Art. IX.] Watson, Manganese Ore- Deposits of Georgia. 185 



are composed of numerous complex manganese-bearing silicates. 

 It was from these older crystalline rocks, during decay, that the 

 manganese is believed to have been originally derived. 



2. Solution, Transportation and Precipitation of the Man- 

 ganese. — Assuming that the original source of the manganese 



Fk;. 17. 



Section through the Westbrook Tract, Paulding Co., Georgia, Showing the 

 Mode of Occurrence of the Ores. 

 A, mica-schist, partially decayed, highly schistose ; B, banded quartzite, 

 30 ft. wide, cut by quartz-stringers containing the ore, which includes man- 

 ganese, manganiferous iron-ore and magnetite. 



was from the older crystalline rocks to the east and south, it 

 remains to show how the manganiferous material reached its 

 present form and position. 



The crystalline rocks of Georgia are composed chiefly of 

 granites, gneisses, schists and basic igneous masses, and they 

 are everywhere deeply decayed, — buried under a thick covering 

 of their residual clays. The essential minerals in these rocks 

 are silicates, many of which are manganese-bearing. Decay in 

 this southern region has been promoted largely by chemical 

 changes in the mineral constituents of the rocks, resulting in 

 mineralogical combinations of simpler and more stable form, 

 totally different from the original forms. The combined action 

 of atmospheric oxygen, water, carbonic and organic acids, and 

 to a less degree, perhaps, certain inorganic acids, has been the 



