COLOR INFLUENCED BY LOCAL CONDITIONS 167 



ponds were dry, and as there were no rains it is mani- 

 fest that the river was made up largely of spring water 

 then. It is very probable that a chemical analysis of the 

 river water at that time would have shown a larger per 

 cent, of minerals than could be found at other times. 

 This condition suggests that the colors of the shells and 

 pearls may possibly be caused by the minerals which are 

 in the running water. 



The colored shells are also smaller and lighter than the 

 white ones and probably do not grow so quickly. 



Investigations of the pearl fisheries of the various 

 rivers of this country and some of the ocean fisheries 

 seem to justify the theory of the mineral origin of the 

 colors of the pearls and shells. 



Illinois is a prairie State. The rivers are fed by creeks 

 and other streams. There are large coal deposits, but 

 they do not influence the colors of pearls, except where 

 the deposits are near the surface and exposed to the ac- 

 tion of the running water. The Spoon River, in Fulton 

 County, has this unfavorable condition, and many of the 

 pearls have a dead yellow color, which is very detri- 

 mental to their value. 



Minerals are scarce in Illinois, and the shells with 

 white nacre predominate. 



The rivers of the State of Tennessee have yielded 

 many fine colored pearls. A large number of these were 

 pink and red. 



Tennesse produces gold, iron, copper and marble. The 

 great iron belt extends 5,400 square miles along the 

 Tennessee River. 



