THE NONMETALLIC MINERALS. 



235 



The Connasauga is between 2,000 and 3,000 feet in thickness. It 

 consists at the base of fine aluminous shales; the upper portion is 

 more calcareous, and locally passes into heavy beds of blue seamy 

 limestone. 



Above Connasauga shale is the Knox dolomite, the most uniform 

 and persistent formation of the southern Appalachian region. It con- 

 sists of from 3,000 to 4,000 feet of gray, semicrystalline, siliceous 

 dolomite. The silica is usually segregated in nodules and beds of 



MAP SHOWING THE 



GEOLOGICAL RELATIONS 



OF THE 



GEORGIA AND ALABAMA BAUXITE DEPOSITS. 



C.W.HAYES 



Fig. 6. 



MAP SHOWING THE GEOLOGICAL RELATIONS OF GEORGIA AND ALABAMA BAUXITE DEPOSITS. 



After C. W. Hayes. 



chert. These remain upon the surface, and with the other insoluble 

 constituents form a heavy residual mantle covering all the outcrops 

 of the formation. It is associated with these residual materials that 

 the extensive deposits of limonite and bauxite are found. The geo- 

 logical structure of the region is complicated and for its details the 

 present reader is referred to Dr. Hayes's original paper. 



Subaerial decomposition has progressed for a long period, and the 

 surface is deeply covered with a mantle of residual material, consisting 

 of the more insoluble portions of the original rock masses. This 



