1 68 Bulletin of Laboratories of Denison University [Voi. xii 



the manganese-ores. The oxides of iron and manganese are 

 often found admixed in different proportions in the same bed. 

 Between the two extremes of pure iron-ore and pure manga- 

 nese-ore occur all gradations in the admixture of the two oxides. 

 In some of the beds the two materials are homogeneously 

 mixed, giving the appearance of a manganese ore when the 

 iron is present in small quantity, and of the usual brown hema- 

 tite-ore when manganese is in small quantity. In still other 

 cases the beds of iron-ore are found incrusted in places at the 

 surface for only a slight depth, with the oxide of manganese, 

 which on being opened proves to be a good deposit of iron-ore 

 and not manganese. 



Analyses of the iron-ores invariably show small percentages 

 of manganese, and conversely the manganese-ores show varying 

 percentages of iron, with intermediate gradations in which the 

 two oxides are present in nearly equal amount, forming a good 

 grade of manganiferous iron-ore. These gradations are shown 

 to some extent in the following partial analyses of samples of 

 the ores from this district: 



Analyses of Cartersville Iron- a?id Manganese- Ores. 



Manganese, 



Iron, 



Phosphorus, 



Chemical Composition. — The hundreds of commercial 

 analyses of the Cartersville manganese ores indicate that the 

 ores do not differ essentially from similar high grade ores oc- 

 curring elsewhere. The average in metallic manganese in the 

 better-grade ores is uniformly high, with correspondingly low 

 iron, silica and phosphorus. Silica will usually average low in 

 those cases where the ore has been properly cleansed. It rarely 

 ranges above lo per cent., and is usually much below this, av- 

 eraging from 2 to 5 per cent. Of course, in many of the 

 lower-grade ores the silica will average considerably above lO 

 per cent. The phosphorus in the Cartersville ores is rarely 

 high enough to detract from the value of the ore. The average 

 in this ingredient for the better-grade ores of the district is 



