196 Bulletin of Laboratoiics of Dcnison University. [Voi. xii 



counties, has manganese been found in the form of the oxide, 

 in place, in the original rocks. The manganese exists here 

 partly as the free oxide in a banded quartzite, and partly as a 

 manganese-bearing magnetite which forms a considerale per- 

 centage of the rock in places. Concentration of the manganese 

 with iron has taken place near the margin of the quartzite in 

 contact with the mica-schist, in quantity sufficient to yield a 

 small amount of workable ore. 



Accompanying the process of rock-decay the retention of 

 manganese in more localized form has been promoted in places. 

 The process is still in progress, and, accompanying it, the ac- 

 cumulation of manganese in those places where the conditions 

 are favorable. 



Briefly stated, then, the manganese-ores of the Georgia 

 Crystalline area represent the secondary accumulations of the 

 insoluble oxides of the metal supplied from the manganese-bear- 

 ing silicates on decomposition, and subsequently concentrated 

 and localized in the residual clays derived from the decay of the 

 underlying siliceous crystalline rocks. In places, accumulation 

 of the oxides has progressed along and near contact-zones in the 

 rocks ; in other places concentration has been in the clays and 

 removed from contacts. 



Methods of Mining the Ore. 



The nature of the ore to be mined in the Georgia area is 

 one of irregular distribution, in the form of nodules and pock- 

 ets, through residual clays, which range in thickness from 25 ft. 

 to several hundred feet. The ore-distribution varies greatly, 

 and the deposits are limited both in depth and lateral extent ; 

 hence, the methods for operating in one place will necessarily 

 vary, more or less, in detail from those in another. As a rule, 

 the deposits are located on the summits and higher slopes 

 of the hills and ridges, though there are many exceptions, for 

 they not infrequently occupy the lower slopes and valley- 

 bottoms. 



The method of mining will depend largely upon the loca- 

 tion of the deposits and their depth below the surface. Open 



