Diamonds and precious stones, a popular account of gems .. . oduces the pearl, but furnishes to commerce vastquantities of mother-of-pearl of the kind mostvalued. There is a prevailing idea that mother-of-pearland the pearl are of the same nature; and, in con- 190 PRECIOUS STONES. sequence of this notion, numberless attempts havebeen made to obtain artificial pearls by means oflittle spheres more or less regularly cut out ofmother-of-pearl. The experiment has never been successful. Alittle serious examination of the subject proves thatthere is nothing to hope from this method. Evenadmitting th
Diamonds and precious stones, a popular account of gems .. . oduces the pearl, but furnishes to commerce vastquantities of mother-of-pearl of the kind mostvalued. There is a prevailing idea that mother-of-pearland the pearl are of the same nature; and, in con- 190 PRECIOUS STONES. sequence of this notion, numberless attempts havebeen made to obtain artificial pearls by means oflittle spheres more or less regularly cut out ofmother-of-pearl. The experiment has never been successful. Alittle serious examination of the subject proves thatthere is nothing to hope from this method. Evenadmitting that mother-of-pearl and pearl are thesame in composition, which has not been scienti-fically proved, it is certain that they are not of thesame constitution. Mother-of-pearl is much harder,and offers infinitely more resistance to the tools ofthe lapidary than the pearl. But that which ismost important to be remarked is, that in the pearlthe constituent layers are concentric, while in thepearls cut out of mother-of-pearl, the layers aremore or \qss Fig. 84.—Pearl. Fig. 85.—Mother-of-pearl. Figs. 84 and 85 establish perfectly to the eye thecomplete difference presented in this respect bymother-of-pearl and the pearl. THE PEARL. I9I They show, at the same time, how the light mustnecessarily undergo very different modifications inthe two cases, and why cut mother-of-pearl cannever have the same optical effects as the pearl. Although pearl molluscs exist in all parts of theworld, there are but few places where their gather-ing has become an industry. One of these placeswas formerly the Red Sea, which, in the time of thePtolemies, produced an abundance of- pearls. Butthe beds are probably exhausted ; at any rate theyare no longer worked. The two regions which fora long time have produced the most beautiful pearlsare the Persian Gulf, and the Straits of Manaafwhich separate Ceylon from the peninsula ofIndia. More recently great quantities of pearl-oystershave been discov
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectgems, booksubjectprec
