CHAPTER XVIII. 



THE INFLUENCE OF LOCAL CONDITIONS UPON THE COLOR 

 OF SHELLS AND PEARLS, 



THE American fresh-water pearls have gained in- 

 ternational fame for their great variety of fancy 

 colors. The crowns of many kingdoms are 

 adorned with one or more of these precious gems. 



The cause of the various colors is something which 

 scientists are unable to explain. The subject has been 

 very sadly neglected and probably there has not been a 

 real need for the knowledge. 



The time has arrived, however, when it is very desir- 

 able to know the exact causes of the various colors. 



Great progress has been made in the science and art 

 of perpetuating the supply of valuable mussels. The 

 growing demand for fresh-water pearls, or, sweet-water 

 pearls as they are often called, will make scientific pearl 

 farming a profitable occupation. 



It is, therefore, very important to know the influences 

 which are the causes of different colors in pearls. 



A single fresh-water pearl which has a brilliant fancy 

 color is a valuable gem, but such a pearl is usually set 

 alone because it cannot be duplicated. If such a gem 

 could be matched perfectly, the value of both pearl? 

 would be greatly enhanced. 



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