, recently introduced by a Japanese firm, appear to have caused some alarm in the gem trade. It has long been known that pearls are the result of local irritation in the pearl-oyster or pearl-mussel, caused by the introduction of some foreign matter—usually the larva of a parasitic organism which spends another part of its life-cycle in an animal that feeds on the mollusc. The mollusc retaliates by coating the unbidden guest with a smooth layer of nacre (identical with the mother-of-pearl layer of its shell, and consisting mainly of the orthorhombic crystalline modification of calcium carbonate corresponding with the mineral aragonite); and the resulting pearl is the elegant tomb of the objectionable parasite. The Chinese have for centuries produced this result artificially by inserting objects between the shell and mantle of the fresh-water mussel, and figures of Buddha on the inner surface of such shells are common. The difficulty hitherto has been to cause the formation of a spherical secretion unattached to the shell of the mollusc. This now appears to have been achieved by Mr. Mikimoto as a result of experiments extending over forty years. It is said that fragments of mother of pearl are inserted in the tissues of the molluscs, which are then returned to the sea for a period of several years. Another obvious method would be to infect the oyster-bed with the appropriate parasite. But, whether the foreign matter is introduced accidentally or intentionally, the result produced by the oyster must be the same. The qualification “artificial” would here apply rather to the pretence that the products are essentially different. Attempts on the part of the trade to discredit what is apparently an interesting scientific discovery are clearly made only with the view of keeping up inflated prices. The same selfish fight was made some years ago against the artificially formed rubies and sapphires (miscalled “synthetic,” “reconstructed,” and even “imitation”), which can be produced much more economically than the naturally formed stones. Strawberries raised in pots under glass are sold without question as strawberries-but wisely at a higher price. Pearls are high in price because of their rarity, but if they were plentiful and the more brightly coloured mother-of-pearl were rare the cry would be very different.