1 66 Bulletin of Laboratojies of Denison University. 



[Vol. xii 



tersville district has been much broken and crushed, and it is 

 thrown into a series of narrow, more or less steep folds or 

 ridges, whose surface is everywhere covered to some depth 

 with its residual decay. Reefs of the hard and fresh rock are 

 often exposed along the crests of the ridges, and to some ex- 

 tent exposures are frequent near the tops and along the steeper 

 slopes of the ridges. 



Fig. 6. 



Section in One of the Openings on the Blue Ridge Mining Co.'s Property, 

 near Cartersville, Georgia, Showing the Mode of Occurrence of the Manganese- 

 Ore in the Residual Clay. 



A, fragments and masses of partially decayed rock ; B, manganese ore ; C, 

 residual clay. 



Horizontal and vertical scale, i in.= 17 ft. 



Shafts have been sunk in several places to a depth of sev- 

 eral hundred feet without piercing the bed-rock. Depths of 

 100 ft. and more in the residual- mantle are common in the dis- 

 trict. In the Chumler Hill section, about 8 miles northeast of 

 Cartersville, several shafts have been sunk to a depth of more 

 than 80 ft. in manganese-mining without encountering the bed- 

 rock. (See Fig. 11.) 



Kinds of Ore. — Only the oxides of manganese occur in 

 the Cartersville district. Of these, pyrolusite and psilomelane 

 greatly predominate, with some manganite and braunite and 

 much of the earthy oxide, wad. These different oxides cannot 

 always be separated, but they usually occur admixed in vary- 



