CHAPTER I. 

 THE FRESH-WATER PEARL. 



PEARLS are lustrous gems produced by certain 

 Moilusks. They consist of thin concentric layers 

 of carbonate of lime interstratified with animal 

 membrane, and are the result of an unusual secretion, 

 primarily caused by the introduction of a parasite or 

 some other object within the mantle. 



The exact composition of a pearl is as follows : 



Carbonate of lime 91.72% 



Organic matter 5-94% 



Water 2.34% 



These gems are divided into two classes, known as 

 Oriental and Fresh- Water Pearls. 



The Oriental, or Ocean Pearl, is produced by the Avi- 

 cula Maryaritifera, or Pearl Oyster. Of this bivalve 

 there are many varieties all differing in size, color, weight 

 and quality of the shell. 



The most important Oriental Pearl Fisheries are the 

 iollowing: Ceylon, Australia, Gambier, South Sea Isl- 

 ands, Arabian Sea, Bands, Costa Rica, Aroe, Haiti, Ma- 

 nilla, Venezuela, Panama and Lower California. 



The Fresh-Water Pearl is produced by a mussel known 

 as Unio Margaritifera. This name is applied to the mus- 

 sels of our country. The name Naiades is a more gen- 



