Their origin ajid formation. 125 



by Pearls had attracted the notice of the ancient 

 Romans and led to a systematic nomenclature. The 

 Unio was the name of the globular Pearl; the tympania 

 of the hemi-spherical ; the elenchus of the pear-shaped ; 

 and the margaritiim of the irregular or baroque 

 Pearl. 



The baroque Pearls often assume very whimsical 

 forms, and advantage has sometimes been taken of 

 this fact by mounting the warty Pearls as grotesque 

 ornaments. Dinglinger, the court jeweller at Dresden 

 in the latter part of the seventeenth century, was 

 famous for his ingenuity in this direction, and some 

 beautiful specimens of Pearl mounted in gold and 

 enamel may be seen in the Jewel Room of the 

 Green Vaults at Dresden. 



The chemical composition of the Pearl as pre- 

 viously stated is carbonate of lime associated with 

 a small proportion of organic matter : it is easily 

 affected, by acids and foetid gases, and may be 

 calcined on exposure to heat. It possesses a lustre 

 peculiar to itself which is known as the "orient.'' 

 Its specific gravity is 2.5 to 2.7, those found on the 

 coast of South America, termed Panama Pearls, 

 being somewhat denser than the Oriental Pearls. 



The beauty and value of Pearls depend on their 



