Art. IX.] Watson, Manganese Ore- Deposits of Georgia. 167 



ing proportions. With the exception of the mineral wad, the 

 ore is usually partially or entirely crystalline, of a dark steel- 

 blue color, and the nodular type which prevails nearly always 

 displays the complete or partially layered or concentric structure 

 of concretionary masses. 



Fig. 7. 



Section in One of tiie Openings at the Dobbins Mine, near Cartersville, 

 Georgia, Siiowing the Occurrence of Manganese-Ore in the Residual Clays. 

 (Modihed from Penrose.) 



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

 residual clay. 



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



Associated Ore-Deposits. — Extensive deposits of brown 

 iron-ore and gray or specular hematite, yellow ocher, and to a 

 less extent barite and bauxite occur somewhat closely associa- 

 ted with the manganese-ores. Of these the deposits of iron-ore 

 and yellow ocher have been extensively mined. The bauxite 

 and barite are of less importance, since the former is only spar- 

 ingly found within the limits of the district, and the latter, 

 while more abundant, is not sufficiently concentrated to admit 

 of profitable working. These are again referred to at some 

 length in a subsequent part of this paper under the origin of 

 the manganese-ores. 



Manganiferoiis Iron- Ores. — The beds of brown iron-ore, 

 which is the prevailing type of iron-deposit in the district, are 

 usually distinct from, though occurring in close relation with. 



